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[mediawiki.git] / includes / GlobalFunctions.php

<?php
/**
 * Global functions used everywhere.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License along
 * with this program; if not, write to the Free Software Foundation, Inc.,
 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
 * http://www.gnu.org/copyleft/gpl.html
 *
 * @file
 */

if ( !defined( 'MEDIAWIKI' ) ) {
        die( "This file is part of MediaWiki, it is not a valid entry point" );
}

use Liuggio\StatsdClient\Sender\SocketSender;
use MediaWiki\Logger\LoggerFactory;
use MediaWiki\Session\SessionManager;
use Wikimedia\ScopedCallback;

// Hide compatibility functions from Doxygen
/// @cond
/**
 * Compatibility functions
 *
 * We support PHP 5.5.9 and up.
 * Re-implementations of newer functions or functions in non-standard
 * PHP extensions may be included here.
 */

// hash_equals function only exists in PHP >= 5.6.0
// https://secure.php.net/hash_equals
if ( !function_exists( 'hash_equals' ) ) {
        /**
         * Check whether a user-provided string is equal to a fixed-length secret string
         * without revealing bytes of the secret string through timing differences.
         *
         * The usual way to compare strings (PHP's === operator or the underlying memcmp()
         * function in C) is to compare corresponding bytes and stop at the first difference,
         * which would take longer for a partial match than for a complete mismatch. This
         * is not secure when one of the strings (e.g. an HMAC or token) must remain secret
         * and the other may come from an attacker. Statistical analysis of timing measurements
         * over many requests may allow the attacker to guess the string's bytes one at a time
         * (and check his guesses) even if the timing differences are extremely small.
         *
         * When making such a security-sensitive comparison, it is essential that the sequence
         * in which instructions are executed and memory locations are accessed not depend on
         * the secret string's value. HOWEVER, for simplicity, we do not attempt to minimize
         * the inevitable leakage of the string's length. That is generally known anyway as
         * a chararacteristic of the hash function used to compute the secret value.
         *
         * Longer explanation: http://www.emerose.com/timing-attacks-explained
         *
         * @codeCoverageIgnore
         * @param string $known_string Fixed-length secret string to compare against
         * @param string $user_string User-provided string
         * @return bool True if the strings are the same, false otherwise
         */
        function hash_equals( $known_string, $user_string ) {
                // Strict type checking as in PHP's native implementation
                if ( !is_string( $known_string ) ) {
                        trigger_error( 'hash_equals(): Expected known_string to be a string, ' .
                                gettype( $known_string ) . ' given', E_USER_WARNING );

                        return false;
                }

                if ( !is_string( $user_string ) ) {
                        trigger_error( 'hash_equals(): Expected user_string to be a string, ' .
                                gettype( $user_string ) . ' given', E_USER_WARNING );

                        return false;
                }

                $known_string_len = strlen( $known_string );
                if ( $known_string_len !== strlen( $user_string ) ) {
                        return false;
                }

                $result = 0;
                for ( $i = 0; $i < $known_string_len; $i++ ) {
                        $result |= ord( $known_string[$i] ) ^ ord( $user_string[$i] );
                }

                return ( $result === 0 );
        }
}
/// @endcond

/**
 * Load an extension
 *
 * This queues an extension to be loaded through
 * the ExtensionRegistry system.
 *
 * @param string $ext Name of the extension to load
 * @param string|null $path Absolute path of where to find the extension.json file
 * @since 1.25
 */
function wfLoadExtension( $ext, $path = null ) {
        if ( !$path ) {
                global $wgExtensionDirectory;
                $path = "$wgExtensionDirectory/$ext/extension.json";
        }
        ExtensionRegistry::getInstance()->queue( $path );
}

/**
 * Load multiple extensions at once
 *
 * Same as wfLoadExtension, but more efficient if you
 * are loading multiple extensions.
 *
 * If you want to specify custom paths, you should interact with
 * ExtensionRegistry directly.
 *
 * @see wfLoadExtension
 * @param string[] $exts Array of extension names to load
 * @since 1.25
 */
function wfLoadExtensions( array $exts ) {
        global $wgExtensionDirectory;
        $registry = ExtensionRegistry::getInstance();
        foreach ( $exts as $ext ) {
                $registry->queue( "$wgExtensionDirectory/$ext/extension.json" );
        }
}

/**
 * Load a skin
 *
 * @see wfLoadExtension
 * @param string $skin Name of the extension to load
 * @param string|null $path Absolute path of where to find the skin.json file
 * @since 1.25
 */
function wfLoadSkin( $skin, $path = null ) {
        if ( !$path ) {
                global $wgStyleDirectory;
                $path = "$wgStyleDirectory/$skin/skin.json";
        }
        ExtensionRegistry::getInstance()->queue( $path );
}

/**
 * Load multiple skins at once
 *
 * @see wfLoadExtensions
 * @param string[] $skins Array of extension names to load
 * @since 1.25
 */
function wfLoadSkins( array $skins ) {
        global $wgStyleDirectory;
        $registry = ExtensionRegistry::getInstance();
        foreach ( $skins as $skin ) {
                $registry->queue( "$wgStyleDirectory/$skin/skin.json" );
        }
}

/**
 * Like array_diff( $a, $b ) except that it works with two-dimensional arrays.
 * @param array $a
 * @param array $b
 * @return array
 */
function wfArrayDiff2( $a, $b ) {
        return array_udiff( $a, $b, 'wfArrayDiff2_cmp' );
}

/**
 * @param array|string $a
 * @param array|string $b
 * @return int
 */
function wfArrayDiff2_cmp( $a, $b ) {
        if ( is_string( $a ) && is_string( $b ) ) {
                return strcmp( $a, $b );
        } elseif ( count( $a ) !== count( $b ) ) {
                return count( $a ) < count( $b ) ? -1 : 1;
        } else {
                reset( $a );
                reset( $b );
                while ( ( list( , $valueA ) = each( $a ) ) && ( list( , $valueB ) = each( $b ) ) ) {
                        $cmp = strcmp( $valueA, $valueB );
                        if ( $cmp !== 0 ) {
                                return $cmp;
                        }
                }
                return 0;
        }
}

/**
 * Appends to second array if $value differs from that in $default
 *
 * @param string|int $key
 * @param mixed $value
 * @param mixed $default
 * @param array $changed Array to alter
 * @throws MWException
 */
function wfAppendToArrayIfNotDefault( $key, $value, $default, &$changed ) {
        if ( is_null( $changed ) ) {
                throw new MWException( 'GlobalFunctions::wfAppendToArrayIfNotDefault got null' );
        }
        if ( $default[$key] !== $value ) {
                $changed[$key] = $value;
        }
}

/**
 * Merge arrays in the style of getUserPermissionsErrors, with duplicate removal
 * e.g.
 *      wfMergeErrorArrays(
 *              [ [ 'x' ] ],
 *              [ [ 'x', '2' ] ],
 *              [ [ 'x' ] ],
 *              [ [ 'y' ] ]
 *      );
 * returns:
 *              [
 *              [ 'x', '2' ],
 *              [ 'x' ],
 *              [ 'y' ]
 *      ]
 *
 * @param array $array1,...
 * @return array
 */
function wfMergeErrorArrays( /*...*/ ) {
        $args = func_get_args();
        $out = [];
        foreach ( $args as $errors ) {
                foreach ( $errors as $params ) {
                        $originalParams = $params;
                        if ( $params[0] instanceof MessageSpecifier ) {
                                $msg = $params[0];
                                $params = array_merge( [ $msg->getKey() ], $msg->getParams() );
                        }
                        # @todo FIXME: Sometimes get nested arrays for $params,
                        # which leads to E_NOTICEs
                        $spec = implode( "\t", $params );
                        $out[$spec] = $originalParams;
                }
        }
        return array_values( $out );
}

/**
 * Insert array into another array after the specified *KEY*
 *
 * @param array $array The array.
 * @param array $insert The array to insert.
 * @param mixed $after The key to insert after
 * @return array
 */
function wfArrayInsertAfter( array $array, array $insert, $after ) {
        // Find the offset of the element to insert after.
        $keys = array_keys( $array );
        $offsetByKey = array_flip( $keys );

        $offset = $offsetByKey[$after];

        // Insert at the specified offset
        $before = array_slice( $array, 0, $offset + 1, true );
        $after = array_slice( $array, $offset + 1, count( $array ) - $offset, true );

        $output = $before + $insert + $after;

        return $output;
}

/**
 * Recursively converts the parameter (an object) to an array with the same data
 *
 * @param object|array $objOrArray
 * @param bool $recursive
 * @return array
 */
function wfObjectToArray( $objOrArray, $recursive = true ) {
        $array = [];
        if ( is_object( $objOrArray ) ) {
                $objOrArray = get_object_vars( $objOrArray );
        }
        foreach ( $objOrArray as $key => $value ) {
                if ( $recursive && ( is_object( $value ) || is_array( $value ) ) ) {
                        $value = wfObjectToArray( $value );
                }

                $array[$key] = $value;
        }

        return $array;
}

/**
 * Get a random decimal value between 0 and 1, in a way
 * not likely to give duplicate values for any realistic
 * number of articles.
 *
 * @note This is designed for use in relation to Special:RandomPage
 *       and the page_random database field.
 *
 * @return string
 */
function wfRandom() {
        // The maximum random value is "only" 2^31-1, so get two random
        // values to reduce the chance of dupes
        $max = mt_getrandmax() + 1;
        $rand = number_format( ( mt_rand() * $max + mt_rand() ) / $max / $max, 12, '.', '' );
        return $rand;
}

/**
 * Get a random string containing a number of pseudo-random hex characters.
 *
 * @note This is not secure, if you are trying to generate some sort
 *       of token please use MWCryptRand instead.
 *
 * @param int $length The length of the string to generate
 * @return string
 * @since 1.20
 */
function wfRandomString( $length = 32 ) {
        $str = '';
        for ( $n = 0; $n < $length; $n += 7 ) {
                $str .= sprintf( '%07x', mt_rand() & 0xfffffff );
        }
        return substr( $str, 0, $length );
}

/**
 * We want some things to be included as literal characters in our title URLs
 * for prettiness, which urlencode encodes by default.  According to RFC 1738,
 * all of the following should be safe:
 *
 * ;:@&=$-_.+!*'(),
 *
 * RFC 1738 says ~ is unsafe, however RFC 3986 considers it an unreserved
 * character which should not be encoded. More importantly, google chrome
 * always converts %7E back to ~, and converting it in this function can
 * cause a redirect loop (T105265).
 *
 * But + is not safe because it's used to indicate a space; &= are only safe in
 * paths and not in queries (and we don't distinguish here); ' seems kind of
 * scary; and urlencode() doesn't touch -_. to begin with.  Plus, although /
 * is reserved, we don't care.  So the list we unescape is:
 *
 * ;:@$!*(),/~
 *
 * However, IIS7 redirects fail when the url contains a colon (see T24709),
 * so no fancy : for IIS7.
 *
 * %2F in the page titles seems to fatally break for some reason.
 *
 * @param string $s
 * @return string
 */
function wfUrlencode( $s ) {
        static $needle;

        if ( is_null( $s ) ) {
                $needle = null;
                return '';
        }

        if ( is_null( $needle ) ) {
                $needle = [ '%3B', '%40', '%24', '%21', '%2A', '%28', '%29', '%2C', '%2F', '%7E' ];
                if ( !isset( $_SERVER['SERVER_SOFTWARE'] ) ||
                        ( strpos( $_SERVER['SERVER_SOFTWARE'], 'Microsoft-IIS/7' ) === false )
                ) {
                        $needle[] = '%3A';
                }
        }

        $s = urlencode( $s );
        $s = str_ireplace(
                $needle,
                [ ';', '@', '$', '!', '*', '(', ')', ',', '/', '~', ':' ],
                $s
        );

        return $s;
}

/**
 * This function takes one or two arrays as input, and returns a CGI-style string, e.g.
 * "days=7&limit=100". Options in the first array override options in the second.
 * Options set to null or false will not be output.
 *
 * @param array $array1 ( String|Array )
 * @param array|null $array2 ( String|Array )
 * @param string $prefix
 * @return string
 */
function wfArrayToCgi( $array1, $array2 = null, $prefix = '' ) {
        if ( !is_null( $array2 ) ) {
                $array1 = $array1 + $array2;
        }

        $cgi = '';
        foreach ( $array1 as $key => $value ) {
                if ( !is_null( $value ) && $value !== false ) {
                        if ( $cgi != '' ) {
                                $cgi .= '&';
                        }
                        if ( $prefix !== '' ) {
                                $key = $prefix . "[$key]";
                        }
                        if ( is_array( $value ) ) {
                                $firstTime = true;
                                foreach ( $value as $k => $v ) {
                                        $cgi .= $firstTime ? '' : '&';
                                        if ( is_array( $v ) ) {
                                                $cgi .= wfArrayToCgi( $v, null, $key . "[$k]" );
                                        } else {
                                                $cgi .= urlencode( $key . "[$k]" ) . '=' . urlencode( $v );
                                        }
                                        $firstTime = false;
                                }
                        } else {
                                if ( is_object( $value ) ) {
                                        $value = $value->__toString();
                                }
                                $cgi .= urlencode( $key ) . '=' . urlencode( $value );
                        }
                }
        }
        return $cgi;
}

/**
 * This is the logical opposite of wfArrayToCgi(): it accepts a query string as
 * its argument and returns the same string in array form.  This allows compatibility
 * with legacy functions that accept raw query strings instead of nice
 * arrays.  Of course, keys and values are urldecode()d.
 *
 * @param string $query Query string
 * @return string[] Array version of input
 */
function wfCgiToArray( $query ) {
        if ( isset( $query[0] ) && $query[0] == '?' ) {
                $query = substr( $query, 1 );
        }
        $bits = explode( '&', $query );
        $ret = [];
        foreach ( $bits as $bit ) {
                if ( $bit === '' ) {
                        continue;
                }
                if ( strpos( $bit, '=' ) === false ) {
                        // Pieces like &qwerty become 'qwerty' => '' (at least this is what php does)
                        $key = $bit;
                        $value = '';
                } else {
                        list( $key, $value ) = explode( '=', $bit );
                }
                $key = urldecode( $key );
                $value = urldecode( $value );
                if ( strpos( $key, '[' ) !== false ) {
                        $keys = array_reverse( explode( '[', $key ) );
                        $key = array_pop( $keys );
                        $temp = $value;
                        foreach ( $keys as $k ) {
                                $k = substr( $k, 0, -1 );
                                $temp = [ $k => $temp ];
                        }
                        if ( isset( $ret[$key] ) ) {
                                $ret[$key] = array_merge( $ret[$key], $temp );
                        } else {
                                $ret[$key] = $temp;
                        }
                } else {
                        $ret[$key] = $value;
                }
        }
        return $ret;
}

/**
 * Append a query string to an existing URL, which may or may not already
 * have query string parameters already. If so, they will be combined.
 *
 * @param string $url
 * @param string|string[] $query String or associative array
 * @return string
 */
function wfAppendQuery( $url, $query ) {
        if ( is_array( $query ) ) {
                $query = wfArrayToCgi( $query );
        }
        if ( $query != '' ) {
                // Remove the fragment, if there is one
                $fragment = false;
                $hashPos = strpos( $url, '#' );
                if ( $hashPos !== false ) {
                        $fragment = substr( $url, $hashPos );
                        $url = substr( $url, 0, $hashPos );
                }

                // Add parameter
                if ( false === strpos( $url, '?' ) ) {
                        $url .= '?';
                } else {
                        $url .= '&';
                }
                $url .= $query;

                // Put the fragment back
                if ( $fragment !== false ) {
                        $url .= $fragment;
                }
        }
        return $url;
}

/**
 * Expand a potentially local URL to a fully-qualified URL. Assumes $wgServer
 * is correct.
 *
 * The meaning of the PROTO_* constants is as follows:
 * PROTO_HTTP: Output a URL starting with http://
 * PROTO_HTTPS: Output a URL starting with https://
 * PROTO_RELATIVE: Output a URL starting with // (protocol-relative URL)
 * PROTO_CURRENT: Output a URL starting with either http:// or https:// , depending
 *    on which protocol was used for the current incoming request
 * PROTO_CANONICAL: For URLs without a domain, like /w/index.php , use $wgCanonicalServer.
 *    For protocol-relative URLs, use the protocol of $wgCanonicalServer
 * PROTO_INTERNAL: Like PROTO_CANONICAL, but uses $wgInternalServer instead of $wgCanonicalServer
 *
 * @todo this won't work with current-path-relative URLs
 * like "subdir/foo.html", etc.
 *
 * @param string $url Either fully-qualified or a local path + query
 * @param string $defaultProto One of the PROTO_* constants. Determines the
 *    protocol to use if $url or $wgServer is protocol-relative
 * @return string|false Fully-qualified URL, current-path-relative URL or false if
 *    no valid URL can be constructed
 */
function wfExpandUrl( $url, $defaultProto = PROTO_CURRENT ) {
        global $wgServer, $wgCanonicalServer, $wgInternalServer, $wgRequest,
                $wgHttpsPort;
        if ( $defaultProto === PROTO_CANONICAL ) {
                $serverUrl = $wgCanonicalServer;
        } elseif ( $defaultProto === PROTO_INTERNAL && $wgInternalServer !== false ) {
                // Make $wgInternalServer fall back to $wgServer if not set
                $serverUrl = $wgInternalServer;
        } else {
                $serverUrl = $wgServer;
                if ( $defaultProto === PROTO_CURRENT ) {
                        $defaultProto = $wgRequest->getProtocol() . '://';
                }
        }

        // Analyze $serverUrl to obtain its protocol
        $bits = wfParseUrl( $serverUrl );
        $serverHasProto = $bits && $bits['scheme'] != '';

        if ( $defaultProto === PROTO_CANONICAL || $defaultProto === PROTO_INTERNAL ) {
                if ( $serverHasProto ) {
                        $defaultProto = $bits['scheme'] . '://';
                } else {
                        // $wgCanonicalServer or $wgInternalServer doesn't have a protocol.
                        // This really isn't supposed to happen. Fall back to HTTP in this
                        // ridiculous case.
                        $defaultProto = PROTO_HTTP;
                }
        }

        $defaultProtoWithoutSlashes = substr( $defaultProto, 0, -2 );

        if ( substr( $url, 0, 2 ) == '//' ) {
                $url = $defaultProtoWithoutSlashes . $url;
        } elseif ( substr( $url, 0, 1 ) == '/' ) {
                // If $serverUrl is protocol-relative, prepend $defaultProtoWithoutSlashes,
                // otherwise leave it alone.
                $url = ( $serverHasProto ? '' : $defaultProtoWithoutSlashes ) . $serverUrl . $url;
        }

        $bits = wfParseUrl( $url );

        // ensure proper port for HTTPS arrives in URL
        // https://phabricator.wikimedia.org/T67184
        if ( $defaultProto === PROTO_HTTPS && $wgHttpsPort != 443 ) {
                $bits['port'] = $wgHttpsPort;
        }

        if ( $bits && isset( $bits['path'] ) ) {
                $bits['path'] = wfRemoveDotSegments( $bits['path'] );
                return wfAssembleUrl( $bits );
        } elseif ( $bits ) {
                # No path to expand
                return $url;
        } elseif ( substr( $url, 0, 1 ) != '/' ) {
                # URL is a relative path
                return wfRemoveDotSegments( $url );
        }

        # Expanded URL is not valid.
        return false;
}

/**
 * This function will reassemble a URL parsed with wfParseURL.  This is useful
 * if you need to edit part of a URL and put it back together.
 *
 * This is the basic structure used (brackets contain keys for $urlParts):
 * [scheme][delimiter][user]:[pass]@[host]:[port][path]?[query]#[fragment]
 *
 * @todo Need to integrate this into wfExpandUrl (see T34168)
 *
 * @since 1.19
 * @param array $urlParts URL parts, as output from wfParseUrl
 * @return string URL assembled from its component parts
 */
function wfAssembleUrl( $urlParts ) {
        $result = '';

        if ( isset( $urlParts['delimiter'] ) ) {
                if ( isset( $urlParts['scheme'] ) ) {
                        $result .= $urlParts['scheme'];
                }

                $result .= $urlParts['delimiter'];
        }

        if ( isset( $urlParts['host'] ) ) {
                if ( isset( $urlParts['user'] ) ) {
                        $result .= $urlParts['user'];
                        if ( isset( $urlParts['pass'] ) ) {
                                $result .= ':' . $urlParts['pass'];
                        }
                        $result .= '@';
                }

                $result .= $urlParts['host'];

                if ( isset( $urlParts['port'] ) ) {
                        $result .= ':' . $urlParts['port'];
                }
        }

        if ( isset( $urlParts['path'] ) ) {
                $result .= $urlParts['path'];
        }

        if ( isset( $urlParts['query'] ) ) {
                $result .= '?' . $urlParts['query'];
        }

        if ( isset( $urlParts['fragment'] ) ) {
                $result .= '#' . $urlParts['fragment'];
        }

        return $result;
}

/**
 * Remove all dot-segments in the provided URL path.  For example,
 * '/a/./b/../c/' becomes '/a/c/'.  For details on the algorithm, please see
 * RFC3986 section 5.2.4.
 *
 * @todo Need to integrate this into wfExpandUrl (see T34168)
 *
 * @param string $urlPath URL path, potentially containing dot-segments
 * @return string URL path with all dot-segments removed
 */
function wfRemoveDotSegments( $urlPath ) {
        $output = '';
        $inputOffset = 0;
        $inputLength = strlen( $urlPath );

        while ( $inputOffset < $inputLength ) {
                $prefixLengthOne = substr( $urlPath, $inputOffset, 1 );
                $prefixLengthTwo = substr( $urlPath, $inputOffset, 2 );
                $prefixLengthThree = substr( $urlPath, $inputOffset, 3 );
                $prefixLengthFour = substr( $urlPath, $inputOffset, 4 );
                $trimOutput = false;

                if ( $prefixLengthTwo == './' ) {
                        # Step A, remove leading "./"
                        $inputOffset += 2;
                } elseif ( $prefixLengthThree == '../' ) {
                        # Step A, remove leading "../"
                        $inputOffset += 3;
                } elseif ( ( $prefixLengthTwo == '/.' ) && ( $inputOffset + 2 == $inputLength ) ) {
                        # Step B, replace leading "/.$" with "/"
                        $inputOffset += 1;
                        $urlPath[$inputOffset] = '/';
                } elseif ( $prefixLengthThree == '/./' ) {
                        # Step B, replace leading "/./" with "/"
                        $inputOffset += 2;
                } elseif ( $prefixLengthThree == '/..' && ( $inputOffset + 3 == $inputLength ) ) {
                        # Step C, replace leading "/..$" with "/" and
                        # remove last path component in output
                        $inputOffset += 2;
                        $urlPath[$inputOffset] = '/';
                        $trimOutput = true;
                } elseif ( $prefixLengthFour == '/../' ) {
                        # Step C, replace leading "/../" with "/" and
                        # remove last path component in output
                        $inputOffset += 3;
                        $trimOutput = true;
                } elseif ( ( $prefixLengthOne == '.' ) && ( $inputOffset + 1 == $inputLength ) ) {
                        # Step D, remove "^.$"
                        $inputOffset += 1;
                } elseif ( ( $prefixLengthTwo == '..' ) && ( $inputOffset + 2 == $inputLength ) ) {
                        # Step D, remove "^..$"
                        $inputOffset += 2;
                } else {
                        # Step E, move leading path segment to output
                        if ( $prefixLengthOne == '/' ) {
                                $slashPos = strpos( $urlPath, '/', $inputOffset + 1 );
                        } else {
                                $slashPos = strpos( $urlPath, '/', $inputOffset );
                        }
                        if ( $slashPos === false ) {
                                $output .= substr( $urlPath, $inputOffset );
                                $inputOffset = $inputLength;
                        } else {
                                $output .= substr( $urlPath, $inputOffset, $slashPos - $inputOffset );
                                $inputOffset += $slashPos - $inputOffset;
                        }
                }

                if ( $trimOutput ) {
                        $slashPos = strrpos( $output, '/' );
                        if ( $slashPos === false ) {
                                $output = '';
                        } else {
                                $output = substr( $output, 0, $slashPos );
                        }
                }
        }

        return $output;
}

/**
 * Returns a regular expression of url protocols
 *
 * @param bool $includeProtocolRelative If false, remove '//' from the returned protocol list.
 *        DO NOT USE this directly, use wfUrlProtocolsWithoutProtRel() instead
 * @return string
 */
function wfUrlProtocols( $includeProtocolRelative = true ) {
        global $wgUrlProtocols;

        // Cache return values separately based on $includeProtocolRelative
        static $withProtRel = null, $withoutProtRel = null;
        $cachedValue = $includeProtocolRelative ? $withProtRel : $withoutProtRel;
        if ( !is_null( $cachedValue ) ) {
                return $cachedValue;
        }

        // Support old-style $wgUrlProtocols strings, for backwards compatibility
        // with LocalSettings files from 1.5
        if ( is_array( $wgUrlProtocols ) ) {
                $protocols = [];
                foreach ( $wgUrlProtocols as $protocol ) {
                        // Filter out '//' if !$includeProtocolRelative
                        if ( $includeProtocolRelative || $protocol !== '//' ) {
                                $protocols[] = preg_quote( $protocol, '/' );
                        }
                }

                $retval = implode( '|', $protocols );
        } else {
                // Ignore $includeProtocolRelative in this case
                // This case exists for pre-1.6 compatibility, and we can safely assume
                // that '//' won't appear in a pre-1.6 config because protocol-relative
                // URLs weren't supported until 1.18
                $retval = $wgUrlProtocols;
        }

        // Cache return value
        if ( $includeProtocolRelative ) {
                $withProtRel = $retval;
        } else {
                $withoutProtRel = $retval;
        }
        return $retval;
}

/**
 * Like wfUrlProtocols(), but excludes '//' from the protocol list. Use this if
 * you need a regex that matches all URL protocols but does not match protocol-
 * relative URLs
 * @return string
 */
function wfUrlProtocolsWithoutProtRel() {
        return wfUrlProtocols( false );
}

/**
 * parse_url() work-alike, but non-broken.  Differences:
 *
 * 1) Does not raise warnings on bad URLs (just returns false).
 * 2) Handles protocols that don't use :// (e.g., mailto: and news:, as well as
 *    protocol-relative URLs) correctly.
 * 3) Adds a "delimiter" element to the array, either '://', ':' or '//' (see (2)).
 *
 * @param string $url A URL to parse
 * @return string[]|bool Bits of the URL in an associative array, per PHP docs, false on failure
 */
function wfParseUrl( $url ) {
        global $wgUrlProtocols; // Allow all protocols defined in DefaultSettings/LocalSettings.php

        // Protocol-relative URLs are handled really badly by parse_url(). It's so
        // bad that the easiest way to handle them is to just prepend 'http:' and
        // strip the protocol out later.
        $wasRelative = substr( $url, 0, 2 ) == '//';
        if ( $wasRelative ) {
                $url = "http:$url";
        }
        MediaWiki\suppressWarnings();
        $bits = parse_url( $url );
        MediaWiki\restoreWarnings();
        // parse_url() returns an array without scheme for some invalid URLs, e.g.
        // parse_url("%0Ahttp://example.com") == [ 'host' => '%0Ahttp', 'path' => 'example.com' ]
        if ( !$bits || !isset( $bits['scheme'] ) ) {
                return false;
        }

        // parse_url() incorrectly handles schemes case-sensitively. Convert it to lowercase.
        $bits['scheme'] = strtolower( $bits['scheme'] );

        // most of the protocols are followed by ://, but mailto: and sometimes news: not, check for it
        if ( in_array( $bits['scheme'] . '://', $wgUrlProtocols ) ) {
                $bits['delimiter'] = '://';
        } elseif ( in_array( $bits['scheme'] . ':', $wgUrlProtocols ) ) {
                $bits['delimiter'] = ':';
                // parse_url detects for news: and mailto: the host part of an url as path
                // We have to correct this wrong detection
                if ( isset( $bits['path'] ) ) {
                        $bits['host'] = $bits['path'];
                        $bits['path'] = '';
                }
        } else {
                return false;
        }

        /* Provide an empty host for eg. file:/// urls (see T30627) */
        if ( !isset( $bits['host'] ) ) {
                $bits['host'] = '';

                // See T47069
                if ( isset( $bits['path'] ) ) {
                        /* parse_url loses the third / for file:///c:/ urls (but not on variants) */
                        if ( substr( $bits['path'], 0, 1 ) !== '/' ) {
                                $bits['path'] = '/' . $bits['path'];
                        }
                } else {
                        $bits['path'] = '';
                }
        }

        // If the URL was protocol-relative, fix scheme and delimiter
        if ( $wasRelative ) {
                $bits['scheme'] = '';
                $bits['delimiter'] = '//';
        }
        return $bits;
}

/**
 * Take a URL, make sure it's expanded to fully qualified, and replace any
 * encoded non-ASCII Unicode characters with their UTF-8 original forms
 * for more compact display and legibility for local audiences.
 *
 * @todo handle punycode domains too
 *
 * @param string $url
 * @return string
 */
function wfExpandIRI( $url ) {
        return preg_replace_callback(
                '/((?:%[89A-F][0-9A-F])+)/i',
                'wfExpandIRI_callback',
                wfExpandUrl( $url )
        );
}

/**
 * Private callback for wfExpandIRI
 * @param array $matches
 * @return string
 */
function wfExpandIRI_callback( $matches ) {
        return urldecode( $matches[1] );
}

/**
 * Make URL indexes, appropriate for the el_index field of externallinks.
 *
 * @param string $url
 * @return array
 */
function wfMakeUrlIndexes( $url ) {
        $bits = wfParseUrl( $url );

        // Reverse the labels in the hostname, convert to lower case
        // For emails reverse domainpart only
        if ( $bits['scheme'] == 'mailto' ) {
                $mailparts = explode( '@', $bits['host'], 2 );
                if ( count( $mailparts ) === 2 ) {
                        $domainpart = strtolower( implode( '.', array_reverse( explode( '.', $mailparts[1] ) ) ) );
                } else {
                        // No domain specified, don't mangle it
                        $domainpart = '';
                }
                $reversedHost = $domainpart . '@' . $mailparts[0];
        } else {
                $reversedHost = strtolower( implode( '.', array_reverse( explode( '.', $bits['host'] ) ) ) );
        }
        // Add an extra dot to the end
        // Why? Is it in wrong place in mailto links?
        if ( substr( $reversedHost, -1, 1 ) !== '.' ) {
                $reversedHost .= '.';
        }
        // Reconstruct the pseudo-URL
        $prot = $bits['scheme'];
        $index = $prot . $bits['delimiter'] . $reversedHost;
        // Leave out user and password. Add the port, path, query and fragment
        if ( isset( $bits['port'] ) ) {
                $index .= ':' . $bits['port'];
        }
        if ( isset( $bits['path'] ) ) {
                $index .= $bits['path'];
        } else {
                $index .= '/';
        }
        if ( isset( $bits['query'] ) ) {
                $index .= '?' . $bits['query'];
        }
        if ( isset( $bits['fragment'] ) ) {
                $index .= '#' . $bits['fragment'];
        }

        if ( $prot == '' ) {
                return [ "http:$index", "https:$index" ];
        } else {
                return [ $index ];
        }
}

/**
 * Check whether a given URL has a domain that occurs in a given set of domains
 * @param string $url URL
 * @param array $domains Array of domains (strings)
 * @return bool True if the host part of $url ends in one of the strings in $domains
 */
function wfMatchesDomainList( $url, $domains ) {
        $bits = wfParseUrl( $url );
        if ( is_array( $bits ) && isset( $bits['host'] ) ) {
                $host = '.' . $bits['host'];
                foreach ( (array)$domains as $domain ) {
                        $domain = '.' . $domain;
                        if ( substr( $host, -strlen( $domain ) ) === $domain ) {
                                return true;
                        }
                }
        }
        return false;
}

/**
 * Sends a line to the debug log if enabled or, optionally, to a comment in output.
 * In normal operation this is a NOP.
 *
 * Controlling globals:
 * $wgDebugLogFile - points to the log file
 * $wgDebugRawPage - if false, 'action=raw' hits will not result in debug output.
 * $wgDebugComments - if on, some debug items may appear in comments in the HTML output.
 *
 * @since 1.25 support for additional context data
 *
 * @param string $text
 * @param string|bool $dest Destination of the message:
 *     - 'all': both to the log and HTML (debug toolbar or HTML comments)
 *     - 'private': excluded from HTML output
 *   For backward compatibility, it can also take a boolean:
 *     - true: same as 'all'
 *     - false: same as 'private'
 * @param array $context Additional logging context data
 */
function wfDebug( $text, $dest = 'all', array $context = [] ) {
        global $wgDebugRawPage, $wgDebugLogPrefix;
        global $wgDebugTimestamps, $wgRequestTime;

        if ( !$wgDebugRawPage && wfIsDebugRawPage() ) {
                return;
        }

        $text = trim( $text );

        if ( $wgDebugTimestamps ) {
                $context['seconds_elapsed'] = sprintf(
                        '%6.4f',
                        microtime( true ) - $wgRequestTime
                );
                $context['memory_used'] = sprintf(
                        '%5.1fM',
                        ( memory_get_usage( true ) / ( 1024 * 1024 ) )
                );
        }

        if ( $wgDebugLogPrefix !== '' ) {
                $context['prefix'] = $wgDebugLogPrefix;
        }
        $context['private'] = ( $dest === false || $dest === 'private' );

        $logger = LoggerFactory::getInstance( 'wfDebug' );
        $logger->debug( $text, $context );
}

/**
 * Returns true if debug logging should be suppressed if $wgDebugRawPage = false
 * @return bool
 */
function wfIsDebugRawPage() {
        static $cache;
        if ( $cache !== null ) {
                return $cache;
        }
        # Check for raw action using $_GET not $wgRequest, since the latter might not be initialised yet
        if ( ( isset( $_GET['action'] ) && $_GET['action'] == 'raw' )
                || (
                        isset( $_SERVER['SCRIPT_NAME'] )
                        && substr( $_SERVER['SCRIPT_NAME'], -8 ) == 'load.php'
                )
        ) {
                $cache = true;
        } else {
                $cache = false;
        }
        return $cache;
}

/**
 * Send a line giving PHP memory usage.
 *
 * @param bool $exact Print exact byte values instead of kibibytes (default: false)
 */
function wfDebugMem( $exact = false ) {
        $mem = memory_get_usage();
        if ( !$exact ) {
                $mem = floor( $mem / 1024 ) . ' KiB';
        } else {
                $mem .= ' B';
        }
        wfDebug( "Memory usage: $mem\n" );
}

/**
 * Send a line to a supplementary debug log file, if configured, or main debug
 * log if not.
 *
 * To configure a supplementary log file, set $wgDebugLogGroups[$logGroup] to
 * a string filename or an associative array mapping 'destination' to the
 * desired filename. The associative array may also contain a 'sample' key
 * with an integer value, specifying a sampling factor. Sampled log events
 * will be emitted with a 1 in N random chance.
 *
 * @since 1.23 support for sampling log messages via $wgDebugLogGroups.
 * @since 1.25 support for additional context data
 * @since 1.25 sample behavior dependent on configured $wgMWLoggerDefaultSpi
 *
 * @param string $logGroup
 * @param string $text
 * @param string|bool $dest Destination of the message:
 *     - 'all': both to the log and HTML (debug toolbar or HTML comments)
 *     - 'private': only to the specific log if set in $wgDebugLogGroups and
 *       discarded otherwise
 *   For backward compatibility, it can also take a boolean:
 *     - true: same as 'all'
 *     - false: same as 'private'
 * @param array $context Additional logging context data
 */
function wfDebugLog(
        $logGroup, $text, $dest = 'all', array $context = []
) {
        $text = trim( $text );

        $logger = LoggerFactory::getInstance( $logGroup );
        $context['private'] = ( $dest === false || $dest === 'private' );
        $logger->info( $text, $context );
}

/**
 * Log for database errors
 *
 * @since 1.25 support for additional context data
 *
 * @param string $text Database error message.
 * @param array $context Additional logging context data
 */
function wfLogDBError( $text, array $context = [] ) {
        $logger = LoggerFactory::getInstance( 'wfLogDBError' );
        $logger->error( trim( $text ), $context );
}

/**
 * Throws a warning that $function is deprecated
 *
 * @param string $function
 * @param string|bool $version Version of MediaWiki that the function
 *    was deprecated in (Added in 1.19).
 * @param string|bool $component Added in 1.19.
 * @param int $callerOffset How far up the call stack is the original
 *    caller. 2 = function that called the function that called
 *    wfDeprecated (Added in 1.20)
 *
 * @return null
 */
function wfDeprecated( $function, $version = false, $component = false, $callerOffset = 2 ) {
        MWDebug::deprecated( $function, $version, $component, $callerOffset + 1 );
}

/**
 * Send a warning either to the debug log or in a PHP error depending on
 * $wgDevelopmentWarnings. To log warnings in production, use wfLogWarning() instead.
 *
 * @param string $msg Message to send
 * @param int $callerOffset Number of items to go back in the backtrace to
 *        find the correct caller (1 = function calling wfWarn, ...)
 * @param int $level PHP error level; defaults to E_USER_NOTICE;
 *        only used when $wgDevelopmentWarnings is true
 */
function wfWarn( $msg, $callerOffset = 1, $level = E_USER_NOTICE ) {
        MWDebug::warning( $msg, $callerOffset + 1, $level, 'auto' );
}

/**
 * Send a warning as a PHP error and the debug log. This is intended for logging
 * warnings in production. For logging development warnings, use WfWarn instead.
 *
 * @param string $msg Message to send
 * @param int $callerOffset Number of items to go back in the backtrace to
 *        find the correct caller (1 = function calling wfLogWarning, ...)
 * @param int $level PHP error level; defaults to E_USER_WARNING
 */
function wfLogWarning( $msg, $callerOffset = 1, $level = E_USER_WARNING ) {
        MWDebug::warning( $msg, $callerOffset + 1, $level, 'production' );
}

/**
 * Log to a file without getting "file size exceeded" signals.
 *
 * Can also log to TCP or UDP with the syntax udp://host:port/prefix. This will
 * send lines to the specified port, prefixed by the specified prefix and a space.
 * @since 1.25 support for additional context data
 *
 * @param string $text
 * @param string $file Filename
 * @param array $context Additional logging context data
 * @throws MWException
 * @deprecated since 1.25 Use \MediaWiki\Logger\LegacyLogger::emit or UDPTransport
 */
function wfErrorLog( $text, $file, array $context = [] ) {
        wfDeprecated( __METHOD__, '1.25' );
        $logger = LoggerFactory::getInstance( 'wfErrorLog' );
        $context['destination'] = $file;
        $logger->info( trim( $text ), $context );
}

/**
 * @todo document
 */
function wfLogProfilingData() {
        global $wgDebugLogGroups, $wgDebugRawPage;

        $context = RequestContext::getMain();
        $request = $context->getRequest();

        $profiler = Profiler::instance();
        $profiler->setContext( $context );
        $profiler->logData();

        $config = $context->getConfig();
        if ( $config->get( 'StatsdServer' ) ) {
                try {
                        $statsdServer = explode( ':', $config->get( 'StatsdServer' ) );
                        $statsdHost = $statsdServer[0];
                        $statsdPort = isset( $statsdServer[1] ) ? $statsdServer[1] : 8125;
                        $statsdSender = new SocketSender( $statsdHost, $statsdPort );
                        $statsdClient = new SamplingStatsdClient( $statsdSender, true, false );
                        $statsdClient->setSamplingRates( $config->get( 'StatsdSamplingRates' ) );
                        $statsdClient->send( $context->getStats()->getBuffer() );
                } catch ( Exception $ex ) {
                        MWExceptionHandler::logException( $ex );
                }
        }

        # Profiling must actually be enabled...
        if ( $profiler instanceof ProfilerStub ) {
                return;
        }

        if ( isset( $wgDebugLogGroups['profileoutput'] )
                && $wgDebugLogGroups['profileoutput'] === false
        ) {
                // Explicitly disabled
                return;
        }
        if ( !$wgDebugRawPage && wfIsDebugRawPage() ) {
                return;
        }

        $ctx = [ 'elapsed' => $request->getElapsedTime() ];
        if ( !empty( $_SERVER['HTTP_X_FORWARDED_FOR'] ) ) {
                $ctx['forwarded_for'] = $_SERVER['HTTP_X_FORWARDED_FOR'];
        }
        if ( !empty( $_SERVER['HTTP_CLIENT_IP'] ) ) {
                $ctx['client_ip'] = $_SERVER['HTTP_CLIENT_IP'];
        }
        if ( !empty( $_SERVER['HTTP_FROM'] ) ) {
                $ctx['from'] = $_SERVER['HTTP_FROM'];
        }
        if ( isset( $ctx['forwarded_for'] ) ||
                isset( $ctx['client_ip'] ) ||
                isset( $ctx['from'] ) ) {
                $ctx['proxy'] = $_SERVER['REMOTE_ADDR'];
        }

        // Don't load $wgUser at this late stage just for statistics purposes
        // @todo FIXME: We can detect some anons even if it is not loaded.
        // See User::getId()
        $user = $context->getUser();
        $ctx['anon'] = $user->isItemLoaded( 'id' ) && $user->isAnon();

        // Command line script uses a FauxRequest object which does not have
        // any knowledge about an URL and throw an exception instead.
        try {
                $ctx['url'] = urldecode( $request->getRequestURL() );
        } catch ( Exception $ignored ) {
                // no-op
        }

        $ctx['output'] = $profiler->getOutput();

        $log = LoggerFactory::getInstance( 'profileoutput' );
        $log->info( "Elapsed: {elapsed}; URL: <{url}>\n{output}", $ctx );
}

/**
 * Increment a statistics counter
 *
 * @param string $key
 * @param int $count
 * @return void
 */
function wfIncrStats( $key, $count = 1 ) {
        $stats = RequestContext::getMain()->getStats();
        $stats->updateCount( $key, $count );
}

/**
 * Check whether the wiki is in read-only mode.
 *
 * @return bool
 */
function wfReadOnly() {
        return wfReadOnlyReason() !== false;
}

/**
 * Check if the site is in read-only mode and return the message if so
 *
 * This checks wfConfiguredReadOnlyReason() and the main load balancer
 * for replica DB lag. This may result in DB connection being made.
 *
 * @return string|bool String when in read-only mode; false otherwise
 */
function wfReadOnlyReason() {
        $readOnly = wfConfiguredReadOnlyReason();
        if ( $readOnly !== false ) {
                return $readOnly;
        }

        static $lbReadOnly = null;
        if ( $lbReadOnly === null ) {
                // Callers use this method to be aware that data presented to a user
                // may be very stale and thus allowing submissions can be problematic.
                $lbReadOnly = wfGetLB()->getReadOnlyReason();
        }

        return $lbReadOnly;
}

/**
 * Get the value of $wgReadOnly or the contents of $wgReadOnlyFile.
 *
 * @return string|bool String when in read-only mode; false otherwise
 * @since 1.27
 */
function wfConfiguredReadOnlyReason() {
        global $wgReadOnly, $wgReadOnlyFile;

        if ( $wgReadOnly === null ) {
                // Set $wgReadOnly for faster access next time
                if ( is_file( $wgReadOnlyFile ) && filesize( $wgReadOnlyFile ) > 0 ) {
                        $wgReadOnly = file_get_contents( $wgReadOnlyFile );
                } else {
                        $wgReadOnly = false;
                }
        }

        return $wgReadOnly;
}

/**
 * Return a Language object from $langcode
 *
 * @param Language|string|bool $langcode Either:
 *                  - a Language object
 *                  - code of the language to get the message for, if it is
 *                    a valid code create a language for that language, if
 *                    it is a string but not a valid code then make a basic
 *                    language object
 *                  - a boolean: if it's false then use the global object for
 *                    the current user's language (as a fallback for the old parameter
 *                    functionality), or if it is true then use global object
 *                    for the wiki's content language.
 * @return Language
 */
function wfGetLangObj( $langcode = false ) {
        # Identify which language to get or create a language object for.
        # Using is_object here due to Stub objects.
        if ( is_object( $langcode ) ) {
                # Great, we already have the object (hopefully)!
                return $langcode;
        }

        global $wgContLang, $wgLanguageCode;
        if ( $langcode === true || $langcode === $wgLanguageCode ) {
                # $langcode is the language code of the wikis content language object.
                # or it is a boolean and value is true
                return $wgContLang;
        }

        global $wgLang;
        if ( $langcode === false || $langcode === $wgLang->getCode() ) {
                # $langcode is the language code of user language object.
                # or it was a boolean and value is false
                return $wgLang;
        }

        $validCodes = array_keys( Language::fetchLanguageNames() );
        if ( in_array( $langcode, $validCodes ) ) {
                # $langcode corresponds to a valid language.
                return Language::factory( $langcode );
        }

        # $langcode is a string, but not a valid language code; use content language.
        wfDebug( "Invalid language code passed to wfGetLangObj, falling back to content language.\n" );
        return $wgContLang;
}

/**
 * This is the function for getting translated interface messages.
 *
 * @see Message class for documentation how to use them.
 * @see https://www.mediawiki.org/wiki/Manual:Messages_API
 *
 * This function replaces all old wfMsg* functions.
 *
 * @param string|string[]|MessageSpecifier $key Message key, or array of keys, or a MessageSpecifier
 * @param mixed $params,... Normal message parameters
 * @return Message
 *
 * @since 1.17
 *
 * @see Message::__construct
 */
function wfMessage( $key /*...*/ ) {
        $message = new Message( $key );

        // We call Message::params() to reduce code duplication
        $params = func_get_args();
        array_shift( $params );
        if ( $params ) {
                call_user_func_array( [ $message, 'params' ], $params );
        }

        return $message;
}

/**
 * This function accepts multiple message keys and returns a message instance
 * for the first message which is non-empty. If all messages are empty then an
 * instance of the first message key is returned.
 *
 * @param string|string[] $keys,... Message keys
 * @return Message
 *
 * @since 1.18
 *
 * @see Message::newFallbackSequence
 */
function wfMessageFallback( /*...*/ ) {
        $args = func_get_args();
        return call_user_func_array( 'Message::newFallbackSequence', $args );
}

/**
 * Replace message parameter keys on the given formatted output.
 *
 * @param string $message
 * @param array $args
 * @return string
 * @private
 */
function wfMsgReplaceArgs( $message, $args ) {
        # Fix windows line-endings
        # Some messages are split with explode("\n", $msg)
        $message = str_replace( "\r", '', $message );

        // Replace arguments
        if ( is_array( $args ) && $args ) {
                if ( is_array( $args[0] ) ) {
                        $args = array_values( $args[0] );
                }
                $replacementKeys = [];
                foreach ( $args as $n => $param ) {
                        $replacementKeys['$' . ( $n + 1 )] = $param;
                }
                $message = strtr( $message, $replacementKeys );
        }

        return $message;
}

/**
 * Fetch server name for use in error reporting etc.
 * Use real server name if available, so we know which machine
 * in a server farm generated the current page.
 *
 * @return string
 */
function wfHostname() {
        static $host;
        if ( is_null( $host ) ) {

                # Hostname overriding
                global $wgOverrideHostname;
                if ( $wgOverrideHostname !== false ) {
                        # Set static and skip any detection
                        $host = $wgOverrideHostname;
                        return $host;
                }

                if ( function_exists( 'posix_uname' ) ) {
                        // This function not present on Windows
                        $uname = posix_uname();
                } else {
                        $uname = false;
                }
                if ( is_array( $uname ) && isset( $uname['nodename'] ) ) {
                        $host = $uname['nodename'];
                } elseif ( getenv( 'COMPUTERNAME' ) ) {
                        # Windows computer name
                        $host = getenv( 'COMPUTERNAME' );
                } else {
                        # This may be a virtual server.
                        $host = $_SERVER['SERVER_NAME'];
                }
        }
        return $host;
}

/**
 * Returns a script tag that stores the amount of time it took MediaWiki to
 * handle the request in milliseconds as 'wgBackendResponseTime'.
 *
 * If $wgShowHostnames is true, the script will also set 'wgHostname' to the
 * hostname of the server handling the request.
 *
 * @return string
 */
function wfReportTime() {
        global $wgRequestTime, $wgShowHostnames;

        $responseTime = round( ( microtime( true ) - $wgRequestTime ) * 1000 );
        $reportVars = [ 'wgBackendResponseTime' => $responseTime ];
        if ( $wgShowHostnames ) {
                $reportVars['wgHostname'] = wfHostname();
        }
        return Skin::makeVariablesScript( $reportVars );
}

/**
 * Safety wrapper for debug_backtrace().
 *
 * Will return an empty array if debug_backtrace is disabled, otherwise
 * the output from debug_backtrace() (trimmed).
 *
 * @param int $limit This parameter can be used to limit the number of stack frames returned
 *
 * @return array Array of backtrace information
 */
function wfDebugBacktrace( $limit = 0 ) {
        static $disabled = null;

        if ( is_null( $disabled ) ) {
                $disabled = !function_exists( 'debug_backtrace' );
                if ( $disabled ) {
                        wfDebug( "debug_backtrace() is disabled\n" );
                }
        }
        if ( $disabled ) {
                return [];
        }

        if ( $limit ) {
                return array_slice( debug_backtrace( DEBUG_BACKTRACE_PROVIDE_OBJECT, $limit + 1 ), 1 );
        } else {
                return array_slice( debug_backtrace(), 1 );
        }
}

/**
 * Get a debug backtrace as a string
 *
 * @param bool|null $raw If true, the return value is plain text. If false, HTML.
 *   Defaults to $wgCommandLineMode if unset.
 * @return string
 * @since 1.25 Supports $raw parameter.
 */
function wfBacktrace( $raw = null ) {
        global $wgCommandLineMode;

        if ( $raw === null ) {
                $raw = $wgCommandLineMode;
        }

        if ( $raw ) {
                $frameFormat = "%s line %s calls %s()\n";
                $traceFormat = "%s";
        } else {
                $frameFormat = "<li>%s line %s calls %s()</li>\n";
                $traceFormat = "<ul>\n%s</ul>\n";
        }

        $frames = array_map( function ( $frame ) use ( $frameFormat ) {
                $file = !empty( $frame['file'] ) ? basename( $frame['file'] ) : '-';
                $line = isset( $frame['line'] ) ? $frame['line'] : '-';
                $call = $frame['function'];
                if ( !empty( $frame['class'] ) ) {
                        $call = $frame['class'] . $frame['type'] . $call;
                }
                return sprintf( $frameFormat, $file, $line, $call );
        }, wfDebugBacktrace() );

        return sprintf( $traceFormat, implode( '', $frames ) );
}

/**
 * Get the name of the function which called this function
 * wfGetCaller( 1 ) is the function with the wfGetCaller() call (ie. __FUNCTION__)
 * wfGetCaller( 2 ) [default] is the caller of the function running wfGetCaller()
 * wfGetCaller( 3 ) is the parent of that.
 *
 * @param int $level
 * @return string
 */
function wfGetCaller( $level = 2 ) {
        $backtrace = wfDebugBacktrace( $level + 1 );
        if ( isset( $backtrace[$level] ) ) {
                return wfFormatStackFrame( $backtrace[$level] );
        } else {
                return 'unknown';
        }
}

/**
 * Return a string consisting of callers in the stack. Useful sometimes
 * for profiling specific points.
 *
 * @param int $limit The maximum depth of the stack frame to return, or false for the entire stack.
 * @return string
 */
function wfGetAllCallers( $limit = 3 ) {
        $trace = array_reverse( wfDebugBacktrace() );
        if ( !$limit || $limit > count( $trace ) - 1 ) {
                $limit = count( $trace ) - 1;
        }
        $trace = array_slice( $trace, -$limit - 1, $limit );
        return implode( '/', array_map( 'wfFormatStackFrame', $trace ) );
}

/**
 * Return a string representation of frame
 *
 * @param array $frame
 * @return string
 */
function wfFormatStackFrame( $frame ) {
        if ( !isset( $frame['function'] ) ) {
                return 'NO_FUNCTION_GIVEN';
        }
        return isset( $frame['class'] ) && isset( $frame['type'] ) ?
                $frame['class'] . $frame['type'] . $frame['function'] :
                $frame['function'];
}

/* Some generic result counters, pulled out of SearchEngine */

/**
 * @todo document
 *
 * @param int $offset
 * @param int $limit
 * @return string
 */
function wfShowingResults( $offset, $limit ) {
        return wfMessage( 'showingresults' )->numParams( $limit, $offset + 1 )->parse();
}

/**
 * Whether the client accept gzip encoding
 *
 * Uses the Accept-Encoding header to check if the client supports gzip encoding.
 * Use this when considering to send a gzip-encoded response to the client.
 *
 * @param bool $force Forces another check even if we already have a cached result.
 * @return bool
 */
function wfClientAcceptsGzip( $force = false ) {
        static $result = null;
        if ( $result === null || $force ) {
                $result = false;
                if ( isset( $_SERVER['HTTP_ACCEPT_ENCODING'] ) ) {
                        # @todo FIXME: We may want to blacklist some broken browsers
                        $m = [];
                        if ( preg_match(
                                        '/\bgzip(?:;(q)=([0-9]+(?:\.[0-9]+)))?\b/',
                                        $_SERVER['HTTP_ACCEPT_ENCODING'],
                                        $m
                                )
                        ) {
                                if ( isset( $m[2] ) && ( $m[1] == 'q' ) && ( $m[2] == 0 ) ) {
                                        $result = false;
                                        return $result;
                                }
                                wfDebug( "wfClientAcceptsGzip: client accepts gzip.\n" );
                                $result = true;
                        }
                }
        }
        return $result;
}

/**
 * Escapes the given text so that it may be output using addWikiText()
 * without any linking, formatting, etc. making its way through. This
 * is achieved by substituting certain characters with HTML entities.
 * As required by the callers, "<nowiki>" is not used.
 *
 * @param string $text Text to be escaped
 * @return string
 */
function wfEscapeWikiText( $text ) {
        global $wgEnableMagicLinks;
        static $repl = null, $repl2 = null;
        if ( $repl === null || defined( 'MW_PARSER_TEST' ) || defined( 'MW_PHPUNIT_TEST' ) ) {
                // Tests depend upon being able to change $wgEnableMagicLinks, so don't cache
                // in those situations
                $repl = [
                        '"' => '&#34;', '&' => '&#38;', "'" => '&#39;', '<' => '&#60;',
                        '=' => '&#61;', '>' => '&#62;', '[' => '&#91;', ']' => '&#93;',
                        '{' => '&#123;', '|' => '&#124;', '}' => '&#125;', ';' => '&#59;',
                        "\n#" => "\n&#35;", "\r#" => "\r&#35;",
                        "\n*" => "\n&#42;", "\r*" => "\r&#42;",
                        "\n:" => "\n&#58;", "\r:" => "\r&#58;",
                        "\n " => "\n&#32;", "\r " => "\r&#32;",
                        "\n\n" => "\n&#10;", "\r\n" => "&#13;\n",
                        "\n\r" => "\n&#13;", "\r\r" => "\r&#13;",
                        "\n\t" => "\n&#9;", "\r\t" => "\r&#9;", // "\n\t\n" is treated like "\n\n"
                        "\n----" => "\n&#45;---", "\r----" => "\r&#45;---",
                        '__' => '_&#95;', '://' => '&#58;//',
                ];

                $magicLinks = array_keys( array_filter( $wgEnableMagicLinks ) );
                // We have to catch everything "\s" matches in PCRE
                foreach ( $magicLinks as $magic ) {
                        $repl["$magic "] = "$magic&#32;";
                        $repl["$magic\t"] = "$magic&#9;";
                        $repl["$magic\r"] = "$magic&#13;";
                        $repl["$magic\n"] = "$magic&#10;";
                        $repl["$magic\f"] = "$magic&#12;";
                }

                // And handle protocols that don't use "://"
                global $wgUrlProtocols;
                $repl2 = [];
                foreach ( $wgUrlProtocols as $prot ) {
                        if ( substr( $prot, -1 ) === ':' ) {
                                $repl2[] = preg_quote( substr( $prot, 0, -1 ), '/' );
                        }
                }
                $repl2 = $repl2 ? '/\b(' . implode( '|', $repl2 ) . '):/i' : '/^(?!)/';
        }
        $text = substr( strtr( "\n$text", $repl ), 1 );
        $text = preg_replace( $repl2, '$1&#58;', $text );
        return $text;
}

/**
 * Sets dest to source and returns the original value of dest
 * If source is NULL, it just returns the value, it doesn't set the variable
 * If force is true, it will set the value even if source is NULL
 *
 * @param mixed $dest
 * @param mixed $source
 * @param bool $force
 * @return mixed
 */
function wfSetVar( &$dest, $source, $force = false ) {
        $temp = $dest;
        if ( !is_null( $source ) || $force ) {
                $dest = $source;
        }
        return $temp;
}

/**
 * As for wfSetVar except setting a bit
 *
 * @param int $dest
 * @param int $bit
 * @param bool $state
 *
 * @return bool
 */
function wfSetBit( &$dest, $bit, $state = true ) {
        $temp = (bool)( $dest & $bit );
        if ( !is_null( $state ) ) {
                if ( $state ) {
                        $dest |= $bit;
                } else {
                        $dest &= ~$bit;
                }
        }
        return $temp;
}

/**
 * A wrapper around the PHP function var_export().
 * Either print it or add it to the regular output ($wgOut).
 *
 * @param mixed $var A PHP variable to dump.
 */
function wfVarDump( $var ) {
        global $wgOut;
        $s = str_replace( "\n", "<br />\n", var_export( $var, true ) . "\n" );
        if ( headers_sent() || !isset( $wgOut ) || !is_object( $wgOut ) ) {
                print $s;
        } else {
                $wgOut->addHTML( $s );
        }
}

/**
 * Provide a simple HTTP error.
 *
 * @param int|string $code
 * @param string $label
 * @param string $desc
 */
function wfHttpError( $code, $label, $desc ) {
        global $wgOut;
        HttpStatus::header( $code );
        if ( $wgOut ) {
                $wgOut->disable();
                $wgOut->sendCacheControl();
        }

        header( 'Content-type: text/html; charset=utf-8' );
        print '<!DOCTYPE html>' .
                '<html><head><title>' .
                htmlspecialchars( $label ) .
                '</title></head><body><h1>' .
                htmlspecialchars( $label ) .
                '</h1><p>' .
                nl2br( htmlspecialchars( $desc ) ) .
                "</p></body></html>\n";
}

/**
 * Clear away any user-level output buffers, discarding contents.
 *
 * Suitable for 'starting afresh', for instance when streaming
 * relatively large amounts of data without buffering, or wanting to
 * output image files without ob_gzhandler's compression.
 *
 * The optional $resetGzipEncoding parameter controls suppression of
 * the Content-Encoding header sent by ob_gzhandler; by default it
 * is left. See comments for wfClearOutputBuffers() for why it would
 * be used.
 *
 * Note that some PHP configuration options may add output buffer
 * layers which cannot be removed; these are left in place.
 *
 * @param bool $resetGzipEncoding
 */
function wfResetOutputBuffers( $resetGzipEncoding = true ) {
        if ( $resetGzipEncoding ) {
                // Suppress Content-Encoding and Content-Length
                // headers from 1.10+s wfOutputHandler
                global $wgDisableOutputCompression;
                $wgDisableOutputCompression = true;
        }
        while ( $status = ob_get_status() ) {
                if ( isset( $status['flags'] ) ) {
                        $flags = PHP_OUTPUT_HANDLER_CLEANABLE | PHP_OUTPUT_HANDLER_REMOVABLE;
                        $deleteable = ( $status['flags'] & $flags ) === $flags;
                } elseif ( isset( $status['del'] ) ) {
                        $deleteable = $status['del'];
                } else {
                        // Guess that any PHP-internal setting can't be removed.
                        $deleteable = $status['type'] !== 0; /* PHP_OUTPUT_HANDLER_INTERNAL */
                }
                if ( !$deleteable ) {
                        // Give up, and hope the result doesn't break
                        // output behavior.
                        break;
                }
                if ( $status['name'] === 'MediaWikiTestCase::wfResetOutputBuffersBarrier' ) {
                        // Unit testing barrier to prevent this function from breaking PHPUnit.
                        break;
                }
                if ( !ob_end_clean() ) {
                        // Could not remove output buffer handler; abort now
                        // to avoid getting in some kind of infinite loop.
                        break;
                }
                if ( $resetGzipEncoding ) {
                        if ( $status['name'] == 'ob_gzhandler' ) {
                                // Reset the 'Content-Encoding' field set by this handler
                                // so we can start fresh.
                                header_remove( 'Content-Encoding' );
                                break;
                        }
                }
        }
}

/**
 * More legible than passing a 'false' parameter to wfResetOutputBuffers():
 *
 * Clear away output buffers, but keep the Content-Encoding header
 * produced by ob_gzhandler, if any.
 *
 * This should be used for HTTP 304 responses, where you need to
 * preserve the Content-Encoding header of the real result, but
 * also need to suppress the output of ob_gzhandler to keep to spec
 * and avoid breaking Firefox in rare cases where the headers and
 * body are broken over two packets.
 */
function wfClearOutputBuffers() {
        wfResetOutputBuffers( false );
}

/**
 * Converts an Accept-* header into an array mapping string values to quality
 * factors
 *
 * @param string $accept
 * @param string $def Default
 * @return float[] Associative array of string => float pairs
 */
function wfAcceptToPrefs( $accept, $def = '*/*' ) {
        # No arg means accept anything (per HTTP spec)
        if ( !$accept ) {
                return [ $def => 1.0 ];
        }

        $prefs = [];

        $parts = explode( ',', $accept );

        foreach ( $parts as $part ) {
                # @todo FIXME: Doesn't deal with params like 'text/html; level=1'
                $values = explode( ';', trim( $part ) );
                $match = [];
                if ( count( $values ) == 1 ) {
                        $prefs[$values[0]] = 1.0;
                } elseif ( preg_match( '/q\s*=\s*(\d*\.\d+)/', $values[1], $match ) ) {
                        $prefs[$values[0]] = floatval( $match[1] );
                }
        }

        return $prefs;
}

/**
 * Checks if a given MIME type matches any of the keys in the given
 * array. Basic wildcards are accepted in the array keys.
 *
 * Returns the matching MIME type (or wildcard) if a match, otherwise
 * NULL if no match.
 *
 * @param string $type
 * @param array $avail
 * @return string
 * @private
 */
function mimeTypeMatch( $type, $avail ) {
        if ( array_key_exists( $type, $avail ) ) {
                return $type;
        } else {
                $mainType = explode( '/', $type )[0];
                if ( array_key_exists( "$mainType/*", $avail ) ) {
                        return "$mainType/*";
                } elseif ( array_key_exists( '*/*', $avail ) ) {
                        return '*/*';
                } else {
                        return null;
                }
        }
}

/**
 * Returns the 'best' match between a client's requested internet media types
 * and the server's list of available types. Each list should be an associative
 * array of type to preference (preference is a float between 0.0 and 1.0).
 * Wildcards in the types are acceptable.
 *
 * @param array $cprefs Client's acceptable type list
 * @param array $sprefs Server's offered types
 * @return string
 *
 * @todo FIXME: Doesn't handle params like 'text/plain; charset=UTF-8'
 * XXX: generalize to negotiate other stuff
 */
function wfNegotiateType( $cprefs, $sprefs ) {
        $combine = [];

        foreach ( array_keys( $sprefs ) as $type ) {
                $subType = explode( '/', $type )[1];
                if ( $subType != '*' ) {
                        $ckey = mimeTypeMatch( $type, $cprefs );
                        if ( $ckey ) {
                                $combine[$type] = $sprefs[$type] * $cprefs[$ckey];
                        }
                }
        }

        foreach ( array_keys( $cprefs ) as $type ) {
                $subType = explode( '/', $type )[1];
                if ( $subType != '*' && !array_key_exists( $type, $sprefs ) ) {
                        $skey = mimeTypeMatch( $type, $sprefs );
                        if ( $skey ) {
                                $combine[$type] = $sprefs[$skey] * $cprefs[$type];
                        }
                }
        }

        $bestq = 0;
        $besttype = null;

        foreach ( array_keys( $combine ) as $type ) {
                if ( $combine[$type] > $bestq ) {
                        $besttype = $type;
                        $bestq = $combine[$type];
                }
        }

        return $besttype;
}

/**
 * Reference-counted warning suppression
 *
 * @deprecated since 1.26, use MediaWiki\suppressWarnings() directly
 * @param bool $end
 */
function wfSuppressWarnings( $end = false ) {
        MediaWiki\suppressWarnings( $end );
}

/**
 * @deprecated since 1.26, use MediaWiki\restoreWarnings() directly
 * Restore error level to previous value
 */
function wfRestoreWarnings() {
        MediaWiki\suppressWarnings( true );
}

/**
 * Get a timestamp string in one of various formats
 *
 * @param mixed $outputtype A timestamp in one of the supported formats, the
 *   function will autodetect which format is supplied and act accordingly.
 * @param mixed $ts Optional timestamp to convert, default 0 for the current time
 * @return string|bool String / false The same date in the format specified in $outputtype or false
 */
function wfTimestamp( $outputtype = TS_UNIX, $ts = 0 ) {
        $ret = MWTimestamp::convert( $outputtype, $ts );
        if ( $ret === false ) {
                wfDebug( "wfTimestamp() fed bogus time value: TYPE=$outputtype; VALUE=$ts\n" );
        }
        return $ret;
}

/**
 * Return a formatted timestamp, or null if input is null.
 * For dealing with nullable timestamp columns in the database.
 *
 * @param int $outputtype
 * @param string $ts
 * @return string
 */
function wfTimestampOrNull( $outputtype = TS_UNIX, $ts = null ) {
        if ( is_null( $ts ) ) {
                return null;
        } else {
                return wfTimestamp( $outputtype, $ts );
        }
}

/**
 * Convenience function; returns MediaWiki timestamp for the present time.
 *
 * @return string
 */
function wfTimestampNow() {
        # return NOW
        return MWTimestamp::now( TS_MW );
}

/**
 * Check if the operating system is Windows
 *
 * @return bool True if it's Windows, false otherwise.
 */
function wfIsWindows() {
        static $isWindows = null;
        if ( $isWindows === null ) {
                $isWindows = strtoupper( substr( PHP_OS, 0, 3 ) ) === 'WIN';
        }
        return $isWindows;
}

/**
 * Check if we are running under HHVM
 *
 * @return bool
 */
function wfIsHHVM() {
        return defined( 'HHVM_VERSION' );
}

/**
 * Tries to get the system directory for temporary files. First
 * $wgTmpDirectory is checked, and then the TMPDIR, TMP, and TEMP
 * environment variables are then checked in sequence, then
 * sys_get_temp_dir(), then upload_tmp_dir from php.ini.
 *
 * NOTE: When possible, use instead the tmpfile() function to create
 * temporary files to avoid race conditions on file creation, etc.
 *
 * @return string
 */
function wfTempDir() {
        global $wgTmpDirectory;

        if ( $wgTmpDirectory !== false ) {
                return $wgTmpDirectory;
        }

        return TempFSFile::getUsableTempDirectory();
}

/**
 * Make directory, and make all parent directories if they don't exist
 *
 * @param string $dir Full path to directory to create
 * @param int $mode Chmod value to use, default is $wgDirectoryMode
 * @param string $caller Optional caller param for debugging.
 * @throws MWException
 * @return bool
 */
function wfMkdirParents( $dir, $mode = null, $caller = null ) {
        global $wgDirectoryMode;

        if ( FileBackend::isStoragePath( $dir ) ) { // sanity
                throw new MWException( __FUNCTION__ . " given storage path '$dir'." );
        }

        if ( !is_null( $caller ) ) {
                wfDebug( "$caller: called wfMkdirParents($dir)\n" );
        }

        if ( strval( $dir ) === '' || is_dir( $dir ) ) {
                return true;
        }

        $dir = str_replace( [ '\\', '/' ], DIRECTORY_SEPARATOR, $dir );

        if ( is_null( $mode ) ) {
                $mode = $wgDirectoryMode;
        }

        // Turn off the normal warning, we're doing our own below
        MediaWiki\suppressWarnings();
        $ok = mkdir( $dir, $mode, true ); // PHP5 <3
        MediaWiki\restoreWarnings();

        if ( !$ok ) {
                // directory may have been created on another request since we last checked
                if ( is_dir( $dir ) ) {
                        return true;
                }

                // PHP doesn't report the path in its warning message, so add our own to aid in diagnosis.
                wfLogWarning( sprintf( "failed to mkdir \"%s\" mode 0%o", $dir, $mode ) );
        }
        return $ok;
}

/**
 * Remove a directory and all its content.
 * Does not hide error.
 * @param string $dir
 */
function wfRecursiveRemoveDir( $dir ) {
        wfDebug( __FUNCTION__ . "( $dir )\n" );
        // taken from https://secure.php.net/manual/en/function.rmdir.php#98622
        if ( is_dir( $dir ) ) {
                $objects = scandir( $dir );
                foreach ( $objects as $object ) {
                        if ( $object != "." && $object != ".." ) {
                                if ( filetype( $dir . '/' . $object ) == "dir" ) {
                                        wfRecursiveRemoveDir( $dir . '/' . $object );
                                } else {
                                        unlink( $dir . '/' . $object );
                                }
                        }
                }
                reset( $objects );
                rmdir( $dir );
        }
}

/**
 * @param int $nr The number to format
 * @param int $acc The number of digits after the decimal point, default 2
 * @param bool $round Whether or not to round the value, default true
 * @return string
 */
function wfPercent( $nr, $acc = 2, $round = true ) {
        $ret = sprintf( "%.${acc}f", $nr );
        return $round ? round( $ret, $acc ) . '%' : "$ret%";
}

/**
 * Safety wrapper around ini_get() for boolean settings.
 * The values returned from ini_get() are pre-normalized for settings
 * set via php.ini or php_flag/php_admin_flag... but *not*
 * for those set via php_value/php_admin_value.
 *
 * It's fairly common for people to use php_value instead of php_flag,
 * which can leave you with an 'off' setting giving a false positive
 * for code that just takes the ini_get() return value as a boolean.
 *
 * To make things extra interesting, setting via php_value accepts
 * "true" and "yes" as true, but php.ini and php_flag consider them false. :)
 * Unrecognized values go false... again opposite PHP's own coercion
 * from string to bool.
 *
 * Luckily, 'properly' set settings will always come back as '0' or '1',
 * so we only have to worry about them and the 'improper' settings.
 *
 * I frickin' hate PHP... :P
 *
 * @param string $setting
 * @return bool
 */
function wfIniGetBool( $setting ) {
        $val = strtolower( ini_get( $setting ) );
        // 'on' and 'true' can't have whitespace around them, but '1' can.
        return $val == 'on'
                || $val == 'true'
                || $val == 'yes'
                || preg_match( "/^\s*[+-]?0*[1-9]/", $val ); // approx C atoi() function
}

/**
 * Version of escapeshellarg() that works better on Windows.
 *
 * Originally, this fixed the incorrect use of single quotes on Windows
 * (https://bugs.php.net/bug.php?id=26285) and the locale problems on Linux in
 * PHP 5.2.6+ (bug backported to earlier distro releases of PHP).
 *
 * @param string ... strings to escape and glue together, or a single array of strings parameter
 * @return string
 */
function wfEscapeShellArg( /*...*/ ) {
        wfInitShellLocale();

        $args = func_get_args();
        if ( count( $args ) === 1 && is_array( reset( $args ) ) ) {
                // If only one argument has been passed, and that argument is an array,
                // treat it as a list of arguments
                $args = reset( $args );
        }

        $first = true;
        $retVal = '';
        foreach ( $args as $arg ) {
                if ( !$first ) {
                        $retVal .= ' ';
                } else {
                        $first = false;
                }

                if ( wfIsWindows() ) {
                        // Escaping for an MSVC-style command line parser and CMD.EXE
                        // @codingStandardsIgnoreStart For long URLs
                        // Refs:
                        //  * https://web.archive.org/web/20020708081031/http://mailman.lyra.org/pipermail/scite-interest/2002-March/000436.html
                        //  * https://technet.microsoft.com/en-us/library/cc723564.aspx
                        //  * T15518
                        //  * CR r63214
                        // Double the backslashes before any double quotes. Escape the double quotes.
                        // @codingStandardsIgnoreEnd
                        $tokens = preg_split( '/(\\\\*")/', $arg, -1, PREG_SPLIT_DELIM_CAPTURE );
                        $arg = '';
                        $iteration = 0;
                        foreach ( $tokens as $token ) {
                                if ( $iteration % 2 == 1 ) {
                                        // Delimiter, a double quote preceded by zero or more slashes
                                        $arg .= str_replace( '\\', '\\\\', substr( $token, 0, -1 ) ) . '\\"';
                                } elseif ( $iteration % 4 == 2 ) {
                                        // ^ in $token will be outside quotes, need to be escaped
                                        $arg .= str_replace( '^', '^^', $token );
                                } else { // $iteration % 4 == 0
                                        // ^ in $token will appear inside double quotes, so leave as is
                                        $arg .= $token;
                                }
                                $iteration++;
                        }
                        // Double the backslashes before the end of the string, because
                        // we will soon add a quote
                        $m = [];
                        if ( preg_match( '/^(.*?)(\\\\+)$/', $arg, $m ) ) {
                                $arg = $m[1] . str_replace( '\\', '\\\\', $m[2] );
                        }

                        // Add surrounding quotes
                        $retVal .= '"' . $arg . '"';
                } else {
                        $retVal .= escapeshellarg( $arg );
                }
        }
        return $retVal;
}

/**
 * Check if wfShellExec() is effectively disabled via php.ini config
 *
 * @return bool|string False or 'disabled'
 * @since 1.22
 */
function wfShellExecDisabled() {
        static $disabled = null;
        if ( is_null( $disabled ) ) {
                if ( !function_exists( 'proc_open' ) ) {
                        wfDebug( "proc_open() is disabled\n" );
                        $disabled = 'disabled';
                } else {
                        $disabled = false;
                }
        }
        return $disabled;
}

/**
 * Execute a shell command, with time and memory limits mirrored from the PHP
 * configuration if supported.
 *
 * @param string|string[] $cmd If string, a properly shell-escaped command line,
 *   or an array of unescaped arguments, in which case each value will be escaped
 *   Example:   [ 'convert', '-font', 'font name' ] would produce "'convert' '-font' 'font name'"
 * @param null|mixed &$retval Optional, will receive the program's exit code.
 *   (non-zero is usually failure). If there is an error from
 *   read, select, or proc_open(), this will be set to -1.
 * @param array $environ Optional environment variables which should be
 *   added to the executed command environment.
 * @param array $limits Optional array with limits(filesize, memory, time, walltime)
 *   this overwrites the global wgMaxShell* limits.
 * @param array $options Array of options:
 *   - duplicateStderr: Set this to true to duplicate stderr to stdout,
 *     including errors from limit.sh
 *   - profileMethod: By default this function will profile based on the calling
 *     method. Set this to a string for an alternative method to profile from
 *
 * @return string Collected stdout as a string
 */
function wfShellExec( $cmd, &$retval = null, $environ = [],
        $limits = [], $options = []
) {
        global $IP, $wgMaxShellMemory, $wgMaxShellFileSize, $wgMaxShellTime,
                $wgMaxShellWallClockTime, $wgShellCgroup;

        $disabled = wfShellExecDisabled();
        if ( $disabled ) {
                $retval = 1;
                return 'Unable to run external programs, proc_open() is disabled.';
        }

        $includeStderr = isset( $options['duplicateStderr'] ) && $options['duplicateStderr'];
        $profileMethod = isset( $options['profileMethod'] ) ? $options['profileMethod'] : wfGetCaller();

        wfInitShellLocale();

        $envcmd = '';
        foreach ( $environ as $k => $v ) {
                if ( wfIsWindows() ) {
                        /* Surrounding a set in quotes (method used by wfEscapeShellArg) makes the quotes themselves
                         * appear in the environment variable, so we must use carat escaping as documented in
                         * https://technet.microsoft.com/en-us/library/cc723564.aspx
                         * Note however that the quote isn't listed there, but is needed, and the parentheses
                         * are listed there but doesn't appear to need it.
                         */
                        $envcmd .= "set $k=" . preg_replace( '/([&|()<>^"])/', '^\\1', $v ) . '&& ';
                } else {
                        /* Assume this is a POSIX shell, thus required to accept variable assignments before the command
                         * http://www.opengroup.org/onlinepubs/009695399/utilities/xcu_chap02.html#tag_02_09_01
                         */
                        $envcmd .= "$k=" . escapeshellarg( $v ) . ' ';
                }
        }
        if ( is_array( $cmd ) ) {
                $cmd = wfEscapeShellArg( $cmd );
        }

        $cmd = $envcmd . $cmd;

        $useLogPipe = false;
        if ( is_executable( '/bin/bash' ) ) {
                $time = intval( isset( $limits['time'] ) ? $limits['time'] : $wgMaxShellTime );
                if ( isset( $limits['walltime'] ) ) {
                        $wallTime = intval( $limits['walltime'] );
                } elseif ( isset( $limits['time'] ) ) {
                        $wallTime = $time;
                } else {
                        $wallTime = intval( $wgMaxShellWallClockTime );
                }
                $mem = intval( isset( $limits['memory'] ) ? $limits['memory'] : $wgMaxShellMemory );
                $filesize = intval( isset( $limits['filesize'] ) ? $limits['filesize'] : $wgMaxShellFileSize );

                if ( $time > 0 || $mem > 0 || $filesize > 0 || $wallTime > 0 ) {
                        $cmd = '/bin/bash ' . escapeshellarg( "$IP/includes/limit.sh" ) . ' ' .
                                escapeshellarg( $cmd ) . ' ' .
                                escapeshellarg(
                                        "MW_INCLUDE_STDERR=" . ( $includeStderr ? '1' : '' ) . ';' .
                                        "MW_CPU_LIMIT=$time; " .
                                        'MW_CGROUP=' . escapeshellarg( $wgShellCgroup ) . '; ' .
                                        "MW_MEM_LIMIT=$mem; " .
                                        "MW_FILE_SIZE_LIMIT=$filesize; " .
                                        "MW_WALL_CLOCK_LIMIT=$wallTime; " .
                                        "MW_USE_LOG_PIPE=yes"
                                );
                        $useLogPipe = true;
                } elseif ( $includeStderr ) {
                        $cmd .= ' 2>&1';
                }
        } elseif ( $includeStderr ) {
                $cmd .= ' 2>&1';
        }
        wfDebug( "wfShellExec: $cmd\n" );

        // Don't try to execute commands that exceed Linux's MAX_ARG_STRLEN.
        // Other platforms may be more accomodating, but we don't want to be
        // accomodating, because very long commands probably include user
        // input. See T129506.
        if ( strlen( $cmd ) > SHELL_MAX_ARG_STRLEN ) {
                throw new Exception( __METHOD__ .
                        '(): total length of $cmd must not exceed SHELL_MAX_ARG_STRLEN' );
        }

        $desc = [
                0 => [ 'file', 'php://stdin', 'r' ],
                1 => [ 'pipe', 'w' ],
                2 => [ 'file', 'php://stderr', 'w' ] ];
        if ( $useLogPipe ) {
                $desc[3] = [ 'pipe', 'w' ];
        }
        $pipes = null;
        $scoped = Profiler::instance()->scopedProfileIn( __FUNCTION__ . '-' . $profileMethod );
        $proc = proc_open( $cmd, $desc, $pipes );
        if ( !$proc ) {
                wfDebugLog( 'exec', "proc_open() failed: $cmd" );
                $retval = -1;
                return '';
        }
        $outBuffer = $logBuffer = '';
        $emptyArray = [];
        $status = false;
        $logMsg = false;

        /* According to the documentation, it is possible for stream_select()
         * to fail due to EINTR. I haven't managed to induce this in testing
         * despite sending various signals. If it did happen, the error
         * message would take the form:
         *
         * stream_select(): unable to select [4]: Interrupted system call (max_fd=5)
         *
         * where [4] is the value of the macro EINTR and "Interrupted system
         * call" is string which according to the Linux manual is "possibly"
         * localised according to LC_MESSAGES.
         */
        $eintr = defined( 'SOCKET_EINTR' ) ? SOCKET_EINTR : 4;
        $eintrMessage = "stream_select(): unable to select [$eintr]";

        $running = true;
        $timeout = null;
        $numReadyPipes = 0;

        while ( $running === true || $numReadyPipes !== 0 ) {
                if ( $running ) {
                        $status = proc_get_status( $proc );
                        // If the process has terminated, switch to nonblocking selects
                        // for getting any data still waiting to be read.
                        if ( !$status['running'] ) {
                                $running = false;
                                $timeout = 0;
                        }
                }

                $readyPipes = $pipes;

                // Clear last error
                // @codingStandardsIgnoreStart Generic.PHP.NoSilencedErrors.Discouraged
                @trigger_error( '' );
                $numReadyPipes = @stream_select( $readyPipes, $emptyArray, $emptyArray, $timeout );
                if ( $numReadyPipes === false ) {
                        // @codingStandardsIgnoreEnd
                        $error = error_get_last();
                        if ( strncmp( $error['message'], $eintrMessage, strlen( $eintrMessage ) ) == 0 ) {
                                continue;
                        } else {
                                trigger_error( $error['message'], E_USER_WARNING );
                                $logMsg = $error['message'];
                                break;
                        }
                }
                foreach ( $readyPipes as $fd => $pipe ) {
                        $block = fread( $pipe, 65536 );
                        if ( $block === '' ) {
                                // End of file
                                fclose( $pipes[$fd] );
                                unset( $pipes[$fd] );
                                if ( !$pipes ) {
                                        break 2;
                                }
                        } elseif ( $block === false ) {
                                // Read error
                                $logMsg = "Error reading from pipe";
                                break 2;
                        } elseif ( $fd == 1 ) {
                                // From stdout
                                $outBuffer .= $block;
                        } elseif ( $fd == 3 ) {
                                // From log FD
                                $logBuffer .= $block;
                                if ( strpos( $block, "\n" ) !== false ) {
                                        $lines = explode( "\n", $logBuffer );
                                        $logBuffer = array_pop( $lines );
                                        foreach ( $lines as $line ) {
                                                wfDebugLog( 'exec', $line );
                                        }
                                }
                        }
                }
        }

        foreach ( $pipes as $pipe ) {
                fclose( $pipe );
        }

        // Use the status previously collected if possible, since proc_get_status()
        // just calls waitpid() which will not return anything useful the second time.
        if ( $running ) {
                $status = proc_get_status( $proc );
        }

        if ( $logMsg !== false ) {
                // Read/select error
                $retval = -1;
                proc_close( $proc );
        } elseif ( $status['signaled'] ) {
                $logMsg = "Exited with signal {$status['termsig']}";
                $retval = 128 + $status['termsig'];
                proc_close( $proc );
        } else {
                if ( $status['running'] ) {
                        $retval = proc_close( $proc );
                } else {
                        $retval = $status['exitcode'];
                        proc_close( $proc );
                }
                if ( $retval == 127 ) {
                        $logMsg = "Possibly missing executable file";
                } elseif ( $retval >= 129 && $retval <= 192 ) {
                        $logMsg = "Probably exited with signal " . ( $retval - 128 );
                }
        }

        if ( $logMsg !== false ) {
                wfDebugLog( 'exec', "$logMsg: $cmd" );
        }

        return $outBuffer;
}

/**
 * Execute a shell command, returning both stdout and stderr. Convenience
 * function, as all the arguments to wfShellExec can become unwieldy.
 *
 * @note This also includes errors from limit.sh, e.g. if $wgMaxShellFileSize is exceeded.
 * @param string|string[] $cmd If string, a properly shell-escaped command line,
 *   or an array of unescaped arguments, in which case each value will be escaped
 *   Example:   [ 'convert', '-font', 'font name' ] would produce "'convert' '-font' 'font name'"
 * @param null|mixed &$retval Optional, will receive the program's exit code.
 *   (non-zero is usually failure)
 * @param array $environ Optional environment variables which should be
 *   added to the executed command environment.
 * @param array $limits Optional array with limits(filesize, memory, time, walltime)
 *   this overwrites the global wgMaxShell* limits.
 * @return string Collected stdout and stderr as a string
 */
function wfShellExecWithStderr( $cmd, &$retval = null, $environ = [], $limits = [] ) {
        return wfShellExec( $cmd, $retval, $environ, $limits,
                [ 'duplicateStderr' => true, 'profileMethod' => wfGetCaller() ] );
}

/**
 * Workaround for https://bugs.php.net/bug.php?id=45132
 * escapeshellarg() destroys non-ASCII characters if LANG is not a UTF-8 locale
 */
function wfInitShellLocale() {
        static $done = false;
        if ( $done ) {
                return;
        }
        $done = true;
        global $wgShellLocale;
        putenv( "LC_CTYPE=$wgShellLocale" );
        setlocale( LC_CTYPE, $wgShellLocale );
}

/**
 * Generate a shell-escaped command line string to run a MediaWiki cli script.
 * Note that $parameters should be a flat array and an option with an argument
 * should consist of two consecutive items in the array (do not use "--option value").
 *
 * @param string $script MediaWiki cli script path
 * @param array $parameters Arguments and options to the script
 * @param array $options Associative array of options:
 *              'php': The path to the php executable
 *              'wrapper': Path to a PHP wrapper to handle the maintenance script
 * @return string
 */
function wfShellWikiCmd( $script, array $parameters = [], array $options = [] ) {
        global $wgPhpCli;
        // Give site config file a chance to run the script in a wrapper.
        // The caller may likely want to call wfBasename() on $script.
        Hooks::run( 'wfShellWikiCmd', [ &$script, &$parameters, &$options ] );
        $cmd = isset( $options['php'] ) ? [ $options['php'] ] : [ $wgPhpCli ];
        if ( isset( $options['wrapper'] ) ) {
                $cmd[] = $options['wrapper'];
        }
        $cmd[] = $script;
        // Escape each parameter for shell
        return wfEscapeShellArg( array_merge( $cmd, $parameters ) );
}

/**
 * wfMerge attempts to merge differences between three texts.
 * Returns true for a clean merge and false for failure or a conflict.
 *
 * @param string $old
 * @param string $mine
 * @param string $yours
 * @param string $result
 * @return bool
 */
function wfMerge( $old, $mine, $yours, &$result ) {
        global $wgDiff3;

        # This check may also protect against code injection in
        # case of broken installations.
        MediaWiki\suppressWarnings();
        $haveDiff3 = $wgDiff3 && file_exists( $wgDiff3 );
        MediaWiki\restoreWarnings();

        if ( !$haveDiff3 ) {
                wfDebug( "diff3 not found\n" );
                return false;
        }

        # Make temporary files
        $td = wfTempDir();
        $oldtextFile = fopen( $oldtextName = tempnam( $td, 'merge-old-' ), 'w' );
        $mytextFile = fopen( $mytextName = tempnam( $td, 'merge-mine-' ), 'w' );
        $yourtextFile = fopen( $yourtextName = tempnam( $td, 'merge-your-' ), 'w' );

        # NOTE: diff3 issues a warning to stderr if any of the files does not end with
        #       a newline character. To avoid this, we normalize the trailing whitespace before
        #       creating the diff.

        fwrite( $oldtextFile, rtrim( $old ) . "\n" );
        fclose( $oldtextFile );
        fwrite( $mytextFile, rtrim( $mine ) . "\n" );
        fclose( $mytextFile );
        fwrite( $yourtextFile, rtrim( $yours ) . "\n" );
        fclose( $yourtextFile );

        # Check for a conflict
        $cmd = wfEscapeShellArg( $wgDiff3, '-a', '--overlap-only', $mytextName,
                $oldtextName, $yourtextName );
        $handle = popen( $cmd, 'r' );

        if ( fgets( $handle, 1024 ) ) {
                $conflict = true;
        } else {
                $conflict = false;
        }
        pclose( $handle );

        # Merge differences
        $cmd = wfEscapeShellArg( $wgDiff3, '-a', '-e', '--merge', $mytextName,
                $oldtextName, $yourtextName );
        $handle = popen( $cmd, 'r' );
        $result = '';
        do {
                $data = fread( $handle, 8192 );
                if ( strlen( $data ) == 0 ) {
                        break;
                }
                $result .= $data;
        } while ( true );
        pclose( $handle );
        unlink( $mytextName );
        unlink( $oldtextName );
        unlink( $yourtextName );

        if ( $result === '' && $old !== '' && !$conflict ) {
                wfDebug( "Unexpected null result from diff3. Command: $cmd\n" );
                $conflict = true;
        }
        return !$conflict;
}

/**
 * Returns unified plain-text diff of two texts.
 * "Useful" for machine processing of diffs.
 *
 * @deprecated since 1.25, use DiffEngine/UnifiedDiffFormatter directly
 *
 * @param string $before The text before the changes.
 * @param string $after The text after the changes.
 * @param string $params Command-line options for the diff command.
 * @return string Unified diff of $before and $after
 */
function wfDiff( $before, $after, $params = '-u' ) {
        if ( $before == $after ) {
                return '';
        }

        global $wgDiff;
        MediaWiki\suppressWarnings();
        $haveDiff = $wgDiff && file_exists( $wgDiff );
        MediaWiki\restoreWarnings();

        # This check may also protect against code injection in
        # case of broken installations.
        if ( !$haveDiff ) {
                wfDebug( "diff executable not found\n" );
                $diffs = new Diff( explode( "\n", $before ), explode( "\n", $after ) );
                $format = new UnifiedDiffFormatter();
                return $format->format( $diffs );
        }

        # Make temporary files
        $td = wfTempDir();
        $oldtextFile = fopen( $oldtextName = tempnam( $td, 'merge-old-' ), 'w' );
        $newtextFile = fopen( $newtextName = tempnam( $td, 'merge-your-' ), 'w' );

        fwrite( $oldtextFile, $before );
        fclose( $oldtextFile );
        fwrite( $newtextFile, $after );
        fclose( $newtextFile );

        // Get the diff of the two files
        $cmd = "$wgDiff " . $params . ' ' . wfEscapeShellArg( $oldtextName, $newtextName );

        $h = popen( $cmd, 'r' );
        if ( !$h ) {
                unlink( $oldtextName );
                unlink( $newtextName );
                throw new Exception( __METHOD__ . '(): popen() failed' );
        }

        $diff = '';

        do {
                $data = fread( $h, 8192 );
                if ( strlen( $data ) == 0 ) {
                        break;
                }
                $diff .= $data;
        } while ( true );

        // Clean up
        pclose( $h );
        unlink( $oldtextName );
        unlink( $newtextName );

        // Kill the --- and +++ lines. They're not useful.
        $diff_lines = explode( "\n", $diff );
        if ( isset( $diff_lines[0] ) && strpos( $diff_lines[0], '---' ) === 0 ) {
                unset( $diff_lines[0] );
        }
        if ( isset( $diff_lines[1] ) && strpos( $diff_lines[1], '+++' ) === 0 ) {
                unset( $diff_lines[1] );
        }

        $diff = implode( "\n", $diff_lines );

        return $diff;
}

/**
 * This function works like "use VERSION" in Perl, the program will die with a
 * backtrace if the current version of PHP is less than the version provided
 *
 * This is useful for extensions which due to their nature are not kept in sync
 * with releases, and might depend on other versions of PHP than the main code
 *
 * Note: PHP might die due to parsing errors in some cases before it ever
 *       manages to call this function, such is life
 *
 * @see perldoc -f use
 *
 * @param string|int|float $req_ver The version to check, can be a string, an integer, or a float
 * @throws MWException
 */
function wfUsePHP( $req_ver ) {
        $php_ver = PHP_VERSION;

        if ( version_compare( $php_ver, (string)$req_ver, '<' ) ) {
                throw new MWException( "PHP $req_ver required--this is only $php_ver" );
        }
}

/**
 * This function works like "use VERSION" in Perl except it checks the version
 * of MediaWiki, the program will die with a backtrace if the current version
 * of MediaWiki is less than the version provided.
 *
 * This is useful for extensions which due to their nature are not kept in sync
 * with releases
 *
 * Note: Due to the behavior of PHP's version_compare() which is used in this
 * function, if you want to allow the 'wmf' development versions add a 'c' (or
 * any single letter other than 'a', 'b' or 'p') as a post-fix to your
 * targeted version number. For example if you wanted to allow any variation
 * of 1.22 use `wfUseMW( '1.22c' )`. Using an 'a' or 'b' instead of 'c' will
 * not result in the same comparison due to the internal logic of
 * version_compare().
 *
 * @see perldoc -f use
 *
 * @deprecated since 1.26, use the "requires' property of extension.json
 * @param string|int|float $req_ver The version to check, can be a string, an integer, or a float
 * @throws MWException
 */
function wfUseMW( $req_ver ) {
        global $wgVersion;

        if ( version_compare( $wgVersion, (string)$req_ver, '<' ) ) {
                throw new MWException( "MediaWiki $req_ver required--this is only $wgVersion" );
        }
}

/**
 * Return the final portion of a pathname.
 * Reimplemented because PHP5's "basename()" is buggy with multibyte text.
 * https://bugs.php.net/bug.php?id=33898
 *
 * PHP's basename() only considers '\' a pathchar on Windows and Netware.
 * We'll consider it so always, as we don't want '\s' in our Unix paths either.
 *
 * @param string $path
 * @param string $suffix String to remove if present
 * @return string
 */
function wfBaseName( $path, $suffix = '' ) {
        if ( $suffix == '' ) {
                $encSuffix = '';
        } else {
                $encSuffix = '(?:' . preg_quote( $suffix, '#' ) . ')?';
        }

        $matches = [];
        if ( preg_match( "#([^/\\\\]*?){$encSuffix}[/\\\\]*$#", $path, $matches ) ) {
                return $matches[1];
        } else {
                return '';
        }
}

/**
 * Generate a relative path name to the given file.
 * May explode on non-matching case-insensitive paths,
 * funky symlinks, etc.
 *
 * @param string $path Absolute destination path including target filename
 * @param string $from Absolute source path, directory only
 * @return string
 */
function wfRelativePath( $path, $from ) {
        // Normalize mixed input on Windows...
        $path = str_replace( '/', DIRECTORY_SEPARATOR, $path );
        $from = str_replace( '/', DIRECTORY_SEPARATOR, $from );

        // Trim trailing slashes -- fix for drive root
        $path = rtrim( $path, DIRECTORY_SEPARATOR );
        $from = rtrim( $from, DIRECTORY_SEPARATOR );

        $pieces = explode( DIRECTORY_SEPARATOR, dirname( $path ) );
        $against = explode( DIRECTORY_SEPARATOR, $from );

        if ( $pieces[0] !== $against[0] ) {
                // Non-matching Windows drive letters?
                // Return a full path.
                return $path;
        }

        // Trim off common prefix
        while ( count( $pieces ) && count( $against )
                && $pieces[0] == $against[0] ) {
                array_shift( $pieces );
                array_shift( $against );
        }

        // relative dots to bump us to the parent
        while ( count( $against ) ) {
                array_unshift( $pieces, '..' );
                array_shift( $against );
        }

        array_push( $pieces, wfBaseName( $path ) );

        return implode( DIRECTORY_SEPARATOR, $pieces );
}

/**
 * Convert an arbitrarily-long digit string from one numeric base
 * to another, optionally zero-padding to a minimum column width.
 *
 * Supports base 2 through 36; digit values 10-36 are represented
 * as lowercase letters a-z. Input is case-insensitive.
 *
 * @deprecated since 1.27 Use Wikimedia\base_convert() directly
 *
 * @param string $input Input number
 * @param int $sourceBase Base of the input number
 * @param int $destBase Desired base of the output
 * @param int $pad Minimum number of digits in the output (pad with zeroes)
 * @param bool $lowercase Whether to output in lowercase or uppercase
 * @param string $engine Either "gmp", "bcmath", or "php"
 * @return string|bool The output number as a string, or false on error
 */
function wfBaseConvert( $input, $sourceBase, $destBase, $pad = 1,
        $lowercase = true, $engine = 'auto'
) {
        return Wikimedia\base_convert( $input, $sourceBase, $destBase, $pad, $lowercase, $engine );
}

/**
 * @deprecated since 1.27, PHP's session generation isn't used with
 *  MediaWiki\Session\SessionManager
 */
function wfFixSessionID() {
        wfDeprecated( __FUNCTION__, '1.27' );
}

/**
 * Reset the session id
 *
 * @deprecated since 1.27, use MediaWiki\Session\SessionManager instead
 * @since 1.22
 */
function wfResetSessionID() {
        wfDeprecated( __FUNCTION__, '1.27' );
        $session = SessionManager::getGlobalSession();
        $delay = $session->delaySave();

        $session->resetId();

        // Make sure a session is started, since that's what the old
        // wfResetSessionID() did.
        if ( session_id() !== $session->getId() ) {
                wfSetupSession( $session->getId() );
        }

        ScopedCallback::consume( $delay );
}

/**
 * Initialise php session
 *
 * @deprecated since 1.27, use MediaWiki\Session\SessionManager instead.
 *  Generally, "using" SessionManager will be calling ->getSessionById() or
 *  ::getGlobalSession() (depending on whether you were passing $sessionId
 *  here), then calling $session->persist().
 * @param bool|string $sessionId
 */
function wfSetupSession( $sessionId = false ) {
        wfDeprecated( __FUNCTION__, '1.27' );

        if ( $sessionId ) {
                session_id( $sessionId );
        }

        $session = SessionManager::getGlobalSession();
        $session->persist();

        if ( session_id() !== $session->getId() ) {
                session_id( $session->getId() );
        }
        MediaWiki\quietCall( 'session_start' );
}

/**
 * Get an object from the precompiled serialized directory
 *
 * @param string $name
 * @return mixed The variable on success, false on failure
 */
function wfGetPrecompiledData( $name ) {
        global $IP;

        $file = "$IP/serialized/$name";
        if ( file_exists( $file ) ) {
                $blob = file_get_contents( $file );
                if ( $blob ) {
                        return unserialize( $blob );
                }
        }
        return false;
}

/**
 * Make a cache key for the local wiki.
 *
 * @param string $args,...
 * @return string
 */
function wfMemcKey( /*...*/ ) {
        return call_user_func_array(
                [ ObjectCache::getLocalClusterInstance(), 'makeKey' ],
                func_get_args()
        );
}

/**
 * Make a cache key for a foreign DB.
 *
 * Must match what wfMemcKey() would produce in context of the foreign wiki.
 *
 * @param string $db
 * @param string $prefix
 * @param string $args,...
 * @return string
 */
function wfForeignMemcKey( $db, $prefix /*...*/ ) {
        $args = array_slice( func_get_args(), 2 );
        $keyspace = $prefix ? "$db-$prefix" : $db;
        return call_user_func_array(
                [ ObjectCache::getLocalClusterInstance(), 'makeKeyInternal' ],
                [ $keyspace, $args ]
        );
}

/**
 * Make a cache key with database-agnostic prefix.
 *
 * Doesn't have a wiki-specific namespace. Uses a generic 'global' prefix
 * instead. Must have a prefix as otherwise keys that use a database name
 * in the first segment will clash with wfMemcKey/wfForeignMemcKey.
 *
 * @since 1.26
 * @param string $args,...
 * @return string
 */
function wfGlobalCacheKey( /*...*/ ) {
        return call_user_func_array(
                [ ObjectCache::getLocalClusterInstance(), 'makeGlobalKey' ],
                func_get_args()
        );
}

/**
 * Get an ASCII string identifying this wiki
 * This is used as a prefix in memcached keys
 *
 * @return string
 */
function wfWikiID() {
        global $wgDBprefix, $wgDBname;
        if ( $wgDBprefix ) {
                return "$wgDBname-$wgDBprefix";
        } else {
                return $wgDBname;
        }
}

/**
 * Split a wiki ID into DB name and table prefix
 *
 * @param string $wiki
 *
 * @return array
 */
function wfSplitWikiID( $wiki ) {
        $bits = explode( '-', $wiki, 2 );
        if ( count( $bits ) < 2 ) {
                $bits[] = '';
        }
        return $bits;
}

/**
 * Get a Database object.
 *
 * @param int $db Index of the connection to get. May be DB_MASTER for the
 *            master (for write queries), DB_REPLICA for potentially lagged read
 *            queries, or an integer >= 0 for a particular server.
 *
 * @param string|string[] $groups Query groups. An array of group names that this query
 *                belongs to. May contain a single string if the query is only
 *                in one group.
 *
 * @param string|bool $wiki The wiki ID, or false for the current wiki
 *
 * Note: multiple calls to wfGetDB(DB_REPLICA) during the course of one request
 * will always return the same object, unless the underlying connection or load
 * balancer is manually destroyed.
 *
 * Note 2: use $this->getDB() in maintenance scripts that may be invoked by
 * updater to ensure that a proper database is being updated.
 *
 * @todo Replace calls to wfGetDB with calls to LoadBalancer::getConnection()
 *       on an injected instance of LoadBalancer.
 *
 * @return Database
 */
function wfGetDB( $db, $groups = [], $wiki = false ) {
        return wfGetLB( $wiki )->getConnection( $db, $groups, $wiki );
}

/**
 * Get a load balancer object.
 *
 * @deprecated since 1.27, use MediaWikiServices::getDBLoadBalancer()
 *              or MediaWikiServices::getDBLoadBalancerFactory() instead.
 *
 * @param string|bool $wiki Wiki ID, or false for the current wiki
 * @return LoadBalancer
 */
function wfGetLB( $wiki = false ) {
        if ( $wiki === false ) {
                return \MediaWiki\MediaWikiServices::getInstance()->getDBLoadBalancer();
        } else {
                $factory = \MediaWiki\MediaWikiServices::getInstance()->getDBLoadBalancerFactory();
                return $factory->getMainLB( $wiki );
        }
}

/**
 * Get the load balancer factory object
 *
 * @deprecated since 1.27, use MediaWikiServices::getDBLoadBalancerFactory() instead.
 *
 * @return LBFactory
 */
function wfGetLBFactory() {
        return \MediaWiki\MediaWikiServices::getInstance()->getDBLoadBalancerFactory();
}

/**
 * Find a file.
 * Shortcut for RepoGroup::singleton()->findFile()
 *
 * @param string $title String or Title object
 * @param array $options Associative array of options (see RepoGroup::findFile)
 * @return File|bool File, or false if the file does not exist
 */
function wfFindFile( $title, $options = [] ) {
        return RepoGroup::singleton()->findFile( $title, $options );
}

/**
 * Get an object referring to a locally registered file.
 * Returns a valid placeholder object if the file does not exist.
 *
 * @param Title|string $title
 * @return LocalFile|null A File, or null if passed an invalid Title
 */
function wfLocalFile( $title ) {
        return RepoGroup::singleton()->getLocalRepo()->newFile( $title );
}

/**
 * Should low-performance queries be disabled?
 *
 * @return bool
 * @codeCoverageIgnore
 */
function wfQueriesMustScale() {
        global $wgMiserMode;
        return $wgMiserMode
                || ( SiteStats::pages() > 100000
                && SiteStats::edits() > 1000000
                && SiteStats::users() > 10000 );
}

/**
 * Get the path to a specified script file, respecting file
 * extensions; this is a wrapper around $wgScriptPath etc.
 * except for 'index' and 'load' which use $wgScript/$wgLoadScript
 *
 * @param string $script Script filename, sans extension
 * @return string
 */
function wfScript( $script = 'index' ) {
        global $wgScriptPath, $wgScript, $wgLoadScript;
        if ( $script === 'index' ) {
                return $wgScript;
        } elseif ( $script === 'load' ) {
                return $wgLoadScript;
        } else {
                return "{$wgScriptPath}/{$script}.php";
        }
}

/**
 * Get the script URL.
 *
 * @return string Script URL
 */
function wfGetScriptUrl() {
        if ( isset( $_SERVER['SCRIPT_NAME'] ) ) {
                /* as it was called, minus the query string.
                 *
                 * Some sites use Apache rewrite rules to handle subdomains,
                 * and have PHP set up in a weird way that causes PHP_SELF
                 * to contain the rewritten URL instead of the one that the
                 * outside world sees.
                 *
                 * If in this mode, use SCRIPT_URL instead, which mod_rewrite
                 * provides containing the "before" URL.
                 */
                return $_SERVER['SCRIPT_NAME'];
        } else {
                return $_SERVER['URL'];
        }
}

/**
 * Convenience function converts boolean values into "true"
 * or "false" (string) values
 *
 * @param bool $value
 * @return string
 */
function wfBoolToStr( $value ) {
        return $value ? 'true' : 'false';
}

/**
 * Get a platform-independent path to the null file, e.g. /dev/null
 *
 * @return string
 */
function wfGetNull() {
        return wfIsWindows() ? 'NUL' : '/dev/null';
}

/**
 * Waits for the replica DBs to catch up to the master position
 *
 * Use this when updating very large numbers of rows, as in maintenance scripts,
 * to avoid causing too much lag. Of course, this is a no-op if there are no replica DBs.
 *
 * By default this waits on the main DB cluster of the current wiki.
 * If $cluster is set to "*" it will wait on all DB clusters, including
 * external ones. If the lag being waiting on is caused by the code that
 * does this check, it makes since to use $ifWritesSince, particularly if
 * cluster is "*", to avoid excess overhead.
 *
 * Never call this function after a big DB write that is still in a transaction.
 * This only makes sense after the possible lag inducing changes were committed.
 *
 * @param float|null $ifWritesSince Only wait if writes were done since this UNIX timestamp
 * @param string|bool $wiki Wiki identifier accepted by wfGetLB
 * @param string|bool $cluster Cluster name accepted by LBFactory. Default: false.
 * @param int|null $timeout Max wait time. Default: 1 day (cli), ~10 seconds (web)
 * @return bool Success (able to connect and no timeouts reached)
 * @deprecated since 1.27 Use LBFactory::waitForReplication
 */
function wfWaitForSlaves(
        $ifWritesSince = null, $wiki = false, $cluster = false, $timeout = null
) {
        if ( $timeout === null ) {
                $timeout = ( PHP_SAPI === 'cli' ) ? 86400 : 10;
        }

        if ( $cluster === '*' ) {
                $cluster = false;
                $wiki = false;
        } elseif ( $wiki === false ) {
                $wiki = wfWikiID();
        }

        try {
                wfGetLBFactory()->waitForReplication( [
                        'wiki' => $wiki,
                        'cluster' => $cluster,
                        'timeout' => $timeout,
                        // B/C: first argument used to be "max seconds of lag"; ignore such values
                        'ifWritesSince' => ( $ifWritesSince > 1e9 ) ? $ifWritesSince : null
                ] );
        } catch ( DBReplicationWaitError $e ) {
                return false;
        }

        return true;
}

/**
 * Count down from $seconds to zero on the terminal, with a one-second pause
 * between showing each number. For use in command-line scripts.
 *
 * @codeCoverageIgnore
 * @param int $seconds
 */
function wfCountDown( $seconds ) {
        for ( $i = $seconds; $i >= 0; $i-- ) {
                if ( $i != $seconds ) {
                        echo str_repeat( "\x08", strlen( $i + 1 ) );
                }
                echo $i;
                flush();
                if ( $i ) {
                        sleep( 1 );
                }
        }
        echo "\n";
}

/**
 * Replace all invalid characters with '-'.
 * Additional characters can be defined in $wgIllegalFileChars (see T22489).
 * By default, $wgIllegalFileChars includes ':', '/', '\'.
 *
 * @param string $name Filename to process
 * @return string
 */
function wfStripIllegalFilenameChars( $name ) {
        global $wgIllegalFileChars;
        $illegalFileChars = $wgIllegalFileChars ? "|[" . $wgIllegalFileChars . "]" : '';
        $name = preg_replace(
                "/[^" . Title::legalChars() . "]" . $illegalFileChars . "/",
                '-',
                $name
        );
        // $wgIllegalFileChars may not include '/' and '\', so we still need to do this
        $name = wfBaseName( $name );
        return $name;
}

/**
 * Set PHP's memory limit to the larger of php.ini or $wgMemoryLimit
 *
 * @return int Resulting value of the memory limit.
 */
function wfMemoryLimit() {
        global $wgMemoryLimit;
        $memlimit = wfShorthandToInteger( ini_get( 'memory_limit' ) );
        if ( $memlimit != -1 ) {
                $conflimit = wfShorthandToInteger( $wgMemoryLimit );
                if ( $conflimit == -1 ) {
                        wfDebug( "Removing PHP's memory limit\n" );
                        MediaWiki\suppressWarnings();
                        ini_set( 'memory_limit', $conflimit );
                        MediaWiki\restoreWarnings();
                        return $conflimit;
                } elseif ( $conflimit > $memlimit ) {
                        wfDebug( "Raising PHP's memory limit to $conflimit bytes\n" );
                        MediaWiki\suppressWarnings();
                        ini_set( 'memory_limit', $conflimit );
                        MediaWiki\restoreWarnings();
                        return $conflimit;
                }
        }
        return $memlimit;
}

/**
 * Set PHP's time limit to the larger of php.ini or $wgTransactionalTimeLimit
 *
 * @return int Prior time limit
 * @since 1.26
 */
function wfTransactionalTimeLimit() {
        global $wgTransactionalTimeLimit;

        $timeLimit = ini_get( 'max_execution_time' );
        // Note that CLI scripts use 0
        if ( $timeLimit > 0 && $wgTransactionalTimeLimit > $timeLimit ) {
                set_time_limit( $wgTransactionalTimeLimit );
        }

        ignore_user_abort( true ); // ignore client disconnects

        return $timeLimit;
}

/**
 * Converts shorthand byte notation to integer form
 *
 * @param string $string
 * @param int $default Returned if $string is empty
 * @return int
 */
function wfShorthandToInteger( $string = '', $default = -1 ) {
        $string = trim( $string );
        if ( $string === '' ) {
                return $default;
        }
        $last = $string[strlen( $string ) - 1];
        $val = intval( $string );
        switch ( $last ) {
                case 'g':
                case 'G':
                        $val *= 1024;
                        // break intentionally missing
                case 'm':
                case 'M':
                        $val *= 1024;
                        // break intentionally missing
                case 'k':
                case 'K':
                        $val *= 1024;
        }

        return $val;
}

/**
 * Get the normalised IETF language tag
 * See unit test for examples.
 *
 * @param string $code The language code.
 * @return string The language code which complying with BCP 47 standards.
 */
function wfBCP47( $code ) {
        $codeSegment = explode( '-', $code );
        $codeBCP = [];
        foreach ( $codeSegment as $segNo => $seg ) {
                // when previous segment is x, it is a private segment and should be lc
                if ( $segNo > 0 && strtolower( $codeSegment[( $segNo - 1 )] ) == 'x' ) {
                        $codeBCP[$segNo] = strtolower( $seg );
                // ISO 3166 country code
                } elseif ( ( strlen( $seg ) == 2 ) && ( $segNo > 0 ) ) {
                        $codeBCP[$segNo] = strtoupper( $seg );
                // ISO 15924 script code
                } elseif ( ( strlen( $seg ) == 4 ) && ( $segNo > 0 ) ) {
                        $codeBCP[$segNo] = ucfirst( strtolower( $seg ) );
                // Use lowercase for other cases
                } else {
                        $codeBCP[$segNo] = strtolower( $seg );
                }
        }
        $langCode = implode( '-', $codeBCP );
        return $langCode;
}

/**
 * Get a specific cache object.
 *
 * @param int|string $cacheType A CACHE_* constants, or other key in $wgObjectCaches
 * @return BagOStuff
 */
function wfGetCache( $cacheType ) {
        return ObjectCache::getInstance( $cacheType );
}

/**
 * Get the main cache object
 *
 * @return BagOStuff
 */
function wfGetMainCache() {
        global $wgMainCacheType;
        return ObjectCache::getInstance( $wgMainCacheType );
}

/**
 * Get the cache object used by the message cache
 *
 * @return BagOStuff
 */
function wfGetMessageCacheStorage() {
        global $wgMessageCacheType;
        return ObjectCache::getInstance( $wgMessageCacheType );
}

/**
 * Get the cache object used by the parser cache
 *
 * @return BagOStuff
 */
function wfGetParserCacheStorage() {
        global $wgParserCacheType;
        return ObjectCache::getInstance( $wgParserCacheType );
}

/**
 * Call hook functions defined in $wgHooks
 *
 * @param string $event Event name
 * @param array $args Parameters passed to hook functions
 * @param string|null $deprecatedVersion Optionally mark hook as deprecated with version number
 *
 * @return bool True if no handler aborted the hook
 * @deprecated since 1.25 - use Hooks::run
 */
function wfRunHooks( $event, array $args = [], $deprecatedVersion = null ) {
        return Hooks::run( $event, $args, $deprecatedVersion );
}

/**
 * Wrapper around php's unpack.
 *
 * @param string $format The format string (See php's docs)
 * @param string $data A binary string of binary data
 * @param int|bool $length The minimum length of $data or false. This is to
 *      prevent reading beyond the end of $data. false to disable the check.
 *
 * Also be careful when using this function to read unsigned 32 bit integer
 * because php might make it negative.
 *
 * @throws MWException If $data not long enough, or if unpack fails
 * @return array Associative array of the extracted data
 */
function wfUnpack( $format, $data, $length = false ) {
        if ( $length !== false ) {
                $realLen = strlen( $data );
                if ( $realLen < $length ) {
                        throw new MWException( "Tried to use wfUnpack on a "
                                . "string of length $realLen, but needed one "
                                . "of at least length $length."
                        );
                }
        }

        MediaWiki\suppressWarnings();
        $result = unpack( $format, $data );
        MediaWiki\restoreWarnings();

        if ( $result === false ) {
                // If it cannot extract the packed data.
                throw new MWException( "unpack could not unpack binary data" );
        }
        return $result;
}

/**
 * Determine if an image exists on the 'bad image list'.
 *
 * The format of MediaWiki:Bad_image_list is as follows:
 *    * Only list items (lines starting with "*") are considered
 *    * The first link on a line must be a link to a bad image
 *    * Any subsequent links on the same line are considered to be exceptions,
 *      i.e. articles where the image may occur inline.
 *
 * @param string $name The image name to check
 * @param Title|bool $contextTitle The page on which the image occurs, if known
 * @param string $blacklist Wikitext of a file blacklist
 * @return bool
 */
function wfIsBadImage( $name, $contextTitle = false, $blacklist = null ) {
        # Handle redirects; callers almost always hit wfFindFile() anyway,
        # so just use that method because it has a fast process cache.
        $file = wfFindFile( $name ); // get the final name
        $name = $file ? $file->getTitle()->getDBkey() : $name;

        # Run the extension hook
        $bad = false;
        if ( !Hooks::run( 'BadImage', [ $name, &$bad ] ) ) {
                return (bool)$bad;
        }

        $cache = ObjectCache::getLocalServerInstance( 'hash' );
        $key = wfMemcKey( 'bad-image-list', ( $blacklist === null ) ? 'default' : md5( $blacklist ) );
        $badImages = $cache->get( $key );

        if ( $badImages === false ) { // cache miss
                if ( $blacklist === null ) {
                        $blacklist = wfMessage( 'bad_image_list' )->inContentLanguage()->plain(); // site list
                }
                # Build the list now
                $badImages = [];
                $lines = explode( "\n", $blacklist );
                foreach ( $lines as $line ) {
                        # List items only
                        if ( substr( $line, 0, 1 ) !== '*' ) {
                                continue;
                        }

                        # Find all links
                        $m = [];
                        if ( !preg_match_all( '/\[\[:?(.*?)\]\]/', $line, $m ) ) {
                                continue;
                        }

                        $exceptions = [];
                        $imageDBkey = false;
                        foreach ( $m[1] as $i => $titleText ) {
                                $title = Title::newFromText( $titleText );
                                if ( !is_null( $title ) ) {
                                        if ( $i == 0 ) {
                                                $imageDBkey = $title->getDBkey();
                                        } else {
                                                $exceptions[$title->getPrefixedDBkey()] = true;
                                        }
                                }
                        }

                        if ( $imageDBkey !== false ) {
                                $badImages[$imageDBkey] = $exceptions;
                        }
                }
                $cache->set( $key, $badImages, 60 );
        }

        $contextKey = $contextTitle ? $contextTitle->getPrefixedDBkey() : false;
        $bad = isset( $badImages[$name] ) && !isset( $badImages[$name][$contextKey] );

        return $bad;
}

/**
 * Determine whether the client at a given source IP is likely to be able to
 * access the wiki via HTTPS.
 *
 * @param string $ip The IPv4/6 address in the normal human-readable form
 * @return bool
 */
function wfCanIPUseHTTPS( $ip ) {
        $canDo = true;
        Hooks::run( 'CanIPUseHTTPS', [ $ip, &$canDo ] );
        return !!$canDo;
}

/**
 * Determine input string is represents as infinity
 *
 * @param string $str The string to determine
 * @return bool
 * @since 1.25
 */
function wfIsInfinity( $str ) {
        $infinityValues = [ 'infinite', 'indefinite', 'infinity', 'never' ];
        return in_array( $str, $infinityValues );
}

/**
 * Returns true if these thumbnail parameters match one that MediaWiki
 * requests from file description pages and/or parser output.
 *
 * $params is considered non-standard if they involve a non-standard
 * width or any non-default parameters aside from width and page number.
 * The number of possible files with standard parameters is far less than
 * that of all combinations; rate-limiting for them can thus be more generious.
 *
 * @param File $file
 * @param array $params
 * @return bool
 * @since 1.24 Moved from thumb.php to GlobalFunctions in 1.25
 */
function wfThumbIsStandard( File $file, array $params ) {
        global $wgThumbLimits, $wgImageLimits, $wgResponsiveImages;

        $multipliers = [ 1 ];
        if ( $wgResponsiveImages ) {
                // These available sizes are hardcoded currently elsewhere in MediaWiki.
                // @see Linker::processResponsiveImages
                $multipliers[] = 1.5;
                $multipliers[] = 2;
        }

        $handler = $file->getHandler();
        if ( !$handler || !isset( $params['width'] ) ) {
                return false;
        }

        $basicParams = [];
        if ( isset( $params['page'] ) ) {
                $basicParams['page'] = $params['page'];
        }

        $thumbLimits = [];
        $imageLimits = [];
        // Expand limits to account for multipliers
        foreach ( $multipliers as $multiplier ) {
                $thumbLimits = array_merge( $thumbLimits, array_map(
                        function ( $width ) use ( $multiplier ) {
                                return round( $width * $multiplier );
                        }, $wgThumbLimits )
                );
                $imageLimits = array_merge( $imageLimits, array_map(
                        function ( $pair ) use ( $multiplier ) {
                                return [
                                        round( $pair[0] * $multiplier ),
                                        round( $pair[1] * $multiplier ),
                                ];
                        }, $wgImageLimits )
                );
        }

        // Check if the width matches one of $wgThumbLimits
        if ( in_array( $params['width'], $thumbLimits ) ) {
                $normalParams = $basicParams + [ 'width' => $params['width'] ];
                // Append any default values to the map (e.g. "lossy", "lossless", ...)
                $handler->normaliseParams( $file, $normalParams );
        } else {
                // If not, then check if the width matchs one of $wgImageLimits
                $match = false;
                foreach ( $imageLimits as $pair ) {
                        $normalParams = $basicParams + [ 'width' => $pair[0], 'height' => $pair[1] ];
                        // Decide whether the thumbnail should be scaled on width or height.
                        // Also append any default values to the map (e.g. "lossy", "lossless", ...)
                        $handler->normaliseParams( $file, $normalParams );
                        // Check if this standard thumbnail size maps to the given width
                        if ( $normalParams['width'] == $params['width'] ) {
                                $match = true;
                                break;
                        }
                }
                if ( !$match ) {
                        return false; // not standard for description pages
                }
        }

        // Check that the given values for non-page, non-width, params are just defaults
        foreach ( $params as $key => $value ) {
                if ( !isset( $normalParams[$key] ) || $normalParams[$key] != $value ) {
                        return false;
                }
        }

        return true;
}

/**
 * Merges two (possibly) 2 dimensional arrays into the target array ($baseArray).
 *
 * Values that exist in both values will be combined with += (all values of the array
 * of $newValues will be added to the values of the array of $baseArray, while values,
 * that exists in both, the value of $baseArray will be used).
 *
 * @param array $baseArray The array where you want to add the values of $newValues to
 * @param array $newValues An array with new values
 * @return array The combined array
 * @since 1.26
 */
function wfArrayPlus2d( array $baseArray, array $newValues ) {
        // First merge items that are in both arrays
        foreach ( $baseArray as $name => &$groupVal ) {
                if ( isset( $newValues[$name] ) ) {
                        $groupVal += $newValues[$name];
                }
        }
        // Now add items that didn't exist yet
        $baseArray += $newValues;

        return $baseArray;
}