Added release notes for 'ContentHandler::runLegacyHooks' removal

[mediawiki.git] / includes / api / ApiResult.php

<?php
/**
 * 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
 */

/**
 * This class represents the result of the API operations.
 * It simply wraps a nested array structure, adding some functions to simplify
 * array's modifications. As various modules execute, they add different pieces
 * of information to this result, structuring it as it will be given to the client.
 *
 * Each subarray may either be a dictionary - key-value pairs with unique keys,
 * or lists, where the items are added using $data[] = $value notation.
 *
 * @since 1.25 this is no longer a subclass of ApiBase
 * @ingroup API
 */
class ApiResult implements ApiSerializable {

        /**
         * Override existing value in addValue(), setValue(), and similar functions
         * @since 1.21
         */
        const OVERRIDE = 1;

        /**
         * For addValue(), setValue() and similar functions, if the value does not
         * exist, add it as the first element. In case the new value has no name
         * (numerical index), all indexes will be renumbered.
         * @since 1.21
         */
        const ADD_ON_TOP = 2;

        /**
         * For addValue() and similar functions, do not check size while adding a value
         * Don't use this unless you REALLY know what you're doing.
         * Values added while the size checking was disabled will never be counted.
         * Ignored for setValue() and similar functions.
         * @since 1.24
         */
        const NO_SIZE_CHECK = 4;

        /**
         * For addValue(), setValue() and similar functions, do not validate data.
         * Also disables size checking. If you think you need to use this, you're
         * probably wrong.
         * @since 1.25
         */
        const NO_VALIDATE = 12;

        /**
         * Key for the 'indexed tag name' metadata item. Value is string.
         * @since 1.25
         */
        const META_INDEXED_TAG_NAME = '_element';

        /**
         * Key for the 'subelements' metadata item. Value is string[].
         * @since 1.25
         */
        const META_SUBELEMENTS = '_subelements';

        /**
         * Key for the 'preserve keys' metadata item. Value is string[].
         * @since 1.25
         */
        const META_PRESERVE_KEYS = '_preservekeys';

        /**
         * Key for the 'content' metadata item. Value is string.
         * @since 1.25
         */
        const META_CONTENT = '_content';

        /**
         * Key for the 'type' metadata item. Value is one of the following strings:
         *  - default: Like 'array' if all (non-metadata) keys are numeric with no
         *    gaps, otherwise like 'assoc'.
         *  - array: Keys are used for ordering, but are not output. In a format
         *    like JSON, outputs as [].
         *  - assoc: In a format like JSON, outputs as {}.
         *  - kvp: For a format like XML where object keys have a restricted
         *    character set, use an alternative output format. For example,
         *    <container><item name="key">value</item></container> rather than
         *    <container key="value" />
         *  - BCarray: Like 'array' normally, 'default' in backwards-compatibility mode.
         *  - BCassoc: Like 'assoc' normally, 'default' in backwards-compatibility mode.
         *  - BCkvp: Like 'kvp' normally. In backwards-compatibility mode, forces
         *    the alternative output format for all formats, for example
         *    [{"name":key,"*":value}] in JSON. META_KVP_KEY_NAME must also be set.
         * @since 1.25
         */
        const META_TYPE = '_type';

        /**
         * Key for the metadata item whose value specifies the name used for the
         * kvp key in the alternative output format with META_TYPE 'kvp' or
         * 'BCkvp', i.e. the "name" in <container><item name="key">value</item></container>.
         * Value is string.
         * @since 1.25
         */
        const META_KVP_KEY_NAME = '_kvpkeyname';

        /**
         * Key for the metadata item that indicates that the KVP key should be
         * added into an assoc value, i.e. {"key":{"val1":"a","val2":"b"}}
         * transforms to {"name":"key","val1":"a","val2":"b"} rather than
         * {"name":"key","value":{"val1":"a","val2":"b"}}.
         * Value is boolean.
         * @since 1.26
         */
        const META_KVP_MERGE = '_kvpmerge';

        /**
         * Key for the 'BC bools' metadata item. Value is string[].
         * Note no setter is provided.
         * @since 1.25
         */
        const META_BC_BOOLS = '_BC_bools';

        /**
         * Key for the 'BC subelements' metadata item. Value is string[].
         * Note no setter is provided.
         * @since 1.25
         */
        const META_BC_SUBELEMENTS = '_BC_subelements';

        private $data, $size, $maxSize;
        private $errorFormatter;

        // Deprecated fields
        private $checkingSize, $mainForContinuation;

        /**
         * @param int|bool $maxSize Maximum result "size", or false for no limit
         * @since 1.25 Takes an integer|bool rather than an ApiMain
         */
        public function __construct( $maxSize ) {
                if ( $maxSize instanceof ApiMain ) {
                        wfDeprecated( 'ApiMain to ' . __METHOD__, '1.25' );
                        $this->errorFormatter = $maxSize->getErrorFormatter();
                        $this->mainForContinuation = $maxSize;
                        $maxSize = $maxSize->getConfig()->get( 'APIMaxResultSize' );
                }

                $this->maxSize = $maxSize;
                $this->checkingSize = true;
                $this->reset();
        }

        /**
         * Set the error formatter
         * @since 1.25
         * @param ApiErrorFormatter $formatter
         */
        public function setErrorFormatter( ApiErrorFormatter $formatter ) {
                $this->errorFormatter = $formatter;
        }

        /**
         * Allow for adding one ApiResult into another
         * @since 1.25
         * @return mixed
         */
        public function serializeForApiResult() {
                return $this->data;
        }

        /************************************************************************//**
         * @name   Content
         * @{
         */

        /**
         * Clear the current result data.
         */
        public function reset() {
                $this->data = [
                        self::META_TYPE => 'assoc', // Usually what's desired
                ];
                $this->size = 0;
        }

        /**
         * Get the result data array
         *
         * The returned value should be considered read-only.
         *
         * Transformations include:
         *
         * Custom: (callable) Applied before other transformations. Signature is
         *  function ( &$data, &$metadata ), return value is ignored. Called for
         *  each nested array.
         *
         * BC: (array) This transformation does various adjustments to bring the
         *  output in line with the pre-1.25 result format. The value array is a
         *  list of flags: 'nobool', 'no*', 'nosub'.
         *  - Boolean-valued items are changed to '' if true or removed if false,
         *    unless listed in META_BC_BOOLS. This may be skipped by including
         *    'nobool' in the value array.
         *  - The tag named by META_CONTENT is renamed to '*', and META_CONTENT is
         *    set to '*'. This may be skipped by including 'no*' in the value
         *    array.
         *  - Tags listed in META_BC_SUBELEMENTS will have their values changed to
         *    [ '*' => $value ]. This may be skipped by including 'nosub' in
         *    the value array.
         *  - If META_TYPE is 'BCarray', set it to 'default'
         *  - If META_TYPE is 'BCassoc', set it to 'default'
         *  - If META_TYPE is 'BCkvp', perform the transformation (even if
         *    the Types transformation is not being applied).
         *
         * Types: (assoc) Apply transformations based on META_TYPE. The values
         * array is an associative array with the following possible keys:
         *  - AssocAsObject: (bool) If true, return arrays with META_TYPE 'assoc'
         *    as objects.
         *  - ArmorKVP: (string) If provided, transform arrays with META_TYPE 'kvp'
         *    and 'BCkvp' into arrays of two-element arrays, something like this:
         *      $output = [];
         *      foreach ( $input as $key => $value ) {
         *          $pair = [];
         *          $pair[$META_KVP_KEY_NAME ?: $ArmorKVP_value] = $key;
         *          ApiResult::setContentValue( $pair, 'value', $value );
         *          $output[] = $pair;
         *      }
         *
         * Strip: (string) Strips metadata keys from the result.
         *  - 'all': Strip all metadata, recursively
         *  - 'base': Strip metadata at the top-level only.
         *  - 'none': Do not strip metadata.
         *  - 'bc': Like 'all', but leave certain pre-1.25 keys.
         *
         * @since 1.25
         * @param array|string|null $path Path to fetch, see ApiResult::addValue
         * @param array $transforms See above
         * @return mixed Result data, or null if not found
         */
        public function getResultData( $path = [], $transforms = [] ) {
                $path = (array)$path;
                if ( !$path ) {
                        return self::applyTransformations( $this->data, $transforms );
                }

                $last = array_pop( $path );
                $ret = &$this->path( $path, 'dummy' );
                if ( !isset( $ret[$last] ) ) {
                        return null;
                } elseif ( is_array( $ret[$last] ) ) {
                        return self::applyTransformations( $ret[$last], $transforms );
                } else {
                        return $ret[$last];
                }
        }

        /**
         * Get the size of the result, i.e. the amount of bytes in it
         * @return int
         */
        public function getSize() {
                return $this->size;
        }

        /**
         * Add an output value to the array by name.
         *
         * Verifies that value with the same name has not been added before.
         *
         * @since 1.25
         * @param array &$arr To add $value to
         * @param string|int|null $name Index of $arr to add $value at,
         *   or null to use the next numeric index.
         * @param mixed $value
         * @param int $flags Zero or more OR-ed flags like OVERRIDE | ADD_ON_TOP.
         */
        public static function setValue( array &$arr, $name, $value, $flags = 0 ) {
                if ( ( $flags & ApiResult::NO_VALIDATE ) !== ApiResult::NO_VALIDATE ) {
                        $value = self::validateValue( $value );
                }

                if ( $name === null ) {
                        if ( $flags & ApiResult::ADD_ON_TOP ) {
                                array_unshift( $arr, $value );
                        } else {
                                array_push( $arr, $value );
                        }
                        return;
                }

                $exists = isset( $arr[$name] );
                if ( !$exists || ( $flags & ApiResult::OVERRIDE ) ) {
                        if ( !$exists && ( $flags & ApiResult::ADD_ON_TOP ) ) {
                                $arr = [ $name => $value ] + $arr;
                        } else {
                                $arr[$name] = $value;
                        }
                } elseif ( is_array( $arr[$name] ) && is_array( $value ) ) {
                        $conflicts = array_intersect_key( $arr[$name], $value );
                        if ( !$conflicts ) {
                                $arr[$name] += $value;
                        } else {
                                $keys = implode( ', ', array_keys( $conflicts ) );
                                throw new RuntimeException(
                                        "Conflicting keys ($keys) when attempting to merge element $name"
                                );
                        }
                } else {
                        throw new RuntimeException(
                                "Attempting to add element $name=$value, existing value is {$arr[$name]}"
                        );
                }
        }

        /**
         * Validate a value for addition to the result
         * @param mixed $value
         * @return array|mixed|string
         */
        private static function validateValue( $value ) {
                global $wgContLang;

                if ( is_object( $value ) ) {
                        // Note we use is_callable() here instead of instanceof because
                        // ApiSerializable is an informal protocol (see docs there for details).
                        if ( is_callable( [ $value, 'serializeForApiResult' ] ) ) {
                                $oldValue = $value;
                                $value = $value->serializeForApiResult();
                                if ( is_object( $value ) ) {
                                        throw new UnexpectedValueException(
                                                get_class( $oldValue ) . '::serializeForApiResult() returned an object of class ' .
                                                        get_class( $value )
                                        );
                                }

                                // Recursive call instead of fall-through so we can throw a
                                // better exception message.
                                try {
                                        return self::validateValue( $value );
                                } catch ( Exception $ex ) {
                                        throw new UnexpectedValueException(
                                                get_class( $oldValue ) . '::serializeForApiResult() returned an invalid value: ' .
                                                        $ex->getMessage(),
                                                0,
                                                $ex
                                        );
                                }
                        } elseif ( is_callable( [ $value, '__toString' ] ) ) {
                                $value = (string)$value;
                        } else {
                                $value = (array)$value + [ self::META_TYPE => 'assoc' ];
                        }
                }
                if ( is_array( $value ) ) {
                        // Work around PHP bug 45959 by copying to a temporary
                        // (in this case, foreach gets $k === "1" but $tmp[$k] assigns as if $k === 1)
                        $tmp = [];
                        foreach ( $value as $k => $v ) {
                                $tmp[$k] = self::validateValue( $v );
                        }
                        $value = $tmp;
                } elseif ( is_float( $value ) && !is_finite( $value ) ) {
                        throw new InvalidArgumentException( 'Cannot add non-finite floats to ApiResult' );
                } elseif ( is_string( $value ) ) {
                        $value = $wgContLang->normalize( $value );
                } elseif ( $value !== null && !is_scalar( $value ) ) {
                        $type = gettype( $value );
                        if ( is_resource( $value ) ) {
                                $type .= '(' . get_resource_type( $value ) . ')';
                        }
                        throw new InvalidArgumentException( "Cannot add $type to ApiResult" );
                }

                return $value;
        }

        /**
         * Add value to the output data at the given path.
         *
         * Path can be an indexed array, each element specifying the branch at which to add the new
         * value. Setting $path to [ 'a', 'b', 'c' ] is equivalent to data['a']['b']['c'] = $value.
         * If $path is null, the value will be inserted at the data root.
         *
         * @param array|string|int|null $path
         * @param string|int|null $name See ApiResult::setValue()
         * @param mixed $value
         * @param int $flags Zero or more OR-ed flags like OVERRIDE | ADD_ON_TOP.
         *   This parameter used to be boolean, and the value of OVERRIDE=1 was specifically
         *   chosen so that it would be backwards compatible with the new method signature.
         * @return bool True if $value fits in the result, false if not
         * @since 1.21 int $flags replaced boolean $override
         */
        public function addValue( $path, $name, $value, $flags = 0 ) {
                $arr = &$this->path( $path, ( $flags & ApiResult::ADD_ON_TOP ) ? 'prepend' : 'append' );

                if ( $this->checkingSize && !( $flags & ApiResult::NO_SIZE_CHECK ) ) {
                        // self::size needs the validated value. Then flag
                        // to not re-validate later.
                        $value = self::validateValue( $value );
                        $flags |= ApiResult::NO_VALIDATE;

                        $newsize = $this->size + self::size( $value );
                        if ( $this->maxSize !== false && $newsize > $this->maxSize ) {
                                $this->errorFormatter->addWarning(
                                        'result', [ 'apiwarn-truncatedresult', Message::numParam( $this->maxSize ) ]
                                );
                                return false;
                        }
                        $this->size = $newsize;
                }

                self::setValue( $arr, $name, $value, $flags );
                return true;
        }

        /**
         * Remove an output value to the array by name.
         * @param array &$arr To remove $value from
         * @param string|int $name Index of $arr to remove
         * @return mixed Old value, or null
         */
        public static function unsetValue( array &$arr, $name ) {
                $ret = null;
                if ( isset( $arr[$name] ) ) {
                        $ret = $arr[$name];
                        unset( $arr[$name] );
                }
                return $ret;
        }

        /**
         * Remove value from the output data at the given path.
         *
         * @since 1.25
         * @param array|string|null $path See ApiResult::addValue()
         * @param string|int|null $name Index to remove at $path.
         *   If null, $path itself is removed.
         * @param int $flags Flags used when adding the value
         * @return mixed Old value, or null
         */
        public function removeValue( $path, $name, $flags = 0 ) {
                $path = (array)$path;
                if ( $name === null ) {
                        if ( !$path ) {
                                throw new InvalidArgumentException( 'Cannot remove the data root' );
                        }
                        $name = array_pop( $path );
                }
                $ret = self::unsetValue( $this->path( $path, 'dummy' ), $name );
                if ( $this->checkingSize && !( $flags & ApiResult::NO_SIZE_CHECK ) ) {
                        $newsize = $this->size - self::size( $ret );
                        $this->size = max( $newsize, 0 );
                }
                return $ret;
        }

        /**
         * Add an output value to the array by name and mark as META_CONTENT.
         *
         * @since 1.25
         * @param array &$arr To add $value to
         * @param string|int $name Index of $arr to add $value at.
         * @param mixed $value
         * @param int $flags Zero or more OR-ed flags like OVERRIDE | ADD_ON_TOP.
         */
        public static function setContentValue( array &$arr, $name, $value, $flags = 0 ) {
                if ( $name === null ) {
                        throw new InvalidArgumentException( 'Content value must be named' );
                }
                self::setContentField( $arr, $name, $flags );
                self::setValue( $arr, $name, $value, $flags );
        }

        /**
         * Add value to the output data at the given path and mark as META_CONTENT
         *
         * @since 1.25
         * @param array|string|null $path See ApiResult::addValue()
         * @param string|int $name See ApiResult::setValue()
         * @param mixed $value
         * @param int $flags Zero or more OR-ed flags like OVERRIDE | ADD_ON_TOP.
         * @return bool True if $value fits in the result, false if not
         */
        public function addContentValue( $path, $name, $value, $flags = 0 ) {
                if ( $name === null ) {
                        throw new InvalidArgumentException( 'Content value must be named' );
                }
                $this->addContentField( $path, $name, $flags );
                $this->addValue( $path, $name, $value, $flags );
        }

        /**
         * Add the numeric limit for a limit=max to the result.
         *
         * @since 1.25
         * @param string $moduleName
         * @param int $limit
         */
        public function addParsedLimit( $moduleName, $limit ) {
                // Add value, allowing overwriting
                $this->addValue( 'limits', $moduleName, $limit,
                        ApiResult::OVERRIDE | ApiResult::NO_SIZE_CHECK );
        }

        /**@}*/

        /************************************************************************//**
         * @name   Metadata
         * @{
         */

        /**
         * Set the name of the content field name (META_CONTENT)
         *
         * @since 1.25
         * @param array &$arr
         * @param string|int $name Name of the field
         * @param int $flags Zero or more OR-ed flags like OVERRIDE | ADD_ON_TOP.
         */
        public static function setContentField( array &$arr, $name, $flags = 0 ) {
                if ( isset( $arr[self::META_CONTENT] ) &&
                        isset( $arr[$arr[self::META_CONTENT]] ) &&
                        !( $flags & self::OVERRIDE )
                ) {
                        throw new RuntimeException(
                                "Attempting to set content element as $name when " . $arr[self::META_CONTENT] .
                                        ' is already set as the content element'
                        );
                }
                $arr[self::META_CONTENT] = $name;
        }

        /**
         * Set the name of the content field name (META_CONTENT)
         *
         * @since 1.25
         * @param array|string|null $path See ApiResult::addValue()
         * @param string|int $name Name of the field
         * @param int $flags Zero or more OR-ed flags like OVERRIDE | ADD_ON_TOP.
         */
        public function addContentField( $path, $name, $flags = 0 ) {
                $arr = &$this->path( $path, ( $flags & ApiResult::ADD_ON_TOP ) ? 'prepend' : 'append' );
                self::setContentField( $arr, $name, $flags );
        }

        /**
         * Causes the elements with the specified names to be output as
         * subelements rather than attributes.
         * @since 1.25 is static
         * @param array &$arr
         * @param array|string|int $names The element name(s) to be output as subelements
         */
        public static function setSubelementsList( array &$arr, $names ) {
                if ( !isset( $arr[self::META_SUBELEMENTS] ) ) {
                        $arr[self::META_SUBELEMENTS] = (array)$names;
                } else {
                        $arr[self::META_SUBELEMENTS] = array_merge( $arr[self::META_SUBELEMENTS], (array)$names );
                }
        }

        /**
         * Causes the elements with the specified names to be output as
         * subelements rather than attributes.
         * @since 1.25
         * @param array|string|null $path See ApiResult::addValue()
         * @param array|string|int $names The element name(s) to be output as subelements
         */
        public function addSubelementsList( $path, $names ) {
                $arr = &$this->path( $path );
                self::setSubelementsList( $arr, $names );
        }

        /**
         * Causes the elements with the specified names to be output as
         * attributes (when possible) rather than as subelements.
         * @since 1.25
         * @param array &$arr
         * @param array|string|int $names The element name(s) to not be output as subelements
         */
        public static function unsetSubelementsList( array &$arr, $names ) {
                if ( isset( $arr[self::META_SUBELEMENTS] ) ) {
                        $arr[self::META_SUBELEMENTS] = array_diff( $arr[self::META_SUBELEMENTS], (array)$names );
                }
        }

        /**
         * Causes the elements with the specified names to be output as
         * attributes (when possible) rather than as subelements.
         * @since 1.25
         * @param array|string|null $path See ApiResult::addValue()
         * @param array|string|int $names The element name(s) to not be output as subelements
         */
        public function removeSubelementsList( $path, $names ) {
                $arr = &$this->path( $path );
                self::unsetSubelementsList( $arr, $names );
        }

        /**
         * Set the tag name for numeric-keyed values in XML format
         * @since 1.25 is static
         * @param array &$arr
         * @param string $tag Tag name
         */
        public static function setIndexedTagName( array &$arr, $tag ) {
                if ( !is_string( $tag ) ) {
                        throw new InvalidArgumentException( 'Bad tag name' );
                }
                $arr[self::META_INDEXED_TAG_NAME] = $tag;
        }

        /**
         * Set the tag name for numeric-keyed values in XML format
         * @since 1.25
         * @param array|string|null $path See ApiResult::addValue()
         * @param string $tag Tag name
         */
        public function addIndexedTagName( $path, $tag ) {
                $arr = &$this->path( $path );
                self::setIndexedTagName( $arr, $tag );
        }

        /**
         * Set indexed tag name on $arr and all subarrays
         *
         * @since 1.25
         * @param array &$arr
         * @param string $tag Tag name
         */
        public static function setIndexedTagNameRecursive( array &$arr, $tag ) {
                if ( !is_string( $tag ) ) {
                        throw new InvalidArgumentException( 'Bad tag name' );
                }
                $arr[self::META_INDEXED_TAG_NAME] = $tag;
                foreach ( $arr as $k => &$v ) {
                        if ( !self::isMetadataKey( $k ) && is_array( $v ) ) {
                                self::setIndexedTagNameRecursive( $v, $tag );
                        }
                }
        }

        /**
         * Set indexed tag name on $path and all subarrays
         *
         * @since 1.25
         * @param array|string|null $path See ApiResult::addValue()
         * @param string $tag Tag name
         */
        public function addIndexedTagNameRecursive( $path, $tag ) {
                $arr = &$this->path( $path );
                self::setIndexedTagNameRecursive( $arr, $tag );
        }

        /**
         * Preserve specified keys.
         *
         * This prevents XML name mangling and preventing keys from being removed
         * by self::stripMetadata().
         *
         * @since 1.25
         * @param array &$arr
         * @param array|string $names The element name(s) to preserve
         */
        public static function setPreserveKeysList( array &$arr, $names ) {
                if ( !isset( $arr[self::META_PRESERVE_KEYS] ) ) {
                        $arr[self::META_PRESERVE_KEYS] = (array)$names;
                } else {
                        $arr[self::META_PRESERVE_KEYS] = array_merge( $arr[self::META_PRESERVE_KEYS], (array)$names );
                }
        }

        /**
         * Preserve specified keys.
         * @since 1.25
         * @see self::setPreserveKeysList()
         * @param array|string|null $path See ApiResult::addValue()
         * @param array|string $names The element name(s) to preserve
         */
        public function addPreserveKeysList( $path, $names ) {
                $arr = &$this->path( $path );
                self::setPreserveKeysList( $arr, $names );
        }

        /**
         * Don't preserve specified keys.
         * @since 1.25
         * @see self::setPreserveKeysList()
         * @param array &$arr
         * @param array|string $names The element name(s) to not preserve
         */
        public static function unsetPreserveKeysList( array &$arr, $names ) {
                if ( isset( $arr[self::META_PRESERVE_KEYS] ) ) {
                        $arr[self::META_PRESERVE_KEYS] = array_diff( $arr[self::META_PRESERVE_KEYS], (array)$names );
                }
        }

        /**
         * Don't preserve specified keys.
         * @since 1.25
         * @see self::setPreserveKeysList()
         * @param array|string|null $path See ApiResult::addValue()
         * @param array|string $names The element name(s) to not preserve
         */
        public function removePreserveKeysList( $path, $names ) {
                $arr = &$this->path( $path );
                self::unsetPreserveKeysList( $arr, $names );
        }

        /**
         * Set the array data type
         *
         * @since 1.25
         * @param array &$arr
         * @param string $type See ApiResult::META_TYPE
         * @param string $kvpKeyName See ApiResult::META_KVP_KEY_NAME
         */
        public static function setArrayType( array &$arr, $type, $kvpKeyName = null ) {
                if ( !in_array( $type, [
                                'default', 'array', 'assoc', 'kvp', 'BCarray', 'BCassoc', 'BCkvp'
                                ], true ) ) {
                        throw new InvalidArgumentException( 'Bad type' );
                }
                $arr[self::META_TYPE] = $type;
                if ( is_string( $kvpKeyName ) ) {
                        $arr[self::META_KVP_KEY_NAME] = $kvpKeyName;
                }
        }

        /**
         * Set the array data type for a path
         * @since 1.25
         * @param array|string|null $path See ApiResult::addValue()
         * @param string $tag See ApiResult::META_TYPE
         * @param string $kvpKeyName See ApiResult::META_KVP_KEY_NAME
         */
        public function addArrayType( $path, $tag, $kvpKeyName = null ) {
                $arr = &$this->path( $path );
                self::setArrayType( $arr, $tag, $kvpKeyName );
        }

        /**
         * Set the array data type recursively
         * @since 1.25
         * @param array &$arr
         * @param string $type See ApiResult::META_TYPE
         * @param string $kvpKeyName See ApiResult::META_KVP_KEY_NAME
         */
        public static function setArrayTypeRecursive( array &$arr, $type, $kvpKeyName = null ) {
                self::setArrayType( $arr, $type, $kvpKeyName );
                foreach ( $arr as $k => &$v ) {
                        if ( !self::isMetadataKey( $k ) && is_array( $v ) ) {
                                self::setArrayTypeRecursive( $v, $type, $kvpKeyName );
                        }
                }
        }

        /**
         * Set the array data type for a path recursively
         * @since 1.25
         * @param array|string|null $path See ApiResult::addValue()
         * @param string $tag See ApiResult::META_TYPE
         * @param string $kvpKeyName See ApiResult::META_KVP_KEY_NAME
         */
        public function addArrayTypeRecursive( $path, $tag, $kvpKeyName = null ) {
                $arr = &$this->path( $path );
                self::setArrayTypeRecursive( $arr, $tag, $kvpKeyName );
        }

        /**@}*/

        /************************************************************************//**
         * @name   Utility
         * @{
         */

        /**
         * Test whether a key should be considered metadata
         *
         * @param string $key
         * @return bool
         */
        public static function isMetadataKey( $key ) {
                return substr( $key, 0, 1 ) === '_';
        }

        /**
         * Apply transformations to an array, returning the transformed array.
         *
         * @see ApiResult::getResultData()
         * @since 1.25
         * @param array $dataIn
         * @param array $transforms
         * @return array|object
         */
        protected static function applyTransformations( array $dataIn, array $transforms ) {
                $strip = isset( $transforms['Strip'] ) ? $transforms['Strip'] : 'none';
                if ( $strip === 'base' ) {
                        $transforms['Strip'] = 'none';
                }
                $transformTypes = isset( $transforms['Types'] ) ? $transforms['Types'] : null;
                if ( $transformTypes !== null && !is_array( $transformTypes ) ) {
                        throw new InvalidArgumentException( __METHOD__ . ':Value for "Types" must be an array' );
                }

                $metadata = [];
                $data = self::stripMetadataNonRecursive( $dataIn, $metadata );

                if ( isset( $transforms['Custom'] ) ) {
                        if ( !is_callable( $transforms['Custom'] ) ) {
                                throw new InvalidArgumentException( __METHOD__ . ': Value for "Custom" must be callable' );
                        }
                        call_user_func_array( $transforms['Custom'], [ &$data, &$metadata ] );
                }

                if ( ( isset( $transforms['BC'] ) || $transformTypes !== null ) &&
                        isset( $metadata[self::META_TYPE] ) && $metadata[self::META_TYPE] === 'BCkvp' &&
                        !isset( $metadata[self::META_KVP_KEY_NAME] )
                ) {
                        throw new UnexpectedValueException( 'Type "BCkvp" used without setting ' .
                                'ApiResult::META_KVP_KEY_NAME metadata item' );
                }

                // BC transformations
                $boolKeys = null;
                if ( isset( $transforms['BC'] ) ) {
                        if ( !is_array( $transforms['BC'] ) ) {
                                throw new InvalidArgumentException( __METHOD__ . ':Value for "BC" must be an array' );
                        }
                        if ( !in_array( 'nobool', $transforms['BC'], true ) ) {
                                $boolKeys = isset( $metadata[self::META_BC_BOOLS] )
                                        ? array_flip( $metadata[self::META_BC_BOOLS] )
                                        : [];
                        }

                        if ( !in_array( 'no*', $transforms['BC'], true ) &&
                                isset( $metadata[self::META_CONTENT] ) && $metadata[self::META_CONTENT] !== '*'
                        ) {
                                $k = $metadata[self::META_CONTENT];
                                $data['*'] = $data[$k];
                                unset( $data[$k] );
                                $metadata[self::META_CONTENT] = '*';
                        }

                        if ( !in_array( 'nosub', $transforms['BC'], true ) &&
                                isset( $metadata[self::META_BC_SUBELEMENTS] )
                        ) {
                                foreach ( $metadata[self::META_BC_SUBELEMENTS] as $k ) {
                                        if ( isset( $data[$k] ) ) {
                                                $data[$k] = [
                                                        '*' => $data[$k],
                                                        self::META_CONTENT => '*',
                                                        self::META_TYPE => 'assoc',
                                                ];
                                        }
                                }
                        }

                        if ( isset( $metadata[self::META_TYPE] ) ) {
                                switch ( $metadata[self::META_TYPE] ) {
                                        case 'BCarray':
                                        case 'BCassoc':
                                                $metadata[self::META_TYPE] = 'default';
                                                break;
                                        case 'BCkvp':
                                                $transformTypes['ArmorKVP'] = $metadata[self::META_KVP_KEY_NAME];
                                                break;
                                }
                        }
                }

                // Figure out type, do recursive calls, and do boolean transform if necessary
                $defaultType = 'array';
                $maxKey = -1;
                foreach ( $data as $k => &$v ) {
                        $v = is_array( $v ) ? self::applyTransformations( $v, $transforms ) : $v;
                        if ( $boolKeys !== null && is_bool( $v ) && !isset( $boolKeys[$k] ) ) {
                                if ( !$v ) {
                                        unset( $data[$k] );
                                        continue;
                                }
                                $v = '';
                        }
                        if ( is_string( $k ) ) {
                                $defaultType = 'assoc';
                        } elseif ( $k > $maxKey ) {
                                $maxKey = $k;
                        }
                }
                unset( $v );

                // Determine which metadata to keep
                switch ( $strip ) {
                        case 'all':
                        case 'base':
                                $keepMetadata = [];
                                break;
                        case 'none':
                                $keepMetadata = &$metadata;
                                break;
                        case 'bc':
                                $keepMetadata = array_intersect_key( $metadata, [
                                        self::META_INDEXED_TAG_NAME => 1,
                                        self::META_SUBELEMENTS => 1,
                                ] );
                                break;
                        default:
                                throw new InvalidArgumentException( __METHOD__ . ': Unknown value for "Strip"' );
                }

                // Type transformation
                if ( $transformTypes !== null ) {
                        if ( $defaultType === 'array' && $maxKey !== count( $data ) - 1 ) {
                                $defaultType = 'assoc';
                        }

                        // Override type, if provided
                        $type = $defaultType;
                        if ( isset( $metadata[self::META_TYPE] ) && $metadata[self::META_TYPE] !== 'default' ) {
                                $type = $metadata[self::META_TYPE];
                        }
                        if ( ( $type === 'kvp' || $type === 'BCkvp' ) &&
                                empty( $transformTypes['ArmorKVP'] )
                        ) {
                                $type = 'assoc';
                        } elseif ( $type === 'BCarray' ) {
                                $type = 'array';
                        } elseif ( $type === 'BCassoc' ) {
                                $type = 'assoc';
                        }

                        // Apply transformation
                        switch ( $type ) {
                                case 'assoc':
                                        $metadata[self::META_TYPE] = 'assoc';
                                        $data += $keepMetadata;
                                        return empty( $transformTypes['AssocAsObject'] ) ? $data : (object)$data;

                                case 'array':
                                        ksort( $data );
                                        $data = array_values( $data );
                                        $metadata[self::META_TYPE] = 'array';
                                        return $data + $keepMetadata;

                                case 'kvp':
                                case 'BCkvp':
                                        $key = isset( $metadata[self::META_KVP_KEY_NAME] )
                                                ? $metadata[self::META_KVP_KEY_NAME]
                                                : $transformTypes['ArmorKVP'];
                                        $valKey = isset( $transforms['BC'] ) ? '*' : 'value';
                                        $assocAsObject = !empty( $transformTypes['AssocAsObject'] );
                                        $merge = !empty( $metadata[self::META_KVP_MERGE] );

                                        $ret = [];
                                        foreach ( $data as $k => $v ) {
                                                if ( $merge && ( is_array( $v ) || is_object( $v ) ) ) {
                                                        $vArr = (array)$v;
                                                        if ( isset( $vArr[self::META_TYPE] ) ) {
                                                                $mergeType = $vArr[self::META_TYPE];
                                                        } elseif ( is_object( $v ) ) {
                                                                $mergeType = 'assoc';
                                                        } else {
                                                                $keys = array_keys( $vArr );
                                                                sort( $keys, SORT_NUMERIC );
                                                                $mergeType = ( $keys === array_keys( $keys ) ) ? 'array' : 'assoc';
                                                        }
                                                } else {
                                                        $mergeType = 'n/a';
                                                }
                                                if ( $mergeType === 'assoc' ) {
                                                        $item = $vArr + [
                                                                $key => $k,
                                                        ];
                                                        if ( $strip === 'none' ) {
                                                                self::setPreserveKeysList( $item, [ $key ] );
                                                        }
                                                } else {
                                                        $item = [
                                                                $key => $k,
                                                                $valKey => $v,
                                                        ];
                                                        if ( $strip === 'none' ) {
                                                                $item += [
                                                                        self::META_PRESERVE_KEYS => [ $key ],
                                                                        self::META_CONTENT => $valKey,
                                                                        self::META_TYPE => 'assoc',
                                                                ];
                                                        }
                                                }
                                                $ret[] = $assocAsObject ? (object)$item : $item;
                                        }
                                        $metadata[self::META_TYPE] = 'array';

                                        return $ret + $keepMetadata;

                                default:
                                        throw new UnexpectedValueException( "Unknown type '$type'" );
                        }
                } else {
                        return $data + $keepMetadata;
                }
        }

        /**
         * Recursively remove metadata keys from a data array or object
         *
         * Note this removes all potential metadata keys, not just the defined
         * ones.
         *
         * @since 1.25
         * @param array|object $data
         * @return array|object
         */
        public static function stripMetadata( $data ) {
                if ( is_array( $data ) || is_object( $data ) ) {
                        $isObj = is_object( $data );
                        if ( $isObj ) {
                                $data = (array)$data;
                        }
                        $preserveKeys = isset( $data[self::META_PRESERVE_KEYS] )
                                ? (array)$data[self::META_PRESERVE_KEYS]
                                : [];
                        foreach ( $data as $k => $v ) {
                                if ( self::isMetadataKey( $k ) && !in_array( $k, $preserveKeys, true ) ) {
                                        unset( $data[$k] );
                                } elseif ( is_array( $v ) || is_object( $v ) ) {
                                        $data[$k] = self::stripMetadata( $v );
                                }
                        }
                        if ( $isObj ) {
                                $data = (object)$data;
                        }
                }
                return $data;
        }

        /**
         * Remove metadata keys from a data array or object, non-recursive
         *
         * Note this removes all potential metadata keys, not just the defined
         * ones.
         *
         * @since 1.25
         * @param array|object $data
         * @param array &$metadata Store metadata here, if provided
         * @return array|object
         */
        public static function stripMetadataNonRecursive( $data, &$metadata = null ) {
                if ( !is_array( $metadata ) ) {
                        $metadata = [];
                }
                if ( is_array( $data ) || is_object( $data ) ) {
                        $isObj = is_object( $data );
                        if ( $isObj ) {
                                $data = (array)$data;
                        }
                        $preserveKeys = isset( $data[self::META_PRESERVE_KEYS] )
                                ? (array)$data[self::META_PRESERVE_KEYS]
                                : [];
                        foreach ( $data as $k => $v ) {
                                if ( self::isMetadataKey( $k ) && !in_array( $k, $preserveKeys, true ) ) {
                                        $metadata[$k] = $v;
                                        unset( $data[$k] );
                                }
                        }
                        if ( $isObj ) {
                                $data = (object)$data;
                        }
                }
                return $data;
        }

        /**
         * Get the 'real' size of a result item. This means the strlen() of the item,
         * or the sum of the strlen()s of the elements if the item is an array.
         * @param mixed $value Validated value (see self::validateValue())
         * @return int
         */
        private static function size( $value ) {
                $s = 0;
                if ( is_array( $value ) ) {
                        foreach ( $value as $k => $v ) {
                                if ( !self::isMetadataKey( $k ) ) {
                                        $s += self::size( $v );
                                }
                        }
                } elseif ( is_scalar( $value ) ) {
                        $s = strlen( $value );
                }

                return $s;
        }

        /**
         * Return a reference to the internal data at $path
         *
         * @param array|string|null $path
         * @param string $create
         *   If 'append', append empty arrays.
         *   If 'prepend', prepend empty arrays.
         *   If 'dummy', return a dummy array.
         *   Else, raise an error.
         * @return array
         */
        private function &path( $path, $create = 'append' ) {
                $path = (array)$path;
                $ret = &$this->data;
                foreach ( $path as $i => $k ) {
                        if ( !isset( $ret[$k] ) ) {
                                switch ( $create ) {
                                        case 'append':
                                                $ret[$k] = [];
                                                break;
                                        case 'prepend':
                                                $ret = [ $k => [] ] + $ret;
                                                break;
                                        case 'dummy':
                                                $tmp = [];
                                                return $tmp;
                                        default:
                                                $fail = implode( '.', array_slice( $path, 0, $i + 1 ) );
                                                throw new InvalidArgumentException( "Path $fail does not exist" );
                                }
                        }
                        if ( !is_array( $ret[$k] ) ) {
                                $fail = implode( '.', array_slice( $path, 0, $i + 1 ) );
                                throw new InvalidArgumentException( "Path $fail is not an array" );
                        }
                        $ret = &$ret[$k];
                }
                return $ret;
        }

        /**
         * Add the correct metadata to an array of vars we want to export through
         * the API.
         *
         * @param array $vars
         * @param bool $forceHash
         * @return array
         */
        public static function addMetadataToResultVars( $vars, $forceHash = true ) {
                // Process subarrays and determine if this is a JS [] or {}
                $hash = $forceHash;
                $maxKey = -1;
                $bools = [];
                foreach ( $vars as $k => $v ) {
                        if ( is_array( $v ) || is_object( $v ) ) {
                                $vars[$k] = ApiResult::addMetadataToResultVars( (array)$v, is_object( $v ) );
                        } elseif ( is_bool( $v ) ) {
                                // Better here to use real bools even in BC formats
                                $bools[] = $k;
                        }
                        if ( is_string( $k ) ) {
                                $hash = true;
                        } elseif ( $k > $maxKey ) {
                                $maxKey = $k;
                        }
                }
                if ( !$hash && $maxKey !== count( $vars ) - 1 ) {
                        $hash = true;
                }

                // Set metadata appropriately
                if ( $hash ) {
                        // Get the list of keys we actually care about. Unfortunately, we can't support
                        // certain keys that conflict with ApiResult metadata.
                        $keys = array_diff( array_keys( $vars ), [
                                ApiResult::META_TYPE, ApiResult::META_PRESERVE_KEYS, ApiResult::META_KVP_KEY_NAME,
                                ApiResult::META_INDEXED_TAG_NAME, ApiResult::META_BC_BOOLS
                        ] );

                        return [
                                ApiResult::META_TYPE => 'kvp',
                                ApiResult::META_KVP_KEY_NAME => 'key',
                                ApiResult::META_PRESERVE_KEYS => $keys,
                                ApiResult::META_BC_BOOLS => $bools,
                                ApiResult::META_INDEXED_TAG_NAME => 'var',
                        ] + $vars;
                } else {
                        return [
                                ApiResult::META_TYPE => 'array',
                                ApiResult::META_BC_BOOLS => $bools,
                                ApiResult::META_INDEXED_TAG_NAME => 'value',
                        ] + $vars;
                }
        }

        /**
         * Format an expiry timestamp for API output
         * @since 1.29
         * @param string $expiry Expiry timestamp, likely from the database
         * @param string $infinity Use this string for infinite expiry
         *  (only use this to maintain backward compatibility with existing output)
         * @return string Formatted expiry
         */
        public static function formatExpiry( $expiry, $infinity = 'infinity' ) {
                static $dbInfinity;
                if ( $dbInfinity === null ) {
                        $dbInfinity = wfGetDB( DB_REPLICA )->getInfinity();
                }

                if ( $expiry === '' || $expiry === null || $expiry === false ||
                        wfIsInfinity( $expiry ) || $expiry === $dbInfinity
                ) {
                        return $infinity;
                } else {
                        return wfTimestamp( TS_ISO_8601, $expiry );
                }
        }

        /**@}*/

}

/**
 * For really cool vim folding this needs to be at the end:
 * vim: foldmarker=@{,@} foldmethod=marker
 */