Properly deprecate srprop=score|hasrelated

[mediawiki.git] / includes / Message.php

<?php
/**
 * Fetching and processing of interface messages.
 *
 * 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
 * @author Niklas Laxström
 */

/**
 * The Message class provides methods which fulfil two basic services:
 *  - fetching interface messages
 *  - processing messages into a variety of formats
 *
 * First implemented with MediaWiki 1.17, the Message class is intended to
 * replace the old wfMsg* functions that over time grew unusable.
 * @see https://www.mediawiki.org/wiki/Manual:Messages_API for equivalences
 * between old and new functions.
 *
 * You should use the wfMessage() global function which acts as a wrapper for
 * the Message class. The wrapper let you pass parameters as arguments.
 *
 * The most basic usage cases would be:
 *
 * @code
 *     // Initialize a Message object using the 'some_key' message key
 *     $message = wfMessage( 'some_key' );
 *
 *     // Using two parameters those values are strings 'value1' and 'value2':
 *     $message = wfMessage( 'some_key',
 *          'value1', 'value2'
 *     );
 * @endcode
 *
 * @section message_global_fn Global function wrapper:
 *
 * Since wfMessage() returns a Message instance, you can chain its call with
 * a method. Some of them return a Message instance too so you can chain them.
 * You will find below several examples of wfMessage() usage.
 *
 * Fetching a message text for interface message:
 *
 * @code
 *    $button = Xml::button(
 *         wfMessage( 'submit' )->text()
 *    );
 * @endcode
 *
 * A Message instance can be passed parameters after it has been constructed,
 * use the params() method to do so:
 *
 * @code
 *     wfMessage( 'welcome-to' )
 *         ->params( $wgSitename )
 *         ->text();
 * @endcode
 *
 * {{GRAMMAR}} and friends work correctly:
 *
 * @code
 *    wfMessage( 'are-friends',
 *        $user, $friend
 *    );
 *    wfMessage( 'bad-message' )
 *         ->rawParams( '<script>...</script>' )
 *         ->escaped();
 * @endcode
 *
 * @section message_language Changing language:
 *
 * Messages can be requested in a different language or in whatever current
 * content language is being used. The methods are:
 *     - Message->inContentLanguage()
 *     - Message->inLanguage()
 *
 * Sometimes the message text ends up in the database, so content language is
 * needed:
 *
 * @code
 *    wfMessage( 'file-log',
 *        $user, $filename
 *    )->inContentLanguage()->text();
 * @endcode
 *
 * Checking whether a message exists:
 *
 * @code
 *    wfMessage( 'mysterious-message' )->exists()
 *    // returns a boolean whether the 'mysterious-message' key exist.
 * @endcode
 *
 * If you want to use a different language:
 *
 * @code
 *    $userLanguage = $user->getOption( 'language' );
 *    wfMessage( 'email-header' )
 *         ->inLanguage( $userLanguage )
 *         ->plain();
 * @endcode
 *
 * @note You can parse the text only in the content or interface languages
 *
 * @section message_compare_old Comparison with old wfMsg* functions:
 *
 * Use full parsing:
 *
 * @code
 *     // old style:
 *     wfMsgExt( 'key', array( 'parseinline' ), 'apple' );
 *     // new style:
 *     wfMessage( 'key', 'apple' )->parse();
 * @endcode
 *
 * Parseinline is used because it is more useful when pre-building HTML.
 * In normal use it is better to use OutputPage::(add|wrap)WikiMsg.
 *
 * Places where HTML cannot be used. {{-transformation is done.
 * @code
 *     // old style:
 *     wfMsgExt( 'key', array( 'parsemag' ), 'apple', 'pear' );
 *     // new style:
 *     wfMessage( 'key', 'apple', 'pear' )->text();
 * @endcode
 *
 * Shortcut for escaping the message too, similar to wfMsgHTML(), but
 * parameters are not replaced after escaping by default.
 * @code
 *     $escaped = wfMessage( 'key' )
 *          ->rawParams( 'apple' )
 *          ->escaped();
 * @endcode
 *
 * @section message_appendix Appendix:
 *
 * @todo
 * - test, can we have tests?
 * - this documentation needs to be extended
 *
 * @see https://www.mediawiki.org/wiki/WfMessage()
 * @see https://www.mediawiki.org/wiki/New_messages_API
 * @see https://www.mediawiki.org/wiki/Localisation
 *
 * @since 1.17
 */
class Message {

        /**
         * In which language to get this message. True, which is the default,
         * means the current interface language, false content language.
         *
         * @var bool
         */
        protected $interface = true;

        /**
         * In which language to get this message. Overrides the $interface
         * variable.
         *
         * @var Language
         */
        protected $language = null;

        /**
         * @var string The message key. If $keysToTry has more than one element,
         * this may change to one of the keys to try when fetching the message text.
         */
        protected $key;

        /**
         * @var string[] List of keys to try when fetching the message.
         */
        protected $keysToTry;

        /**
         * @var array List of parameters which will be substituted into the message.
         */
        protected $parameters = array();

        /**
         * Format for the message.
         * Supported formats are:
         * * text (transform)
         * * escaped (transform+htmlspecialchars)
         * * block-parse
         * * parse (default)
         * * plain
         *
         * @var string
         */
        protected $format = 'parse';

        /**
         * @var bool Whether database can be used.
         */
        protected $useDatabase = true;

        /**
         * @var Title Title object to use as context.
         */
        protected $title = null;

        /**
         * @var Content Content object representing the message.
         */
        protected $content = null;

        /**
         * @var string
         */
        protected $message;

        /**
         * @since 1.17
         *
         * @param string|string[] $key Message key or array of message keys to try and use the first
         * non-empty message for.
         * @param array $params Message parameters.
         * @param Language $language Optional language of the message, defaults to $wgLang.
         *
         * @throws InvalidArgumentException
         */
        public function __construct( $key, $params = array(), Language $language = null ) {
                global $wgLang;

                if ( !is_string( $key ) && !is_array( $key ) ) {
                        throw new InvalidArgumentException( '$key must be a string or an array' );
                }

                $this->keysToTry = (array)$key;

                if ( empty( $this->keysToTry ) ) {
                        throw new InvalidArgumentException( '$key must not be an empty list' );
                }

                $this->key = reset( $this->keysToTry );

                $this->parameters = array_values( $params );
                $this->language = $language ? $language : $wgLang;
        }

        /**
         * @since 1.24
         *
         * @return bool True if this is a multi-key message, that is, if the key provided to the
         * constructor was a fallback list of keys to try.
         */
        public function isMultiKey() {
                return count( $this->keysToTry ) > 1;
        }

        /**
         * @since 1.24
         *
         * @return string[] The list of keys to try when fetching the message text,
         * in order of preference.
         */
        public function getKeysToTry() {
                return $this->keysToTry;
        }

        /**
         * Returns the message key.
         *
         * If a list of multiple possible keys was supplied to the constructor, this method may
         * return any of these keys. After the message ahs been fetched, this method will return
         * the key that was actually used to fetch the message.
         *
         * @since 1.21
         *
         * @return string
         */
        public function getKey() {
                return $this->key;
        }

        /**
         * Returns the message parameters.
         *
         * @since 1.21
         *
         * @return array
         */
        public function getParams() {
                return $this->parameters;
        }

        /**
         * Returns the message format.
         *
         * @since 1.21
         *
         * @return string
         */
        public function getFormat() {
                return $this->format;
        }

        /**
         * Returns the Language of the Message.
         *
         * @since 1.23
         *
         * @return Language
         */
        public function getLanguage() {
                return $this->language;
        }

        /**
         * Factory function that is just wrapper for the real constructor. It is
         * intended to be used instead of the real constructor, because it allows
         * chaining method calls, while new objects don't.
         *
         * @since 1.17
         *
         * @param string|string[] $key Message key or array of keys.
         * @param mixed $param,... Parameters as strings.
         *
         * @return Message
         */
        public static function newFromKey( $key /*...*/ ) {
                $params = func_get_args();
                array_shift( $params );
                return new self( $key, $params );
        }

        /**
         * Factory function accepting multiple message keys and returning 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.
         *
         * @since 1.18
         *
         * @param string|string[] $keys,... Message keys, or first argument as an array of all the
         * message keys.
         *
         * @return Message
         */
        public static function newFallbackSequence( /*...*/ ) {
                $keys = func_get_args();
                if ( func_num_args() == 1 ) {
                        if ( is_array( $keys[0] ) ) {
                                // Allow an array to be passed as the first argument instead
                                $keys = array_values( $keys[0] );
                        } else {
                                // Optimize a single string to not need special fallback handling
                                $keys = $keys[0];
                        }
                }
                return new self( $keys );
        }

        /**
         * Adds parameters to the parameter list of this message.
         *
         * @since 1.17
         *
         * @param mixed $params,... Parameters as strings, or a single argument that is
         * an array of strings.
         *
         * @return Message $this
         */
        public function params( /*...*/ ) {
                $args = func_get_args();
                if ( isset( $args[0] ) && is_array( $args[0] ) ) {
                        $args = $args[0];
                }
                $args_values = array_values( $args );
                $this->parameters = array_merge( $this->parameters, $args_values );
                return $this;
        }

        /**
         * Add parameters that are substituted after parsing or escaping.
         * In other words the parsing process cannot access the contents
         * of this type of parameter, and you need to make sure it is
         * sanitized beforehand.  The parser will see "$n", instead.
         *
         * @since 1.17
         *
         * @param mixed $params,... Raw parameters as strings, or a single argument that is
         * an array of raw parameters.
         *
         * @return Message $this
         */
        public function rawParams( /*...*/ ) {
                $params = func_get_args();
                if ( isset( $params[0] ) && is_array( $params[0] ) ) {
                        $params = $params[0];
                }
                foreach ( $params as $param ) {
                        $this->parameters[] = self::rawParam( $param );
                }
                return $this;
        }

        /**
         * Add parameters that are numeric and will be passed through
         * Language::formatNum before substitution
         *
         * @since 1.18
         *
         * @param mixed $param,... Numeric parameters, or a single argument that is
         * an array of numeric parameters.
         *
         * @return Message $this
         */
        public function numParams( /*...*/ ) {
                $params = func_get_args();
                if ( isset( $params[0] ) && is_array( $params[0] ) ) {
                        $params = $params[0];
                }
                foreach ( $params as $param ) {
                        $this->parameters[] = self::numParam( $param );
                }
                return $this;
        }

        /**
         * Add parameters that are durations of time and will be passed through
         * Language::formatDuration before substitution
         *
         * @since 1.22
         *
         * @param int|int[] $param,... Duration parameters, or a single argument that is
         * an array of duration parameters.
         *
         * @return Message $this
         */
        public function durationParams( /*...*/ ) {
                $params = func_get_args();
                if ( isset( $params[0] ) && is_array( $params[0] ) ) {
                        $params = $params[0];
                }
                foreach ( $params as $param ) {
                        $this->parameters[] = self::durationParam( $param );
                }
                return $this;
        }

        /**
         * Add parameters that are expiration times and will be passed through
         * Language::formatExpiry before substitution
         *
         * @since 1.22
         *
         * @param string|string[] $param,... Expiry parameters, or a single argument that is
         * an array of expiry parameters.
         *
         * @return Message $this
         */
        public function expiryParams( /*...*/ ) {
                $params = func_get_args();
                if ( isset( $params[0] ) && is_array( $params[0] ) ) {
                        $params = $params[0];
                }
                foreach ( $params as $param ) {
                        $this->parameters[] = self::expiryParam( $param );
                }
                return $this;
        }

        /**
         * Add parameters that are time periods and will be passed through
         * Language::formatTimePeriod before substitution
         *
         * @since 1.22
         *
         * @param int|int[] $param,... Time period parameters, or a single argument that is
         * an array of time period parameters.
         *
         * @return Message $this
         */
        public function timeperiodParams( /*...*/ ) {
                $params = func_get_args();
                if ( isset( $params[0] ) && is_array( $params[0] ) ) {
                        $params = $params[0];
                }
                foreach ( $params as $param ) {
                        $this->parameters[] = self::timeperiodParam( $param );
                }
                return $this;
        }

        /**
         * Add parameters that are file sizes and will be passed through
         * Language::formatSize before substitution
         *
         * @since 1.22
         *
         * @param int|int[] $param,... Size parameters, or a single argument that is
         * an array of size parameters.
         *
         * @return Message $this
         */
        public function sizeParams( /*...*/ ) {
                $params = func_get_args();
                if ( isset( $params[0] ) && is_array( $params[0] ) ) {
                        $params = $params[0];
                }
                foreach ( $params as $param ) {
                        $this->parameters[] = self::sizeParam( $param );
                }
                return $this;
        }

        /**
         * Add parameters that are bitrates and will be passed through
         * Language::formatBitrate before substitution
         *
         * @since 1.22
         *
         * @param int|int[] $param,... Bit rate parameters, or a single argument that is
         * an array of bit rate parameters.
         *
         * @return Message $this
         */
        public function bitrateParams( /*...*/ ) {
                $params = func_get_args();
                if ( isset( $params[0] ) && is_array( $params[0] ) ) {
                        $params = $params[0];
                }
                foreach ( $params as $param ) {
                        $this->parameters[] = self::bitrateParam( $param );
                }
                return $this;
        }

        /**
         * Set the language and the title from a context object
         *
         * @since 1.19
         *
         * @param IContextSource $context
         *
         * @return Message $this
         */
        public function setContext( IContextSource $context ) {
                $this->inLanguage( $context->getLanguage() );
                $this->title( $context->getTitle() );
                $this->interface = true;

                return $this;
        }

        /**
         * Request the message in any language that is supported.
         * As a side effect interface message status is unconditionally
         * turned off.
         *
         * @since 1.17
         *
         * @param Language|string $lang Language code or Language object.
         *
         * @return Message $this
         * @throws MWException
         */
        public function inLanguage( $lang ) {
                if ( $lang instanceof Language || $lang instanceof StubUserLang ) {
                        $this->language = $lang;
                } elseif ( is_string( $lang ) ) {
                        if ( $this->language->getCode() != $lang ) {
                                $this->language = Language::factory( $lang );
                        }
                } else {
                        $type = gettype( $lang );
                        throw new MWException( __METHOD__ . " must be "
                                . "passed a String or Language object; $type given"
                        );
                }
                $this->message = null;
                $this->interface = false;
                return $this;
        }

        /**
         * Request the message in the wiki's content language,
         * unless it is disabled for this message.
         *
         * @since 1.17
         * @see $wgForceUIMsgAsContentMsg
         *
         * @return Message $this
         */
        public function inContentLanguage() {
                global $wgForceUIMsgAsContentMsg;
                if ( in_array( $this->key, (array)$wgForceUIMsgAsContentMsg ) ) {
                        return $this;
                }

                global $wgContLang;
                $this->inLanguage( $wgContLang );
                return $this;
        }

        /**
         * Allows manipulating the interface message flag directly.
         * Can be used to restore the flag after setting a language.
         *
         * @since 1.20
         *
         * @param bool $interface
         *
         * @return Message $this
         */
        public function setInterfaceMessageFlag( $interface ) {
                $this->interface = (bool)$interface;
                return $this;
        }

        /**
         * Enable or disable database use.
         *
         * @since 1.17
         *
         * @param bool $useDatabase
         *
         * @return Message $this
         */
        public function useDatabase( $useDatabase ) {
                $this->useDatabase = (bool)$useDatabase;
                return $this;
        }

        /**
         * Set the Title object to use as context when transforming the message
         *
         * @since 1.18
         *
         * @param Title $title
         *
         * @return Message $this
         */
        public function title( $title ) {
                $this->title = $title;
                return $this;
        }

        /**
         * Returns the message as a Content object.
         *
         * @return Content
         */
        public function content() {
                if ( !$this->content ) {
                        $this->content = new MessageContent( $this );
                }

                return $this->content;
        }

        /**
         * Returns the message parsed from wikitext to HTML.
         *
         * @since 1.17
         *
         * @return string HTML
         */
        public function toString() {
                $string = $this->fetchMessage();

                if ( $string === false ) {
                        $key = htmlspecialchars( $this->key );
                        if ( $this->format === 'plain' ) {
                                return '<' . $key . '>';
                        }
                        return '&lt;' . $key . '&gt;';
                }

                # Replace $* with a list of parameters for &uselang=qqx.
                if ( strpos( $string, '$*' ) !== false ) {
                        $paramlist = '';
                        if ( $this->parameters !== array() ) {
                                $paramlist = ': $' . implode( ', $', range( 1, count( $this->parameters ) ) );
                        }
                        $string = str_replace( '$*', $paramlist, $string );
                }

                # Replace parameters before text parsing
                $string = $this->replaceParameters( $string, 'before' );

                # Maybe transform using the full parser
                if ( $this->format === 'parse' ) {
                        $string = $this->parseText( $string );
                        $string = Parser::stripOuterParagraph( $string );
                } elseif ( $this->format === 'block-parse' ) {
                        $string = $this->parseText( $string );
                } elseif ( $this->format === 'text' ) {
                        $string = $this->transformText( $string );
                } elseif ( $this->format === 'escaped' ) {
                        $string = $this->transformText( $string );
                        $string = htmlspecialchars( $string, ENT_QUOTES, 'UTF-8', false );
                }

                # Raw parameter replacement
                $string = $this->replaceParameters( $string, 'after' );

                return $string;
        }

        /**
         * Magic method implementation of the above (for PHP >= 5.2.0), so we can do, eg:
         *     $foo = Message::get( $key );
         *     $string = "<abbr>$foo</abbr>";
         *
         * @since 1.18
         *
         * @return string
         */
        public function __toString() {
                // PHP doesn't allow __toString to throw exceptions and will
                // trigger a fatal error if it does. So, catch any exceptions.

                try {
                        return $this->toString();
                } catch ( Exception $ex ) {
                        try {
                                trigger_error( "Exception caught in " . __METHOD__ . " (message " . $this->key . "): "
                                        . $ex, E_USER_WARNING );
                        } catch ( Exception $ex ) {
                                // Doh! Cause a fatal error after all?
                        }

                        if ( $this->format === 'plain' ) {
                                return '<' . $this->key . '>';
                        }
                        return '&lt;' . $this->key . '&gt;';
                }
        }

        /**
         * Fully parse the text from wikitext to HTML.
         *
         * @since 1.17
         *
         * @return string Parsed HTML.
         */
        public function parse() {
                $this->format = 'parse';
                return $this->toString();
        }

        /**
         * Returns the message text. {{-transformation is done.
         *
         * @since 1.17
         *
         * @return string Unescaped message text.
         */
        public function text() {
                $this->format = 'text';
                return $this->toString();
        }

        /**
         * Returns the message text as-is, only parameters are substituted.
         *
         * @since 1.17
         *
         * @return string Unescaped untransformed message text.
         */
        public function plain() {
                $this->format = 'plain';
                return $this->toString();
        }

        /**
         * Returns the parsed message text which is always surrounded by a block element.
         *
         * @since 1.17
         *
         * @return string HTML
         */
        public function parseAsBlock() {
                $this->format = 'block-parse';
                return $this->toString();
        }

        /**
         * Returns the message text. {{-transformation is done and the result
         * is escaped excluding any raw parameters.
         *
         * @since 1.17
         *
         * @return string Escaped message text.
         */
        public function escaped() {
                $this->format = 'escaped';
                return $this->toString();
        }

        /**
         * Check whether a message key has been defined currently.
         *
         * @since 1.17
         *
         * @return bool
         */
        public function exists() {
                return $this->fetchMessage() !== false;
        }

        /**
         * Check whether a message does not exist, or is an empty string
         *
         * @since 1.18
         * @todo FIXME: Merge with isDisabled()?
         *
         * @return bool
         */
        public function isBlank() {
                $message = $this->fetchMessage();
                return $message === false || $message === '';
        }

        /**
         * Check whether a message does not exist, is an empty string, or is "-".
         *
         * @since 1.18
         *
         * @return bool
         */
        public function isDisabled() {
                $message = $this->fetchMessage();
                return $message === false || $message === '' || $message === '-';
        }

        /**
         * @since 1.17
         *
         * @param mixed $raw
         *
         * @return array Array with a single "raw" key.
         */
        public static function rawParam( $raw ) {
                return array( 'raw' => $raw );
        }

        /**
         * @since 1.18
         *
         * @param mixed $num
         *
         * @return array Array with a single "num" key.
         */
        public static function numParam( $num ) {
                return array( 'num' => $num );
        }

        /**
         * @since 1.22
         *
         * @param int $duration
         *
         * @return int[] Array with a single "duration" key.
         */
        public static function durationParam( $duration ) {
                return array( 'duration' => $duration );
        }

        /**
         * @since 1.22
         *
         * @param string $expiry
         *
         * @return string[] Array with a single "expiry" key.
         */
        public static function expiryParam( $expiry ) {
                return array( 'expiry' => $expiry );
        }

        /**
         * @since 1.22
         *
         * @param number $period
         *
         * @return number[] Array with a single "period" key.
         */
        public static function timeperiodParam( $period ) {
                return array( 'period' => $period );
        }

        /**
         * @since 1.22
         *
         * @param int $size
         *
         * @return int[] Array with a single "size" key.
         */
        public static function sizeParam( $size ) {
                return array( 'size' => $size );
        }

        /**
         * @since 1.22
         *
         * @param int $bitrate
         *
         * @return int[] Array with a single "bitrate" key.
         */
        public static function bitrateParam( $bitrate ) {
                return array( 'bitrate' => $bitrate );
        }

        /**
         * Substitutes any parameters into the message text.
         *
         * @since 1.17
         *
         * @param string $message The message text.
         * @param string $type Either "before" or "after".
         *
         * @return string
         */
        protected function replaceParameters( $message, $type = 'before' ) {
                $replacementKeys = array();
                foreach ( $this->parameters as $n => $param ) {
                        list( $paramType, $value ) = $this->extractParam( $param );
                        if ( $type === $paramType ) {
                                $replacementKeys['$' . ( $n + 1 )] = $value;
                        }
                }
                $message = strtr( $message, $replacementKeys );
                return $message;
        }

        /**
         * Extracts the parameter type and preprocessed the value if needed.
         *
         * @since 1.18
         *
         * @param mixed $param Parameter as defined in this class.
         *
         * @return array Array with the parameter type (either "before" or "after") and the value.
         */
        protected function extractParam( $param ) {
                if ( is_array( $param ) ) {
                        if ( isset( $param['raw'] ) ) {
                                return array( 'after', $param['raw'] );
                        } elseif ( isset( $param['num'] ) ) {
                                // Replace number params always in before step for now.
                                // No support for combined raw and num params
                                return array( 'before', $this->language->formatNum( $param['num'] ) );
                        } elseif ( isset( $param['duration'] ) ) {
                                return array( 'before', $this->language->formatDuration( $param['duration'] ) );
                        } elseif ( isset( $param['expiry'] ) ) {
                                return array( 'before', $this->language->formatExpiry( $param['expiry'] ) );
                        } elseif ( isset( $param['period'] ) ) {
                                return array( 'before', $this->language->formatTimePeriod( $param['period'] ) );
                        } elseif ( isset( $param['size'] ) ) {
                                return array( 'before', $this->language->formatSize( $param['size'] ) );
                        } elseif ( isset( $param['bitrate'] ) ) {
                                return array( 'before', $this->language->formatBitrate( $param['bitrate'] ) );
                        } else {
                                $warning = 'Invalid parameter for message "' . $this->getKey() . '": ' .
                                        htmlspecialchars( serialize( $param ) );
                                trigger_error( $warning, E_USER_WARNING );
                                $e = new Exception;
                                wfDebugLog( 'Bug58676', $warning . "\n" . $e->getTraceAsString() );

                                return array( 'before', '[INVALID]' );
                        }
                } elseif ( $param instanceof Message ) {
                        // Message objects should not be before parameters because
                        // then they'll get double escaped. If the message needs to be
                        // escaped, it'll happen right here when we call toString().
                        return array( 'after', $param->toString() );
                } else {
                        return array( 'before', $param );
                }
        }

        /**
         * Wrapper for what ever method we use to parse wikitext.
         *
         * @since 1.17
         *
         * @param string $string Wikitext message contents.
         *
         * @return string Wikitext parsed into HTML.
         */
        protected function parseText( $string ) {
                $out = MessageCache::singleton()->parse(
                        $string,
                        $this->title,
                        /*linestart*/true,
                        $this->interface,
                        $this->language
                );

                return $out instanceof ParserOutput ? $out->getText() : $out;
        }

        /**
         * Wrapper for what ever method we use to {{-transform wikitext.
         *
         * @since 1.17
         *
         * @param string $string Wikitext message contents.
         *
         * @return string Wikitext with {{-constructs replaced with their values.
         */
        protected function transformText( $string ) {
                return MessageCache::singleton()->transform(
                        $string,
                        $this->interface,
                        $this->language,
                        $this->title
                );
        }

        /**
         * Wrapper for what ever method we use to get message contents.
         *
         * @since 1.17
         *
         * @return string
         * @throws MWException If message key array is empty.
         */
        protected function fetchMessage() {
                if ( $this->message === null ) {
                        $cache = MessageCache::singleton();

                        foreach ( $this->keysToTry as $key ) {
                                $message = $cache->get( $key, $this->useDatabase, $this->language );
                                if ( $message !== false && $message !== '' ) {
                                        break;
                                }
                        }

                        // NOTE: The constructor makes sure keysToTry isn't empty,
                        //       so we know that $key and $message are initialized.
                        $this->key = $key;
                        $this->message = $message;
                }
                return $this->message;
        }

}

/**
 * Variant of the Message class.
 *
 * Rather than treating the message key as a lookup
 * value (which is passed to the MessageCache and
 * translated as necessary), a RawMessage key is
 * treated as the actual message.
 *
 * All other functionality (parsing, escaping, etc.)
 * is preserved.
 *
 * @since 1.21
 */
class RawMessage extends Message {

        /**
         * Call the parent constructor, then store the key as
         * the message.
         *
         * @see Message::__construct
         *
         * @param string $text Message to use.
         * @param array $params Parameters for the message.
         *
         * @throws InvalidArgumentException
         */
        public function __construct( $text, $params = array() ) {
                if ( !is_string( $text ) ) {
                        throw new InvalidArgumentException( '$text must be a string' );
                }

                parent::__construct( $text, $params );

                // The key is the message.
                $this->message = $text;
        }

        /**
         * Fetch the message (in this case, the key).
         *
         * @return string
         */
        public function fetchMessage() {
                // Just in case the message is unset somewhere.
                if ( $this->message === null ) {
                        $this->message = $this->key;
                }

                return $this->message;
        }

}