[lhc/web/wiklou.git] / includes / content / Content.php

<?php
/**
 * A content object represents page content, e.g. the text to show on a page.
 * Content objects have no knowledge about how they relate to wiki pages.
 *
 * 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
 *
 * @since 1.21
 *
 * @file
 * @ingroup Content
 *
 * @author Daniel Kinzler
 */

/**
 * Base interface for content objects.
 *
 * @ingroup Content
 */
interface Content {

        /**
         * @since 1.21
         *
         * @return string A string representing the content in a way useful for
         *   building a full text search index. If no useful representation exists,
         *   this method returns an empty string.
         *
         * @todo: test that this actually works
         * @todo: make sure this also works with LuceneSearch / WikiSearch
         */
        public function getTextForSearchIndex();

        /**
         * @since 1.21
         *
         * @return string|false The wikitext to include when another page includes this
         * content, or false if the content is not includable in a wikitext page.
         *
         * @todo allow native handling, bypassing wikitext representation, like
         *    for includable special pages.
         * @todo allow transclusion into other content models than Wikitext!
         * @todo used in WikiPage and MessageCache to get message text. Not so
         *    nice. What should we use instead?!
         */
        public function getWikitextForTransclusion();

        /**
         * Returns a textual representation of the content suitable for use in edit
         * summaries and log messages.
         *
         * @since 1.21
         *
         * @param $maxLength int Maximum length of the summary text
         * @return string The summary text
         */
        public function getTextForSummary( $maxLength = 250 );

        /**
         * Returns native representation of the data. Interpretation depends on
         * the data model used, as given by getDataModel().
         *
         * @since 1.21
         *
         * @return mixed The native representation of the content. Could be a
         *    string, a nested array structure, an object, a binary blob...
         *    anything, really.
         *
         * @note Caller must be aware of content model!
         */
        public function getNativeData();

        /**
         * Returns the content's nominal size in bogo-bytes.
         *
         * @return int
         */
        public function getSize();

        /**
         * Returns the ID of the content model used by this Content object.
         * Corresponds to the CONTENT_MODEL_XXX constants.
         *
         * @since 1.21
         *
         * @return String The model id
         */
        public function getModel();

        /**
         * Convenience method that returns the ContentHandler singleton for handling
         * the content model that this Content object uses.
         *
         * Shorthand for ContentHandler::getForContent( $this )
         *
         * @since 1.21
         *
         * @return ContentHandler
         */
        public function getContentHandler();

        /**
         * Convenience method that returns the default serialization format for the
         * content model that this Content object uses.
         *
         * Shorthand for $this->getContentHandler()->getDefaultFormat()
         *
         * @since 1.21
         *
         * @return String
         */
        public function getDefaultFormat();

        /**
         * Convenience method that returns the list of serialization formats
         * supported for the content model that this Content object uses.
         *
         * Shorthand for $this->getContentHandler()->getSupportedFormats()
         *
         * @since 1.21
         *
         * @return Array of supported serialization formats
         */
        public function getSupportedFormats();

        /**
         * Returns true if $format is a supported serialization format for this
         * Content object, false if it isn't.
         *
         * Note that this should always return true if $format is null, because null
         * stands for the default serialization.
         *
         * Shorthand for $this->getContentHandler()->isSupportedFormat( $format )
         *
         * @since 1.21
         *
         * @param $format string The format to check
         * @return bool Whether the format is supported
         */
        public function isSupportedFormat( $format );

        /**
         * Convenience method for serializing this Content object.
         *
         * Shorthand for $this->getContentHandler()->serializeContent( $this, $format )
         *
         * @since 1.21
         *
         * @param $format null|string The desired serialization format (or null for
         *    the default format).
         * @return string Serialized form of this Content object
         */
        public function serialize( $format = null );

        /**
         * Returns true if this Content object represents empty content.
         *
         * @since 1.21
         *
         * @return bool Whether this Content object is empty
         */
        public function isEmpty();

        /**
         * Returns whether the content is valid. This is intended for local validity
         * checks, not considering global consistency.
         *
         * Content needs to be valid before it can be saved.
         *
         * This default implementation always returns true.
         *
         * @since 1.21
         *
         * @return boolean
         */
        public function isValid();

        /**
         * Returns true if this Content objects is conceptually equivalent to the
         * given Content object.
         *
         * Contract:
         *
         * - Will return false if $that is null.
         * - Will return true if $that === $this.
         * - Will return false if $that->getModel() != $this->getModel().
         * - Will return false if $that->getNativeData() is not equal to $this->getNativeData(),
         *   where the meaning of "equal" depends on the actual data model.
         *
         * Implementations should be careful to make equals() transitive and reflexive:
         *
         * - $a->equals( $b ) <=> $b->equals( $a )
         * - $a->equals( $b ) &&  $b->equals( $c ) ==> $a->equals( $c )
         *
         * @since 1.21
         *
         * @param $that Content The Content object to compare to
         * @return bool True if this Content object is equal to $that, false otherwise.
         */
        public function equals( Content $that = null );

        /**
         * Return a copy of this Content object. The following must be true for the
         * object returned:
         *
         * if $copy = $original->copy()
         *
         * - get_class($original) === get_class($copy)
         * - $original->getModel() === $copy->getModel()
         * - $original->equals( $copy )
         *
         * If and only if the Content object is immutable, the copy() method can and
         * should return $this. That is, $copy === $original may be true, but only
         * for immutable content objects.
         *
         * @since 1.21
         *
         * @return Content. A copy of this object
         */
        public function copy( );

        /**
         * Returns true if this content is countable as a "real" wiki page, provided
         * that it's also in a countable location (e.g. a current revision in the
         * main namespace).
         *
         * @since 1.21
         *
         * @param $hasLinks Bool: If it is known whether this content contains
         *    links, provide this information here, to avoid redundant parsing to
         *    find out.
         * @return boolean
         */
        public function isCountable( $hasLinks = null );

        /**
         * Parse the Content object and generate a ParserOutput from the result.
         * $result->getText() can be used to obtain the generated HTML. If no HTML
         * is needed, $generateHtml can be set to false; in that case,
         * $result->getText() may return null.
         *
         * @param $title Title The page title to use as a context for rendering
         * @param $revId null|int The revision being rendered (optional)
         * @param $options null|ParserOptions Any parser options
         * @param $generateHtml Boolean Whether to generate HTML (default: true). If false,
         *        the result of calling getText() on the ParserOutput object returned by
         *        this method is undefined.
         *
         * @since 1.21
         *
         * @return ParserOutput
         */
        public function getParserOutput( Title $title,
                $revId = null,
                ParserOptions $options = null, $generateHtml = true );
        // TODO: make RenderOutput and RenderOptions base classes

        /**
         * Returns a list of DataUpdate objects for recording information about this
         * Content in some secondary data store. If the optional second argument,
         * $old, is given, the updates may model only the changes that need to be
         * made to replace information about the old content with information about
         * the new content.
         *
         * This default implementation calls
         * $this->getParserOutput( $content, $title, null, null, false ),
         * and then calls getSecondaryDataUpdates( $title, $recursive ) on the
         * resulting ParserOutput object.
         *
         * Subclasses may implement this to determine the necessary updates more
         * efficiently, or make use of information about the old content.
         *
         * @param $title Title The context for determining the necessary updates
         * @param $old Content|null An optional Content object representing the
         *    previous content, i.e. the content being replaced by this Content
         *    object.
         * @param $recursive boolean Whether to include recursive updates (default:
         *    false).
         * @param $parserOutput ParserOutput|null Optional ParserOutput object.
         *    Provide if you have one handy, to avoid re-parsing of the content.
         *
         * @return Array. A list of DataUpdate objects for putting information
         *    about this content object somewhere.
         *
         * @since 1.21
         */
        public function getSecondaryDataUpdates( Title $title,
                Content $old = null,
                $recursive = true, ParserOutput $parserOutput = null
        );

        /**
         * Construct the redirect destination from this content and return an
         * array of Titles, or null if this content doesn't represent a redirect.
         * The last element in the array is the final destination after all redirects
         * have been resolved (up to $wgMaxRedirects times).
         *
         * @since 1.21
         *
         * @return Array of Titles, with the destination last
         */
        public function getRedirectChain();

        /**
         * Construct the redirect destination from this content and return a Title,
         * or null if this content doesn't represent a redirect.
         * This will only return the immediate redirect target, useful for
         * the redirect table and other checks that don't need full recursion.
         *
         * @since 1.21
         *
         * @return Title: The corresponding Title
         */
        public function getRedirectTarget();

        /**
         * Construct the redirect destination from this content and return the
         * Title, or null if this content doesn't represent a redirect.
         *
         * This will recurse down $wgMaxRedirects times or until a non-redirect
         * target is hit in order to provide (hopefully) the Title of the final
         * destination instead of another redirect.
         *
         * There is usually no need to override the default behaviour, subclasses that
         * want to implement redirects should override getRedirectTarget().
         *
         * @since 1.21
         *
         * @return Title
         */
        public function getUltimateRedirectTarget();

        /**
         * Returns whether this Content represents a redirect.
         * Shorthand for getRedirectTarget() !== null.
         *
         * @since 1.21
         *
         * @return bool
         */
        public function isRedirect();

        /**
         * If this Content object is a redirect, this method updates the redirect target.
         * Otherwise, it does nothing.
         *
         * @since 1.21
         *
         * @param Title $target the new redirect target
         *
         * @return Content a new Content object with the updated redirect (or $this if this Content object isn't a redirect)
         */
        public function updateRedirect( Title $target );

        /**
         * Returns the section with the given ID.
         *
         * @since 1.21
         *
         * @param $sectionId string The section's ID, given as a numeric string.
         *    The ID "0" retrieves the section before the first heading, "1" the
         *    text between the first heading (included) and the second heading
         *    (excluded), etc.
         * @return Content|Boolean|null The section, or false if no such section
         *    exist, or null if sections are not supported.
         */
        public function getSection( $sectionId );

        /**
         * Replaces a section of the content and returns a Content object with the
         * section replaced.
         *
         * @since 1.21
         *
         * @param $section null/false or a section number (0, 1, 2, T1, T2...), or "new"
         * @param $with Content: new content of the section
         * @param $sectionTitle String: new section's subject, only if $section is 'new'
         * @return string Complete article text, or null if error
         */
        public function replaceSection( $section, Content $with, $sectionTitle = '' );

        /**
         * Returns a Content object with pre-save transformations applied (or this
         * object if no transformations apply).
         *
         * @since 1.21
         *
         * @param $title Title
         * @param $user User
         * @param $parserOptions null|ParserOptions
         * @return Content
         */
        public function preSaveTransform( Title $title, User $user, ParserOptions $parserOptions );

        /**
         * Returns a new WikitextContent object with the given section heading
         * prepended, if supported. The default implementation just returns this
         * Content object unmodified, ignoring the section header.
         *
         * @since 1.21
         *
         * @param $header string
         * @return Content
         */
        public function addSectionHeader( $header );

        /**
         * Returns a Content object with preload transformations applied (or this
         * object if no transformations apply).
         *
         * @since 1.21
         *
         * @param $title Title
         * @param $parserOptions null|ParserOptions
         * @return Content
         */
        public function preloadTransform( Title $title, ParserOptions $parserOptions );

        /**
         * Prepare Content for saving. Called before Content is saved by WikiPage::doEditContent() and in
         * similar places.
         *
         * This may be used to check the content's consistency with global state. This function should
         * NOT write any information to the database.
         *
         * Note that this method will usually be called inside the same transaction bracket that will be used
         * to save the new revision.
         *
         * Note that this method is called before any update to the page table is performed. This means that
         * $page may not yet know a page ID.
         *
         * @since 1.21
         *
         * @param WikiPage $page The page to be saved.
         * @param int      $flags bitfield for use with EDIT_XXX constants, see WikiPage::doEditContent()
         * @param int      $baseRevId the ID of the current revision
         * @param User     $user
         *
         * @return Status A status object indicating whether the content was successfully prepared for saving.
         *                If the returned status indicates an error, a rollback will be performed and the
         *                transaction aborted.
         *
         * @see see WikiPage::doEditContent()
         */
        public function prepareSave( WikiPage $page, $flags, $baseRevId, User $user );

        /**
         * Returns a list of updates to perform when this content is deleted.
         * The necessary updates may be taken from the Content object, or depend on
         * the current state of the database.
         *
         * @since 1.21
         *
         * @param $page WikiPage the deleted page
         * @param $parserOutput null|ParserOutput optional parser output object
         *    for efficient access to meta-information about the content object.
         *    Provide if you have one handy.
         *
         * @return array A list of DataUpdate instances that will clean up the
         *    database after deletion.
         */
        public function getDeletionUpdates( WikiPage $page,
                ParserOutput $parserOutput = null );

        /**
         * Returns true if this Content object matches the given magic word.
         *
         * @since 1.21
         *
         * @param MagicWord $word the magic word to match
         *
         * @return bool whether this Content object matches the given magic word.
         */
        public function matchMagicWord( MagicWord $word );

        /**
         * Converts this content object into another content object with the given content model,
         * if that is possible.
         *
         * @param String  $toModel the desired content model, use the CONTENT_MODEL_XXX flags.
         * @param String  $lossy flag, set to "lossy" to allow lossy conversion. If lossy conversion is
         * not allowed, full round-trip conversion is expected to work without losing information.
         *
         * @return Content|bool A content object with the content model $toModel, or false if
         * that conversion is not supported.
         */
        public function convert( $toModel, $lossy = '' );

                // TODO: ImagePage and CategoryPage interfere with per-content action handlers
        // TODO: nice&sane integration of GeSHi syntax highlighting
        //   [11:59] <vvv> Hooks are ugly; make CodeHighlighter interface and a
        //   config to set the class which handles syntax highlighting
        //   [12:00] <vvv> And default it to a DummyHighlighter
}