<?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.
 *
 * @since 1.WD
 */
interface Content {

	/**
	 * @since WD.1
	 *
	 * @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 WD.1
	 *
	 * @return String 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 WD.1
	 *
	 * @param int $maxlength 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 WD.1
	 *
	 * @return mixed the native representation of the content. Could be a string, a nested array
	 *         structure, an object, a binary blob... anything, really.
	 *
	 * @NOTE: review all calls carefully, 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 objects.
	 * Corresponds to the CONTENT_MODEL_XXX constants.
	 *
	 * @since WD.1
	 *
	 * @return int the model id
	 */
	public function getModel();

	/**
	 * Convenience method that returns the ContentHandler singleton for handling the content
	 * model this Content object uses.
	 *
	 * Shorthand for ContentHandler::getForContent( $this )
	 *
	 * @since WD.1
	 *
	 * @return ContentHandler
	 */
	public function getContentHandler();

	/**
	 * Convenience method that returns the default serialization format for the content model
	 * model this Content object uses.
	 *
	 * Shorthand for $this->getContentHandler()->getDefaultFormat()
	 *
	 * @since WD.1
	 *
	 * @return ContentHandler
	 */
	public function getDefaultFormat();

	/**
	 * Convenience method that returns the list of serialization formats supported
	 * for the content model model this Content object uses.
	 *
	 * Shorthand for $this->getContentHandler()->getSupportedFormats()
	 *
	 * @since WD.1
	 *
	 * @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 WD.1
	 *
	 * @param String $format 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 WD.1
	 *
	 * @param null|String $format 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 WD.1
	 *
	 * @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 WD.1
	 *
	 * @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->getModelName() != $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 WD.1
	 *
	 * @param Content $that 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 WD.1
	 *
	 * @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 WD.1
	 *
	 * @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 ) ;

	/**
	 * Convenience method, shorthand for
	 * $this->getContentHandler()->getParserOutput( $this, $title, $revId, $options, $generateHtml )
	 *
	 * @note: subclasses should NOT override this to provide custom rendering.
	 *        Override ContentHandler::getParserOutput() instead!
	 *
	 * @param Title $title
	 * @param null $revId
	 * @param null|ParserOptions $options
	 * @param Boolean $generateHtml whether to generate Html (default: true). If false,
	 *        the result of calling getText() on the ParserOutput object returned by
	 *        this method is undefined.
	 *
	 * @since WD.1
	 *
	 * @return ParserOutput
	 */
	public function getParserOutput( Title $title, $revId = null, ParserOptions $options = null, $generateHtml = true );

	/**
	 * 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 WD.1
	 *
	 * @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 WD.1
	 *
	 * @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.
	 *
	 * @since WD.1
	 *
	 * @return Title
	 */
	public function getUltimateRedirectTarget();

	/**
	 * Returns whether this Content represents a redirect.
	 * Shorthand for getRedirectTarget() !== null.
	 *
	 * @since WD.1
	 *
	 * @return bool
	 */
	public function isRedirect();

	/**
	 * Returns the section with the given id.
	 *
	 * @since WD.1
	 *
	 * @param String $sectionId 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 WD.1
	 *
	 * @param $section empty/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 WD.1
	 *
	 * @param Title $title
	 * @param User $user
	 * @param null|ParserOptions $popts
	 * @return Content
	 */
	public function preSaveTransform( Title $title, User $user, ParserOptions $popts );

	/**
	 * 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 WD.1
	 *
	 * @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 WD.1
	 *
	 * @param Title $title
	 * @param null|ParserOptions $popts
	 * @return Content
	 */
	public function preloadTransform( Title $title, ParserOptions $popts );

	# TODO: handle ImagePage and CategoryPage
	# TODO: make sure we cover lucene search / wikisearch.
	# TODO: make sure ReplaceTemplates still works
	# FUTURE: 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

	# TODO: make sure we cover the external editor interface (does anyone actually use that?!)

	# TODO: tie into API to provide contentModel for Revisions
	# TODO: tie into API to provide serialized version and contentFormat for Revisions
	# TODO: tie into API edit interface
	# FUTURE: make EditForm plugin for EditPage

	# FUTURE: special type for redirects?!
	# FUTURE: MultipartMultipart < WikipageContent (Main + Links + X)
	# FUTURE: LinksContent < LanguageLinksContent, CategoriesContent

// @TODO: add support for ar_content_format, ar_content_model, rev_content_format, rev_content_model to API
}


/**
 * 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.
 *
 * @since 1.WD
 */
abstract class AbstractContent implements Content {

	/**
	 * Name of the content model this Content object represents.
	 * Use with CONTENT_MODEL_XXX constants
	 *
	 * @var String $model_id
	 */
	protected $model_id;

	/**
	 * @param int $model_id
	 */
	public function __construct( $model_id = null ) {
		$this->model_id = $model_id;
	}

	/**
	 * Returns the id of the content model used by this content objects.
	 * Corresponds to the CONTENT_MODEL_XXX constants.
	 *
	 * @since WD.1
	 *
	 * @return int the model id
	 */
	public function getModel() {
		return $this->model_id;
	}

	/**
	 * Throws an MWException if $model_id is not the id of the content model
	 * supported by this Content object.
	 *
	 * @param int $model_id the model to check
	 *
	 * @throws MWException
	 */
	protected function checkModelID( $model_id ) {
		if ( $model_id !== $this->model_id ) {
			$model_name = ContentHandler::getContentModelName( $model_id );
			$own_model_name = ContentHandler::getContentModelName( $this->model_id );

			throw new MWException( "Bad content model: expected {$this->model_id} ($own_model_name) but got found $model_id ($model_name)." );
		}
	}

	/**
	 * Convenience method that returns the ContentHandler singleton for handling the content
	 * model this Content object uses.
	 *
	 * Shorthand for ContentHandler::getForContent( $this )
	 *
	 * @since WD.1
	 *
	 * @return ContentHandler
	 */
	public function getContentHandler() {
		return ContentHandler::getForContent( $this );
	}

	/**
	 * Convenience method that returns the default serialization format for the content model
	 * model this Content object uses.
	 *
	 * Shorthand for $this->getContentHandler()->getDefaultFormat()
	 *
	 * @since WD.1
	 *
	 * @return ContentHandler
	 */
	public function getDefaultFormat() {
		return $this->getContentHandler()->getDefaultFormat();
	}

	/**
	 * Convenience method that returns the list of serialization formats supported
	 * for the content model model this Content object uses.
	 *
	 * Shorthand for $this->getContentHandler()->getSupportedFormats()
	 *
	 * @since WD.1
	 *
	 * @return array of supported serialization formats
	 */
	public function getSupportedFormats() {
		return $this->getContentHandler()->getSupportedFormats();
	}

	/**
	 * Returns true if $format is a supported serialization format for this Content object,
	 * false if it isn't.
	 *
	 * Note that this will always return true if $format is null, because null stands for the
	 * default serialization.
	 *
	 * Shorthand for $this->getContentHandler()->isSupportedFormat( $format )
	 *
	 * @since WD.1
	 *
	 * @param String $format the format to check
	 * @return bool whether the format is supported
	 */
	public function isSupportedFormat( $format ) {
		if ( !$format ) {
			return true; // this means "use the default"
		}

		return $this->getContentHandler()->isSupportedFormat( $format );
	}

	/**
	 * Throws an MWException if $this->isSupportedFormat( $format ) doesn't return true.
	 *
	 * @param $format
	 * @throws MWException
	 */
	protected function checkFormat( $format ) {
		if ( !$this->isSupportedFormat( $format ) ) {
			throw new MWException( "Format $format is not supported for content model " . $this->getModel() );
		}
	}

	/**
	 * Convenience method for serializing this Content object.
	 *
	 * Shorthand for $this->getContentHandler()->serializeContent( $this, $format )
	 *
	 * @since WD.1
	 *
	 * @param null|String $format the desired serialization format (or null for the default format).
	 * @return String serialized form of this Content object
	 */
	public function serialize( $format = null ) {
		return $this->getContentHandler()->serializeContent( $this, $format );
	}

	/**
	 * Returns true if this Content object represents empty content.
	 *
	 * @since WD.1
	 *
	 * @return bool whether this Content object is empty
	 */
	public function isEmpty() {
		return $this->getSize() == 0;
	}

	/**
	 * Returns if the content is valid. This is intended for local validity checks, not considering global consistency.
	 * It needs to be valid before it can be saved.
	 *
	 * This default implementation always returns true.
	 *
	 * @since WD.1
	 *
	 * @return boolean
	 */
	public function isValid() {
		return true;
	}

	/**
	 * Returns true if this Content objects is conceptually equivalent to the given Content object.
	 *
	 * Will returns false if $that is null.
	 * Will return true if $that === $this.
	 * Will return false if $that->getModelName() != $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 WD.1
	 *
	 * @param Content $that the Content object to compare to
	 * @return bool true if this Content object is euqual to $that, false otherwise.
	 */
	public function equals( Content $that = null ) {
		if ( is_null( $that ) ){
			return false;
		}

		if ( $that === $this ) {
			return true;
		}

		if ( $that->getModel() !== $this->getModel() ) {
			return false;
		}

		return $this->getNativeData() === $that->getNativeData();
	}

	/**
	 * Convenience method, shorthand for
	 * $this->getContentHandler()->getParserOutput( $this, $title, $revId, $options, $generateHtml )
	 *
	 * @note: subclasses should NOT override this to provide custom rendering.
	 *        Override ContentHandler::getParserOutput() instead!
	 *
	 * @param Title $title
	 * @param null $revId
	 * @param null|ParserOptions $options
	 * @param Boolean $generateHtml whether to generate Html (default: true). If false,
	 *        the result of calling getText() on the ParserOutput object returned by
	 *        this method is undefined.
	 *
	 * @since WD.1
	 *
	 * @return ParserOutput
	 */
	public function getParserOutput( Title $title, $revId = null, ParserOptions $options = null, $generateHtml = true ) {
		return $this->getContentHandler()->getParserOutput( $this, $title, $revId, $options, $generateHtml );
	}

	/**
	 * 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).
	 *
	 * There is usually no need to override the default behaviour, subclasses that
	 * want to implement redirects should override getRedirectTarget().
	 *
	 * @since WD.1
	 *
	 * @return Array of Titles, with the destination last
	 * @note: migrated here from Title::newFromRedirectArray
	 */
	public function getRedirectChain() {
		global $wgMaxRedirects;
		$title = $this->getRedirectTarget();
		if ( is_null( $title ) ) {
			return null;
		}
		// recursive check to follow double redirects
		$recurse = $wgMaxRedirects;
		$titles = array( $title );
		while ( --$recurse > 0 ) {
			if ( $title->isRedirect() ) {
				$page = WikiPage::factory( $title );
				$newtitle = $page->getRedirectTarget();
			} else {
				break;
			}
			// Redirects to some special pages are not permitted
			if ( $newtitle instanceOf Title && $newtitle->isValidRedirectTarget() ) {
				// the new title passes the checks, so make that our current title so that further recursion can be checked
				$title = $newtitle;
				$titles[] = $newtitle;
			} else {
				break;
			}
		}
		return $titles;
	}

	/**
	 * Construct the redirect destination from this content and return a Title,
	 * or null if this content doesn't represent a redirect.
	 *
	 * This shall only return the immediate redirect target, useful for
	 * the redirect table and other checks that don't need full recursion.
	 *
	 * This implementation always returns null, subclasses should implement it
	 * according to their data model.
	 *
	 * @since WD.1
	 *
	 * @return Title: The corresponding Title
	 */
	public function getRedirectTarget() {
		return null;
	}

	/**
	 * 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 WD.1
	 *
	 * @return Title
	 * @note: migrated here from Title::newFromRedirectRecurse
	 */
	public function getUltimateRedirectTarget() {
		$titles = $this->getRedirectChain();
		return $titles ? array_pop( $titles ) : null;
	}

	/**
	 * @since WD.1
	 *
	 * @return bool
	 */
	public function isRedirect() {
		return $this->getRedirectTarget() !== null;
	}

	/**
	 * Returns the section with the given id.
	 *
	 * The default implementation returns null.
	 *
	 * @since WD.1
	 *
	 * @param String $sectionId 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 ) {
		return null;
	}

	/**
	 * Replaces a section of the content and returns a Content object with the section replaced.
	 *
	 * @since WD.1
	 *
	 * @param $section empty/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 = ''  ) {
		return null;
	}

	/**
	 * Returns a Content object with pre-save transformations applied (or this object if no transformations apply).
	 *
	 * @since WD.1
	 *
	 * @param Title $title
	 * @param User $user
	 * @param null|ParserOptions $popts
	 * @return Content
	 */
	public function preSaveTransform( Title $title, User $user, ParserOptions $popts ) {
		return $this;
	}

	/**
	 * 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 WD.1
	 *
	 * @param $header String
	 * @return Content
	 */
	public function addSectionHeader( $header ) {
		return $this;
	}

	/**
	 * Returns a Content object with preload transformations applied (or this object if no transformations apply).
	 *
	 * @since WD.1
	 *
	 * @param Title $title
	 * @param null|ParserOptions $popts
	 * @return Content
	 */
	public function preloadTransform( Title $title, ParserOptions $popts ) {
		return $this;
	}
}

/**
 * Content object implementation for representing flat text.
 *
 * TextContent instances are immutable
 *
 * @since WD.1
 */
abstract class TextContent extends AbstractContent {

	public function __construct( $text, $model_id = null ) {
		parent::__construct( $model_id );

		$this->mText = $text;
	}

	public function copy() {
		return $this; #NOTE: this is ok since TextContent are immutable.
	}

	public function getTextForSummary( $maxlength = 250 ) {
		global $wgContLang;

		$text = $this->getNativeData();

		$truncatedtext = $wgContLang->truncate(
			preg_replace( "/[\n\r]/", ' ', $text ),
			max( 0, $maxlength ) );

		return $truncatedtext;
	}

	/**
	 * returns the text's size in bytes.
	 *
	 * @return int the size
	 */
	public function getSize( ) {
		$text = $this->getNativeData( );
		return strlen( $text );
	}

	/**
	 * Returns true if this content is not a redirect, and $wgArticleCountMethod is "any".
	 *
	 * @param $hasLinks Bool: if it is known whether this content contains links, provide this information here,
	 *                        to avoid redundant parsing to find out.
	 *
	 * @return bool true if the content is countable
	 */
	public function isCountable( $hasLinks = null ) {
		global $wgArticleCountMethod;

		if ( $this->isRedirect( ) ) {
			return false;
		}

		if (  $wgArticleCountMethod === 'any' ) {
			return true;
		}

		return false;
	}

	/**
	 * Returns the text represented by this Content object, as a string.
	 *
	 * @return String the raw text
	 */
	public function getNativeData( ) {
		$text = $this->mText;
		return $text;
	}

	/**
	 * Returns the text represented by this Content object, as a string.
	 *
	 * @return String the raw text
	 */
	public function getTextForSearchIndex( ) {
		return $this->getNativeData();
	}

	/**
	 * Returns the text represented by this Content object, as a string.
	 *
	 * @return String the raw text
	 */
	public function getWikitextForTransclusion( ) {
		return $this->getNativeData();
	}

	/**
	 * Diff this content object with another content object..
	 *
	 * @since WD.diff
	 *
	 * @param Content $that the other content object to compare this content object to
	 * @param Language $lang the language object to use for text segmentation. If not given, $wgContentLang is used.
	 *
	 * @return DiffResult a diff representing the changes that would have to be made to this content object
	 *         to make it equal to $that.
	 */
	public function diff( Content $that, Language $lang = null ) {
		global $wgContLang;

		$this->checkModelID( $that->getModel() );

		#@todo: could implement this in DifferenceEngine and just delegate here?

		if ( !$lang ) $lang = $wgContLang;

		$otext = $this->getNativeData();
		$ntext = $this->getNativeData();

		# Note: Use native PHP diff, external engines don't give us abstract output
		$ota = explode( "\n", $wgContLang->segmentForDiff( $otext ) );
		$nta = explode( "\n", $wgContLang->segmentForDiff( $ntext ) );

		$diff = new Diff( $ota, $nta );
		return $diff;
	}


}

/**
 * @since WD.1
 */
class WikitextContent extends TextContent {

	public function __construct( $text ) {
		parent::__construct($text, CONTENT_MODEL_WIKITEXT);
	}

	/**
	 * Returns the section with the given id.
	 *
	 * @param String $section
	 *
	 * @internal param String $sectionId the section's id
	 * @return Content|false|null the section, or false if no such section exist, or null if sections are not supported
	 */
	public function getSection( $section ) {
		global $wgParser;

		$text = $this->getNativeData();
		$sect = $wgParser->getSection( $text, $section, false );

		return  new WikitextContent( $sect );
	}

	/**
	 * Replaces a section in the wikitext
	 *
	 * @param $section      empty/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'
	 *
	 * @throws MWException
	 * @return Content Complete article content, or null if error
	 */
	public function replaceSection( $section, Content $with, $sectionTitle = '' ) {
		wfProfileIn( __METHOD__ );

		$myModelId = $this->getModel();
		$sectionModelId = $with->getModel();

		if ( $sectionModelId != $myModelId  ) {
			$myModelName = ContentHandler::getContentModelName( $myModelId );
			$sectionModelName = ContentHandler::getContentModelName( $sectionModelId );

			throw new MWException( "Incompatible content model for section: document uses $myModelId ($myModelName), "
								. "section uses $sectionModelId ($sectionModelName)." );
		}

		$oldtext = $this->getNativeData();
		$text = $with->getNativeData();

		if ( $section === '' ) {
			return $with; #XXX: copy first?
		} if ( $section == 'new' ) {
			# Inserting a new section
			$subject = $sectionTitle ? wfMsgForContent( 'newsectionheaderdefaultlevel', $sectionTitle ) . "\n\n" : '';
			if ( wfRunHooks( 'PlaceNewSection', array( $this, $oldtext, $subject, &$text ) ) ) {
				$text = strlen( trim( $oldtext ) ) > 0
					? "{$oldtext}\n\n{$subject}{$text}"
					: "{$subject}{$text}";
			}
		} else {
			# Replacing an existing section; roll out the big guns
			global $wgParser;

			$text = $wgParser->replaceSection( $oldtext, $section, $text );
		}

		$newContent = new WikitextContent( $text );

		wfProfileOut( __METHOD__ );
		return $newContent;
	}

	/**
	 * Returns a new WikitextContent object with the given section heading prepended.
	 *
	 * @param $header String
	 * @return Content
	 */
	public function addSectionHeader( $header ) {
		$text = wfMsgForContent( 'newsectionheaderdefaultlevel', $header ) . "\n\n" . $this->getNativeData();

		return new WikitextContent( $text );
	}

	/**
	 * Returns a Content object with pre-save transformations applied using Parser::preSaveTransform().
	 *
	 * @param Title $title
	 * @param User $user
	 * @param ParserOptions $popts
	 * @return Content
	 */
	public function preSaveTransform( Title $title, User $user, ParserOptions $popts ) {
		global $wgParser;

		$text = $this->getNativeData();
		$pst = $wgParser->preSaveTransform( $text, $title, $user, $popts );

		return new WikitextContent( $pst );
	}

	/**
	 * Returns a Content object with preload transformations applied (or this object if no transformations apply).
	 *
	 * @param Title $title
	 * @param ParserOptions $popts
	 * @return Content
	 */
	public function preloadTransform( Title $title, ParserOptions $popts ) {
		global $wgParser;

		$text = $this->getNativeData();
		$plt = $wgParser->getPreloadText( $text, $title, $popts );

		return new WikitextContent( $plt );
	}

	/**
	 * Implement redirect extraction for wikitext.
	 *
	 * @return null|Title
	 *
	 * @note: migrated here from Title::newFromRedirectInternal()
	 *
	 * @see Content::getRedirectTarget
	 * @see AbstractContent::getRedirectTarget
	 */
	public function getRedirectTarget() {
		global $wgMaxRedirects;
		if ( $wgMaxRedirects < 1 ) {
			//redirects are disabled, so quit early
			return null;
		}
		$redir = MagicWord::get( 'redirect' );
		$text = trim( $this->getNativeData() );
		if ( $redir->matchStartAndRemove( $text ) ) {
			// Extract the first link and see if it's usable
			// Ensure that it really does come directly after #REDIRECT
			// Some older redirects included a colon, so don't freak about that!
			$m = array();
			if ( preg_match( '!^\s*:?\s*\[{2}(.*?)(?:\|.*?)?\]{2}!', $text, $m ) ) {
				// Strip preceding colon used to "escape" categories, etc.
				// and URL-decode links
				if ( strpos( $m[1], '%' ) !== false ) {
					// Match behavior of inline link parsing here;
					$m[1] = rawurldecode( ltrim( $m[1], ':' ) );
				}
				$title = Title::newFromText( $m[1] );
				// If the title is a redirect to bad special pages or is invalid, return null
				if ( !$title instanceof Title || !$title->isValidRedirectTarget() ) {
					return null;
				}
				return $title;
			}
		}
		return null;
	}

	/**
	 * Returns true if this content is not a redirect, and this content's text is countable according to
	 * the criteria defined by $wgArticleCountMethod.
	 *
	 * @param Bool        $hasLinks  if it is known whether this content contains links, provide this information here,
	 *                               to avoid redundant parsing to find out.
	 * @param null|\Title $title
	 *
	 * @internal param \IContextSource $context context for parsing if necessary
	 *
	 * @return bool true if the content is countable
	 */
	public function isCountable( $hasLinks = null, Title $title = null ) {
		global $wgArticleCountMethod;

		if ( $this->isRedirect( ) ) {
			return false;
		}

		$text = $this->getNativeData();

		switch ( $wgArticleCountMethod ) {
			case 'any':
				return true;
			case 'comma':
				return strpos( $text,  ',' ) !== false;
			case 'link':
				if ( $hasLinks === null ) { # not known, find out
					if ( !$title ) {
						$context = RequestContext::getMain();
						$title = $context->getTitle();
					}

					$po = $this->getParserOutput( $title, null, null, false );
					$links = $po->getLinks();
					$hasLinks = !empty( $links );
				}

				return $hasLinks;
		}

		return false;
	}

	public function getTextForSummary( $maxlength = 250 ) {
		$truncatedtext = parent::getTextForSummary( $maxlength );

		#clean up unfinished links
		#XXX: make this optional? wasn't there in autosummary, but required for deletion summary.
		$truncatedtext = preg_replace( '/\[\[([^\]]*)\]?$/', '$1', $truncatedtext );

		return $truncatedtext;
	}

}

/**
 * @since WD.1
 */
class MessageContent extends TextContent {
	public function __construct( $msg_key, $params = null, $options = null ) {
		parent::__construct(null, CONTENT_MODEL_WIKITEXT); #XXX: messages may be wikitext, html or plain text! and maybe even something else entirely.

		$this->mMessageKey = $msg_key;

		$this->mParameters = $params;

		if ( is_null( $options ) ) {
			$options = array();
		}
		elseif ( is_string( $options ) ) {
			$options = array( $options );
		}

		$this->mOptions = $options;
	}

	/**
	 * Returns the message as rendered HTML, using the options supplied to the constructor plus "parse".
	 * @return String the message text, parsed
	 */
	public function getHtml(  ) {
		$opt = array_merge( $this->mOptions, array('parse') );

		return wfMsgExt( $this->mMessageKey, $this->mParameters, $opt );
	}


	/**
	 * Returns the message as raw text, using the options supplied to the constructor minus "parse" and "parseinline".
	 *
	 * @return String the message text, unparsed.
	 */
	public function getNativeData( ) {
		$opt = array_diff( $this->mOptions, array('parse', 'parseinline') );

		return wfMsgExt( $this->mMessageKey, $this->mParameters, $opt );
	}

}

/**
 * @since WD.1
 */
class JavaScriptContent extends TextContent {
	public function __construct( $text ) {
		parent::__construct($text, CONTENT_MODEL_JAVASCRIPT);
	}

	/**
	 * Returns a Content object with pre-save transformations applied using Parser::preSaveTransform().
	 *
	 * @param Title $title
	 * @param User $user
	 * @param ParserOptions $popts
	 * @return Content
	 */
	public function preSaveTransform( Title $title, User $user, ParserOptions $popts ) {
		global $wgParser;
		// @todo: make pre-save transformation optional for script pages

		$text = $this->getNativeData();
		$pst = $wgParser->preSaveTransform( $text, $title, $user, $popts );

		return new JavaScriptContent( $pst );
	}

}

/**
 * @since WD.1
 */
class CssContent extends TextContent {
	public function __construct( $text ) {
		parent::__construct($text, CONTENT_MODEL_CSS);
	}

	/**
	 * Returns a Content object with pre-save transformations applied using Parser::preSaveTransform().
	 *
	 * @param Title $title
	 * @param User $user
	 * @param ParserOptions $popts
	 * @return Content
	 */
	public function preSaveTransform( Title $title, User $user, ParserOptions $popts ) {
		global $wgParser;
		// @todo: make pre-save transformation optional for script pages

		$text = $this->getNativeData();
		$pst = $wgParser->preSaveTransform( $text, $title, $user, $popts );

		return new CssContent( $pst );
	}

}