wikimedia/mediawiki-core

<?php
/**
 * Renders a diff for a single slot.
 *
 * 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
 * @ingroup DifferenceEngine
 */

use MediaWiki\Context\IContextSource;
use MediaWiki\Output\OutputPage;
use MediaWiki\Title\Title;
use Wikimedia\Assert\Assert;

/**
 * Renders a diff for a single slot (that is, a diff between two content objects).
 *
 * Callers should obtain instances of this class by invoking ContentHandler::getSlotDiffRenderer
 * on the content handler of the new content object (ie. the one shown on the right side
 * of the diff), or of the old one if the new one does not exist.
 *
 * The default implementation just does a text diff on the native text representation.
 * Content handler extensions can subclass this to provide a more appropriate diff method by
 * overriding ContentHandler::getSlotDiffRendererInternal. Other extensions that want to interfere
 * with diff generation in some way can use the GetSlotDiffRenderer hook.
 *
 * @stable to extend
 * @ingroup DifferenceEngine
 */
abstract class SlotDiffRenderer {

    /**
     * Get a diff between two content objects. One of them might be null (meaning a slot was
     * created or removed), but both cannot be. $newContent (or if it's null then $oldContent)
     * must have the same content model that was used to obtain this diff renderer.
     * @param Content|null $oldContent
     * @param Content|null $newContent
     * @return string HTML. One or more <tr> tags, or an empty string if the inputs are identical.
     * @throws IncompatibleDiffTypesException
     */
    abstract public function getDiff( Content $oldContent = null, Content $newContent = null );

    /**
     * Localize language-independent text returned by getDiff(), making it
     * suitable for display. Subclasses overriding this should arrange for
     * injection of a MessageLocalizer.
     *
     * @param string $diff
     * @param array $options Associative array of options:
     *   - reducedLineNumbers: If true, remove "line 1" but allow other line numbers
     * @return string
     */
    public function localizeDiff( string $diff, array $options = [] ) {
        return $diff;
    }

    /**
     * Get the content to add above the main diff table.
     *
     * @since 1.41
     * @param IContextSource $context
     * @param Title $newTitle
     * @return (string|null)[] An array of HTML fragments to assemble into the prefix
     *   area. They will be deduplicated and sorted by key.
     */
    public function getTablePrefix( IContextSource $context, Title $newTitle ): array {
        return [];
    }

    /**
     * Add modules needed for correct styling/behavior of the diff.
     * @stable to override
     * @param OutputPage $output
     */
    public function addModules( OutputPage $output ) {
    }

    /**
     * Return any extra keys to split the diff cache by.
     * @stable to override
     * @return string[]
     */
    public function getExtraCacheKeys() {
        return [];
    }

    /**
     * Helper method to normalize the input of getDiff().
     * Verifies that at least one of $oldContent and $newContent is not null, verifies that
     * they are instances of one of the allowed classes (if provided), and replaces null with
     * empty content.
     * @param Content|null &$oldContent
     * @param Content|null &$newContent
     * @param string|array|null $allowedClasses
     * @throws IncompatibleDiffTypesException
     */
    protected function normalizeContents(
        Content &$oldContent = null, Content &$newContent = null, $allowedClasses = null
    ) {
        if ( !$oldContent && !$newContent ) {
            throw new InvalidArgumentException( '$oldContent and $newContent cannot both be null' );
        }

        if ( $allowedClasses ) {
            if ( is_string( $allowedClasses ) ) {
                $allowedClasses = explode( '|', $allowedClasses );
            }
            $allowedClassesOrNull = array_merge( $allowedClasses, [ 'null' ] );

            // The new content (or the old one if the new one is null) must always match the renderer
            // since the ContentHandler of that model should be used to create it
            Assert::parameterType( $allowedClassesOrNull, $newContent, '$newContent' );
            if ( !$newContent ) {
                Assert::parameterType( $allowedClassesOrNull, $oldContent, '$oldContent' );
            }

            // If there are two content objects, the old one can be arbitrary as it is possible
            // to generate a diff between any two revisions; so an incompatible model should be
            // handled as a user error, not a logic error.
            if ( $oldContent && $newContent ) {
                $allowed = false;
                foreach ( $allowedClasses as $class ) {
                    if ( $oldContent instanceof $class ) {
                        $allowed = true;
                        break;
                    }
                }
                if ( !$allowed ) {
                    throw new IncompatibleDiffTypesException( $oldContent->getModel(), $newContent->getModel() );
                }
            }
        }

        if ( !$oldContent ) {
            $oldContent = $newContent->getContentHandler()->makeEmptyContent();
        } elseif ( !$newContent ) {
            $newContent = $oldContent->getContentHandler()->makeEmptyContent();
        }
    }

}