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[mediawiki.git] / includes / media / MediaHandler.php

<?php
/**
 * Media-handling base classes and generic functionality.
 *
 * 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 Media
 */

/**
 * Base media handler class
 *
 * @ingroup Media
 */
abstract class MediaHandler {
        const TRANSFORM_LATER = 1;
        const METADATA_GOOD = true;
        const METADATA_BAD = false;
        const METADATA_COMPATIBLE = 2; // for old but backwards compatible.
        /**
         * Instance cache
         */
        static $handlers = array();

        /**
         * Get a MediaHandler for a given MIME type from the instance cache
         *
         * @param $type string
         *
         * @return MediaHandler
         */
        static function getHandler( $type ) {
                global $wgMediaHandlers;
                if ( !isset( $wgMediaHandlers[$type] ) ) {
                        wfDebug( __METHOD__ . ": no handler found for $type.\n" );
                        return false;
                }
                $class = $wgMediaHandlers[$type];
                if ( !isset( self::$handlers[$class] ) ) {
                        self::$handlers[$class] = new $class;
                        if ( !self::$handlers[$class]->isEnabled() ) {
                                self::$handlers[$class] = false;
                        }
                }
                return self::$handlers[$class];
        }

        /**
         * Get an associative array mapping magic word IDs to parameter names.
         * Will be used by the parser to identify parameters.
         */
        abstract function getParamMap();

        /**
         * Validate a thumbnail parameter at parse time.
         * Return true to accept the parameter, and false to reject it.
         * If you return false, the parser will do something quiet and forgiving.
         *
         * @param $name
         * @param $value
         */
        abstract function validateParam( $name, $value );

        /**
         * Merge a parameter array into a string appropriate for inclusion in filenames
         *
         * @param $params array Array of parameters that have been through normaliseParams.
         */
        abstract function makeParamString( $params );

        /**
         * Parse a param string made with makeParamString back into an array
         *
         * @param $str string
         */
        abstract function parseParamString( $str );

        /**
         * Changes the parameter array as necessary, ready for transformation.
         * Should be idempotent.
         * Returns false if the parameters are unacceptable and the transform should fail
         * @param $image
         * @param $params
         */
        abstract function normaliseParams( $image, &$params );

        /**
         * Get an image size array like that returned by getimagesize(), or false if it
         * can't be determined.
         *
         * @param $image File: the image object, or false if there isn't one
         * @param string $path the filename
         * @return Array Follow the format of PHP getimagesize() internal function. See http://www.php.net/getimagesize
         */
        abstract function getImageSize( $image, $path );

        /**
         * Get handler-specific metadata which will be saved in the img_metadata field.
         *
         * @param $image File: the image object, or false if there isn't one.
         *   Warning, FSFile::getPropsFromPath might pass an (object)array() instead (!)
         * @param string $path the filename
         * @return String
         */
        function getMetadata( $image, $path ) {
                return '';
        }

        /**
         * Get metadata version.
         *
         * This is not used for validating metadata, this is used for the api when returning
         * metadata, since api content formats should stay the same over time, and so things
         * using ForiegnApiRepo can keep backwards compatibility
         *
         * All core media handlers share a common version number, and extensions can
         * use the GetMetadataVersion hook to append to the array (they should append a unique
         * string so not to get confusing). If there was a media handler named 'foo' with metadata
         * version 3 it might add to the end of the array the element 'foo=3'. if the core metadata
         * version is 2, the end version string would look like '2;foo=3'.
         *
         * @return string version string
         */
        static function getMetadataVersion() {
                $version = Array( '2' ); // core metadata version
                wfRunHooks( 'GetMetadataVersion', Array( &$version ) );
                return implode( ';', $version );
        }

        /**
         * Convert metadata version.
         *
         * By default just returns $metadata, but can be used to allow
         * media handlers to convert between metadata versions.
         *
         * @param $metadata Mixed String or Array metadata array (serialized if string)
         * @param $version Integer target version
         * @return Array serialized metadata in specified version, or $metadata on fail.
         */
        function convertMetadataVersion( $metadata, $version = 1 ) {
                if ( !is_array( $metadata ) ) {

                        //unserialize to keep return parameter consistent.
                        wfSuppressWarnings();
                        $ret = unserialize( $metadata );
                        wfRestoreWarnings();
                        return $ret;
                }
                return $metadata;
        }

        /**
         * Get a string describing the type of metadata, for display purposes.
         *
         * @return string
         */
        function getMetadataType( $image ) {
                return false;
        }

        /**
         * Check if the metadata string is valid for this handler.
         * If it returns MediaHandler::METADATA_BAD (or false), Image
         * will reload the metadata from the file and update the database.
         * MediaHandler::METADATA_GOOD for if the metadata is a-ok,
         * MediaHanlder::METADATA_COMPATIBLE if metadata is old but backwards
         * compatible (which may or may not trigger a metadata reload).
         * @return bool
         */
        function isMetadataValid( $image, $metadata ) {
                return self::METADATA_GOOD;
        }

        /**
         * Get a MediaTransformOutput object representing an alternate of the transformed
         * output which will call an intermediary thumbnail assist script.
         *
         * Used when the repository has a thumbnailScriptUrl option configured.
         *
         * Return false to fall back to the regular getTransform().
         * @return bool
         */
        function getScriptedTransform( $image, $script, $params ) {
                return false;
        }

        /**
         * Get a MediaTransformOutput object representing the transformed output. Does not
         * actually do the transform.
         *
         * @param $image File: the image object
         * @param string $dstPath filesystem destination path
         * @param string $dstUrl Destination URL to use in output HTML
         * @param array $params Arbitrary set of parameters validated by $this->validateParam()
         * @return MediaTransformOutput
         */
        final function getTransform( $image, $dstPath, $dstUrl, $params ) {
                return $this->doTransform( $image, $dstPath, $dstUrl, $params, self::TRANSFORM_LATER );
        }

        /**
         * Get a MediaTransformOutput object representing the transformed output. Does the
         * transform unless $flags contains self::TRANSFORM_LATER.
         *
         * @param $image File: the image object
         * @param string $dstPath filesystem destination path
         * @param string $dstUrl destination URL to use in output HTML
         * @param array $params arbitrary set of parameters validated by $this->validateParam()
         *   Note: These parameters have *not* gone through $this->normaliseParams()
         * @param $flags Integer: a bitfield, may contain self::TRANSFORM_LATER
         *
         * @return MediaTransformOutput
         */
        abstract function doTransform( $image, $dstPath, $dstUrl, $params, $flags = 0 );

        /**
         * Get the thumbnail extension and MIME type for a given source MIME type
         *
         * @param String $ext Extension of original file
         * @param String $mime Mime type of original file
         * @param Array $params Handler specific rendering parameters
         * @return array thumbnail extension and MIME type
         */
        function getThumbType( $ext, $mime, $params = null ) {
                $magic = MimeMagic::singleton();
                if ( !$ext || $magic->isMatchingExtension( $ext, $mime ) === false ) {
                        // The extension is not valid for this mime type and we do
                        // recognize the mime type
                        $extensions = $magic->getExtensionsForType( $mime );
                        if ( $extensions ) {
                                return array( strtok( $extensions, ' ' ), $mime );
                        }
                }

                // The extension is correct (true) or the mime type is unknown to
                // MediaWiki (null)
                return array( $ext, $mime );
        }

        /**
         * Get useful response headers for GET/HEAD requests for a file with the given metadata
         * @param $metadata mixed Result of the getMetadata() function of this handler for a file
         * @return Array
         */
        public function getStreamHeaders( $metadata ) {
                return array();
        }

        /**
         * True if the handled types can be transformed
         * @return bool
         */
        function canRender( $file ) {
                return true;
        }

        /**
         * True if handled types cannot be displayed directly in a browser
         * but can be rendered
         * @return bool
         */
        function mustRender( $file ) {
                return false;
        }

        /**
         * True if the type has multi-page capabilities
         * @return bool
         */
        function isMultiPage( $file ) {
                return false;
        }

        /**
         * Page count for a multi-page document, false if unsupported or unknown
         * @return bool
         */
        function pageCount( $file ) {
                return false;
        }

        /**
         * The material is vectorized and thus scaling is lossless
         * @return bool
         */
        function isVectorized( $file ) {
                return false;
        }

        /**
         * The material is an image, and is animated.
         * In particular, video material need not return true.
         * @note Before 1.20, this was a method of ImageHandler only
         * @return bool
         */
        function isAnimatedImage( $file ) {
                return false;
        }

        /**
         * If the material is animated, we can animate the thumbnail
         * @since 1.20
         * @return bool If material is not animated, handler may return any value.
         */
        function canAnimateThumbnail( $file ) {
                return true;
        }

        /**
         * False if the handler is disabled for all files
         * @return bool
         */
        function isEnabled() {
                return true;
        }

        /**
         * Get an associative array of page dimensions
         * Currently "width" and "height" are understood, but this might be
         * expanded in the future.
         * Returns false if unknown.
         *
         * It is expected that handlers for paged media (e.g. DjVuHandler)
         * will override this method so that it gives the correct results
         * for each specific page of the file, using the $page argument.
         *
         * @note For non-paged media, use getImageSize.
         *
         * @param $image File
         * @param $page What page to get dimensions of
         * @return array|bool
         */
        function getPageDimensions( $image, $page ) {
                $gis = $this->getImageSize( $image, $image->getLocalRefPath() );
                if ( $gis ) {
                        return array(
                                'width' => $gis[0],
                                'height' => $gis[1]
                        );
                } else {
                        return false;
                }
        }

        /**
         * Generic getter for text layer.
         * Currently overloaded by PDF and DjVu handlers
         * @return bool
         */
        function getPageText( $image, $page ) {
                return false;
        }

        /**
         * Get an array structure that looks like this:
         *
         * array(
         *    'visible' => array(
         *       'Human-readable name' => 'Human readable value',
         *       ...
         *    ),
         *    'collapsed' => array(
         *       'Human-readable name' => 'Human readable value',
         *       ...
         *    )
         * )
         * The UI will format this into a table where the visible fields are always
         * visible, and the collapsed fields are optionally visible.
         *
         * The function should return false if there is no metadata to display.
         */

        /**
         * @todo FIXME: I don't really like this interface, it's not very flexible
         * I think the media handler should generate HTML instead. It can do
         * all the formatting according to some standard. That makes it possible
         * to do things like visual indication of grouped and chained streams
         * in ogg container files.
         * @return bool
         */
        function formatMetadata( $image ) {
                return false;
        }

        /** sorts the visible/invisible field.
         * Split off from ImageHandler::formatMetadata, as used by more than
         * one type of handler.
         *
         * This is used by the media handlers that use the FormatMetadata class
         *
         * @param array $metadataArray metadata array
         * @return array for use displaying metadata.
         */
        function formatMetadataHelper( $metadataArray ) {
                $result = array(
                        'visible' => array(),
                        'collapsed' => array()
                );

                $formatted = FormatMetadata::getFormattedData( $metadataArray );
                // Sort fields into visible and collapsed
                $visibleFields = $this->visibleMetadataFields();
                foreach ( $formatted as $name => $value ) {
                        $tag = strtolower( $name );
                        self::addMeta( $result,
                                in_array( $tag, $visibleFields ) ? 'visible' : 'collapsed',
                                'exif',
                                $tag,
                                $value
                        );
                }
                return $result;
        }

        /**
         * Get a list of metadata items which should be displayed when
         * the metadata table is collapsed.
         *
         * @return array of strings
         * @access protected
         */
        function visibleMetadataFields() {
                $fields = array();
                $lines = explode( "\n", wfMessage( 'metadata-fields' )->inContentLanguage()->text() );
                foreach ( $lines as $line ) {
                        $matches = array();
                        if ( preg_match( '/^\\*\s*(.*?)\s*$/', $line, $matches ) ) {
                                $fields[] = $matches[1];
                        }
                }
                $fields = array_map( 'strtolower', $fields );
                return $fields;
        }

        /**
         * This is used to generate an array element for each metadata value
         * That array is then used to generate the table of metadata values
         * on the image page
         *
         * @param &$array Array An array containing elements for each type of visibility
         * and each of those elements being an array of metadata items. This function adds
         * a value to that array.
         * @param string $visibility ('visible' or 'collapsed') if this value is hidden
         * by default.
         * @param string $type type of metadata tag (currently always 'exif')
         * @param string $id the name of the metadata tag (like 'artist' for example).
         * its name in the table displayed is the message "$type-$id" (Ex exif-artist ).
         * @param string $value thingy goes into a wikitext table; it used to be escaped but
         * that was incompatible with previous practise of customized display
         * with wikitext formatting via messages such as 'exif-model-value'.
         * So the escaping is taken back out, but generally this seems a confusing
         * interface.
         * @param string $param value to pass to the message for the name of the field
         * as $1. Currently this parameter doesn't seem to ever be used.
         *
         * Note, everything here is passed through the parser later on (!)
         */
        protected static function addMeta( &$array, $visibility, $type, $id, $value, $param = false ) {
                $msg = wfMessage( "$type-$id", $param );
                if ( $msg->exists() ) {
                        $name = $msg->text();
                } else {
                        // This is for future compatibility when using instant commons.
                        // So as to not display as ugly a name if a new metadata
                        // property is defined that we don't know about
                        // (not a major issue since such a property would be collapsed
                        // by default).
                        wfDebug( __METHOD__ . ' Unknown metadata name: ' . $id . "\n" );
                        $name = wfEscapeWikiText( $id );
                }
                $array[$visibility][] = array(
                        'id' => "$type-$id",
                        'name' => $name,
                        'value' => $value
                );
        }

        /**
         * Used instead of getLongDesc if there is no handler registered for file.
         *
         * @param $file File
         * @return string
         */
        function getShortDesc( $file ) {
                global $wgLang;
                return htmlspecialchars( $wgLang->formatSize( $file->getSize() ) );
        }

        /**
         * Short description. Shown on Special:Search results.
         *
         * @param $file File
         * @return string
         */
        function getLongDesc( $file ) {
                global $wgLang;
                return wfMessage( 'file-info', htmlspecialchars( $wgLang->formatSize( $file->getSize() ) ),
                        $file->getMimeType() )->parse();
        }

        /**
         * Long description. Shown under image on image description page surounded by ().
         *
         * @param $file File
         * @return string
         */
        static function getGeneralShortDesc( $file ) {
                global $wgLang;
                return $wgLang->formatSize( $file->getSize() );
        }

        /**
         * Used instead of getShortDesc if there is no handler registered for file.
         *
         * @param $file File
         * @return string
         */
        static function getGeneralLongDesc( $file ) {
                global $wgLang;
                return wfMessage( 'file-info', $wgLang->formatSize( $file->getSize() ),
                        $file->getMimeType() )->parse();
        }

        /**
         * Calculate the largest thumbnail width for a given original file size
         * such that the thumbnail's height is at most $maxHeight.
         * @param $boxWidth Integer Width of the thumbnail box.
         * @param $boxHeight Integer Height of the thumbnail box.
         * @param $maxHeight Integer Maximum height expected for the thumbnail.
         * @return Integer.
         */
        public static function fitBoxWidth( $boxWidth, $boxHeight, $maxHeight ) {
                $idealWidth = $boxWidth * $maxHeight / $boxHeight;
                $roundedUp = ceil( $idealWidth );
                if ( round( $roundedUp * $boxHeight / $boxWidth ) > $maxHeight ) {
                        return floor( $idealWidth );
                } else {
                        return $roundedUp;
                }
        }

        /**
         * Shown in file history box on image description page.
         *
         * @param File $file
         * @return String Dimensions
         */
        function getDimensionsString( $file ) {
                return '';
        }

        /**
         * Modify the parser object post-transform.
         *
         * This is often used to do $parser->addOutputHook(),
         * in order to add some javascript to render a viewer.
         * See TimedMediaHandler or OggHandler for an example.
         *
         * @param Parser $parser
         * @param File $file
         */
        function parserTransformHook( $parser, $file ) {}

        /**
         * File validation hook called on upload.
         *
         * If the file at the given local path is not valid, or its MIME type does not
         * match the handler class, a Status object should be returned containing
         * relevant errors.
         *
         * @param string $fileName The local path to the file.
         * @return Status object
         */
        function verifyUpload( $fileName ) {
                return Status::newGood();
        }

        /**
         * Check for zero-sized thumbnails. These can be generated when
         * no disk space is available or some other error occurs
         *
         * @param string $dstPath The location of the suspect file
         * @param int $retval Return value of some shell process, file will be deleted if this is non-zero
         * @return bool True if removed, false otherwise
         */
        function removeBadFile( $dstPath, $retval = 0 ) {
                if ( file_exists( $dstPath ) ) {
                        $thumbstat = stat( $dstPath );
                        if ( $thumbstat['size'] == 0 || $retval != 0 ) {
                                $result = unlink( $dstPath );

                                if ( $result ) {
                                        wfDebugLog( 'thumbnail',
                                                sprintf( 'Removing bad %d-byte thumbnail "%s". unlink() succeeded',
                                                        $thumbstat['size'], $dstPath ) );
                                } else {
                                        wfDebugLog( 'thumbnail',
                                                sprintf( 'Removing bad %d-byte thumbnail "%s". unlink() failed',
                                                        $thumbstat['size'], $dstPath ) );
                                }
                                return true;
                        }
                }
                return false;
        }

        /**
         * Remove files from the purge list.
         *
         * This is used by some video handlers to prevent ?action=purge
         * from removing a transcoded video, which is expensive to
         * regenerate.
         *
         * @see LocalFile::purgeThumbnails
         *
         * @param array $files
         * @param array $options Purge options. Currently will always be
         *  an array with a single key 'forThumbRefresh' set to true.
         */
        public function filterThumbnailPurgeList( &$files, $options ) {
                // Do nothing
        }

        /*
         * True if the handler can rotate the media
         * @since 1.21
         * @return bool
         */
        public static function canRotate() {
                return false;
        }
}