<?php
/**
 * Implements Special:UploadStash
 *
 * Web access for files temporarily stored by UploadStash.
 *
 * For example -- files that were uploaded with the UploadWizard extension are stored temporarily
 * before committing them to the db. But we want to see their thumbnails and get other information
 * about them.
 *
 * Since this is based on the user's session, in effect this creates a private temporary file area.
 * However, the URLs for the files cannot be shared.
 *
 * @file
 * @ingroup SpecialPage
 * @ingroup Upload
 */

class SpecialUploadStash extends UnlistedSpecialPage {
	// UploadStash
	private $stash;

	// Since we are directly writing the file to STDOUT,
	// we should not be reading in really big files and serving them out.
	//
	// We also don't want people using this as a file drop, even if they
	// share credentials.
	//
	// This service is really for thumbnails and other such previews while
	// uploading.
	const MAX_SERVE_BYTES = 1048576; // 1MB

	public function __construct() {
		parent::__construct( 'UploadStash', 'upload' );
		try {
			$this->stash = RepoGroup::singleton()->getLocalRepo()->getUploadStash();
		} catch ( UploadStashNotAvailableException $e ) {
		}
	}

	/**
	 * Execute page -- can output a file directly or show a listing of them.
	 *
	 * @param $subPage String: subpage, e.g. in http://example.com/wiki/Special:UploadStash/foo.jpg, the "foo.jpg" part
	 * @return Boolean: success
	 */
	public function execute( $subPage ) {
		$this->checkPermissions();

		if ( $subPage === null || $subPage === '' ) {
			return $this->showUploads();
		}
		return $this->showUpload( $subPage );
	}

	/**
	 * If file available in stash, cats it out to the client as a simple HTTP response.
	 * n.b. Most sanity checking done in UploadStashLocalFile, so this is straightforward.
	 *
	 * @param $key String: the key of a particular requested file
	 */
	public function showUpload( $key ) {
		// prevent callers from doing standard HTML output -- we'll take it from here
		$this->getOutput()->disable();

		try {
			$params = $this->parseKey( $key );
			if ( $params['type'] === 'thumb' ) {
				return $this->outputThumbFromStash( $params['file'], $params['params'] );
			} else {
				return $this->outputLocalFile( $params['file'] );
			}
		} catch( UploadStashFileNotFoundException $e ) {
			$code = 404;
			$message = $e->getMessage();
		} catch( UploadStashZeroLengthFileException $e ) {
			$code = 500;
			$message = $e->getMessage();
		} catch( UploadStashBadPathException $e ) {
			$code = 500;
			$message = $e->getMessage();
		} catch( SpecialUploadStashTooLargeException $e ) {
			$code = 500;
			$message = 'Cannot serve a file larger than ' . self::MAX_SERVE_BYTES . ' bytes. ' . $e->getMessage();
		} catch( Exception $e ) {
			$code = 500;
			$message = $e->getMessage();
		}

		throw new HttpError( $code, $message );
	}

	/**
	 * Parse the key passed to the SpecialPage. Returns an array containing
	 * the associated file object, the type ('file' or 'thumb') and if
	 * application the transform parameters
	 *
	 * @param string $key
	 * @return array
	 */
	private function parseKey( $key ) {
		$type = strtok( $key, '/' );

		if ( $type !== 'file' && $type !== 'thumb' ) {
			throw new UploadStashBadPathException( "Unknown type '$type'" );
		}
		$fileName = strtok( '/' );
		$thumbPart = strtok( '/' );
		$file = $this->stash->getFile( $fileName );
		if ( $type === 'thumb' ) {
			$srcNamePos = strrpos( $thumbPart, $fileName );
			if ( $srcNamePos === false || $srcNamePos < 1 ) {
				throw new UploadStashBadPathException( 'Unrecognized thumb name' );
			}
			$paramString = substr( $thumbPart, 0, $srcNamePos - 1 );

			$handler = $file->getHandler();
			$params = $handler->parseParamString( $paramString );
			return array( 'file' => $file, 'type' => $type, 'params' => $params );
		}

		return array( 'file' => $file, 'type' => $type );
	}

	/**
	 * Get a thumbnail for file, either generated locally or remotely, and stream it out
	 *
	 * @param $file
	 * @param $params array
	 *
	 * @return boolean success
	 */
	private function outputThumbFromStash( $file, $params ) {

		// this global, if it exists, points to a "scaler", as you might find in the Wikimedia Foundation cluster. See outputRemoteScaledThumb()
		// this is part of our horrible NFS-based system, we create a file on a mount point here, but fetch the scaled file from somewhere else that
		// happens to share it over NFS
		global $wgUploadStashScalerBaseUrl;

		$flags = 0;
		if ( $wgUploadStashScalerBaseUrl ) {
			$this->outputRemoteScaledThumb( $file, $params, $flags );
		} else {
			$this->outputLocallyScaledThumb( $file, $params, $flags );
		}
	}

	/**
	 * Scale a file (probably with a locally installed imagemagick, or similar) and output it to STDOUT.
	 * @param $file: File object
	 * @param $params: scaling parameters ( e.g. array( width => '50' ) );
	 * @param $flags: scaling flags ( see File:: constants )
	 * @throws MWException
	 * @return boolean success
	 */
	private function outputLocallyScaledThumb( $file, $params, $flags ) {

		// n.b. this is stupid, we insist on re-transforming the file every time we are invoked. We rely
		// on HTTP caching to ensure this doesn't happen.

		$flags |= File::RENDER_NOW;

		$thumbnailImage = $file->transform( $params, $flags );
		if ( !$thumbnailImage ) {
			throw new MWException( 'Could not obtain thumbnail' );
		}

		// we should have just generated it locally
		if ( !$thumbnailImage->getStoragePath() ) {
			throw new UploadStashFileNotFoundException( "no local path for scaled item" );
		}

		// now we should construct a File, so we can get mime and other such info in a standard way
		// n.b. mimetype may be different from original (ogx original -> jpeg thumb)
		$thumbFile = new UnregisteredLocalFile( false, 
			$this->stash->repo, $thumbnailImage->getStoragePath(), false );
		if ( !$thumbFile ) {
			throw new UploadStashFileNotFoundException( "couldn't create local file object for thumbnail" );
		}

		return $this->outputLocalFile( $thumbFile );

	}

	/**
	 * Scale a file with a remote "scaler", as exists on the Wikimedia Foundation cluster, and output it to STDOUT.
	 * Note: unlike the usual thumbnail process, the web client never sees the cluster URL; we do the whole HTTP transaction to the scaler ourselves
	 *  and cat the results out.
	 * Note: We rely on NFS to have propagated the file contents to the scaler. However, we do not rely on the thumbnail being created in NFS and then
	 *   propagated back to our filesystem. Instead we take the results of the HTTP request instead.
	 * Note: no caching is being done here, although we are instructing the client to cache it forever.
	 * @param $file: File object
	 * @param $params: scaling parameters ( e.g. array( width => '50' ) );
	 * @param $flags: scaling flags ( see File:: constants )
	 * @throws MWException
	 * @return boolean success
	 */
	private function outputRemoteScaledThumb( $file, $params, $flags ) {

		// this global probably looks something like 'http://upload.wikimedia.org/wikipedia/test/thumb/temp'
		// do not use trailing slash
		global $wgUploadStashScalerBaseUrl;
		$scalerBaseUrl = $wgUploadStashScalerBaseUrl;

		if( preg_match( '/^\/\//', $scalerBaseUrl ) ) {
			// this is apparently a protocol-relative URL, which makes no sense in this context,
			// since this is used for communication that's internal to the application.
			// default to http.
			$scalerBaseUrl = wfExpandUrl( $scalerBaseUrl, PROTO_CANONICAL );
		}

		// We need to use generateThumbName() instead of thumbName(), because
		// the suffix needs to match the file name for the remote thumbnailer
		// to work
		$scalerThumbName = $file->generateThumbName( $file->getName(), $params );
		$scalerThumbUrl = $scalerBaseUrl . '/' . $file->getUrlRel() .
			'/' . rawurlencode( $scalerThumbName );

		// make a curl call to the scaler to create a thumbnail
		$httpOptions = array(
			'method' => 'GET',
			'timeout' => 'default'
		);
		$req = MWHttpRequest::factory( $scalerThumbUrl, $httpOptions );
		$status = $req->execute();
		if ( ! $status->isOK() ) {
			$errors = $status->getErrorsArray();
			$errorStr = "Fetching thumbnail failed: " . print_r( $errors, 1 );
			$errorStr .= "\nurl = $scalerThumbUrl\n";
			throw new MWException( $errorStr );
		}
		$contentType = $req->getResponseHeader( "content-type" );
		if ( ! $contentType ) {
			throw new MWException( "Missing content-type header" );
		}
		return $this->outputContents( $req->getContent(), $contentType );
	}

	/**
	 * Output HTTP response for file
	 * Side effect: writes HTTP response to STDOUT.
	 *
	 * @param $file File object with a local path (e.g. UnregisteredLocalFile, LocalFile. Oddly these don't share an ancestor!)
	 */
	private function outputLocalFile( File $file ) {
		if ( $file->getSize() > self::MAX_SERVE_BYTES ) {
			throw new SpecialUploadStashTooLargeException();
		}
		return $file->getRepo()->streamFile( $file->getPath(),
			array( 'Content-Transfer-Encoding: binary',
				'Expires: Sun, 17-Jan-2038 19:14:07 GMT' )
		);
	}

	/**
	 * Output HTTP response of raw content
	 * Side effect: writes HTTP response to STDOUT.
	 * @param String $content: content
	 * @param String $mimeType: mime type
	 */
	private function outputContents( $content, $contentType ) {
		$size = strlen( $content );
		if ( $size > self::MAX_SERVE_BYTES ) {
			throw new SpecialUploadStashTooLargeException();
		}
		self::outputFileHeaders( $contentType, $size );
		print $content;
		return true;
	}

	/**
	 * Output headers for streaming
	 * XXX unsure about encoding as binary; if we received from HTTP perhaps we should use that encoding, concatted with semicolon to mimeType as it usually is.
	 * Side effect: preps PHP to write headers to STDOUT.
	 * @param String $contentType : string suitable for content-type header
	 * @param String $size: length in bytes
	 */
	private static function outputFileHeaders( $contentType, $size ) {
		header( "Content-Type: $contentType", true );
		header( 'Content-Transfer-Encoding: binary', true );
		header( 'Expires: Sun, 17-Jan-2038 19:14:07 GMT', true );
		header( "Content-Length: $size", true );
	}

	/**
	 * Static callback for the HTMLForm in showUploads, to process
	 * Note the stash has to be recreated since this is being called in a static context.
	 * This works, because there really is only one stash per logged-in user, despite appearances.
	 *
	 * @return Status
	 */
	public static function tryClearStashedUploads( $formData ) {
		if ( isset( $formData['Clear'] ) ) {
			$stash = RepoGroup::singleton()->getLocalRepo()->getUploadStash();
			wfDebug( "stash has: " . print_r( $stash->listFiles(), true ) );
			if ( ! $stash->clear() ) {
				return Status::newFatal( 'uploadstash-errclear' );
			}
		}
		return Status::newGood();
	}

	/**
	 * Default action when we don't have a subpage -- just show links to the uploads we have,
	 * Also show a button to clear stashed files
	 * @param Status : $status - the result of processRequest
	 */
	private function showUploads( $status = null ) {
		if ( $status === null ) {
			$status = Status::newGood();
		}

		// sets the title, etc.
		$this->setHeaders();
		$this->outputHeader();

		// create the form, which will also be used to execute a callback to process incoming form data
		// this design is extremely dubious, but supposedly HTMLForm is our standard now?

		$form = new HTMLForm( array(
			'Clear' => array(
				'type' => 'hidden',
				'default' => true,
				'name' => 'clear',
			)
		), $this->getContext(), 'clearStashedUploads' );
		$form->setSubmitCallback( array( __CLASS__ , 'tryClearStashedUploads' ) );
		$form->setTitle( $this->getTitle() );
		$form->setSubmitText( wfMsg( 'uploadstash-clear' ) );

		$form->prepareForm();
		$formResult = $form->tryAuthorizedSubmit();

		// show the files + form, if there are any, or just say there are none
		$refreshHtml = Html::element( 'a',
			array( 'href' => $this->getTitle()->getLocalURL() ),
			wfMsg( 'uploadstash-refresh' ) );
		$files = $this->stash->listFiles();
		if ( $files && count( $files ) ) {
			sort( $files );
			$fileListItemsHtml = '';
			foreach ( $files as $file ) {
				// TODO: Use Linker::link or even construct the list in plain wikitext
				$fileListItemsHtml .= Html::rawElement( 'li', array(),
					Html::element( 'a', array( 'href' =>
						$this->getTitle( "file/$file" )->getLocalURL() ), $file )
				);
			}
			$this->getOutput()->addHtml( Html::rawElement( 'ul', array(), $fileListItemsHtml ) );
			$form->displayForm( $formResult );
			$this->getOutput()->addHtml( Html::rawElement( 'p', array(), $refreshHtml ) );
		} else {
			$this->getOutput()->addHtml( Html::rawElement( 'p', array(),
				Html::element( 'span', array(), wfMsg( 'uploadstash-nofiles' ) )
				. ' '
				. $refreshHtml
			) );
		}

		return true;
	}
}

class SpecialUploadStashTooLargeException extends MWException {};
