<?php
/**
 * Temporary storage for uploaded files.
 *
 * 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
 */

/**
 * UploadStash is intended to accomplish a few things:
 *   - Enable applications to temporarily stash files without publishing them to
 *     the wiki.
 *      - Several parts of MediaWiki do this in similar ways: UploadBase,
 *        UploadWizard, and FirefoggChunkedExtension.
 *        And there are several that reimplement stashing from scratch, in
 *        idiosyncratic ways. The idea is to unify them all here.
 *        Mostly all of them are the same except for storing some custom fields,
 *        which we subsume into the data array.
 *   - Enable applications to find said files later, as long as the db table or
 *     temp files haven't been purged.
 *   - Enable the uploading user (and *ONLY* the uploading user) to access said
 *     files, and thumbnails of said files, via a URL. We accomplish this using
 *     a database table, with ownership checking as you might expect. See
 *     SpecialUploadStash, which implements a web interface to some files stored
 *     this way.
 *
 * UploadStash right now is *mostly* intended to show you one user's slice of
 * the entire stash. The user parameter is only optional because there are few
 * cases where we clean out the stash from an automated script. In the future we
 * might refactor this.
 *
 * UploadStash represents the entire stash of temporary files.
 * UploadStashFile is a filestore for the actual physical disk files.
 * UploadFromStash extends UploadBase, and represents a single stashed file as
 * it is moved from the stash to the regular file repository
 *
 * @ingroup Upload
 */
class UploadStash {
	// Format of the key for files -- has to be suitable as a filename itself (e.g. ab12cd34ef.jpg)
	const KEY_FORMAT_REGEX = '/^[\w-\.]+\.\w*$/';
	const MAX_US_PROPS_SIZE = 65535;

	/**
	 * repository that this uses to store temp files
	 * public because we sometimes need to get a LocalFile within the same repo.
	 *
	 * @var LocalRepo
	 */
	public $repo;

	// array of initialized repo objects
	protected $files = [];

	// cache of the file metadata that's stored in the database
	protected $fileMetadata = [];

	// fileprops cache
	protected $fileProps = [];

	// current user
	protected $user, $userId, $isLoggedIn;

	/**
	 * Represents a temporary filestore, with metadata in the database.
	 * Designed to be compatible with the session stashing code in UploadBase
	 * (should replace it eventually).
	 *
	 * @param FileRepo $repo
	 * @param User $user (default null)
	 */
	public function __construct( FileRepo $repo, $user = null ) {
		// this might change based on wiki's configuration.
		$this->repo = $repo;

		// if a user was passed, use it. otherwise, attempt to use the global.
		// this keeps FileRepo from breaking when it creates an UploadStash object
		if ( $user ) {
			$this->user = $user;
		} else {
			global $wgUser;
			$this->user = $wgUser;
		}

		if ( is_object( $this->user ) ) {
			$this->userId = $this->user->getId();
			$this->isLoggedIn = $this->user->isLoggedIn();
		}
	}

	/**
	 * Get a file and its metadata from the stash.
	 * The noAuth param is a bit janky but is required for automated scripts
	 * which clean out the stash.
	 *
	 * @param string $key Key under which file information is stored
	 * @param bool $noAuth (optional) Don't check authentication. Used by maintenance scripts.
	 * @throws UploadStashFileNotFoundException
	 * @throws UploadStashNotLoggedInException
	 * @throws UploadStashWrongOwnerException
	 * @throws UploadStashBadPathException
	 * @return UploadStashFile
	 */
	public function getFile( $key, $noAuth = false ) {
		if ( !preg_match( self::KEY_FORMAT_REGEX, $key ) ) {
			throw new UploadStashBadPathException(
				wfMessage( 'uploadstash-bad-path-bad-format', $key )
			);
		}

		if ( !$noAuth && !$this->isLoggedIn ) {
			throw new UploadStashNotLoggedInException(
				wfMessage( 'uploadstash-not-logged-in' )
			);
		}

		if ( !isset( $this->fileMetadata[$key] ) ) {
			if ( !$this->fetchFileMetadata( $key ) ) {
				// If nothing was received, it's likely due to replication lag.
				// Check the master to see if the record is there.
				$this->fetchFileMetadata( $key, DB_MASTER );
			}

			if ( !isset( $this->fileMetadata[$key] ) ) {
				throw new UploadStashFileNotFoundException(
					wfMessage( 'uploadstash-file-not-found', $key )
				);
			}

			// create $this->files[$key]
			$this->initFile( $key );

			// fetch fileprops
			if ( strlen( $this->fileMetadata[$key]['us_props'] ) ) {
				$this->fileProps[$key] = unserialize( $this->fileMetadata[$key]['us_props'] );
			} else { // b/c for rows with no us_props
				wfDebug( __METHOD__ . " fetched props for $key from file\n" );
				$path = $this->fileMetadata[$key]['us_path'];
				$this->fileProps[$key] = $this->repo->getFileProps( $path );
			}
		}

		if ( !$this->files[$key]->exists() ) {
			wfDebug( __METHOD__ . " tried to get file at $key, but it doesn't exist\n" );
			// @todo Is this not an UploadStashFileNotFoundException case?
			throw new UploadStashBadPathException(
				wfMessage( 'uploadstash-bad-path' )
			);
		}

		if ( !$noAuth ) {
			if ( $this->fileMetadata[$key]['us_user'] != $this->userId ) {
				throw new UploadStashWrongOwnerException(
					wfMessage( 'uploadstash-wrong-owner', $key )
				);
			}
		}

		return $this->files[$key];
	}

	/**
	 * Getter for file metadata.
	 *
	 * @param string $key Key under which file information is stored
	 * @return array
	 */
	public function getMetadata( $key ) {
		$this->getFile( $key );

		return $this->fileMetadata[$key];
	}

	/**
	 * Getter for fileProps
	 *
	 * @param string $key Key under which file information is stored
	 * @return array
	 */
	public function getFileProps( $key ) {
		$this->getFile( $key );

		return $this->fileProps[$key];
	}

	/**
	 * Stash a file in a temp directory and record that we did this in the
	 * database, along with other metadata.
	 *
	 * @param string $path Path to file you want stashed
	 * @param string $sourceType The type of upload that generated this file
	 *   (currently, I believe, 'file' or null)
	 * @throws UploadStashBadPathException
	 * @throws UploadStashFileException
	 * @throws UploadStashNotLoggedInException
	 * @return UploadStashFile|null File, or null on failure
	 */
	public function stashFile( $path, $sourceType = null ) {
		if ( !is_file( $path ) ) {
			wfDebug( __METHOD__ . " tried to stash file at '$path', but it doesn't exist\n" );
			throw new UploadStashBadPathException(
				wfMessage( 'uploadstash-bad-path' )
			);
		}

		$mwProps = new MWFileProps( MediaWiki\MediaWikiServices::getInstance()->getMimeAnalyzer() );
		$fileProps = $mwProps->getPropsFromPath( $path, true );
		wfDebug( __METHOD__ . " stashing file at '$path'\n" );

		// we will be initializing from some tmpnam files that don't have extensions.
		// most of MediaWiki assumes all uploaded files have good extensions. So, we fix this.
		$extension = self::getExtensionForPath( $path );
		if ( !preg_match( "/\\.\\Q$extension\\E$/", $path ) ) {
			$pathWithGoodExtension = "$path.$extension";
		} else {
			$pathWithGoodExtension = $path;
		}

		// If no key was supplied, make one.  a mysql insertid would be totally
		// reasonable here, except that for historical reasons, the key is this
		// random thing instead.  At least it's not guessable.
		// Some things that when combined will make a suitably unique key.
		// see: http://www.jwz.org/doc/mid.html
		list( $usec, $sec ) = explode( ' ', microtime() );
		$usec = substr( $usec, 2 );
		$key = Wikimedia\base_convert( $sec . $usec, 10, 36 ) . '.' .
			Wikimedia\base_convert( mt_rand(), 10, 36 ) . '.' .
			$this->userId . '.' .
			$extension;

		$this->fileProps[$key] = $fileProps;

		if ( !preg_match( self::KEY_FORMAT_REGEX, $key ) ) {
			throw new UploadStashBadPathException(
				wfMessage( 'uploadstash-bad-path-bad-format', $key )
			);
		}

		wfDebug( __METHOD__ . " key for '$path': $key\n" );

		// if not already in a temporary area, put it there
		$storeStatus = $this->repo->storeTemp( basename( $pathWithGoodExtension ), $path );

		if ( !$storeStatus->isOK() ) {
			// It is a convention in MediaWiki to only return one error per API
			// exception, even if multiple errors are available. We use reset()
			// to pick the "first" thing that was wrong, preferring errors to
			// warnings. This is a bit lame, as we may have more info in the
			// $storeStatus and we're throwing it away, but to fix it means
			// redesigning API errors significantly.
			// $storeStatus->value just contains the virtual URL (if anything)
			// which is probably useless to the caller.
			$error = $storeStatus->getErrorsArray();
			$error = reset( $error );
			if ( !count( $error ) ) {
				$error = $storeStatus->getWarningsArray();
				$error = reset( $error );
				if ( !count( $error ) ) {
					$error = [ 'unknown', 'no error recorded' ];
				}
			}
			// At this point, $error should contain the single "most important"
			// error, plus any parameters.
			$errorMsg = array_shift( $error );
			throw new UploadStashFileException( wfMessage( $errorMsg, $error ) );
		}
		$stashPath = $storeStatus->value;

		// fetch the current user ID
		if ( !$this->isLoggedIn ) {
			throw new UploadStashNotLoggedInException(
				wfMessage( 'uploadstash-not-logged-in' )
			);
		}

		// insert the file metadata into the db.
		wfDebug( __METHOD__ . " inserting $stashPath under $key\n" );
		$dbw = $this->repo->getMasterDB();

		$serializedFileProps = serialize( $fileProps );
		if ( strlen( $serializedFileProps ) > self::MAX_US_PROPS_SIZE ) {
			// Database is going to truncate this and make the field invalid.
			// Prioritize important metadata over file handler metadata.
			// File handler should be prepared to regenerate invalid metadata if needed.
			$fileProps['metadata'] = false;
			$serializedFileProps = serialize( $fileProps );
		}

		$this->fileMetadata[$key] = [
			'us_user' => $this->userId,
			'us_key' => $key,
			'us_orig_path' => $path,
			'us_path' => $stashPath, // virtual URL
			'us_props' => $dbw->encodeBlob( $serializedFileProps ),
			'us_size' => $fileProps['size'],
			'us_sha1' => $fileProps['sha1'],
			'us_mime' => $fileProps['mime'],
			'us_media_type' => $fileProps['media_type'],
			'us_image_width' => $fileProps['width'],
			'us_image_height' => $fileProps['height'],
			'us_image_bits' => $fileProps['bits'],
			'us_source_type' => $sourceType,
			'us_timestamp' => $dbw->timestamp(),
			'us_status' => 'finished'
		];

		$dbw->insert(
			'uploadstash',
			$this->fileMetadata[$key],
			__METHOD__
		);

		// store the insertid in the class variable so immediate retrieval
		// (possibly laggy) isn't necesary.
		$this->fileMetadata[$key]['us_id'] = $dbw->insertId();

		# create the UploadStashFile object for this file.
		$this->initFile( $key );

		return $this->getFile( $key );
	}

	/**
	 * Remove all files from the stash.
	 * Does not clean up files in the repo, just the record of them.
	 *
	 * @throws UploadStashNotLoggedInException
	 * @return bool Success
	 */
	public function clear() {
		if ( !$this->isLoggedIn ) {
			throw new UploadStashNotLoggedInException(
				wfMessage( 'uploadstash-not-logged-in' )
			);
		}

		wfDebug( __METHOD__ . ' clearing all rows for user ' . $this->userId . "\n" );
		$dbw = $this->repo->getMasterDB();
		$dbw->delete(
			'uploadstash',
			[ 'us_user' => $this->userId ],
			__METHOD__
		);

		# destroy objects.
		$this->files = [];
		$this->fileMetadata = [];

		return true;
	}

	/**
	 * Remove a particular file from the stash.  Also removes it from the repo.
	 *
	 * @param string $key
	 * @throws UploadStashNoSuchKeyException|UploadStashNotLoggedInException
	 * @throws UploadStashWrongOwnerException
	 * @return bool Success
	 */
	public function removeFile( $key ) {
		if ( !$this->isLoggedIn ) {
			throw new UploadStashNotLoggedInException(
				wfMessage( 'uploadstash-not-logged-in' )
			);
		}

		$dbw = $this->repo->getMasterDB();

		// this is a cheap query. it runs on the master so that this function
		// still works when there's lag. It won't be called all that often.
		$row = $dbw->selectRow(
			'uploadstash',
			'us_user',
			[ 'us_key' => $key ],
			__METHOD__
		);

		if ( !$row ) {
			throw new UploadStashNoSuchKeyException(
				wfMessage( 'uploadstash-no-such-key', $key )
			);
		}

		if ( $row->us_user != $this->userId ) {
			throw new UploadStashWrongOwnerException(
				wfMessage( 'uploadstash-wrong-owner', $key )
			);
		}

		return $this->removeFileNoAuth( $key );
	}

	/**
	 * Remove a file (see removeFile), but doesn't check ownership first.
	 *
	 * @param string $key
	 * @return bool Success
	 */
	public function removeFileNoAuth( $key ) {
		wfDebug( __METHOD__ . " clearing row $key\n" );

		// Ensure we have the UploadStashFile loaded for this key
		$this->getFile( $key, true );

		$dbw = $this->repo->getMasterDB();

		$dbw->delete(
			'uploadstash',
			[ 'us_key' => $key ],
			__METHOD__
		);

		/** @todo Look into UnregisteredLocalFile and find out why the rv here is
		 *  sometimes wrong (false when file was removed). For now, ignore.
		 */
		$this->files[$key]->remove();

		unset( $this->files[$key] );
		unset( $this->fileMetadata[$key] );

		return true;
	}

	/**
	 * List all files in the stash.
	 *
	 * @throws UploadStashNotLoggedInException
	 * @return array
	 */
	public function listFiles() {
		if ( !$this->isLoggedIn ) {
			throw new UploadStashNotLoggedInException(
				wfMessage( 'uploadstash-not-logged-in' )
			);
		}

		$dbr = $this->repo->getReplicaDB();
		$res = $dbr->select(
			'uploadstash',
			'us_key',
			[ 'us_user' => $this->userId ],
			__METHOD__
		);

		if ( !is_object( $res ) || $res->numRows() == 0 ) {
			// nothing to do.
			return false;
		}

		// finish the read before starting writes.
		$keys = [];
		foreach ( $res as $row ) {
			array_push( $keys, $row->us_key );
		}

		return $keys;
	}

	/**
	 * Find or guess extension -- ensuring that our extension matches our MIME type.
	 * Since these files are constructed from php tempnames they may not start off
	 * with an extension.
	 * XXX this is somewhat redundant with the checks that ApiUpload.php does with incoming
	 * uploads versus the desired filename. Maybe we can get that passed to us...
	 * @param string $path
	 * @throws UploadStashFileException
	 * @return string
	 */
	public static function getExtensionForPath( $path ) {
		global $wgFileBlacklist;
		// Does this have an extension?
		$n = strrpos( $path, '.' );
		$extension = null;
		if ( $n !== false ) {
			$extension = $n ? substr( $path, $n + 1 ) : '';
		} else {
			// If not, assume that it should be related to the MIME type of the original file.
			$magic = MediaWiki\MediaWikiServices::getInstance()->getMimeAnalyzer();
			$mimeType = $magic->guessMimeType( $path );
			$extensions = explode( ' ', $magic->getExtensionsForType( $mimeType ) );
			if ( count( $extensions ) ) {
				$extension = $extensions[0];
			}
		}

		if ( is_null( $extension ) ) {
			throw new UploadStashFileException(
				wfMessage( 'uploadstash-no-extension' )
			);
		}

		$extension = File::normalizeExtension( $extension );
		if ( in_array( $extension, $wgFileBlacklist ) ) {
			// The file should already be checked for being evil.
			// However, if somehow we got here, we definitely
			// don't want to give it an extension of .php and
			// put it in a web accesible directory.
			return '';
		}

		return $extension;
	}

	/**
	 * Helper function: do the actual database query to fetch file metadata.
	 *
	 * @param string $key
	 * @param int $readFromDB Constant (default: DB_REPLICA)
	 * @return bool
	 */
	protected function fetchFileMetadata( $key, $readFromDB = DB_REPLICA ) {
		// populate $fileMetadata[$key]
		$dbr = null;
		if ( $readFromDB === DB_MASTER ) {
			// sometimes reading from the master is necessary, if there's replication lag.
			$dbr = $this->repo->getMasterDB();
		} else {
			$dbr = $this->repo->getReplicaDB();
		}

		$row = $dbr->selectRow(
			'uploadstash',
			[
				'us_user', 'us_key', 'us_orig_path', 'us_path', 'us_props',
				'us_size', 'us_sha1', 'us_mime', 'us_media_type',
				'us_image_width', 'us_image_height', 'us_image_bits',
				'us_source_type', 'us_timestamp', 'us_status',
			],
			[ 'us_key' => $key ],
			__METHOD__
		);

		if ( !is_object( $row ) ) {
			// key wasn't present in the database. this will happen sometimes.
			return false;
		}

		$this->fileMetadata[$key] = (array)$row;
		$this->fileMetadata[$key]['us_props'] = $dbr->decodeBlob( $row->us_props );

		return true;
	}

	/**
	 * Helper function: Initialize the UploadStashFile for a given file.
	 *
	 * @param string $key Key under which to store the object
	 * @throws UploadStashZeroLengthFileException
	 * @return bool
	 */
	protected function initFile( $key ) {
		$file = new UploadStashFile( $this->repo, $this->fileMetadata[$key]['us_path'], $key );
		if ( $file->getSize() === 0 ) {
			throw new UploadStashZeroLengthFileException(
				wfMessage( 'uploadstash-zero-length' )
			);
		}
		$this->files[$key] = $file;

		return true;
	}
}

/**
 * @ingroup Upload
 */
class UploadStashFile extends UnregisteredLocalFile {
	private $fileKey;
	private $urlName;
	protected $url;

	/**
	 * A LocalFile wrapper around a file that has been temporarily stashed,
	 * so we can do things like create thumbnails for it. Arguably
	 * UnregisteredLocalFile should be handling its own file repo but that
	 * class is a bit retarded currently.
	 *
	 * @param FileRepo $repo Repository where we should find the path
	 * @param string $path Path to file
	 * @param string $key Key to store the path and any stashed data under
	 * @throws UploadStashBadPathException
	 * @throws UploadStashFileNotFoundException
	 */
	public function __construct( $repo, $path, $key ) {
		$this->fileKey = $key;

		// resolve mwrepo:// urls
		if ( $repo->isVirtualUrl( $path ) ) {
			$path = $repo->resolveVirtualUrl( $path );
		} else {
			// check if path appears to be sane, no parent traversals,
			// and is in this repo's temp zone.
			$repoTempPath = $repo->getZonePath( 'temp' );
			if ( ( !$repo->validateFilename( $path ) ) ||
				( strpos( $path, $repoTempPath ) !== 0 )
			) {
				wfDebug( "UploadStash: tried to construct an UploadStashFile "
					. "from a file that should already exist at '$path', but path is not valid\n" );
				throw new UploadStashBadPathException(
					wfMessage( 'uploadstash-bad-path-invalid' )
				);
			}

			// check if path exists! and is a plain file.
			if ( !$repo->fileExists( $path ) ) {
				wfDebug( "UploadStash: tried to construct an UploadStashFile from "
					. "a file that should already exist at '$path', but path is not found\n" );
				throw new UploadStashFileNotFoundException(
					wfMessage( 'uploadstash-file-not-found-not-exists' )
				);
			}
		}

		parent::__construct( false, $repo, $path, false );

		$this->name = basename( $this->path );
	}

	/**
	 * A method needed by the file transforming and scaling routines in File.php
	 * We do not necessarily care about doing the description at this point
	 * However, we also can't return the empty string, as the rest of MediaWiki
	 * demands this (and calls to imagemagick convert require it to be there)
	 *
	 * @return string Dummy value
	 */
	public function getDescriptionUrl() {
		return $this->getUrl();
	}

	/**
	 * Get the path for the thumbnail (actually any transformation of this file)
	 * The actual argument is the result of thumbName although we seem to have
	 * buggy code elsewhere that expects a boolean 'suffix'
	 *
	 * @param string $thumbName Name of thumbnail (e.g. "120px-123456.jpg" ),
	 *   or false to just get the path
	 * @return string Path thumbnail should take on filesystem, or containing
	 *   directory if thumbname is false
	 */
	public function getThumbPath( $thumbName = false ) {
		$path = dirname( $this->path );
		if ( $thumbName !== false ) {
			$path .= "/$thumbName";
		}

		return $path;
	}

	/**
	 * Return the file/url base name of a thumbnail with the specified parameters.
	 * We override this because we want to use the pretty url name instead of the
	 * ugly file name.
	 *
	 * @param array $params Handler-specific parameters
	 * @param int $flags Bitfield that supports THUMB_* constants
	 * @return string|null Base name for URL, like '120px-12345.jpg', or null if there is no handler
	 */
	function thumbName( $params, $flags = 0 ) {
		return $this->generateThumbName( $this->getUrlName(), $params );
	}

	/**
	 * Helper function -- given a 'subpage', return the local URL,
	 * e.g. /wiki/Special:UploadStash/subpage
	 * @param string $subPage
	 * @return string Local URL for this subpage in the Special:UploadStash space.
	 */
	private function getSpecialUrl( $subPage ) {
		return SpecialPage::getTitleFor( 'UploadStash', $subPage )->getLocalURL();
	}

	/**
	 * Get a URL to access the thumbnail
	 * This is required because the model of how files work requires that
	 * the thumbnail urls be predictable. However, in our model the URL is
	 * not based on the filename (that's hidden in the db)
	 *
	 * @param string $thumbName Basename of thumbnail file -- however, we don't
	 *   want to use the file exactly
	 * @return string URL to access thumbnail, or URL with partial path
	 */
	public function getThumbUrl( $thumbName = false ) {
		wfDebug( __METHOD__ . " getting for $thumbName \n" );

		return $this->getSpecialUrl( 'thumb/' . $this->getUrlName() . '/' . $thumbName );
	}

	/**
	 * The basename for the URL, which we want to not be related to the filename.
	 * Will also be used as the lookup key for a thumbnail file.
	 *
	 * @return string Base url name, like '120px-123456.jpg'
	 */
	public function getUrlName() {
		if ( !$this->urlName ) {
			$this->urlName = $this->fileKey;
		}

		return $this->urlName;
	}

	/**
	 * Return the URL of the file, if for some reason we wanted to download it
	 * We tend not to do this for the original file, but we do want thumb icons
	 *
	 * @return string Url
	 */
	public function getUrl() {
		if ( !isset( $this->url ) ) {
			$this->url = $this->getSpecialUrl( 'file/' . $this->getUrlName() );
		}

		return $this->url;
	}

	/**
	 * Parent classes use this method, for no obvious reason, to return the path
	 * (relative to wiki root, I assume). But with this class, the URL is
	 * unrelated to the path.
	 *
	 * @return string Url
	 */
	public function getFullUrl() {
		return $this->getUrl();
	}

	/**
	 * Getter for file key (the unique id by which this file's location &
	 * metadata is stored in the db)
	 *
	 * @return string File key
	 */
	public function getFileKey() {
		return $this->fileKey;
	}

	/**
	 * Remove the associated temporary file
	 * @return status Success
	 */
	public function remove() {
		if ( !$this->repo->fileExists( $this->path ) ) {
			// Maybe the file's already been removed? This could totally happen in UploadBase.
			return true;
		}

		return $this->repo->freeTemp( $this->path );
	}

	public function exists() {
		return $this->repo->fileExists( $this->path );
	}
}

/**
 * @ingroup Upload
 */
class UploadStashException extends MWException implements ILocalizedException {
	/** @var string|array|MessageSpecifier */
	protected $messageSpec;

	/**
	 * @param string|array|MessageSpecifier $messageSpec See Message::newFromSpecifier
	 * @param int $code Exception code
	 * @param Exception|Throwable $previous The previous exception used for the exception chaining.
	 */
	public function __construct( $messageSpec, $code = 0, $previous = null ) {
		$this->messageSpec = $messageSpec;

		$msg = $this->getMessageObject()->text();
		$msg = preg_replace( '!</?(var|kbd|samp|code)>!', '"', $msg );
		$msg = Sanitizer::stripAllTags( $msg );
		parent::__construct( $msg, $code, $previous );
	}

	public function getMessageObject() {
		return Message::newFromSpecifier( $this->messageSpec );
	}
}

/**
 * @ingroup Upload
 */
class UploadStashFileNotFoundException extends UploadStashException {
}

/**
 * @ingroup Upload
 */
class UploadStashBadPathException extends UploadStashException {
}

/**
 * @ingroup Upload
 */
class UploadStashFileException extends UploadStashException {
}

/**
 * @ingroup Upload
 */
class UploadStashZeroLengthFileException extends UploadStashException {
}

/**
 * @ingroup Upload
 */
class UploadStashNotLoggedInException extends UploadStashException {
}

/**
 * @ingroup Upload
 */
class UploadStashWrongOwnerException extends UploadStashException {
}

/**
 * @ingroup Upload
 */
class UploadStashNoSuchKeyException extends UploadStashException {
}