<?php
  /**
   * Minification of CSS stylesheets.
   *
   * Copyright 2010 Wikimedia Foundation
   *
   * Licensed under the Apache License, Version 2.0 (the "License"); you may
   * not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   * 		http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software distributed
   * under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS
   * OF ANY KIND, either express or implied. See the License for the
   * specific language governing permissions and limitations under the License.
   *
   * @file
   * @version 0.1.1 -- 2010-09-11
   * @author Trevor Parscal <tparscal@wikimedia.org>
   * @copyright Copyright 2010 Wikimedia Foundation
   * @license http://www.apache.org/licenses/LICENSE-2.0
   */
  
  /**
   * Transforms CSS data
   *
   * This class provides minification, URL remapping, URL extracting, and data-URL embedding.
   */
  class CSSMin {
  
  	/* Constants */
  
  	/**
  	 * Maximum file size to still qualify for in-line embedding as a data-URI
  	 *
  	 * 24,576 is used because Internet Explorer has a 32,768 byte limit for data URIs,
  	 * which when base64 encoded will result in a 1/3 increase in size.
  	 */
  	const EMBED_SIZE_LIMIT = 24576;
  	const URL_REGEX = 'url\(\s*[\'"]?(?P<file>[^\?\)\'"]*)(?P<query>\??[^\)\'"]*)[\'"]?\s*\)';
  
  	/* Protected Static Members */
  
  	/** @var array List of common image files extensions and mime-types */
  	protected static $mimeTypes = array(
  		'gif' => 'image/gif',
  		'jpe' => 'image/jpeg',
  		'jpeg' => 'image/jpeg',
  		'jpg' => 'image/jpeg',
  		'png' => 'image/png',
  		'tif' => 'image/tiff',
  		'tiff' => 'image/tiff',
  		'xbm' => 'image/x-xbitmap',
  	);
  
  	/* Static Methods */
  
  	/**
  	 * Gets a list of local file paths which are referenced in a CSS style sheet
  	 *
  	 * @param $source string CSS data to remap
  	 * @param $path string File path where the source was read from (optional)
  	 * @return array List of local file references
  	 */
  	public static function getLocalFileReferences( $source, $path = null ) {
  		$files = array();
  		$rFlags = PREG_OFFSET_CAPTURE | PREG_SET_ORDER;
  		if ( preg_match_all( '/' . self::URL_REGEX . '/', $source, $matches, $rFlags ) ) {
  			foreach ( $matches as $match ) {
  				$file = ( isset( $path )
  					? rtrim( $path, '/' ) . '/'
  					: '' ) . "{$match['file'][0]}";
  
  				// Only proceed if we can access the file
  				if ( !is_null( $path ) && file_exists( $file ) ) {
  					$files[] = $file;
  				}
  			}
  		}
  		return $files;
  	}
  
  	/**
  	 * @param $file string
  	 * @return bool|string
  	 */
  	protected static function getMimeType( $file ) {
  		$realpath = realpath( $file );
  		// Try a couple of different ways to get the mime-type of a file, in order of
  		// preference
  		if (
  			$realpath
  			&& function_exists( 'finfo_file' )
  			&& function_exists( 'finfo_open' )
  			&& defined( 'FILEINFO_MIME_TYPE' )
  		) {
  			// As of PHP 5.3, this is how you get the mime-type of a file; it uses the Fileinfo
  			// PECL extension
  			return finfo_file( finfo_open( FILEINFO_MIME_TYPE ), $realpath );
  		} elseif ( function_exists( 'mime_content_type' ) ) {
  			// Before this was deprecated in PHP 5.3, this was how you got the mime-type of a file
  			return mime_content_type( $file );
  		} else {
  			// Worst-case scenario has happened, use the file extension to infer the mime-type
  			$ext = strtolower( pathinfo( $file, PATHINFO_EXTENSION ) );
  			if ( isset( self::$mimeTypes[$ext] ) ) {
  				return self::$mimeTypes[$ext];
  			}
  		}
  		return false;
  	}
  
  	/**
  	 * Remaps CSS URL paths and automatically embeds data URIs for URL rules
  	 * preceded by an /* @embed * / comment
  	 *
  	 * @param $source string CSS data to remap
  	 * @param $local string File path where the source was read from
  	 * @param $remote string URL path to the file
  	 * @param $embedData bool If false, never do any data URI embedding, even if / * @embed * / is found
  	 * @return string Remapped CSS data
  	 */
  	public static function remap( $source, $local, $remote, $embedData = true ) {
  		$pattern = '/((?P<embed>\s*\/\*\s*\@embed\s*\*\/)(?P<pre>[^\;\}]*))?' .
  			self::URL_REGEX . '(?P<post>[^;]*)[\;]?/';
  		$offset = 0;
  		while ( preg_match( $pattern, $source, $match, PREG_OFFSET_CAPTURE, $offset ) ) {
  			// Skip fully-qualified URLs and data URIs
  			$urlScheme = parse_url( $match['file'][0], PHP_URL_SCHEME );
  			if ( $urlScheme ) {
  				// Move the offset to the end of the match, leaving it alone
  				$offset = $match[0][1] + strlen( $match[0][0] );
  				continue;
  			}
  			// URLs with absolute paths like /w/index.php need to be expanded
  			// to absolute URLs but otherwise left alone
  			if ( $match['file'][0] !== '' && $match['file'][0][0] === '/' ) {
  				// Replace the file path with an expanded (possibly protocol-relative) URL
  				// ...but only if wfExpandUrl() is even available.
  				// This will not be the case if we're running outside of MW
  				$lengthIncrease = 0;
  				if ( function_exists( 'wfExpandUrl' ) ) {
  					$expanded = wfExpandUrl( $match['file'][0], PROTO_RELATIVE );
  					$origLength = strlen( $match['file'][0] );
  					$lengthIncrease = strlen( $expanded ) - $origLength;
  					$source = substr_replace( $source, $expanded,
  						$match['file'][1], $origLength
  					);
  				}
  				// Move the offset to the end of the match, leaving it alone
  				$offset = $match[0][1] + strlen( $match[0][0] ) + $lengthIncrease;
  				continue;
  			}
  			// Shortcuts
  			$embed = $match['embed'][0];
  			$pre = $match['pre'][0];
  			$post = $match['post'][0];
  			$query = $match['query'][0];
  			$url = "{$remote}/{$match['file'][0]}";
  			$file = "{$local}/{$match['file'][0]}";
  			// bug 27052 - Guard against double slashes, because foo//../bar
  			// apparently resolves to foo/bar on (some?) clients
  			$url = preg_replace( '#([^:])//+#', '\1/', $url );
  			$replacement = false;
  			if ( $local !== false && file_exists( $file ) ) {
  				// Add version parameter as a time-stamp in ISO 8601 format,
  				// using Z for the timezone, meaning GMT
  				$url .= '?' . gmdate( 'Y-m-d\TH:i:s\Z', round( filemtime( $file ), -2 ) );
  				// Embedding requires a bit of extra processing, so let's skip that if we can
  				if ( $embedData && $embed ) {
  					$type = self::getMimeType( $file );
  					// Detect when URLs were preceeded with embed tags, and also verify file size is
  					// below the limit
  					if (
  						$type
  						&& $match['embed'][1] > 0
  						&& filesize( $file ) < self::EMBED_SIZE_LIMIT
  					) {
  						// Strip off any trailing = symbols (makes browsers freak out)
  						$data = base64_encode( file_get_contents( $file ) );
  						// Build 2 CSS properties; one which uses a base64 encoded data URI in place
  						// of the @embed comment to try and retain line-number integrity, and the
  						// other with a remapped an versioned URL and an Internet Explorer hack
  						// making it ignored in all browsers that support data URIs
  						$replacement = "{$pre}url(data:{$type};base64,{$data}){$post};";
  						$replacement .= "{$pre}url({$url}){$post}!ie;";
  					}
  				}
  				if ( $replacement === false ) {
  					// Assume that all paths are relative to $remote, and make them absolute
  					$replacement = "{$embed}{$pre}url({$url}){$post};";
  				}
  			} elseif ( $local === false ) {
  				// Assume that all paths are relative to $remote, and make them absolute
  				$replacement = "{$embed}{$pre}url({$url}{$query}){$post};";
  			}
  			if ( $replacement !== false ) {
  				// Perform replacement on the source
  				$source = substr_replace(
  					$source, $replacement, $match[0][1], strlen( $match[0][0] )
  				);
  				// Move the offset to the end of the replacement in the source
  				$offset = $match[0][1] + strlen( $replacement );
  				continue;
  			}
  			// Move the offset to the end of the match, leaving it alone
  			$offset = $match[0][1] + strlen( $match[0][0] );
  		}
  		return $source;
  	}
  
  	/**
  	 * Removes whitespace from CSS data
  	 *
  	 * @param $css string CSS data to minify
  	 * @return string Minified CSS data
  	 */
  	public static function minify( $css ) {
  		return trim(
  			str_replace(
  				array( '; ', ': ', ' {', '{ ', ', ', '} ', ';}' ),
  				array( ';', ':', '{', '{', ',', '}', '}' ),
  				preg_replace( array( '/\s+/', '/\/\*.*?\*\//s' ), array( ' ', '' ), $css )
  			)
  		);
  	}
  }