1<?php
2
3namespace Drupal\Core\Asset;
4
5use Drupal\Component\Utility\Unicode;
6use Drupal\Core\StreamWrapper\StreamWrapperManager;
7
8/**
9 * Optimizes a CSS asset.
10 */
11class CssOptimizer implements AssetOptimizerInterface {
12
13  /**
14   * The base path used by rewriteFileURI().
15   *
16   * @var string
17   */
18  public $rewriteFileURIBasePath;
19
20  /**
21   * {@inheritdoc}
22   */
23  public function optimize(array $css_asset) {
24    if ($css_asset['type'] != 'file') {
25      throw new \Exception('Only file CSS assets can be optimized.');
26    }
27    if (!$css_asset['preprocess']) {
28      throw new \Exception('Only file CSS assets with preprocessing enabled can be optimized.');
29    }
30
31    return $this->processFile($css_asset);
32  }
33
34  /**
35   * Processes the contents of a CSS asset for cleanup.
36   *
37   * @param string $contents
38   *   The contents of the CSS asset.
39   *
40   * @return string
41   *   Contents of the CSS asset.
42   */
43  public function clean($contents) {
44    // Remove multiple charset declarations for standards compliance (and fixing
45    // Safari problems).
46    $contents = preg_replace('/^@charset\s+[\'"](\S*?)\b[\'"];/i', '', $contents);
47
48    return $contents;
49  }
50
51  /**
52   * Build aggregate CSS file.
53   */
54  protected function processFile($css_asset) {
55    $contents = $this->loadFile($css_asset['data'], TRUE);
56
57    $contents = $this->clean($contents);
58
59    // Get the parent directory of this file, relative to the Drupal root.
60    $css_base_path = substr($css_asset['data'], 0, strrpos($css_asset['data'], '/'));
61    // Store base path.
62    $this->rewriteFileURIBasePath = $css_base_path . '/';
63
64    // Anchor all paths in the CSS with its base URL, ignoring external and absolute paths.
65    return preg_replace_callback('/url\(\s*[\'"]?(?![a-z]+:|\/+)([^\'")]+)[\'"]?\s*\)/i', [$this, 'rewriteFileURI'], $contents);
66  }
67
68  /**
69   * Loads the stylesheet and resolves all @import commands.
70   *
71   * Loads a stylesheet and replaces @import commands with the contents of the
72   * imported file. Use this instead of file_get_contents when processing
73   * stylesheets.
74   *
75   * The returned contents are compressed removing white space and comments only
76   * when CSS aggregation is enabled. This optimization will not apply for
77   * color.module enabled themes with CSS aggregation turned off.
78   *
79   * Note: the only reason this method is public is so color.module can call it;
80   * it is not on the AssetOptimizerInterface, so future refactorings can make
81   * it protected.
82   *
83   * @param $file
84   *   Name of the stylesheet to be processed.
85   * @param $optimize
86   *   Defines if CSS contents should be compressed or not.
87   * @param $reset_basepath
88   *   Used internally to facilitate recursive resolution of @import commands.
89   *
90   * @return
91   *   Contents of the stylesheet, including any resolved @import commands.
92   */
93  public function loadFile($file, $optimize = NULL, $reset_basepath = TRUE) {
94    // These statics are not cache variables, so we don't use drupal_static().
95    static $_optimize, $basepath;
96    if ($reset_basepath) {
97      $basepath = '';
98    }
99    // Store the value of $optimize for preg_replace_callback with nested
100    // @import loops.
101    if (isset($optimize)) {
102      $_optimize = $optimize;
103    }
104
105    // Stylesheets are relative one to each other. Start by adding a base path
106    // prefix provided by the parent stylesheet (if necessary).
107    if ($basepath && !StreamWrapperManager::getScheme($file)) {
108      $file = $basepath . '/' . $file;
109    }
110    // Store the parent base path to restore it later.
111    $parent_base_path = $basepath;
112    // Set the current base path to process possible child imports.
113    $basepath = dirname($file);
114
115    // Load the CSS stylesheet. We suppress errors because themes may specify
116    // stylesheets in their .info.yml file that don't exist in the theme's path,
117    // but are merely there to disable certain module CSS files.
118    $content = '';
119    if ($contents = @file_get_contents($file)) {
120      // If a BOM is found, convert the file to UTF-8, then use substr() to
121      // remove the BOM from the result.
122      if ($encoding = (Unicode::encodingFromBOM($contents))) {
123        $contents = mb_substr(Unicode::convertToUtf8($contents, $encoding), 1);
124      }
125      // If no BOM, check for fallback encoding. Per CSS spec the regex is very strict.
126      elseif (preg_match('/^@charset "([^"]+)";/', $contents, $matches)) {
127        if ($matches[1] !== 'utf-8' && $matches[1] !== 'UTF-8') {
128          $contents = substr($contents, strlen($matches[0]));
129          $contents = Unicode::convertToUtf8($contents, $matches[1]);
130        }
131      }
132
133      // Return the processed stylesheet.
134      $content = $this->processCss($contents, $_optimize);
135    }
136
137    // Restore the parent base path as the file and its children are processed.
138    $basepath = $parent_base_path;
139    return $content;
140  }
141
142  /**
143   * Loads stylesheets recursively and returns contents with corrected paths.
144   *
145   * This function is used for recursive loading of stylesheets and
146   * returns the stylesheet content with all url() paths corrected.
147   *
148   * @param array $matches
149   *   An array of matches by a preg_replace_callback() call that scans for
150   *   @import-ed CSS files, except for external CSS files.
151   *
152   * @return
153   *   The contents of the CSS file at $matches[1], with corrected paths.
154   *
155   * @see \Drupal\Core\Asset\AssetOptimizerInterface::loadFile()
156   */
157  protected function loadNestedFile($matches) {
158    $filename = $matches[1];
159    // Load the imported stylesheet and replace @import commands in there as
160    // well.
161    $file = $this->loadFile($filename, NULL, FALSE);
162
163    // Determine the file's directory.
164    $directory = dirname($filename);
165    // If the file is in the current directory, make sure '.' doesn't appear in
166    // the url() path.
167    $directory = $directory == '.' ? '' : $directory . '/';
168
169    // Alter all internal asset paths. Leave external paths alone. We don't need
170    // to normalize absolute paths here because that will be done later.
171    return preg_replace('/url\(\s*([\'"]?)(?![a-z]+:|\/+)([^\'")]+)([\'"]?)\s*\)/i', 'url(\1' . $directory . '\2\3)', $file);
172  }
173
174  /**
175   * Processes the contents of a stylesheet for aggregation.
176   *
177   * @param $contents
178   *   The contents of the stylesheet.
179   * @param $optimize
180   *   (optional) Boolean whether CSS contents should be minified. Defaults to
181   *   FALSE.
182   *
183   * @return
184   *   Contents of the stylesheet including the imported stylesheets.
185   */
186  protected function processCss($contents, $optimize = FALSE) {
187    // Remove unwanted CSS code that cause issues.
188    $contents = $this->clean($contents);
189
190    if ($optimize) {
191      // Perform some safe CSS optimizations.
192      // Regexp to match comment blocks.
193      $comment = '/\*[^*]*\*+(?:[^/*][^*]*\*+)*/';
194      // Regexp to match double quoted strings.
195      $double_quot = '"[^"\\\\]*(?:\\\\.[^"\\\\]*)*"';
196      // Regexp to match single quoted strings.
197      $single_quot = "'[^'\\\\]*(?:\\\\.[^'\\\\]*)*'";
198      // Strip all comment blocks, but keep double/single quoted strings.
199      $contents = preg_replace(
200        "<($double_quot|$single_quot)|$comment>Ss",
201        "$1",
202        $contents
203      );
204      // Remove certain whitespace.
205      // There are different conditions for removing leading and trailing
206      // whitespace.
207      // @see http://php.net/manual/regexp.reference.subpatterns.php
208      $contents = preg_replace('<
209        # Do not strip any space from within single or double quotes
210          (' . $double_quot . '|' . $single_quot . ')
211        # Strip leading and trailing whitespace.
212        | \s*([@{};,])\s*
213        # Strip only leading whitespace from:
214        # - Closing parenthesis: Retain "@media (bar) and foo".
215        | \s+([\)])
216        # Strip only trailing whitespace from:
217        # - Opening parenthesis: Retain "@media (bar) and foo".
218        # - Colon: Retain :pseudo-selectors.
219        | ([\(:])\s+
220      >xSs',
221        // Only one of the four capturing groups will match, so its reference
222        // will contain the wanted value and the references for the
223        // two non-matching groups will be replaced with empty strings.
224        '$1$2$3$4',
225        $contents
226      );
227      // End the file with a new line.
228      $contents = trim($contents);
229      $contents .= "\n";
230    }
231
232    // Replaces @import commands with the actual stylesheet content.
233    // This happens recursively but omits external files and local files
234    // with supports- or media-query qualifiers, as those are conditionally
235    // loaded depending on the user agent.
236    $contents = preg_replace_callback('/@import\s*(?:url\(\s*)?[\'"]?(?![a-z]+:)(?!\/\/)([^\'"\()]+)[\'"]?\s*\)?\s*;/', [$this, 'loadNestedFile'], $contents);
237
238    return $contents;
239  }
240
241  /**
242   * Prefixes all paths within a CSS file for processFile().
243   *
244   * Note: the only reason this method is public is so color.module can call it;
245   * it is not on the AssetOptimizerInterface, so future refactorings can make
246   * it protected.
247   *
248   * @param array $matches
249   *   An array of matches by a preg_replace_callback() call that scans for
250   *   url() references in CSS files, except for external or absolute ones.
251   *
252   * @return string
253   *   The file path.
254   */
255  public function rewriteFileURI($matches) {
256    // Prefix with base and remove '../' segments where possible.
257    $path = $this->rewriteFileURIBasePath . $matches[1];
258    $last = '';
259    while ($path != $last) {
260      $last = $path;
261      $path = preg_replace('`(^|/)(?!\.\./)([^/]+)/\.\./`', '$1', $path);
262    }
263    return 'url(' . file_url_transform_relative(file_create_url($path)) . ')';
264  }
265
266}
267