<?php

/**
 * @file
 * Provides imagecache style generation of css/js aggregates.
 */

/**
 * Implements hook_menu().
 */
function agrcache_menu() {
  $directory_path = variable_get('file_public_path', conf_path() . '/files');

  foreach (array('css', 'js') as $type) {
    $items[$directory_path . "/$type/%"] = array(
      'title' => "Generate $type aggregate",
      'page callback' => 'agrcache_generate_aggregate',
      'page arguments' => array(count(explode('/', $directory_path)) + 1, $type),
      'access callback' => TRUE,
      'type' => MENU_CALLBACK,
    );
  }
  return $items;
}

/**
 * Implements hook_element_info_alter().
 */
function agrcache_element_info_alter(&$type) {
  // Swap in our own aggregation callback.
  if (isset($type['styles']['#aggregate_callback'])) {
    $type['styles']['#aggregate_callback'] = 'agrcache_aggregate_css';
  }
}

/**
 * Implements hook_theme_registry_alter().
 */
function agrcache_theme_registry_alter(&$theme_registry) {
  // For JavaScript there is no nice hook_elements() implementation to hook
  // into, aggregation is done inline in drupal_get_js(). So instead take over
  // template_preprocess_html.
  // @see http://drupal.org/node/330082
  // @see http://drupal.org/node/352951
  $index = array_search('template_process_html', $theme_registry['html']['process functions']);
  $theme_registry['html']['process functions'][$index] = '_agrcache_process_html';
}

/**
 * Replacement for template_process_html().
 */
function _agrcache_process_html(&$variables) {
  // Render page_top and page_bottom into top level variables.
  $variables['page_top'] = drupal_render($variables['page']['page_top']);
  $variables['page_bottom'] = drupal_render($variables['page']['page_bottom']);
  // Place the rendered HTML for the page body into a top level variable.
  $variables['page']              = $variables['page']['#children'];
  $variables['page_bottom'] .= agrcache_get_js('footer');

  $variables['head']    = drupal_get_html_head();
  $variables['css']     = drupal_add_css();
  $variables['styles']  = drupal_get_css();
  $variables['scripts'] = agrcache_get_js();
}

/**
 * Replacement for drupal_get_js().
 */
function agrcache_get_js($scope = 'header', $javascript = NULL, $skip_alter = FALSE) {
  if (!isset($javascript)) {
    $javascript = drupal_add_js();
  }
  if (empty($javascript)) {
    return '';
  }

  // Allow modules to alter the JavaScript.
  if (!$skip_alter) {
    drupal_alter('js', $javascript);
  }

  // Filter out elements of the given scope.
  $items = array();
  foreach ($javascript as $key => $item) {
    if ($item['scope'] == $scope) {
      $items[$key] = $item;
    }
  }

  $output = '';
  // The index counter is used to keep aggregated and non-aggregated files in
  // order by weight.
  $index = 1;
  $processed = array();
  $files = array();
  $preprocess_js = (variable_get('preprocess_js', FALSE) && (!defined('MAINTENANCE_MODE') || MAINTENANCE_MODE != 'update'));

  // A dummy query-string is added to filenames, to gain control over
  // browser-caching. The string changes on every update or full cache
  // flush, forcing browsers to load a new copy of the files, as the
  // URL changed. Files that should not be cached (see drupal_add_js())
  // get REQUEST_TIME as query-string instead, to enforce reload on every
  // page request.
  $default_query_string = variable_get('css_js_query_string', '0');

  // For inline Javascript to validate as XHTML, all Javascript containing
  // XHTML needs to be wrapped in CDATA. To make that backwards compatible
  // with HTML 4, we need to comment out the CDATA-tag.
  $embed_prefix = "\n<!--//--><![CDATA[//><!--\n";
  $embed_suffix = "\n//--><!]]>\n";

  // Since Javascript may look for arguments in the url and act on them, some
  // third-party code might require the use of a different query string.
  $js_version_string = variable_get('drupal_js_version_query_string', 'v=');

  // Sort the JavaScript so that it appears in the correct order.
  uasort($items, 'drupal_sort_css_js');

  // Provide the page with information about the individual JavaScript files
  // used, information not otherwise available when aggregation is enabled.
  $setting['ajaxPageState']['js'] = array_fill_keys(array_keys($items), 1);
  unset($setting['ajaxPageState']['js']['settings']);
  drupal_add_js($setting, 'setting');

  // If we're outputting the header scope, then this might be the final time
  // that drupal_get_js() is running, so add the setting to this output as well
  // as to the drupal_add_js() cache. If $items['settings'] doesn't exist, it's
  // because drupal_get_js() was intentionally passed a $javascript argument
  // stripped off settings, potentially in order to override how settings get
  // output, so in this case, do not add the setting to this output.
  if ($scope == 'header' && isset($items['settings'])) {
    $items['settings']['data'][] = $setting;
  }

  // Loop through the JavaScript to construct the rendered output.
  $element = array(
    '#tag' => 'script', 
    '#value' => '', 
    '#attributes' => array(
      'type' => 'text/javascript',
    ),
  );
  foreach ($items as $item) {
    $query_string =  empty($item['version']) ? $default_query_string : $js_version_string . $item['version'];

    switch ($item['type']) {
      case 'setting':
        $js_element = $element;
        $js_element['#value_prefix'] = $embed_prefix;
        $js_element['#value'] = 'jQuery.extend(Drupal.settings, ' . drupal_json_encode(drupal_array_merge_deep_array($item['data'])) . ");";
        $js_element['#value_suffix'] = $embed_suffix;
        $output .= theme('html_tag', array('element' => $js_element));
        break;

      case 'inline':
        $js_element = $element;
        if ($item['defer']) {
          $js_element['#attributes']['defer'] = 'defer';
        }
        $js_element['#value_prefix'] = $embed_prefix;
        $js_element['#value'] = $item['data'];
        $js_element['#value_suffix'] = $embed_suffix;
        $processed[$index++] = theme('html_tag', array('element' => $js_element));
        break;

      case 'file':
        $js_element = $element;
        if (!$item['preprocess'] || !$preprocess_js) {
          if ($item['defer']) {
            $js_element['#attributes']['defer'] = 'defer';
          }
          $query_string_separator = (strpos($item['data'], '?') !== FALSE) ? '&' : '?';
          $js_element['#attributes']['src'] = file_create_url($item['data']) . $query_string_separator . ($item['cache'] ? $query_string : REQUEST_TIME);
          $processed[$index++] = theme('html_tag', array('element' => $js_element));
        }
        else {
          // By increasing the index for each aggregated file, we maintain
          // the relative ordering of JS by weight. We also set the key such
          // that groups are split by items sharing the same 'group' value and
          // 'every_page' flag. While this potentially results in more aggregate
          // files, it helps make each one more reusable across a site visit,
          // leading to better front-end performance of a website as a whole.
          // See drupal_add_js() for details.
          $key = 'aggregate_' . $item['group'] . '_' . $item['every_page'] . '_' . $index;
          $processed[$key] = '';
          $files[$key][$item['data']] = $item;
        }
        break;

      case 'external':
        $js_element = $element;
        // Preprocessing for external JavaScript files is ignored.
        if ($item['defer']) {
          $js_element['#attributes']['defer'] = 'defer';
        }
        $js_element['#attributes']['src'] = $item['data'];
        $processed[$index++] = theme('html_tag', array('element' => $js_element));
        break;
    }
  }

  // Aggregate any remaining JS files that haven't already been output.
  // This is the only hunk of code change from drupal_get_js().
  if ($preprocess_js && count($files) > 0) {
    $map = array();
    foreach ($files as $key => $file_set) {

      $data = agrcache_build_aggregate_cache($file_set, 'js');
      $uri = $data['uri'];
      if (!empty($data['#write_cache'])) {
        $map['files'][$data['key']] = $data['uri'];
        $map['callbacks'][$data['uri']] = $file_set;
      }
      // Only include the file if was written successfully. Errors are logged
      // using watchdog.
      if ($uri) {
        $preprocess_file = file_create_url($uri);
        $js_element = $element;
        $js_element['#attributes']['src'] = $preprocess_file;
        $processed[$key] = theme('html_tag', array('element' => $js_element));
      }
    }
  }

  if (!empty($map)) {
    agrcache_add_to_variable('agrcache_js_cache_files', $map);
  }

  // Keep the order of JS files consistent as some are preprocessed and others are not.
  // Make sure any inline or JS setting variables appear last after libraries have loaded.
  return implode('', $processed) . $output;
}

/**
 * Replacement for drupal_aggregate_css().
 */
function agrcache_aggregate_css(&$css_groups) {
  $preprocess_css = (variable_get('preprocess_css', FALSE) && (!defined('MAINTENANCE_MODE') || MAINTENANCE_MODE != 'update'));

  $map = array();
  // For each group that needs aggregation, aggregate its items.
  foreach ($css_groups as $key => $group) {
    switch ($group['type']) {
      // If a file group can be aggregated into a single file, do so, and set
      // the group's data property to the file path of the aggregate file.
      case 'file':
        if ($group['preprocess'] && $preprocess_css) {
          $data = agrcache_build_aggregate_cache($group['items'], 'css');
          if ($data) {
            $css_groups[$key]['data'] = $data['uri'];
            if (!empty($data['#write_cache'])) {
              $map['files'][$data['key']] = $data['uri'];
              $map['callbacks'][$data['uri']] = $group['items'];
            }
          }
        }
        break;
        // Aggregate all inline CSS content into the group's data property.
      case 'inline':
        $css_groups[$key]['data'] = '';
        foreach ($group['items'] as $item) {
          $css_groups[$key]['data'] .= drupal_load_stylesheet_content($item['data'], $item['preprocess']);
        }
        break;
    }
  }
  if (!empty($map)) {
    agrcache_add_to_variable('agrcache_css_cache_files', $map);
  }
}

/**
 * Replacement for drupal_build_css_cache() and drupal_build_js_cache().
 */
function agrcache_build_aggregate_cache($files, $type) {
  $data = '';
  $uri = '';
  $map = variable_get('agrcache_' . $type . '_cache_files', array());
  $key = hash('sha256', serialize($files));
  if (isset($map['files'][$key])) {
    return array('uri' => $map['files'][$key]);
  }
  else {
    // To ensure a new filenames are created only when the contents of the
    // hashed files changes, use a hash of the contents for the filename.
    $function = 'agrcache_collect_' . $type . '_group';
    $data = $function($files);
    if ($data) {

      // Prefix filename to prevent blocking by firewalls which reject files
      // starting with "ad*".
      $filename = $type . '_' . drupal_hash_base64($data) . ".$type";
      // Create the aggregate directory within the files folder.
      $path = "public://$type";
      $uri = $path . '/' . $filename;

      return array(
        'key' => $key,
        'uri' => $uri,
        '#write_cache' => TRUE,
      );
    }
    else {
      return FALSE;
    }
  }
}

/**
 * Collect javascript files.
 */
function agrcache_collect_js_group($js) {
  // JavaScript aggregation currently only collects the files together, so
  // re-use agrcache_process_js_group();
  return agrcache_process_js_group($js);
}

/**
 * College CSS files.
 */
function agrcache_collect_css_group($css) {
  $contents = '';
  foreach ($css as $stylesheet) {
    if ($stylesheet['type'] == 'file' && file_exists($stylesheet['data'])) {
      $contents .= file_get_contents($stylesheet['data']);
    }
  }
  return $contents;
}

/**
 * Process a js group for aggregation.
 */
function agrcache_process_js_group($js) {
  $data = '';
  foreach ($js as $path => $info) {
    if ($info['preprocess']) {
      // Append a ';' and a newline after each JS file to prevent them from running together.
      $data .= file_get_contents($path) . ";\n";
    }
  }
  return $data;
}

/**
 * Aggregate and compress css groups.
 */
function agrcache_process_css_group($css) {
  // Build aggregate CSS file.
  $data = '';
  foreach ($css as $stylesheet) {
    // Only 'file' stylesheets can be aggregated.
    if ($stylesheet['type'] == 'file') {
      $contents = drupal_load_stylesheet($stylesheet['data'], TRUE);

      // Build the base URL of this CSS file: start with the full URL.
      $css_base_url = file_create_url($stylesheet['data']);
      // Move to the parent.
      $css_base_url = substr($css_base_url, 0, strrpos($css_base_url, '/'));
      // Simplify to a relative URL if the stylesheet URL starts with the
      // base URL of the website.
      if (substr($css_base_url, 0, strlen($GLOBALS['base_root'])) == $GLOBALS['base_root']) {
        $css_base_url = substr($css_base_url, strlen($GLOBALS['base_root']));
      }

      _drupal_build_css_path(NULL, $css_base_url . '/');
      // Anchor all paths in the CSS with its base URL, ignoring external and absolute paths.
      $data .= preg_replace_callback('/url\(\s*[\'"]?(?![a-z]+:|\/+)([^\'")]+)[\'"]?\s*\)/i', '_drupal_build_css_path', $contents);
    }
  }

  // Per the W3C specification at http://www.w3.org/TR/REC-CSS2/cascade.html#at-import,
  // @import rules must proceed any other style, so we move those to the top.
  $regexp = '/@import[^;]+;/i';
  preg_match_all($regexp, $data, $matches);
  $data = preg_replace($regexp, '', $data);
  $data = implode('', $matches[0]) . $data;

  return $data;
}

/**
 * Menu callback to generate a css aggregate.
 */
function agrcache_generate_aggregate($filename, $type) {
  // Recreate the full uri from the filename.
  $path = "public://$type";
  $uri = $path . '/' . $filename;
  $map = variable_get('agrcache_' . $type . '_cache_files', array());
  $compression = variable_get($type . '_gzip_compression', TRUE) && variable_get('clean_url', 0) && extension_loaded('zlib');

  // This callback should only be called if the file does not already exist on
  // disk since the webserver will serve the file directly, bypassing PHP when it does.
  // However it is possible that the file was created during bootstrap by another request.
  if (file_exists($uri)) {
    $data = file_get_contents($uri);
    if ($compression) {
      $compressed = gzencode($data, 9, FORCE_GZIP);
    }
  }
  elseif (isset($map['callbacks'][$uri])) {
    // @todo: consider adding locking here.
    // @see drupal.org/node/886488
    $function = 'agrcache_process_' . $type . '_group';
    $data = $function($map['callbacks'][$uri]);
    // Check file_exists() again, in case the file was built during processing.
    if (!file_exists($uri)) {
      // Create the file.
      file_prepare_directory($path, FILE_CREATE_DIRECTORY);
      if (!file_exists($uri) && !file_unmanaged_save_data($data, $uri, FILE_EXISTS_REPLACE)) {
        drupal_add_http_header('Status', '503 Service Unavailable');
        print t('Error generating aggregate');
        drupal_exit();
      }
      // If gzip compression is enabled, clean URLs are enabled (which means
      // that rewrite rules are working) and the zlib extension is available then
      // create a gzipped version of this file. This file is served conditionally
      // to browsers that accept gzip using .htaccess rules.
      if ($compression) {
        $compressed = gzencode($data, 9, FORCE_GZIP);
        if (!file_exists($uri . '.gz') && !file_unmanaged_save_data($compressed, $uri . '.gz', FILE_EXISTS_REPLACE)) {
          drupal_add_http_header('Status', '503 Service Unavailable');
          print t('Error generating aggregate');
          drupal_exit();
        }
      }
    }
    $content_type = $type == 'css' ? 'text/css' : 'application/javascript';
    $headers = array();
    $headers['Content-Type'] = $content_type;
    // Ensure this file can be cached by browsers and reverse proxies.
    $headers['Cache-Control'] = 'public, max-age=1209600';
    // Since the file name is based on a hash of file contents, there is no
    // problem allowing the browser to cache it for as long as possible.
    // Set this to two weeks since that's what .htaccess does if mod_expires
    // is enabled.
    $headers['Expires'] = gmdate(DATE_RFC1123, REQUEST_TIME + 1209600);

    // When possible, serve the gzip version of the file via PHP.
    if (!empty($compressed) && isset($_SERVER['HTTP_ACCEPT_ENCODING']) && strpos($_SERVER['HTTP_ACCEPT_ENCODING'], 'gzip') !== FALSE) {
      $headers['Content-Encoding'] = 'gzip';
      $data = $compressed;
      ini_set('zlib.output_compression', '0');
    }
    foreach ($headers as $key => $value) {
      drupal_add_http_header($key, $value);
    }
    print $data;
    drupal_exit();
  }
  else {
    watchdog('agrcache', 'Received request for a non-existent css aggregate @uri', array('@uri' => $uri));
  }
}

/**
 * Merge the existing value of a variable from the database with new values.
 *
 * @param $name
 *   The name of the variable.
 * @param $values
 *   An array of values to add.
 * @param $default
 *   The default value of the variable, as passed to variable_get().
 *   This defaults to an empty array().
 */
function agrcache_add_to_variable($name, $values, $default = array()) {
  // This function bypasses variable_get() on purpose. Since when dealing with
  // 'volatile' variables such as css and javascript maps that may be updated
  // by multiple threads, it is necessary to minimize the potential race
  // condition where threads may overwrite the value of the variable with a
  // version missing values that were just added by a previous process.
  // This approach lowers the window for that race condition to the time
  // between the database query and variable_set(), which should be only a
  // couple of milliseconds compared to up to over a second between
  // variable_initialize() and reaching this function.
  $original = $default;
  $result = db_query('SELECT value FROM {variable} WHERE name = :name', array(':name' => $name))->fetchField();
  if ($result) {
    $original = unserialize($result);
  }
  variable_set($name, array_merge_recursive($original, $values));
}