<?php

/**
 * @file
 * External library handling for Drupal modules.
 */

/**
 * Implements hook_flush_caches().
 */
function libraries_flush_caches() {
  // Clear static caches.
  // We don't clear the 'libraries_load' static cache, because that could result
  // in libraries that had been loaded before the cache flushing to be loaded
  // again afterwards.
  foreach (array('libraries_get_path', 'libraries_info') as $name) {
    drupal_static_reset($name);
  }

  // @todo When upgrading from 1.x, update.php attempts to flush caches before
  //   the cache table has been created.
  // @see http://drupal.org/node/1477932
  if (db_table_exists('cache_libraries')) {
    return array('cache_libraries');
  }
}

/**
 * Gets the path of a library.
 *
 * @param $name
 *   The machine name of a library to return the path for.
 * @param $base_path
 *   Whether to prefix the resulting path with base_path().
 *
 * @return string
 *   The path to the specified library or FALSE if the library wasn't found.
 *
 * @ingroup libraries
 */
function libraries_get_path($name, $base_path = FALSE) {
  $libraries = &drupal_static(__FUNCTION__);

  if (!isset($libraries)) {
    $libraries = libraries_get_libraries();
  }

  $path = ($base_path ? base_path() : '');
  if (!isset($libraries[$name])) {
    return FALSE;
  }
  else {
    $path .= $libraries[$name];
  }

  return $path;
}

/**
 * Returns an array of library directories.
 *
 * Returns an array of library directories from the all-sites directory
 * (i.e. sites/all/libraries/), the profiles directory, and site-specific
 * directory (i.e. sites/somesite/libraries/). The returned array will be keyed
 * by the library name. Site-specific libraries are prioritized over libraries
 * in the default directories. That is, if a library with the same name appears
 * in both the site-wide directory and site-specific directory, only the
 * site-specific version will be listed.
 *
 * @return array
 *   A list of library directories.
 *
 * @ingroup libraries
 */
function libraries_get_libraries() {
  $searchdir = array();
  $profile = drupal_get_path('profile', drupal_get_profile());
  $config = conf_path();

  // Similar to 'modules' and 'themes' directories in the root directory,
  // certain distributions may want to place libraries into a 'libraries'
  // directory in Drupal's root directory.
  $searchdir[] = 'libraries';

  // Similar to 'modules' and 'themes' directories inside an installation
  // profile, installation profiles may want to place libraries into a
  // 'libraries' directory.
  $searchdir[] = "$profile/libraries";

  // Always search sites/all/libraries.
  $searchdir[] = 'sites/all/libraries';

  // Also search sites/<domain>/*.
  $searchdir[] = "$config/libraries";

  // Retrieve list of directories.
  $directories = array();
  $nomask = array('CVS');
  foreach ($searchdir as $dir) {
    if (is_dir($dir) && $handle = opendir($dir)) {
      while (FALSE !== ($file = readdir($handle))) {
        if (!in_array($file, $nomask) && $file[0] != '.') {
          if (is_dir("$dir/$file")) {
            $directories[$file] = "$dir/$file";
          }
        }
      }
      closedir($handle);
    }
  }

  return $directories;
}

/**
 * Looks for library info files.
 *
 * This function scans the following directories for info files:
 * - libraries
 * - profiles/$profilename/libraries
 * - sites/all/libraries
 * - sites/$sitename/libraries
 * - any directories specified via hook_libraries_info_file_paths()
 *
 * @return array
 *   An array of info files, keyed by library name. The values are the paths of
 *   the files.
 */
function libraries_scan_info_files() {
  $profile = drupal_get_path('profile', drupal_get_profile());
  $config = conf_path();

  // Build a list of directories.
  $directories = module_invoke_all('libraries_info_file_paths');
  $directories[] = 'libraries';
  $directories[] = "$profile/libraries";
  $directories[] = 'sites/all/libraries';
  $directories[] = "$config/libraries";

  // Scan for info files.
  $files = array();
  foreach ($directories as $dir) {
    if (file_exists($dir)) {
      $files = array_merge($files, file_scan_directory($dir, '@^[A-Za-z0-9._-]+\.libraries\.info$@', array(
        'key' => 'name',
        'recurse' => FALSE,
      )));
    }
  }

  foreach ($files as $filename => $file) {
    $files[basename($filename, '.libraries')] = $file;
    unset($files[$filename]);
  }

  return $files;
}

/**
 * Invokes library callbacks.
 *
 * @param $group
 *   A string containing the group of callbacks that is to be applied. Should be
 *   either 'info', 'pre-detect', 'post-detect', or 'load'.
 * @param $library
 *   An array of library information, passed by reference.
 */
function libraries_invoke($group, &$library) {
  // When introducing new callback groups in newer versions, stale cached
  // library information somehow reaches this point during the database update
  // before clearing the library cache.
  if (empty($library['callbacks'][$group])) {
    return;
  }

  foreach ($library['callbacks'][$group] as $callback) {
    libraries_traverse_library($library, $callback);
  }
}

/**
 * Helper function to apply a callback to all parts of a library.
 *
 * Because library declarations can include variants and versions, and those
 * version declarations can in turn include variants, modifying e.g. the 'files'
 * property everywhere it is declared can be quite cumbersome, in which case
 * this helper function is useful.
 *
 * @param $library
 *   An array of library information, passed by reference.
 * @param $callback
 *   A string containing the callback to apply to all parts of a library.
 */
function libraries_traverse_library(&$library, $callback) {
  // Always apply the callback to the top-level library.
  $callback($library, NULL, NULL);

  // Apply the callback to versions.
  if (isset($library['versions'])) {
    foreach ($library['versions'] as $version_string => &$version) {
      $callback($version, $version_string, NULL);
      // Versions can include variants as well.
      if (isset($version['variants'])) {
        foreach ($version['variants'] as $version_variant_name => &$version_variant) {
          $callback($version_variant, $version_string, $version_variant_name);
        }
      }
    }
  }

  // Apply the callback to variants.
  if (isset($library['variants'])) {
    foreach ($library['variants'] as $variant_name => &$variant) {
      $callback($variant, NULL, $variant_name);
    }
  }
}

/**
 * Library info callback to make all 'files' properties consistent.
 *
 * This turns libraries' file information declared as e.g.
 * @code
 * $library['files']['js'] = array('example_1.js', 'example_2.js');
 * @endcode
 * into
 * @code
 * $library['files']['js'] = array(
 *   'example_1.js' => array(),
 *   'example_2.js' => array(),
 * );
 * @endcode
 * It does the same for the 'integration files' property.
 *
 * @param $library
 *   An associative array of library information or a part of it, passed by
 *   reference.
 * @param $version
 *   If the library information belongs to a specific version, the version
 *   string. NULL otherwise.
 * @param $variant
 *   If the library information belongs to a specific variant, the variant name.
 *   NULL otherwise.
 *
 * @see libraries_info()
 * @see libraries_invoke()
 */
function libraries_prepare_files(&$library, $version = NULL, $variant = NULL) {
  // Both the 'files' property and the 'integration files' property contain file
  // declarations, and we want to make both consistent.
  $file_types = array();
  if (isset($library['files'])) {
    $file_types[] = &$library['files'];
  }
  if (isset($library['integration files'])) {
    // Integration files are additionally keyed by module.
    foreach ($library['integration files'] as &$integration_files) {
      $file_types[] = &$integration_files;
    }
  }
  foreach ($file_types as &$files) {
    // Go through all supported types of files.
    foreach (array('js', 'css', 'php') as $type) {
      if (isset($files[$type])) {
        foreach ($files[$type] as $key => $value) {
          // Unset numeric keys and turn the respective values into keys.
          if (is_numeric($key)) {
            $files[$type][$value] = array();
            unset($files[$type][$key]);
          }
        }
      }
    }
  }
}

/**
 * Library post-detect callback to process and detect dependencies.
 *
 * It checks whether each of the dependencies of a library are installed and
 * available in a compatible version.
 *
 * @param $library
 *   An associative array of library information or a part of it, passed by
 *   reference.
 * @param $version
 *   If the library information belongs to a specific version, the version
 *   string. NULL otherwise.
 * @param $variant
 *   If the library information belongs to a specific variant, the variant name.
 *   NULL otherwise.
 *
 * @see libraries_info()
 * @see libraries_invoke()
 */
function libraries_detect_dependencies(&$library, $version = NULL, $variant = NULL) {
  if (isset($library['dependencies'])) {
    foreach ($library['dependencies'] as &$dependency_string) {
      $dependency_info = drupal_parse_dependency($dependency_string);
      $dependency = libraries_detect($dependency_info['name']);
      if (!$dependency['installed']) {
        $library['installed'] = FALSE;
        $library['error'] = 'missing dependency';
        $library['error message'] = t('The %dependency library, which the %library library depends on, is not installed.', array(
          '%dependency' => $dependency['name'],
          '%library' => $library['name'],
        ));
      }
      elseif (drupal_check_incompatibility($dependency_info, $dependency['version'])) {
        $library['installed'] = FALSE;
        $library['error'] = 'incompatible dependency';
        $library['error message'] = t('The version %dependency_version of the %dependency library is not compatible with the %library library.', array(
          '%dependency_version' => $dependency['version'],
          '%dependency' => $dependency['name'],
          '%library' => $library['name'],
        ));
      }

      // Remove the version string from the dependency, so libraries_load() can
      // load the libraries directly.
      $dependency_string = $dependency_info['name'];
    }
  }
}

/**
 * Returns information about registered libraries.
 *
 * The returned information is unprocessed; i.e., as registered by modules.
 *
 * @param $name
 *   (optional) The machine name of a library to return registered information
 *   for. If omitted, information about all registered libraries is returned.
 *
 * @return array|false
 *   An associative array containing registered information for all libraries,
 *   the registered information for the library specified by $name, or FALSE if
 *   the library $name is not registered.
 *
 * @see hook_libraries_info()
 *
 * @todo Re-introduce support for include file plugin system - either by copying
 *   Wysiwyg's code, or directly switching to CTools.
 */
function &libraries_info($name = NULL) {
  // This static cache is re-used by libraries_detect() to save memory.
  $libraries = &drupal_static(__FUNCTION__);

  if (!isset($libraries)) {
    $libraries = array();

    // Gather information from hook_libraries_info() in enabled modules.
    foreach (module_implements('libraries_info') as $module) {
      foreach (module_invoke($module, 'libraries_info') as $machine_name => $properties) {
        $properties['info type'] = 'module';
        $properties['module'] = $module;
        $libraries[$machine_name] = $properties;
      }
    }

    // Gather information from hook_libraries_info() in enabled themes.
    $themes = array();
    foreach (list_themes() as $theme_name => $theme_info) {
      if ($theme_info->status && file_exists(drupal_get_path('theme', $theme_name) . '/template.php')) {
        // Collect a list of viable themes for re-use when calling the alter
        // hook.
        $themes[] = $theme_name;

        include_once drupal_get_path('theme', $theme_name) . '/template.php';

        $function = $theme_name . '_libraries_info';
        if (function_exists($function)) {
          foreach ($function() as $machine_name => $properties) {
            $properties['info type'] = 'theme';
            $properties['theme'] = $theme_name;
            $libraries[$machine_name] = $properties;
          }
        }
      }
    }

    // Gather information from .info files.
    // .info files override module definitions.
    foreach (libraries_scan_info_files() as $machine_name => $file) {
      $properties = drupal_parse_info_file($file->uri);
      $properties['info type'] = 'info file';
      $properties['info file'] = $file->uri;
      $libraries[$machine_name] = $properties;
    }

    // Provide defaults.
    foreach ($libraries as $machine_name => &$properties) {
      libraries_info_defaults($properties, $machine_name);
    }

    // Allow enabled modules and themes to alter the registered libraries.
    // drupal_alter() only takes the currently active theme into account, not
    // all enabled themes.
    foreach (module_implements('libraries_info_alter') as $module) {
      $function = $module . '_libraries_info_alter';
      $function($libraries);
    }
    foreach ($themes as $theme) {
      $function = $theme . '_libraries_info_alter';
      // The template.php file was included above.
      if (function_exists($function)) {
        $function($libraries);
      }
    }

    // Invoke callbacks in the 'info' group.
    foreach ($libraries as &$properties) {
      libraries_invoke('info', $properties);
    }
  }

  if (isset($name)) {
    if (!empty($libraries[$name])) {
      return $libraries[$name];
    }
    else {
      $false = FALSE;
      return $false;
    }
  }
  return $libraries;
}

/**
 * Applies default properties to a library definition.
 *
 * @library
 *   An array of library information, passed by reference.
 * @name
 *   The machine name of the passed-in library.
 */
function libraries_info_defaults(&$library, $name) {
  $library += array(
    'machine name' => $name,
    'name' => $name,
    'vendor url' => '',
    'download url' => '',
    'path' => '',
    'library path' => NULL,
    'version callback' => 'libraries_get_version',
    'version arguments' => array(),
    'files' => array(),
    'dependencies' => array(),
    'variants' => array(),
    'versions' => array(),
    'integration files' => array(),
    'callbacks' => array(),
    // @todo Remove in 7.x-3.x
    'post-load integration files' => FALSE,
  );
  $library['callbacks'] += array(
    'info' => array(),
    'pre-detect' => array(),
    'post-detect' => array(),
    'pre-dependencies-load' => array(),
    'pre-load' => array(),
    'post-load' => array(),
  );

  // Add our own callbacks before any others.
  array_unshift($library['callbacks']['info'], 'libraries_prepare_files');
  array_unshift($library['callbacks']['post-detect'], 'libraries_detect_dependencies');

  return $library;
}

/**
 * Tries to detect a library and its installed version.
 *
 * @param $name
 *   The machine name of a library to return registered information for.
 *
 * @return array|false
 *   An associative array containing registered information for the library
 *   specified by $name, or FALSE if the library $name is not registered.
 *   In addition to the keys returned by libraries_info(), the following keys
 *   are contained:
 *   - installed: A boolean indicating whether the library is installed. Note
 *     that not only the top-level library, but also each variant contains this
 *     key.
 *   - version: If the version could be detected, the full version string.
 *   - error: If an error occurred during library detection, one of the
 *     following error statuses: "not found", "not detected", "not supported".
 *   - error message: If an error occurred during library detection, a detailed
 *     error message.
 *
 * @see libraries_info()
 */
function libraries_detect($name) {
  // Re-use the statically cached value of libraries_info() to save memory.
  $library = &libraries_info($name);

  // Exit early if the library was not found.
  if ($library === FALSE) {
    return $library;
  }

  // If 'installed' is set, library detection ran already.
  if (isset($library['installed'])) {
    return $library;
  }

  $library['installed'] = FALSE;

  // Check whether the library exists.
  if (!isset($library['library path'])) {
    $library['library path'] = libraries_get_path($library['machine name']);
  }
  if ($library['library path'] === FALSE || !file_exists($library['library path'])) {
    $library['error'] = 'not found';
    $library['error message'] = t('The %library library could not be found.', array(
      '%library' => $library['name'],
    ));
    return $library;
  }

  // Invoke callbacks in the 'pre-detect' group.
  libraries_invoke('pre-detect', $library);

  // Detect library version, if not hardcoded.
  if (!isset($library['version'])) {
    // We support both a single parameter, which is an associative array, and an
    // indexed array of multiple parameters.
    if (isset($library['version arguments'][0])) {
      // Add the library as the first argument.
      $library['version'] = call_user_func_array($library['version callback'], array_merge(array($library), $library['version arguments']));
    }
    else {
      $library['version'] = call_user_func($library['version callback'], $library, $library['version arguments']);
    }
    if (empty($library['version'])) {
      $library['error'] = 'not detected';
      $library['error message'] = t('The version of the %library library could not be detected.', array(
        '%library' => $library['name'],
      ));
      return $library;
    }
  }

  // Determine to which supported version the installed version maps.
  if (!empty($library['versions'])) {
    ksort($library['versions']);
    $version = 0;
    foreach ($library['versions'] as $supported_version => $version_properties) {
      if (version_compare($library['version'], $supported_version, '>=')) {
        $version = $supported_version;
      }
    }
    if (!$version) {
      $library['error'] = 'not supported';
      $library['error message'] = t('The installed version %version of the %library library is not supported.', array(
        '%version' => $library['version'],
        '%library' => $library['name'],
      ));
      return $library;
    }

    // Apply version specific definitions and overrides.
    $library = array_merge($library, $library['versions'][$version]);
    unset($library['versions']);
  }

  // Check each variant if it is installed.
  if (!empty($library['variants'])) {
    foreach ($library['variants'] as $variant_name => &$variant) {
      // If no variant callback has been set, assume the variant to be
      // installed.
      if (!isset($variant['variant callback'])) {
        $variant['installed'] = TRUE;
      }
      else {
        // We support both a single parameter, which is an associative array,
        // and an indexed array of multiple parameters.
        if (isset($variant['variant arguments'][0])) {
          // Add the library as the first argument, and the variant name as the second.
          $variant['installed'] = call_user_func_array($variant['variant callback'], array_merge(array($library, $variant_name), $variant['variant arguments']));
        }
        else {
          $variant['installed'] = $variant['variant callback']($library, $variant_name, $variant['variant arguments']);
        }
        if (!$variant['installed']) {
          $variant['error'] = 'not found';
          $variant['error message'] = t('The %variant variant of the %library library could not be found.', array(
            '%variant' => $variant_name,
            '%library' => $library['name'],
          ));
        }
      }
    }
  }

  // If we end up here, the library should be usable.
  $library['installed'] = TRUE;

  // Invoke callbacks in the 'post-detect' group.
  libraries_invoke('post-detect', $library);

  return $library;
}

/**
 * Loads a library.
 *
 * @param $name
 *   The name of the library to load.
 * @param $variant
 *   The name of the variant to load. Note that only one variant of a library
 *   can be loaded within a single request. The variant that has been passed
 *   first is used; different variant names in subsequent calls are ignored.
 *
 * @return
 *   An associative array of the library information as returned from
 *   libraries_info(). The top-level properties contain the effective definition
 *   of the library (variant) that has been loaded. Additionally:
 *   - installed: Whether the library is installed, as determined by
 *     libraries_detect_library().
 *   - loaded: Either the amount of library files that have been loaded, or
 *     FALSE if the library could not be loaded.
 *   See hook_libraries_info() for more information.
 */
function libraries_load($name, $variant = NULL) {
  $loaded = &drupal_static(__FUNCTION__, array());

  if (!isset($loaded[$name])) {
    $library = cache_get($name, 'cache_libraries');
    if ($library) {
      $library = $library->data;
    }
    else {
      $library = libraries_detect($name);
      cache_set($name, $library, 'cache_libraries');
    }

    // Exit early if the library was not found.
    if ($library === FALSE) {
      $loaded[$name] = $library;
      return $loaded[$name];
    }

    // If a variant was specified, override the top-level properties with the
    // variant properties.
    if (isset($variant)) {
      // Ensure that the $variant key exists, and if it does not, set its
      // 'installed' property to FALSE by default. This will prevent the loading
      // of the library files below.
      $library['variants'] += array($variant => array('installed' => FALSE));
      $library = array_merge($library, $library['variants'][$variant]);
    }
    // Regardless of whether a specific variant was requested or not, there can
    // only be one variant of a library within a single request.
    unset($library['variants']);

    // Invoke callbacks in the 'pre-dependencies-load' group.
    libraries_invoke('pre-dependencies-load', $library);

    // If the library (variant) is installed, load it.
    $library['loaded'] = FALSE;
    if ($library['installed']) {
      // Load library dependencies.
      if (isset($library['dependencies'])) {
        foreach ($library['dependencies'] as $dependency) {
          libraries_load($dependency);
        }
      }

      // Invoke callbacks in the 'pre-load' group.
      libraries_invoke('pre-load', $library);

      // Load all the files associated with the library.
      $library['loaded'] = libraries_load_files($library);

      // Invoke callbacks in the 'post-load' group.
      libraries_invoke('post-load', $library);
    }
    $loaded[$name] = $library;
  }

  return $loaded[$name];
}

/**
 * Loads a library's files.
 *
 * @param $library
 *   An array of library information as returned by libraries_info().
 *
 * @return
 *   The number of loaded files.
 */
function libraries_load_files($library) {
  // As this key was added after 7.x-2.1 cached library structures might not
  // have it.
  $library += array('post-load integration files' => FALSE);

  // Load integration files.
  if (!$library['post-load integration files'] && !empty($library['integration files'])) {
    $enabled_themes = array();
    foreach (list_themes() as $theme_name => $theme) {
      if ($theme->status) {
        $enabled_themes[] = $theme_name;
      }
    }
    foreach ($library['integration files'] as $provider => $files) {
      if (module_exists($provider)) {
        libraries_load_files(array(
          'files' => $files,
          'path' => '',
          'library path' => drupal_get_path('module', $provider),
          'post-load integration files' => FALSE,
        ));
      }
      elseif (in_array($provider, $enabled_themes)) {
        libraries_load_files(array(
          'files' => $files,
          'path' => '',
          'library path' => drupal_get_path('theme', $provider),
          'post-load integration files' => FALSE,
        ));
      }
    }
  }

  // Construct the full path to the library for later use.
  $path = $library['library path'];
  $path = ($library['path'] !== '' ? $path . '/' . $library['path'] : $path);

  // Count the number of loaded files for the return value.
  $count = 0;

  // Load both the JavaScript and the CSS files.
  // The parameters for drupal_add_js() and drupal_add_css() require special
  // handling.
  // @see drupal_process_attached()
  foreach (array('js', 'css') as $type) {
    if (!empty($library['files'][$type])) {
      foreach ($library['files'][$type] as $data => $options) {
        // If the value is not an array, it's a filename and passed as first
        // (and only) argument.
        if (!is_array($options)) {
          $data = $options;
          $options = array();
        }
        // In some cases, the first parameter ($data) is an array. Arrays can't
        // be passed as keys in PHP, so we have to get $data from the value
        // array.
        if (is_numeric($data)) {
          $data = $options['data'];
          unset($options['data']);
        }
        // Prepend the library path to the file name.
        $data = "$path/$data";
        // Apply the default group if the group isn't explicitly given.
        if (!isset($options['group'])) {
          $options['group'] = ($type == 'js') ? JS_DEFAULT : CSS_DEFAULT;
        }
        call_user_func('drupal_add_' . $type, $data, $options);
        $count++;
      }
    }
  }

  // Load PHP files.
  if (!empty($library['files']['php'])) {
    foreach ($library['files']['php'] as $file => $array) {
      $file_path = DRUPAL_ROOT . '/' . $path . '/' . $file;
      if (file_exists($file_path)) {
        _libraries_require_once($file_path);
        $count++;
      }
    }
  }

  // Load integration files.
  if ($library['post-load integration files'] && !empty($library['integration files'])) {
    $enabled_themes = array();
    foreach (list_themes() as $theme_name => $theme) {
      if ($theme->status) {
        $enabled_themes[] = $theme_name;
      }
    }
    foreach ($library['integration files'] as $provider => $files) {
      if (module_exists($provider)) {
        libraries_load_files(array(
          'files' => $files,
          'path' => '',
          'library path' => drupal_get_path('module', $provider),
          'post-load integration files' => FALSE,
        ));
      }
      elseif (in_array($provider, $enabled_themes)) {
        libraries_load_files(array(
          'files' => $files,
          'path' => '',
          'library path' => drupal_get_path('theme', $provider),
          'post-load integration files' => FALSE,
        ));
      }
    }
  }

  return $count;
}

/**
 * Wrapper function for require_once.
 *
 * A library file could set a $path variable in file scope. Requiring such a
 * file directly in libraries_load_files() would lead to the local $path
 * variable being overridden after the require_once statement. This would
 * break loading further files. Therefore we use this trivial wrapper which has
 * no local state that can be tampered with.
 *
 * @param $file_path
 *   The file path of the file to require.
 */
function _libraries_require_once($file_path) {
  require_once $file_path;
}


/**
 * Gets the version information from an arbitrary library.
 *
 * @param $library
 *   An associative array containing all information about the library.
 * @param $options
 *   An associative array containing with the following keys:
 *   - file: The filename to parse for the version, relative to the library
 *     path. For example: 'docs/changelog.txt'.
 *   - pattern: A string containing a regular expression (PCRE) to match the
 *     library version. For example: '@version\s+([0-9a-zA-Z\.-]+)@'. Note that
 *     the returned version is not the match of the entire pattern (i.e.
 *     '@version 1.2.3' in the above example) but the match of the first
 *     sub-pattern (i.e. '1.2.3' in the above example).
 *   - lines: (optional) The maximum number of lines to search the pattern in.
 *     Defaults to 20.
 *   - cols: (optional) The maximum number of characters per line to take into
 *     account. Defaults to 200. In case of minified or compressed files, this
 *     prevents reading the entire file into memory.
 *
 * @return
 *   A string containing the version of the library.
 *
 * @see libraries_get_path()
 */
function libraries_get_version($library, $options) {
  // Provide defaults.
  $options += array(
    'file' => '',
    'pattern' => '',
    'lines' => 20,
    'cols' => 200,
  );

  $file = DRUPAL_ROOT . '/' . $library['library path'] . '/' . $options['file'];
  if (empty($options['file']) || !file_exists($file)) {
    return;
  }
  $file = fopen($file, 'r');
  while ($options['lines'] && $line = fgets($file, $options['cols'])) {
    if (preg_match($options['pattern'], $line, $version)) {
      fclose($file);
      return $version[1];
    }
    $options['lines']--;
  }
  fclose($file);
}

/**
 * Implements hook_help().
 */
function libraries_help($path, $arg) {
  switch ($path) {
    case 'admin/reports/libraries':
      return t('Click on a library for a status report or detailed installation instructions in case the library is not installed correctly.');
  }
}

/**
 * Implements hook_menu().
 */
function libraries_menu() {
  $items = array();
  $items['admin/reports/libraries'] = array(
    'title' => 'Libraries',
    'description' => 'An overview of libraries installed on this site.',
    'page callback' => 'drupal_get_form',
    'page arguments' => array('libraries_admin_overview'),
    'access arguments' => array('access site reports'),
    'file' => 'libraries.admin.inc'
  );
  $items['admin/reports/libraries/%'] = array(
    'title' => 'Library status report',
    'description' => 'Status overview for a single library',
    'page callback' => 'drupal_get_form',
    'page arguments' => array('libraries_admin_library_status_form', 3),
    'access arguments' => array('access site reports'),
    'file' => 'libraries.admin.inc'
  );
  return $items;
}
