<?php

/**
 * @file
 *  Extended Path Aliases.
 *
 *  Automatically generates and recognises aliases beyond the base path, e.g.
 *  generates and accepts "about-us/edit" for "node/123/edit" and "user/rik/track"
 *  for "user/7/track".
 *  These aliases may be used anywhere where you are prompted to enter page
 *  specifications, including wildcards, like "about-us*".
 *  Examples of modules and pages that particularly benefit are:
 *  o any page displaying a revision or links to revisions
 *  o any page with View, Edit, Track etc tabs
 *  o the tabs on the "My account" page, Edit, Track etc.
 *  o Statistics on top visited pages etc.
 *  o the page-specific block visibility settings at Site building >> Blocks >> configure
 *  o same for any other module that has an include/exclude pages input box, e.g
 *    the Smart menus, Smart tabs modules
 */

define('PATH_ALIAS_XT_DEFAULT_NODE_OR_USER_MATCH', '{(^node|^user)/([0-9]+)/(.*)}');

/**
 * Implementation of hook_boot().
 *
 * The mere presence of this empty-bodied hook, guarantees that the functions
 * in this module, in particular custom_url_rewrite_inbound, are known to core
 * just in time. Important for path.inc/drupal_get_normal_path().
 */
function path_alias_xt_boot() {
  return;
}

/**
 * Implementation of hook_menu().
 *
 * Define configuration options for Extended Path Aliases.
 */
function path_alias_xt_menu() {
  $items['admin/settings/path_alias_xt'] = array(
    'title' => 'Extended path aliases',
    'description' => 'Advanced settings',
    'page callback' => 'drupal_get_form',
    'page arguments' => array('_path_alias_xt_admin_settings'),
    'access arguments' => array('administer site configuration'),
  );
  return $items;
}

/**
 * Menu callback for admin settings.
 */
function _path_alias_xt_admin_settings() {
  $form['path_alias_xt_regex_pattern'] = array(
    '#type' => 'textfield',
    '#title' => t('Regular expression to match node and user internal paths'),
    '#default_value' => variable_get('path_alias_xt_regex_pattern', PATH_ALIAS_XT_DEFAULT_NODE_OR_USER_MATCH),
    '#description' => t("While you can always reset this configuration without permanent damage to your site, a change to this expression may break all extended aliases. Change only when you know what you're doing.")
  );
  return system_settings_form($form);
}

/**
 * This is used to override the call drupal_get_path_alias(), which occurs
 * for instance in the block.module. There is no hook available for this.
 *
 * @param $path
 * @param $path_language
 * @return string
 *   The alias for $path or $path if no alias was found.
 */
function path_alias_xt_get_path_alias($path, $path_language = '') {
  global $user;
  if (preg_match('{^user/([0-9]+)\z}', $path, $matches) && $matches[1] == $user->uid) {
    // For logged-in user rather than applying 'user/%' alias, return 'user'
    // alias, if it exists.
    if ($user_alias = drupal_lookup_path('alias', 'user', $path_language)) {
      return $user_alias;
    }
  }
  if ($alias = drupal_lookup_path('alias', $path, $path_language)) {
    return $alias;
  }
  $pattern = variable_get('path_alias_xt_regex_pattern', PATH_ALIAS_XT_DEFAULT_NODE_OR_USER_MATCH);
  if (preg_match($pattern, $path, $matches)) {
    // $matches[0] equals $path, eg 'node/123/edit'
    // $matches[1] will equal either 'node' or 'user'
    // $matches[2] will be either the node or user id, e.g '123'
    // $matches[3] is the path extension, e.g. 'edit'
    if ($matches[1] == 'user' && $matches[2] == $user->uid) {
        // For logged-in user rather than applying 'user/%' alias, return 'user'
        // alias, if it exists.
        if ($user_alias = drupal_lookup_path('alias', 'user', $path_language)) {
          return "$user_alias/$matches[3]";
        }
    }
    if ($alias = drupal_lookup_path('alias', "$matches[1]/$matches[2]", $path_language)) {
      return "$alias/$matches[3]";
    }
  }
  return $path;
}

/**
 * Implementation of pseudo-hook custom_url_rewrite_inbound().
 *
 * Because we modify drupal_get_path_alias(), we also have to implement the
 * complimentary action in drupal_get_normal_path().
 * Fortunately, while drupal_get_path_alias() can't be overridden,
 * drupal_get_normal_path() does let us override its behaviour by implementing
 * custom_url_rewrite_inbound().
 *
 * @param $result
 *   The internal path as calculated and passed to us by drupal_get_normal_path().
 *   When no alternative internal path was found by that function, we apply our
 *   algorithm to create an internal (aka normal) path.
 * @param $path
 *   The original path or its alias.
 * @param $path_language
 *
 * @see includes/path.inc
 */
function custom_url_rewrite_inbound(&$result, $path, $path_language) {
  if (!empty($path) && $result == $path) { // drupal_get_normal_path() did not find an alias
    // If the path exists as a menu item (incl. paged views), abort.
    if (_path_alias_xt_get_menu_item($path)) {
      return;
    }
    $candidate_alias = $path;
    while ($pos = strrpos($candidate_alias, '/')) {
      $candidate_alias = substr($candidate_alias, 0, $pos);
      if ($src = drupal_lookup_path('source', $candidate_alias, $path_language)) {
        if ($src == 'user') {
          global $user;
          // Insert uid into path
          $src .= '/'. $user->uid;
        }
        $result = $src . substr($path, $pos);
        return;
      }
    }
  }
}

function _path_alias_xt_get_menu_item($path) {
  return db_result(db_query("SELECT path FROM {menu_router} WHERE path='%s'", $path));
}

/**
 * Implementation of pseudo-hook custom_url_rewrite_outbound().
 *
 * This gets called from url($path). If path_alias_xt has been properly
 * installed, i.e. the body of drupal_get_path_alias() has been manually or
 * programmatically (PECL runkit) overridden, then this function is effectively
 * a NO-OP, as drupal_get_path_alias will have done the work already.
 * If Domain Access (or another module implementing it) is enabled, we make sure
 * not to implement it here, to avoid a clash. This means that with Domain
 * Access enabled, the body of drupal_get_path_alias() should definitely be
 * overridden, as described in the README.
 *
 * @see includes/common.inc
 *
 * @param $path
 *   The path as calculated and passed to us by the function url().
 *   If no alias was found by that function, using drupal_get_path_alias(),
 *   which we override with a call to path_alias_xt_get_path_alias(), we apply
 *   our algorithm for assembly of the extended path alias.
 * @param $options
 * @param $original_path
 */
if (!function_exists('custom_url_rewrite_outbound')) {

  function custom_url_rewrite_outbound(&$path, &$options, $original_path) {
    if ($path == $original_path) {
      $pattern = variable_get('path_alias_xt_regex_pattern', PATH_ALIAS_XT_DEFAULT_NODE_OR_USER_MATCH);
      if (preg_match($pattern, $path, $matches)) {
        // Provided drupal_get_path_alias() has been overridden to call
        // path_alias_xt_get_path_alias() (manually or via the runkit), this code
        // won't be reached. It's here just in case the override is omitted.
        if ($alias = drupal_lookup_path('alias', "$matches[1]/$matches[2]")) {
          // E.g 'node/1/edit' becomes 'about-us/edit', if 'about-us' is an
          // alias for 'node/1'.
          $path = "$alias/$matches[3]";
        }
      }
    }
  }

}

// Purists look away...
// There is no suitable hook to override core's drupal_get_path_alias()
// behaviour. So we either take on the impossible task of rewriting all modules
// that call it, or we redefine its body to make a simple call back to this
// module. We can do this programmatically by taking advantage of the PECL
// runkit extension. The runkit needs to be compiled and placed in the
// /extensions (or /ext) directory pointed to by the extension_dir directive in
// php.ini

// Dynamically load the runkit. This may not be supported on multi-threaded web
// servers.
// If the line below produces an error on your system, comment it out and make
// sure that you have "extension=runkit.so" in your php.ini. Alternatively,
// apply the simple edit to includes/path.inc as described in the README file.
//dl('runkit.so');

function path_alias_xt_init() {
  if (function_exists('runkit_function_redefine') /* && function_exists('drupal_get_path_alias')*/) {
    $args = '$path, $path_language=""';
    $body = 'return path_alias_xt_get_path_alias($path, $path_language);';
    runkit_function_redefine('drupal_get_path_alias', $args, $body);
  }
}