<?php
// $Id: notifications.module,v 1.6.2.9.2.50.2.7 2009-04-24 00:10:28 jareyero Exp $

/**
 * @file
 * Notifications module
 *
 * This is the base module of the notifications framework. It handles event processing, queueing,
 * message composition and sending.
 * 
 * Different subscriptions types are provided by plug-in modules implementing hook_notifications()
 * Most of the UI is implemented in notifications_ui module
 * The messaging framework is used for message delivery
 * Token module is used for token replacement in messages 
 * 
 * This is based on the previous subscriptions module
 * 
 * Development Seed, http://www.developmentseed.org, 2007 
 *
 */

// Define some values for subscription status
// Blocked subscriptions, for blocked users
define('NOTIFICATIONS_SUBSCRIPTION_BLOCKED', 0);
// Enabled ones, will produce notifications
define('NOTIFICATIONS_SUBSCRIPTION_ACTIVE', 1);
// Temporarily disabled ones, maybe user on holidays
define('NOTIFICATIONS_SUBSCRIPTION_INACTIVE', 2);

/**
 * Implementation of hook_menu().
 */
function notifications_menu() {
  // Administration. This one will override messaging menu item
  $items['admin/messaging'] = array(
    'title' => 'Messaging & Notifications',
    'access arguments' => array('administer notifications'),
    'description' => 'Administer and configure messaging and notifications',
    'page callback' => 'system_admin_menu_block_page',
    'file' => 'system.admin.inc',
    'file path' => drupal_get_path('module', 'system'),
  );
  $items['admin/messaging/subscriptions'] = array(
    'title' => 'Manage subscriptions',
    'description' => 'Manage existing subscriptions and queue.',
    'page callback' => 'notifications_admin_status_page',
    'access arguments' => array('administer notifications'),
    'file' => 'notifications.admin.inc',
  );
  $items['admin/messaging/subscriptions/overview'] = array(
    'title' => 'Overview',
    'description' => 'Subscriptions overview.',
    'type' => MENU_DEFAULT_LOCAL_TASK,
    'weight' => -10,
    'file' => 'notifications.admin.inc',
  );
  $items['admin/messaging/subscriptions/admin'] = array(
    'title' => 'Administer',
    'description' => 'Administer subscriptions.',
    'type' => MENU_LOCAL_TASK,
    'page callback' => 'drupal_get_form',
    'page arguments' => array('notifications_manage_admin_subscriptions'),
    'access arguments' => array('administer notifications'),
    'file' => 'notifications.manage.inc',
  );
  $items['admin/messaging/subscriptions/queue'] = array(
    'title' => 'Queue',
    'description' => 'Notifications queue.',
    'page callback' => 'notifications_admin_queue',
    'type' => MENU_LOCAL_TASK,
    'access arguments' => array('administer notifications'),
    'file' => 'notifications.admin.inc',
  );
  
  // Site settings
  $items['admin/messaging/notifications'] = array(
    'title' => 'Notifications Settings',
    'description' => 'Site settings for user notifications.',
    'page callback' => 'drupal_get_form',
    'page arguments' => array('notifications_settings_form'),
    'access arguments' => array('administer site configuration'),
    'file' => 'notifications.admin.inc',
  );
  $items['admin/messaging/notifications/settings'] = array(
    'title' => 'General',
    'weight' => -10,
    'type' => MENU_DEFAULT_LOCAL_TASK,
    'file' => 'notifications.admin.inc',
  );
  $items['admin/messaging/notifications/intervals'] = array(
    'title' => 'Intervals',
    'page callback' => 'drupal_get_form',
    'page arguments' => array('notifications_send_intervals_form'),
    'type' => MENU_LOCAL_TASK,
    'access arguments' => array('administer site configuration'),
    'file' => 'notifications.admin.inc',
  );
  $items['admin/messaging/notifications/events'] = array(
    'title' => 'Events',
    'page callback' => 'drupal_get_form',
    'page arguments' => array('notifications_admin_events_form'),
    'type' => MENU_LOCAL_TASK,
    'access arguments' => array('administer site configuration'),
    'file' => 'notifications.admin.inc',
  );
  // Subscribe links. For this items access will be checked later in the page
  $items['notifications/subscribe/%user'] = array(
    'type' => MENU_CALLBACK,
    'page callback' => 'notifications_page_subscribe',
    'page arguments' => array(2),
    'access callback' => 'notifications_access_subscribe',
    'access arguments' => array(2),
    'file' => 'notifications.pages.inc',
  );
  // Unsubscribe links This page will need to work with anonymous users
  $items['notifications/unsubscribe'] = array(
    'type' => MENU_CALLBACK,
    'page callback' => 'notifications_page_unsubscribe',
    'page arguments' => array(2, 3),
    'access callback' => TRUE,
    'file' => 'notifications.pages.inc',
  );
  // Edit subscription
  $items['notifications/subscription/%notifications_subscription'] = array(
    'type' => MENU_CALLBACK,
    'title' => 'Edit subscription',
    'page callback' => 'drupal_get_form',
    'page arguments' => array('notifications_subscription_form', 2),
    'access callback' => 'notifications_subscription_access',
    'access arguments' => array('edit', 2),
    'file' => 'notifications.pages.inc',
  );
  $items['user/%user/notifications'] = array(
    'type' => MENU_LOCAL_TASK,
    'title' => 'Notifications',
    //'page callback' => 'notifications_page_user_overview',
    //'page arguments' => array(1),
    'page callback' => 'drupal_get_form',
    'page arguments' => array('notifications_user_overview', 1),
    'access callback' => 'notifications_access_user',
    'access arguments' => array(1),
    'file' => 'notifications.pages.inc',
  );
  $items['user/%user/notifications/overview'] = array(
    'type' => MENU_DEFAULT_LOCAL_TASK,
    'title' => 'Overview',
    'weight' => -10,
  );  
  $items['user/%user/notifications/subscriptions'] = array(
    'type' => MENU_LOCAL_TASK,
    'title' => 'Subscriptions',
    'page callback' => 'drupal_get_form',
    'page arguments' => array('notifications_manage_user_subscriptions', 1),
    'access callback' => 'notifications_access_user',
    'access arguments' => array(1, 'manage'),
    'file' => 'notifications.manage.inc',
  );
  $items['user/%user/notifications/update/%'] = array(
    'type' => MENU_CALLBACK,
    'title' => 'Update subscriptions',
    'page callback' => 'drupal_get_form',
    'page arguments' => array('notifications_update_user_subscriptions', 1, 4),
    'access callback' => 'notifications_access_user',
    'access arguments' => array(1, 'maintain'),
    'file' => 'notifications.pages.inc',
  );  
  // Some autocomplete callbacks
  $items['notifications/autocomplete/node/title'] = array(
    'title' => 'Node title autocomplete',
    'page callback' => 'notifications_node_autocomplete_title',
    'access arguments' => array('access content'),
    'type' => MENU_CALLBACK,
    'file' => 'notifications.node.inc',
  );
  // Some autocomplete callbacks
  $items['notifications/autocomplete/node/type'] = array(
    'title' => 'Node title autocomplete',
    'page callback' => 'notifications_node_autocomplete_type',
    'access arguments' => array('access content'),
    'type' => MENU_CALLBACK,
    'file' => 'notifications.node.inc',
  );
  return $items;
}

/**
 * Menu access callback for user subscriptions
 * 
 * @param $account
 *   User account to which these subscriptions below
 * @param $op
 *   - maintain = create / delete
 *   - manage = use the per account administration page
 */
function notifications_access_user($account, $op = 'maintain') {
  global $user;
  
  if (user_access('administer notifications') || user_access('manage all subscriptions')) {
    return TRUE;
  }
  else {
    return $account->uid && $user->uid == $account->uid &&
      (($op == 'maintain' && user_access('maintain own subscriptions')) || ($op == 'manage' && user_access('manage own subscriptions')));
  }
}

/**
 * Menu access callback, add a given subscription type
 */
function notifications_access_user_add($account = NULL, $type = NULL) {
  global $user;
  
  $account = $account ? $account : $user;
  
  if (notifications_access_user($account)) {
    if ($type && ($access = notifications_subscription_types($type, 'access'))) {
      return user_access($access, $account);
    }
    else {
      return TRUE;
    }
  }
}

/**
 * Menu access callback for subscribe links
 * 
 * More access checking depending on subscription type will be done at the destination page
 */
function notifications_access_subscribe($account) {
  global $user;
  
  if (user_access('administer notifications') || user_access('manage all subscriptions')) return TRUE;
  
  return $account && $account->uid && ($user->uid == $account->uid) && user_access('maintain own subscriptions');
}

/**
 * Menu loading, subscription
 */
function notifications_subscription_load($sid) {
  return notifications_load_subscription($sid);
}

/**
 * Menu access callback
 */
function notifications_subscription_access($op, $subscription, $account = NULL) {
  global $user;
  
  $account = $account ? $account : $user;
  
  if (user_access('administer notifications') || user_access('manage all subscriptions')) return TRUE;
  
  switch ($op) {
    case 'edit':
    case 'unsubscribe':
      return $account->uid && ($subscription->uid == $account->uid) && user_access('maintain own subscriptions');
  }

  return FALSE;
}

/**
 * Implementation of hook_perms()
 * 
 * This module defines the following permissions
 * - administer notifications = Full access to all administration for the module
 * - maintain own subscriptions = Create / delete own subscriptions
 * - manage own subscriptions = Access the subscriptions management tab
 * - manage all subscriptions = Administer other users subscriptions
 */
function notifications_perm() {
  return array('administer notifications', 'maintain own subscriptions', 'manage own subscriptions', 'manage all subscriptions');
}

/**
 * Implementation of hook_user().
 */
function notifications_user($type, $edit, &$user, $category = NULL) {
  switch ($type) {
    case 'delete';
      // Delete related data on tables
      notifications_delete_subscriptions(array('uid' => $user->uid));
      break;
    case 'update':
      if (isset($edit['status'])) {
        if ($edit['status'] == 0) { // user is being blocked now
          // Delete pending notifications and block existing active subscriptions
          db_query('UPDATE {notifications} SET status = %d WHERE status = %d AND uid = %d', NOTIFICATIONS_SUBSCRIPTION_BLOCKED, NOTIFICATIONS_SUBSCRIPTION_ACTIVE, $user->uid);
          notifications_queue_clean(array('uid' => $user->uid));
        }
        else {
          // User may be being unblocked, unblock subscriptions if any
          db_query('UPDATE {notifications} SET status = %d WHERE status = %d AND uid = %d', NOTIFICATIONS_SUBSCRIPTION_ACTIVE, NOTIFICATIONS_SUBSCRIPTION_BLOCKED, $user->uid);
        }
      }
      break;
  }
}

/**
 * Clean queue for a user and update event tracker
 */
function notifications_queue_clean($params) {
  require_once drupal_get_path('module', 'notifications') .'/notifications.cron.inc';
  notifications_queue_delete($params);
  notifications_event_clean(TRUE);
}

/**
 * Implementation of hook_form_alter()
 */
function notifications_form_alter(&$form, $form_state, $form_id) {
  switch ($form_id) {
    // Default send interval for user form
    case 'user_profile_form':
      if ($form['_category']['#value'] == 'account' && (user_access('maintain own subscriptions') || user_access('administer notifications'))) {
        $form['messaging']['#title'] = t('Messaging and Notifications settings');
        $send_intervals = _notifications_send_intervals();
        $form['messaging']['notifications_send_interval'] = array(
          '#type' => 'select',
          '#title' => t('Default send interval'),
          '#options' => $send_intervals,
          '#default_value' => notifications_user_setting('send_interval', $form['_account']['#value']),
          '#disabled' => count($send_intervals) == 1,
          '#description' => t('Default send interval for subscriptions.'),
        );    
      }
  }
}

/**
 * Gets a user setting, defaults to default system setting for each
 * 
 * @param $name
 *   Setting name
 * @param $account
 *   Optional user account, will default to current user
 * @param $default
 *   Optional default to return if this is not set
 */
function notifications_user_setting($name, $account = NULL, $default = NULL) {
  global $user;

  $account = $account ? $account : $user;
  // Default send method is taken from messaging module
  if ($name == 'send_method') {
    return messaging_method_default($account);
  } 
  $field = 'notifications_'. $name;
  if (isset($account->$field)) {
    return $account->$field;
  }
  else {
    return variable_get('notifications_default_'. $name, $default);
  }
}

/**
 * Process subscriptions events
 * 
 * @param $event
 *   Array with event parameters
 */
function notifications_event($event) {
  global $user;
  // Fill in event with default values
  $event += array(
    'uid' => $user->uid,
    'load_args' => '',
    'created' => time(),
    'module' => 'notifications', // Module that triggered the event
    'type' => '', // Object/event type
    'action' => '', // Action that happened to the object
    'params' => array(), // Object parameters
  );
  
  // Check whether we have to save and queue this event, defaults to yes if not set
  $info = variable_get('notifications_events', array());
  if (isset($info[$event['type']][$event['action']]) && !$info[$event['type']][$event['action']]) {
    // Do not store nor queue this event, can be changed by plug-in modules
    $event += array(
      'save' => FALSE,
      'queue' => FALSE,
    );
  }
  else {
    $event += array(
      'save' => TRUE, 
      'queue' => TRUE,
    );   
  }

  $event = (object)$event;

  // Notify other modules we are about to trigger some subscriptions event
  // Modules can do cleanup operations or modify event properties
  notifications_module_invoke('event trigger', $event);
  
  // Store event, unles marked not to be saved 
  if ($event->save) {
    drupal_write_record('notifications_event', $event);
  }
  // Send event to queue for subscriptions, unless marked not to
  if ($event->queue) {
    notifications_queue($event);
  }
  
  return $event;
}

/**
 * Queue events for notifications adding query conditions from plug-ins
 * 
 * This is an example of the resulting query
 *
 * INSERT INTO {notifications_queue} (uid, sid, module, eid, send_interval, send_method, cron, created, conditions)
 * SELECT DISTINCT s.uid, s.sid, s.module, 34, s.send_interval, s.send_method, s.cron, 1230578161, s.conditions FROM notifications s 
 * INNER JOIN notifications_fields f ON s.sid = f.sid 
 * WHERE s.status = 1 AND s.event_type = 'node' AND s.send_interval >= 0 
 * AND ((f.field = 'nid' AND f.value = '2') OR (f.field = 'type' AND f.value = 'story') OR (f.field = 'author' AND f.value = '1'))
 * GROUP BY s.uid, s.sid, s.module, s.send_interval, s.send_method, s.cron, s.conditions 
 * HAVING s.conditions = count(f.sid)
 *
 * @param $event
 *   Event array.
 */
function notifications_queue($event) {
  $query = array();
  // Build big insert query using the query builder. The fields for this event type will be added by the plug-ins. 
  // If no arguments retrieved, skip this step
  if ($query_args = notifications_module_information('query', 'event', $event->type, $event)) {
    $query['insert'] = array('uid', 'destination', 'sid', 'module', 'eid', 'send_interval', 'send_method', 'cron', 'created', 'conditions');
    $query['into'] = '{notifications_queue}';
    $query['distinct'] = TRUE;
    $query['select'] = array('s.uid', 's.destination', 's.sid', 's.module', '%d', 's.send_interval', 's.send_method', 's.cron', '%d', 's.conditions');
    $query['from'] = array('{notifications} s');
    $query['select args'] = array($event->eid, $event->created);
    $query['join'] = array('INNER JOIN {notifications_fields} f ON s.sid = f.sid');
    $query['where'] = array('s.status = 1', "s.event_type = '%s'", 's.send_interval >= 0');
    $query['where args'] = array($event->type);
    // Add one more condition if we don't send notifications on own posts
    if (!variable_get('notifications_sendself', 0) && !empty($event->uid)) {
      $query['where'][] = 's.uid <> %d';
      $query['where args'][] = $event->uid;
    }    
    // Some group by fields are not really needed but added for pgsql compatibility
    $query['group'] = array('s.uid', 's.destination', 's.sid', 's.module', 's.send_interval', 's.send_method', 's.cron', 's.conditions');
    
    // We throw in all the conditions and check the number of matching conditions
    // that must be equal to the subscription conditions number    
    $query['having'] = array('s.conditions = count(f.sid)');

    // We add parameters for each module separately
    foreach ($query_args as $query_params) {
      $query = notifications_query_build($query_params, $query);
    }
    
    // Give a chance to other modules to alter the query or empty it so we don't throw it
    drupal_alter('notifications_query', $query);
    
    // Finally we build the SELECT part of the query and glue it to the INSERT
    if ($query) {
      list($sql, $args) = notifications_query_sql($query);
      db_query($sql, $args);
    }
  }

  // Modules can do cleanup operations or modify the queue
  notifications_module_invoke('event queued', $event, $query);
  
  // Now update event counter with rows in notifications_queue or delete if no rows
  if ($count = db_result(db_query('SELECT COUNT(*) FROM {notifications_queue} WHERE eid = %d', $event->eid))) {
    db_query('UPDATE {notifications_event} SET counter = %d WHERE eid = %d', $count, $event->eid);
    // If immediate sending enabled, store eid for sending on page exit.
    notifications_send_immediate($event->eid);
  }
  else {
    db_query('DELETE FROM {notifications_event} WHERE eid = %d', $event->eid);
  }

}

/**
 * Store / return events for immediate sending
 */
function notifications_send_immediate($eid = 0) {
  static $events;
  
  if (!$eid) {
    return $events;
  }
  elseif (variable_get('notifications_send_immediate', 0)) {
    $events[] = $eid;
  }
}

/**
 * Implementation of hook_exit()
 * 
 * This is where the immediate sending is done if enabled, so we are sure all other modules
 * have finished node processing when node update.
 */
function notifications_exit() {
  if ($events = notifications_send_immediate()) {
    require_once drupal_get_path('module', 'notifications') .'/notifications.cron.inc';
    foreach ($events as $eid) {
      notifications_process_rows(array('cron' => 1, 'eid' => $eid, 'send_interval' => 0));
    }    
  }
}

/**
 * Query builder for subscriptions
 * 
 * This adds up query elements into a big array so they can be later rendered as SQL
 * 
 * @see notifications_query_sql()
 * 
 * @param $params
 *   Array of query conditions
 * @param $query
 *   Base query to build upon
 */
function notifications_query_build($params, $query = array()) {
  foreach ($params as $name => $elements) {
    if ($name == 'fields') {
      // Fields elements have some special handling, they have the form: field => value
      foreach ($elements as $field => $value ) {
        // Use field definition provided by hook_notifications('subscription fields') and handle array values with IN conditions
        // Workaround to have a valid one because not all modules provide the information yet (og?)
        if (notifications_subscription_fields($field, 'type') == 'int') {
          $type = 'int';
          $fieldval = 'intval';
        }
        else {
          $type = 'char';
          $fieldval = 'value';
        }
        if (is_array($value)) {
          $query['fields'][] = "f.field = '%s' AND f.$fieldval IN (". db_placeholders($value, $type) .")";
          $query['fields args'][] = $field;
          $query['fields args'] = empty($query['fields args']) ? $value : array_merge($query['fields args'], $value);
        }
        else {
          $query['fields'][] = "f.field = '%s' AND f.$fieldval = " . db_type_placeholder($type);
          $query['fields args'][] = $field;
          $query['fields args'][] = $value;
        }
      }
    }
    else {
      if ($name == 'fields sql') {
        // These are added as 'fields' parameters without further parsing
        $name = 'fields';
      }
      if (is_array($elements)) {
        $query[$name] = empty($query[$name]) ? $elements : array_merge($query[$name], $elements);
      }
      else {
        $query[$name][] = $elements;
      }
    }
  }
 
  return $query;
}

/**
 * Build the SQL statement from query elements
 * 
 * It will build INSERT + SELECT or SELECT queries from its elements
 * 
 * @return array()
 *   list($sql, $args);
 */
function notifications_query_sql($query) {
  $sql = '';
  if (!empty($query['insert'])) {
    $sql .= 'INSERT INTO ' . $query['into'] . ' ('. implode(', ', $query['insert']) .') ';
  }
  $sql .= !empty($query['distinct']) ? 'SELECT DISTINCT ' : 'SELECT ';
  $sql .=  implode(', ', $query['select']);
  $sql .= ' FROM '. implode(', ', $query['from']);
  if (!empty($query['join'])) {
    $sql .= ' '. implode(' ', $query['join']);
  }  
  
  // Where conditions come from 'where' and 'fields' elements
  // Field conditions are OR'd and added into the other conditions
  $where = !empty($query['where']) ? $query['where'] : array();
  if (!empty($query['fields'])) {
    $where[] = '('. implode(') OR (', $query['fields']) .')';
  }  
  if ($where) {
    $sql .= ' WHERE ('. implode(') AND (', $where) .')';
  }  
  if (!empty($query['group'])) {
    $sql .= ' GROUP BY '. implode(', ', $query['group']);
  }
  if (!empty($query['having'])) {
    $sql .= ' HAVING '. implode(' AND ', $query['having']);
  }
  // Merge all args, start with generic ones for subscription queries, then other groups
  $args = !empty($query['args']) ? $query['args'] : array();
  foreach (array('select', 'join', 'where', 'fields', 'having') as $key) {
    if (!empty($query[$key .' args'])) {
      $args = array_merge($args, $query[$key .' args']);
    }
  }
 
  return array($sql, $args);
}

/**
 * Get subscription for a given user
 * 
 * @param $uid
 *   User id
 * @param $event_type
 *   Event type
 * @param $oid
 *   Object id for caching. I.e. for a node it will be nid
 * @param $object
 *   Object to check subscriptions to. I.e. $node
 * 
 * @return
 *   Array of subscriptions for this user and object indexed by sid 
 */
function notifications_user_get_subscriptions($uid, $event_type, $oid, $object = NULL, $refresh = FALSE) {
  static $subscriptions;

  if ($refresh || !isset($subscriptions[$uid][$event_type][$oid])) {
    $subscriptions[$uid][$event_type][$oid] = array();
    $query_args = notifications_module_information('query', 'user', $event_type, $object);
    // Base query
    $query = array(
      'select' => array('s.*', 'f.*'),
      'from' => array('{notifications} s'),
      'join' => array('INNER JOIN {notifications_fields} f ON s.sid = f.sid'),
      'where' => array('s.uid = %d', "s.event_type = '%s'"),
      'where args' => array($uid, $event_type),
    );
    foreach ($query_args as $query_params) {
      $query = notifications_query_build($query_params, $query);
    }
   
    // Build the query merging all the parts
    list($sql, $args) = notifications_query_sql($query);  
    $result = db_query($sql, $args);

    while ($sub = db_fetch_object($result)) {
      if (!isset($subscriptions[$uid][$event_type][$oid][$sub->sid])) {
        $subscriptions[$uid][$event_type][$oid][$sub->sid] = $sub;
      }
      $subscriptions[$uid][$event_type][$oid][$sub->sid]->fields[$sub->field] = $sub->value;
    }
  }

  return $subscriptions[$uid][$event_type][$oid];
}

/**
 * Update or create subscription
 * 
 * This function checks for duplicated subscriptions before saving.
 * If a similar subscription is found it will be updated.
 * If no subscription is found and it is new, the sid will be added into the object.
 * 
 * @param $subscription
 *   Subscription object or array
 * @return integer
 *   Failure to write a record will return FALSE. Otherwise SAVED_NEW or SAVED_UPDATED is returned depending on the operation performed.
 */
function notifications_save_subscription(&$subscription) {
  global $user;
  
  $result = FALSE;
  $subscription = (object)$subscription;
  $subscription->conditions = count($subscription->fields);
  $account = $subscription->uid ? messaging_load_user($subscription->uid) : $user;
  
  // Default values for fields: send_interval, send_method, cron, etc...
  foreach (_notifications_subscription_defaults($account) as $field => $value) {
    if (!isset($subscription->$field)) {
      $subscription->$field = $value;
    }
  }
  // Fill in event type if not set
  if (empty($subscription->event_type)) {
    $subscription->event_type = notifications_subscription_types($subscription->type, 'event_type');
  }
  if (!empty($subscription->sid)) {
    $op = 'update';
    $result = drupal_write_record('notifications', $subscription, 'sid');
  }
  elseif ($duplicate = notifications_get_subscriptions(array('uid' => $subscription->uid, 'type' => $subscription->type, 'event_type' => $subscription->event_type, 'module' => $subscription->module, 'send_method' => $subscription->send_method, 'send_interval' => $subscription->send_interval), $subscription->fields, TRUE)) {
    // We've found duplicates, resolve conflict updating first, deleting the rest
    // It is possible that we had a disabled one, this updating will fix it
    $update = array_shift($duplicate);
    unset($subscription->sid); // It may be 0
    foreach ($subscription as $key => $value) {
      if (isset($value)) {
        $update->$key = $value;
      }
    }
    $subscription = $update;
    // If there are more, delete, keep the table clean
    while (array_shift($duplicate)) {
      notifications_delete_subscription($duplicate->sid);
    }
    return notifications_save_subscription($subscription);  
  }
  else {
    $op = 'insert';    
    $result = drupal_write_record('notifications', $subscription);
  }
  
  // If the operation has worked so far, update fields and inform other modules
  if ($result !== FALSE) {
    if ($op == 'update') {
      db_query("DELETE FROM {notifications_fields} WHERE sid = %d", $subscription->sid);
    }    
    // There may be subscriptions with no fields, some people are coding such plug-ins.
    if (!empty($subscription->fields)) {
      foreach ($subscription->fields as $name => $value) {
        if (is_array($value)) {
          db_query("INSERT INTO {notifications_fields} (sid, field, value, intval) VALUES(%d, '%s', '%s', %d)", $subscription->sid, $value['type'], $value['value'], (int)$value['value']);
        }
        else { 
          db_query("INSERT INTO {notifications_fields} (sid, field, value, intval) VALUES(%d, '%s', '%s', %d)", $subscription->sid, $name, $value, (int)$value);
        }
      }
    }
    notifications_module_invoke($op, $subscription);
  }

  return $result;
}

/**
 * Get an individual subscription.
 *
 * @param $subs
 *   Either a subscription object or a subscription id (sid).
 * @param $refresh
 *   Force cache refresh
 * @return
 *   Subscriptions object.
 */
function notifications_load_subscription($subs, $refresh = FALSE) {
  static $cache = array();
  if (is_object($subs)) {
    $sid = $subs->sid;
    $subscription = $subs;
  }
  else {
    $sid = $subs;
  }
  if ($refresh || !array_key_exists($sid, $cache)) {
    if (!isset($subscription)) {
      $subscription = db_fetch_object(db_query("SELECT * FROM {notifications} WHERE sid = %d", $sid));
    }
    if ($subscription) {
      $subscription->fields = array();
      $result = db_query("SELECT * FROM {notifications_fields} WHERE sid = %d", $sid);
      while ($condition = db_fetch_object($result)) {
        $subscription->fields[$condition->field] = $condition->value;
      }
    }
    $cache[$sid] = $subscription;
  }
  return $cache[$sid];
}

/**
 * Delete subscription and clean up related data.
 * 
 * It also removes pending notifications related to that subscription 
 * 
 * @param $sid
 *   Id of subscriptin to delete
 */
function notifications_delete_subscription($sid) {
  foreach (array('notifications', 'notifications_fields', 'notifications_queue') as $table) {
    db_query("DELETE FROM {". $table ."} WHERE sid = %d", $sid);
  }
}

/**
 * Delete multiple subscriptions and clean up related data (pending notifications, fields).
 * 
 * Warning: If !$limit, it will delete also subscriptions with more conditions than the fields passed.
 * 
 * @param array $params
 *   Array of multiple conditions in the notifications table to delete subscriptions
 * @param array $conditions
 *   Array of multiple conditions in the notifications_fields table to delete subscriptions
 * @param $limit
 *   Whether to limit the result to subscriptions with exactly that condition fields
 */
function notifications_delete_subscriptions($params, $conditions = array(), $limit = FALSE) {
  // Build query conditions using the query builder
  $query = notifications_subscriptions_query_build($params, $conditions, $limit);
  $query['select'][] = 'n.sid';
  list($sql, $args) = notifications_query_sql($query);
  // Query notifications that meet these conditions and build an array
  $result = db_query($sql, $args);
  $delete = array();
  while ($n = db_fetch_object($result)) {
    $delete[] = $n->sid;
  }
  // This is the actual deletion. We've fetched the values from the db so this needs no escaping.
  if ($delete) {
    $placeholders = db_placeholders($delete);
    foreach (array('notifications_fields', 'notifications_queue', 'notifications') as $table) {
      db_query('DELETE FROM {' . $table . '} WHERE sid IN (' . $placeholders . ')', $delete);
    }
  }
}

/**
 * Query builder for subscriptions
 * 
 * Builds queries for 'notifications' and 'notifications_fields' tables using schema
 * and fields (subscription fields) information.
 * 
 * @param array $params
 *   Array of multiple conditions in the notifications table. 
 * @param array $conditions
 *   Array of multiple conditions in the notifications_fields table. The array elements may be 
 *   - single field => value pairs 
 *   - or key => array('type' => field, 'value' => value)
 *   If value is null, it just checks that a condition for the given field type exists
 * @param $limit
 *   Whether to limit the result to subscriptions with exactly that condition fields
 * 
 * @return array()
 *   Structured array with 'join', 'where', 'args' elements
 */
function notifications_subscriptions_query_build($params, $conditions = array(), $limit = FALSE) {
  $join = $where = $args = array();
  $schema = drupal_get_schema('notifications');
  
  // If we limit this query to the number of conditions add a new param
  if ($limit && $conditions) {
    $params += array('conditions' => count($conditions));
  }
  // Add conditions for main notifications table
  foreach ($params as $field => $value) {
    if (in_array($schema['fields'][$field]['type'], array('serial', 'int'))) {
      $where[] =  'n.'. $field ." = %d";
    }
    else {
      $where[] =  'n.'. $field ." = '%s'";
    }
    $args[] = $value;
  }
  
  // Now we need to join once the fields table for each condition
  if ($conditions) {
    $index = 0;
    foreach ($conditions as $key => $data) {
      if (is_array($data)) {
        $field = $data['type'];
        $value = $data['value'];
      }
      else {
        $field = $key;
        $value = $data;
      }
      $alias = 'nf'. $index++;
      $join[] = "INNER JOIN {notifications_fields} $alias ON n.sid = $alias.sid";
      $where[] = "$alias.field = '%s'";
      $args[] = $field;
      // If null value, do not check value, we just check that a condition for this field type exists
      if (!is_null($value)) {
        if (notifications_subscription_fields($field, 'type') == 'int') {
          $where[] = "$alias.intval = %d";        
        }
        else {
          $where[] = "$alias.value = '%s'";
        }        
        $args[] = $value;
      }
    }
  }
  // Return query array
  return array('from' => array('{notifications} n'), 'join' => $join, 'where' => $where, 'args' => $args);
}

/**
 * Get subscriptions that fit a set of conditions.
 *
 * @param $params
 *   Array of parameters for the query
 * @param $conditions
 *   Optional array of condition fields
 * @param $limit
 *   Whether to limit the result to subscriptions with exactly that condition fields
 * @param $key
 *   Optional key field to use as the array index. Will default to sid 
 *   For notifications with one field, it may be 'value' or 'intval'
 * @param $pager
 *   Whether to throw a pager query 
 * @return
 *   Array of subscriptions indexed by uid, module, field, value, author
 * 
 * @todo Check field types for building the query
 */
function notifications_get_subscriptions($params, $conditions = array(), $limit = TRUE, $key = 'sid', $pager = NULL) {
  // Build query conditions using the query builder
  $query = notifications_subscriptions_query_build($params, $conditions, $limit);
  $query['select'][] = 'n.*';
  list ($sql, $args) = notifications_query_sql($query);
    
  if ($pager) {
    $sql .= ' ORDER BY n.sid';
    $result = pager_query($sql, $pager, 0, NULL, $args);
  }
  else {
    $result = db_query($sql, $args);
  }
  $subscriptions = array();
  while ($subs = db_fetch_object($result)) {
    $load = notifications_load_subscription($subs);
    if ($key == 'value' || $key == 'intval') {
      $field = array_shift(_notifications_fields($load->fields));
      $subscriptions[$field->value] = $load;
    }
    else {
      $subscriptions[$subs->$key] = $load;
    }  
  }
  return $subscriptions;
}

/**
 * Get info about subscription types
 *
 * @param $type
 *   String, the subscriptions type OPTIONAL
 * @param $field
 *   String, a specific field to retrieve info from OPTIONAL
 *
 * @return
 *   Information for a given field and type
 *   or information for a given field for all types
 */
function notifications_subscription_types($type = NULL, $field = NULL) {
  static $types;
  
  if (!isset($types)) {
    $types = notifications_module_information('subscription types');
    drupal_alter('notifications_subscription_types', $types);
  }
  
  return notifications_info($types, $type, $field);
}

/**
 * Get information about subscriptions fields
 */
function notifications_subscription_fields($type = NULL, $property = NULL) {
  static $fields;
  if (!isset($fields)) {
    $fields = notifications_module_information('subscription fields');
    drupal_alter('notifications_subscription_fields', $fields);
  }
  return notifications_info($fields, $type, $property);
}

/**
 * Get information from an array of data
 */
function notifications_info(&$data, $type = NULL, $field = NULL) {
  if ($field && $type) {
    return isset($data[$type][$field]) ? $data[$type][$field] : NULL;
  }
  elseif ($field) {
    $return = array();
    foreach ($data as $id => $info) {
      $return[$id] = $info[$field];
    }
    return $return;
  }
  elseif ($type) {
    return isset($data[$type]) ? $data[$type] : array();
  }
  else {
    return $data;
  }  
}

/**
 * Information about digesting method for a send interval.
 * 
 * @return array()
 *   Ditest information for that interval, or all the information if no interval
 */
function notifications_digest_method($send_interval = NULL, $refresh = FALSE) {
  static $digest_methods, $intervals;
  
  if (!isset($digest_methods) || $refresh) {
    // Method information
    foreach (notifications_module_information('digest methods') as $method) {
      $digest_methods[$method['type']] = $method;
    }
    // Mapping interval -> method
    $intervals = variable_get('notifications_digest_methods', array());
  }
  if (is_null($send_interval)) {
    return $digest_methods;
  }
  elseif (!empty($intervals[$send_interval]) && isset($digest_methods[$intervals[$send_interval]])) {
    return $digest_methods[$intervals[$send_interval]];
  }
  else {
    // Default, that will be 'short' if interval > 0, none otherwise
    return ($send_interval > 0) ? $digest_methods['short'] : NULL;
  }
}

/**
 * Invokes hook_notifications() with a single parameter or more but not needing
 * an object to be passed as reference.
 */
function notifications_module_information($op, $arg0 = NULL, $arg1 = NULL, $arg2 = NULL) {
  $object = NULL;
  return notifications_module_invoke($op, $arg0, $arg1, $arg2);
}

/**
 * Invokes hook_notifications() in every module.
 *
 * We cannot use module_invoke() for this, because the arguments need to
 * be passed by reference.
 */
function notifications_module_invoke($op, &$arg0, $arg1 = NULL, $arg2 = NULL) {
  $result = array();
  foreach (module_implements('notifications') as $module) {
    $function = $module .'_notifications';
    if ($return = $function($op, $arg0, $arg1, $arg2)) {
      $result = array_merge($result, $return);
    }
  }
  return $result;
}

/**
 * Implementation of hook_messaging()
 * 
 * This hook provides information about the mensaje templates this module uses and related tokens.
 * 
 * Depending on $op, this hook takes different parameters and returns different pieces of information:
 * 
 * - 'message groups'
 *   Get array of message groups, each of which will have one or more keys for different templates
 *   Each group should have a unique key, so it should start with the module name
 * - 'message keys'
 *   Get message template parts for a given group ($arg1)
 *   Return array of key => name for each part
 * - 'messages'
 *   Get default message templates for a given group ($arg1).
 *   It should return default texts, indexed by message key that will be the default templates
 *   These templates may be edited on the 'Messaging templates' page
 * - 'tokens'
 *   Get available tokens for a given message group and key ($arg1).
 *   Return array of token keys that will be available for this message templates
 *   The tokens themselves may be default tokens (provided by token module) or we can add new
 *   tokens implementing hook_token_list() and hook_token_value()
 * 
 * @param $op
 *   Operation, type of information to retrieve
 * @param $arg1, $arg2...
 *   Different parameters depending on $op
 */
function notifications_messaging($op, $arg1 = NULL, $arg2 = NULL, $arg3 = NULL, $arg4 = NULL) {
  switch ($op) {
    case 'message types':
      $info['notifications'] = array(
        'name' => t('Notifications'),
        'description' => t('Messages coming from user subscriptions and system events')
      );
      return $info;
    case 'message groups':
      // Generic notifications event
      $info['notifications-event'] = array(
        'module' => 'notifications',
        'name' => t('Notifications event'),
        'description' => t('Common parts for all Notifications messages for a single event. This is useful for defining a common header and/or footer for all these messages.'),
      );
      $info['notifications-digest'] = array(
        'module' => 'notifications',
        'name' => t('Notifications digest'),
        'description' => t('Depending on your settings for each Send interval, Notifications may be digested, this is grouped and summarized in a single message. These are the common parts for Notifications digests.'),
      );
      return $info;
    case 'message keys':      
      $type = $arg1;
      switch ($type) {
        case 'notifications-event':
          // Event notifications
          return array(
            'subject' => t('Subject'),
            'header' => t('Header'),
            'main' => t('Content'),
            'footer' => t('Footer'),
          );
        case 'notifications-digest':
          return array(
            'subject' => t('Subject'),
            'header' =>  t('Header'),
            'main' => t('Line for digested events'),
            'closing' => t('Group closing'),
            'footer' => t('Footer'),
          );
      }
      break;
    case 'messages':
      $type = $arg1;
      // Event notifications
      if ($type == 'notifications-event') {
        return array(
          'subject' => t('Event notification for [user] from [site-name]'),
          'header' => t("Greetings [user],"),
          'main' => t("A item to which you are subscribed has been updated"),
          'footer' => array(
              t('This is an automatic message from [site-name]'),
              t('To manage your subscriptions, browse to [subscriptions-manage]'),
              t('You can unsubscribe at [unsubscribe-url]'),
          ),
        );
      }
      // Digested messages
      if ($type == 'notifications-digest') {
        return array(
          'subject' => t('[site-name] subscription update for [user]'),
          'header' => t("Greetings, [user].\n\nThese are your messages"),
          'main' => t("A [type] has been updated: [title]\n\n[event_list]"),
          'closing' => '...',
          'footer' => array(
            t('This is an automatic message from [site-name]'),
            t('To manage your subscriptions, browse to [subscriptions-manage]'),
          ),        
        );
      }
      break;
    case 'tokens':
      $type = explode('-', $arg1);
      $tokens = array();
      // These are the token groups that will be used for this module's messages
      if ($type[0] == 'notifications') {
        $tokens = array('subscription', 'user');
        if ($type[1] == 'event') {
          $tokens[] = 'event';
        }
      }
      return $tokens;
    case 'method update':
      // A messaging method has been disabled ($arg1) and replaced by the new one ($arg2)
      // Update subscriptions
      db_query("UPDATE {notifications} SET send_method = '%s' WHERE send_method = '%s'", $arg2, $arg1);
      // Purge notifications queue, we may lost some notifications but it's the safest option.
      db_query("DELETE FROM {notifications_queue} WHERE send_method = '%s'", $arg1);
      break;
  }
}

/**
 * Implementation of hook_token_values()
 * 
 * @ TODO: Work out event tokens
 */
function notifications_token_values($type, $object = NULL, $options = array()) {
  switch ($type) {
    case 'subscription':
      $values = array();
      if ($subscription = $object) {
        $link = notifications_get_link('unsubscribe', array('sid' => $subscription->sid, 'signed' => TRUE, 'destination' => FALSE, 'absolute' => TRUE));
        $values['unsubscribe-url'] = url($link['href'], $link['options']);      
      }
      return $values;
    case 'user':
      if ($account = $object) {
        $values['subscriptions-manage'] = $account->uid ? url("user/$account->uid/notifications", array('absolute' => TRUE)) : '';
        $link = notifications_get_link('unsubscribe', array('uid' => $account->uid, 'signed' => TRUE, 'destination' => FALSE, 'absolute' => TRUE));
        $values['unsubscribe-url-global'] = url($link['href'], $link['options']);
        return $values;
      }
  }
}

/**
 * Implementation of hook_token_list(). Documents the individual
 * tokens handled by the module.
 */
function notifications_token_list($type = 'all') {
  $tokens = array();
  if ($type == 'user' || $type == 'all') {
    $tokens['user']['subscriptions-manage']    = t('The url for the current user to manage subscriptions.');
    $tokens['user']['unsubscribe-url-global'] = t('The url to allow a user to delete all their subscriptions.');
  }
  if ($type == 'subscription' || $type == 'all') {
    $tokens['subscription']['unsubscribe-url']      = t('The url for disabling a specific subscription.');
  }
  if ($type == 'event' || $type == 'all') {
    $tokens['event']['event-list'] = t('List of events for message digests');
    $tokens['event']['event-detail'] = t('Detailed information for event');
  }
  return $tokens;
}

/**
 * Get event types
 */
function notifications_event_types($type = NULL, $action = NULL) {
  static $info;

  if (!$info) {
    $types = notifications_module_information('event types');
    foreach ($types as $type_info) {
      $info[$type_info['type']][$type_info['action']] = $type_info;
    }
    drupal_alter('notifications_event_types', $info);
  }
  if ($action) {
    if (isset($info[$type][$action])) {
      // The event provides a proper action defined
      return $info[$type][$action];
    }
    elseif (isset($info[$type]['default'])) {
      // The event provides a default action, go for it
      return $info[$type]['default'];
    }
    else {
      // We better make the code break, than return an empty array()
      return NULL; 
    }
  }
  elseif ($type) {
    return isset($info[$type]) ? $info[$type] : array();
  }
  else {
    return $info;
  }
}

/**
 * Implementation of hook_cron()
 */
function notifications_cron() {
  include_once drupal_get_path('module', 'notifications') .'/notifications.cron.inc';
  notifications_process_run();
}

/**
 * Return link array for subscriptions
 * 
 * @param $type
 *   Link type: 'subscribe' | 'unsubscribe'
 * @param $params
 *   Aditional parameters for the subscription, may be
 *   - uid, the user for which the link is generated
 *   - confirm, whether to show confirmation page or not
 *   - signed, to produce a signed link that can be used by anonymous users (Example: unsubscribe link in emails)
 *   - Other subscription parameters: type, fields...
 */
function notifications_get_link($type, $params) {
  global $user;
  $params += array(
    'uid' => $user->uid,
    'confirm' => TRUE,
    'signed' => FALSE,
    'destination' => $_GET['q'],
    'query' => array(),
  );
  switch ($type) {
    case 'subscribe':
      $elements = array(
        'subscribe',
        $params['uid'],
        $params['type'],
        implode(',', array_keys($params['fields'])),
        implode(',', $params['fields'])
      );
      break;
    case 'unsubscribe':
      // The unsubscribe link can be for a single subscription or all subscriptions for a user
      if (!empty($params['sid'])) {      
        $elements = array('unsubscribe', 'sid', $params['sid']);        
      }
      elseif (!empty($params['uid'])) {
        $elements = array('unsubscribe', 'uid', $params['uid']); 
      }
      break;
  }
  // Build query string using named parameters
  $query = $params['query'];
  if ($params['destination']) {
    $query['destination'] = $params['destination'];
  }
  // To skip the confirmation form, the link must be signed
  // Note tat the query string will be 'confirm=1' to skip confirmation form
  if (!$params['confirm']) {
    $query['confirm'] = 1;
    $params['signed'] = 1;
  }
  if ($params['signed']) {
    $query['signature'] =  _notifications_signature($elements, !$params['confirm']);
  }
  // Build final link parameters
  $options['query'] = $query;
  foreach (array('absolute', 'html') as $name) {
    if (isset($params[$name])) {
      $options[$name] = $params[$name];
    }
  }
  return array(
    'href' => 'notifications/'. implode('/', $elements),
    'options' => $options,
  );
}

/**
 * Check access to objects
 * 
 * This will check permissions for subscriptions and events before subscribing
 * and before getting updates.
 * 
 * @param $type
 *   Type of object to check for access. Possible values:
 *   - 'event', will check access to event objects
 *   - 'subscription', will check access to subscribed objects
 */
function notifications_user_allowed($type, $account, $object = NULL) {

  // Invoke notifications hook and check for a FALSE return value
  
  $permissions = notifications_module_information('access', $type, $account, $object);

  if ($permissions) {
    return !in_array(FALSE, $permissions);
  }
  else {
    // If no module has anthing to say about access I guess it will be true
    return TRUE;
  }
}

/**
 * Implementation of notifications_hook()
 * 
 * Check access permissions to subscriptions
 */
function notifications_notifications($op, &$arg0, $arg1 = NULL, $arg2 = NULL) {
  switch ($op) {
    case 'access':
      if ($arg0 == 'subscription') {
        $account = $arg1;
        $subscription = $arg2;
        // First we check valid subscription type
        $access = FALSE;
        if ($subscription->type && ($info = notifications_subscription_types($subscription->type))) {
          // To allow mixed subscription types to work we dont have a fixed field list
          // Then check specific access to this type. Each type must have a permission
          if (!empty($info['access callback'])) {
            $access = call_user_func($info['access callback'], $account, $subscription);
          }
          elseif (!empty($info['access']) && user_access($info['access'], $account)|| user_access('administer notifications', $account)) {
           // Check matching fields
            if (!array_diff($info['fields'], array_keys($subscription->fields))) {
              $access = TRUE;
            }
          }
        }
        return array($access);
      }
      break;

    case 'digest methods':
      // Return array of digesting engines
      $info['short'] = array(
        'type' => 'short',
        'name' => t('Short'),
        'description' => t('Produces one line per event, grouped by object'),
        'digest callback' => 'notifications_process_digest_short',
      );
      $info['long'] = array(
        'type' => 'long',
        'name' => t('Long'),
        'description' => t('Adds full information for each event'),
        'digest callback' => 'notifications_process_digest_long',
      );
      return $info;
  }
}

/**
 * List of send intervals. These may be overriden in a variable.
 */
function _notifications_send_intervals() {
  return variable_get('notifications_send_intervals',
    array(
      // -1 => t('Never'),
      0 => t('Immediately'),
      3600 => t('Every hour'),
      43200 => t('Twice a day'),
      86400 => t('Daily'),
      604800 => t('Weekly'),  
    )
  );
}

/**
 * List of send methods
 */
function _notifications_send_methods($account = NULL) {
  return variable_get('notifications_send_methods', messaging_method_list($account));
}

/**
 * Signature for url parameters
 * 
 * @param $params
 *   Subscription parameters
 * @param $skip_confirm
 *   TRUE to skip confirmation form
 */
function _notifications_signature($params, $skip_confirm = FALSE) {
  return md5('notifications:'. drupal_get_private_key() .':'. ($skip_confirm ? 1 : 0) .':'. implode(':', $params));
}

/**
 * Default values for subscription
 */
function _notifications_subscription_defaults($account = NULL) {
  return array(
    'send_interval' => notifications_user_setting('send_interval', $account, 0),
    'send_method' => notifications_user_setting('send_method', $account, ''),
    'module' => 'notifications',
    'status' => NOTIFICATIONS_SUBSCRIPTION_ACTIVE,
    'destination' => '',
    'cron' => 1,
  ); 
}

/**
 * Status list
 */
function _notifications_subscription_status() {
  return array(
    NOTIFICATIONS_SUBSCRIPTION_ACTIVE => t('active'),
    NOTIFICATIONS_SUBSCRIPTION_BLOCKED => t('blocked'),
    NOTIFICATIONS_SUBSCRIPTION_INACTIVE => t('inactive'),
 );
}

/**
 * Build list of subscription types
 * 
 * Note: some custom types may have user defined strings, that's why the check_plain() everywhere
 */
function _notifications_subscription_types($format = 'short', $filter = NULL) {
  $options = array();  
  foreach (notifications_subscription_types() as $type => $info) {
    if (!$filter || count(array_intersect_assoc($filter, $info)) == count($filter)) {
      switch ($format) {
        case 'short':
          $options[$type] = check_plain($info['title']);
          break;
        case 'long':
          $options[$type] = '<strong>'. check_plain($info['title']) .'</strong>.';
          if (!empty($info['description'])) { 
            $options[$type] .= ' '. check_plain($info['description']);
          }
          break;
      }
    }
  }
  return $options;
}

/**
 * Normalize field format
 * 
 * Converts notifications field into an array with known structure
 * which will be an array containing objects with key, type, value pairs
 * 
 * In some parts, fields are a key => value array
 * They can be also an array of arrays or objects
 */
function _notifications_fields($source) {
  $result = array();
  if ($source) {
    foreach ($source as $key => $data) {
      if (is_object($data)) {
        $field = $data;
      }
      elseif (is_array($data)) {
        $field = (object)$data;
        $field->key = $key;
      }
      else {
        $field = new Stdclass();
        $field->key = $key;
        $field->type = $key;
        $field->value = $data;
      }
      $result[] = $field;
    }
  }
  return $result;
}

/**
 * Callback for module dependent data
 * 
 * Some data stored in the notifications system is meant to be processed by other modules and
 * this is indicated by a module column in the data.
 * 
 * This function calls the module function if available, defaulting to the notifications provided
 * function when not. The arguments are passed as is
 * 
 * @param $module
 *   Module name
 * @param $function
 *   Function name in module
 */
 function notifications_callback() {
   $args = func_get_args();
   $module = array_shift($args);
   $function = array_shift($args);
   if ($module && function_exists($module .'_notifications_'. $function)) {
     $callback = $module .'_notifications_'. $function;
   }
   else {
     $callback = 'notifications_'. $function;
   }
   return call_user_func_array($callback, $args);
 }

/**
 * Generic subscriptions content form
 * 
 * Builds a form for a user to manage its own subscriptions with
 * some generic parameters
 * 
 * Currently it only manages simple condition fields
 * @param $account 
 *   User account
 * @param $type
 *   Subscription type
 * @param $subscriptions
 *   Current subscriptions of this type. If null they'll be loaded
 * @param $list
 *   Array with available subscriptions indexed by field value
 * @param $defaults
 *   Default value for subscriptions
 * @param $options
 *   Optional, array of aditional options for the form
 */
function notifications_user_form($form_state, $account, $type, $subscriptions, $list, $defaults, $options = array()) {
  // Complete defaults
  $info = notifications_subscription_types($type);
  $field = $info['fields'][0];
  $field_title = !empty($options['title']) ? $options['title'] : '';
  if (is_null($subscriptions)) {
    // Fetch subscriptions with given parameters
    $subscriptions = notifications_get_subscriptions(array('type' => $type, 'event_type' => $info['event_type'], 'uid' => $account->uid), TRUE, 'value');
  }
  $defaults += array(
    'sid' => 0,
    'type' => $type,
    'event_type' => $info['event_type'],
  );
  $defaults += _notifications_subscription_defaults($account);
  // Hide Send method column if only one
  $send_methods = _notifications_send_methods();
  $header = array(theme('table_select_header_cell'), $field_title, t('Send interval'));
  if (count($send_methods) > 1) {
    $header[] = t('Send method');
  }  
  $form['defaults'] = array('#type' => 'value', '#value' => $defaults);  
  $form['account'] = array('#type' => 'value', '#value' => $account);
  $form['current'] = array('#type' => 'value', '#value' => $subscriptions);
  $form['subscription_fields'] = array('#type' => 'value', '#value' => array());
  $form['subscriptions'] = array(
    '#tree' => TRUE,
    '#theme' => 'notifications_form_table',
    '#header' => $header,
  );  


  foreach ($list as $key => $title) {
    $rowdefaults = isset($subscriptions[$key]) ? (array)($subscriptions[$key]) : $defaults;
    $rowdefaults += $rowdefaults;
    $form['subscriptions']['checkbox'][$key] = array(
      '#type' => 'checkbox',
      '#default_value' => $rowdefaults['sid'],
    );
    $form['subscriptions']['title'][$key] = array(
      '#value' => $title,
    );
    $form['subscriptions']['send_interval'][$key] = array(
      '#type' => 'select',
      '#options' => _notifications_send_intervals(),
      '#default_value' => $rowdefaults['send_interval'],
    );
    // Hide send methods if only one available
    if (count($send_methods) > 1) {
      $form['subscriptions']['send_method'][$key] = array(
        '#type' => 'select',
        '#options' => _notifications_send_methods(),
        '#default_value' => $rowdefaults['send_method'],
      );
    }
    else {
      $form['subscriptions']['send_method'][$key] = array('#type' => 'value', '#value' => $rowdefaults['send_method']);
    }
    // Pass on the fields for processing
    $form['subscription_fields']['#value'][$key] = array($field => $key);
  
  }
  $form['submit'] = array('#type' => 'submit', '#value' => t('Save'));

  return $form; 
}

/**
 * Process generic form submission
 */
function notifications_user_form_submit($form, &$form_state) {
  $form_values = $form_state['values'];
  $account = $form_values['account'];
  $current = $form_values['current'];
  $defaults = $form_values['defaults'];
  $defaults += array('uid' => $account->uid);
  $fields = $form_values['subscription_fields'];
  $values = $form_values['subscriptions'];
  $check = 'checkbox';

  foreach ($values[$check] as $index => $value) {
    $subscription = NULL;
    if ($value) {
      // Checked, save only if new or changed
      if (!isset($current[$index])) {
        $subscription = $defaults;
      }
      elseif ($current[$index]->send_interval != $values['send_interval'][$index] || $current[$index]->send_method != $values['send_method'][$index]) {
        $subscription = (array)($current[$index]);        
      }
      // Complete and save
      if ($subscription) {
        $subscription['send_interval'] = $values['send_interval'][$index];
        $subscription['send_method'] = $values['send_method'][$index];
        $subscription['fields'] = $fields[$index];
        notifications_save_subscription($subscription);
      }
    }
    elseif (isset($current[$index])) {
      notifications_delete_subscription($current[$index]->sid);
    }
  }
}

/**
 * Display a form field for a notifications_field
 */
function notifications_subscription_form_field($type, $value = NULL) {
  $info = notifications_subscription_fields($type);
  
  if (!empty($info['options callback'])) {
    $element['#type'] = 'select';
    $element['#options'] =  call_user_func($info['options callback']);
  }
  elseif (!empty($info['autocomplete path'])) {
    $element['#type'] = 'textfield';
    $element['#autocomplete_path'] = $info['autocomplete path'];
    if ($value) {
      if (!empty($info['autocomplete callback'])) {
        $value = call_user_func($info['autocomplete callback'], $value);
      }
      elseif (!empty($info['format callback']))  {
        $value = call_user_func($info['format callback'], $value, FALSE);
      }      
    }
  }
  else {
    $element['#type'] = 'textfield';
    if ($value) {
      $value = check_plain($value);
    }
  }
  if ($value) {

    $element['#default_value'] = $value;
  }
  return $element;
}

/**
 * Format subscription for display
 * 
 * @return array()
 *   Array with type_name, field_names (array), field_values (array)
 */
function notifications_format_subscription($subscription, $format = 'short', $html = TRUE) {
  // Build array and add subscription type name
  $info = notifications_subscription_types($subscription->type);
  $names = $values = array();
 
  // Get field names and values formatting each field
  if (!empty($subscription->fields)) {
    foreach (_notifications_fields($subscription->fields) as $field) {
      $item = notifications_format_subscription_field($field->type, $field->value, $html);
      $names[] = $item['name'];
      $values[] = $item['value'];
    }
  }
  // If this subscription has a name, use it, otherwise build it using fields and values
  if (!empty($info['name'])) {
    $value_name = $info['name'];
  }
  else {
    $value_name = implode(', ', $values);
  }
  // Now do the formatting
  switch ($format) {
    case 'array':
      return array('type' => $info['title'], 'name' => $value_name, 'names' => $names, 'values' => $values);
    case 'short':
      return t('@type: !values', array('@type' => $info['title'], '!values' => $value_name));
    case 'long':
      return t('Subscription %id of type %type to: !values', array('%id' => $subscription->sid, '%type' => $info['title'], '!values' => $value_name));
  }
}

/**
 * Format subscriptions field for display and get some more information
 * 
 * @return array()
 *   Array with 'name' and 'value' elements
 */
function notifications_format_subscription_field($type, $value, $html = TRUE) {
  $format_name = $format_value = t('Unknown');
 
  if ($info = notifications_subscription_fields($type)) {
    $format_name = $info['name'];
    if (!empty($info['format callback'])) {
      $format_value = call_user_func($info['format callback'], $value, $html);
    } 
    elseif (!empty($info['options callback'])) {
      $options = call_user_func($info['options callback']);
      $format_value = isset($options[$value]) ? $options[$value] : t('Not available');
    }
    else {
      $format_value = check_plain($value);
    }
  }

  return array('name' => $format_name, 'value' => $format_value);
}

/**
 * Implementation of hook_theme()
 */
function notifications_theme() {
  return array(
    'notifications_form_table' => array(
      'arguments' => array('element' => NULL),
      'file' => 'notifications.admin.inc',
    ),
    'notifications_send_intervals' => array(
      'arguments' => array('element' => NULL),
      'file' => 'notifications.admin.inc',
    ),
    'notifications_digest_short_body' => array(
      'arguments' => array('text' => NULL, 'list' => NULL),
      'file' => 'notifications.cron.inc',
    ),
    'notifications_digest_short_line' => array(
      'arguments' => array('line' => NULL, 'group' => NULL),
      'file' => 'notifications.cron.inc',
    ),
    'notifications_digest_long_body' => array(
      'arguments' => array('header' => NULL, 'content' => NULL, 'footer' => NULL),
      'file' => 'notifications.cron.inc',
    ),
    'notifications_manage_subscriptions' => array(
      'arguments' => array('form' => NULL),
      'file' => 'notifications.manage.inc',
    ),
    'notifications_subscriptions_filter_form' => array(
      'arguments' => array('form' => NULL),
      'file' => 'notifications.manage.inc',
    ),
    'notifications_table_form' => array(
      'arguments' => array('form' => NULL),
      'file' => 'notifications.admin.inc',
    ),
    'notifications_subscription_fields' => array(
      'arguments' => array('form' => NULL),
      'file' => 'notifications.pages.inc',
    ),
  );
}

/**
 * Short hand for info logs
 */
function notifications_log($message = NULL, $variables = NULL) {
  return _notifications_log('info', $message, $variables);
}

/**
 * Quick logging for debugging and manual queue processing
 */
function _notifications_log($type, $message = NULL, $variables = NULL, $severity = WATCHDOG_NOTICE) {
  static $logs;
  
  if ($message) {
    $logs[] = array($type, $message, $variables, $severity);
  }
  else {
    return $logs ? array_map('_notifications_log_format', $logs) : '';
  }
}

/**
 * Format notifications log
 */
function _notifications_log_format($log) {
  list($type, $string, $args, $severity) = $log;
 
  if ($args) {
    // Transform arguments before inserting them.
    $append = array();
    foreach ($args as $key => $value) {      
      if (is_array($value) || is_object($value)) {
        $value = print_r($value, TRUE);
      }
      switch ($key[0]) {
        case '@':
          // Escaped only.
          $args[$key] = check_plain($value);
          break;
        case '%':
          $args[$key] = theme('placeholder', $value);
          break;
        case '!':
          // Pass-through.
          $args[$key] = $value;
          break;
        default:
          // Append to string a key value pair, different from watchdog format
          $append[] = ' <strong>'. $key .'</strong>= '. check_plain($value);
          break;
      }
    }
    $string = strtr($string, $args);
    $append ? $string .= ' '. implode(', ', $append) : NULL;
  }

  return '<strong> '. $type .'</strong>: '. $string;
}