<?php
// $Id: simplenews_analytics.module,v 1.3 2009-02-09 14:40:45 sutharsan Exp $

/**
 * @file
 * Add Google Analytics tags to links in simplenews emails.
 */
 
/**
 * Implementation of hook_menu().
 */
function simplenews_analytics_menu() {
  $items['admin/settings/simplenews/google_analytics'] = array(
    'title' => 'Google Analytics tags',
    'description' => 'Add google Analytics tags to newsletter links.',
    'type' => MENU_NORMAL_ITEM,
    'page callback' => 'drupal_get_form',
    'page arguments' => array('simplenews_analytics_admin'),
    'access arguments' => array('administer simplenews settings'),
    'weight' => -7.9,
  );

  return $items;
}

/**
 * Implemetation of hook_mail_alter().
 *
 * Add Google Analysics codes to email links.
 * 
 * @param $message
 *  Mail message array.
 */
function simplenews_analytics_mail_alter(&$message) {
  if (strpos($message['id'], 'simplenews') !== FALSE) {
    // Parse message body array.
    if (isset($message['body'])) {
      _simplenews_analytics_get_context($message['params']['context']);
      _simplenews_analytics_parse_body($message['body']);
    }
  }
}

/**
 * Simplenews Google Analytics settings
 */
function simplenews_analytics_admin(&$form_state) {
  $form['simplenews_analytics_utm_source'] = array(
    '#type' => 'textfield',
    '#title' => t('Campaign source'),
    '#required' => TRUE,
    '#size' => 60,
    '#maxlength' => 128,
    '#default_value' => variable_get('simplenews_analytics_utm_source', 'newsletter'),
  );
  $form['simplenews_analytics_utm_medium'] = array(
    '#type' => 'textfield',
    '#title' => t('Campaign medium'),
    '#required' => TRUE,
    '#size' => 60,
    '#maxlength' => 128,
    '#default_value' => variable_get('simplenews_analytics_utm_medium', 'email'),
  );
  $form['simplenews_analytics_utm_campaign'] = array(
    '#type' => 'textfield',
    '#title' => t('Campaign name'),
    '#required' => TRUE,
    '#size' => 60,
    '#maxlength' => 128,
    '#default_value' => variable_get('simplenews_analytics_utm_campaign', '!newsletter_name'),
    '#description' => t('Newsletter name, product, promo code, or slogan. Use <em>!newsletter_name</em> to use the name of the newsletter series.'),
  );
  $form['simplenews_analytics_current_domain'] = array(
    '#type' => 'checkbox',
    '#title' => t('Limit to current domain'),
    '#default_value' => variable_get('simplenews_analytics_current_domain', TRUE),
    '#description' => t('When checked, the Google Analytics tags will only be added to links to the current domain (%domain).', array('%domain' => _simplenews_analytics_current_domain())),
  );
  
  return system_settings_form($form);
}

/**
 * Implementation of hook_help().
 */
function simplenews_analytics_help($path, $arg) {
  switch ($path) {
    case 'admin/help#simplenews_analytics':
      $help = '<p>'. t('Simplenews Google Analytics adds tags to links in in the email. This helps you to track clicks in your email newsletters with Google Analytics.') ."<br />\n";
      $help .= t("Permission 'administer simplenews settings' is used. No additional permissions are required.") ."</p>\n";
      return $help;
    case 'admin/settings/simplenews/google_analytics':
      $help = '<p>'. t('See <a href="!ga_url">Google Analytics URL builder</a> for tag information and examples.', array('!ga_url' => 'http://www.google.com/support/googleanalytics/bin/answer.py?hl=en&answer=55578')) ."</p>\n";
      return $help;
  }
}

/**
 * Recursively parse email message body array.
 *
 * @param $text
 *  Mail message body text (array or string).
 */
function _simplenews_analytics_parse_body(&$text) {
  if (is_array($text)) {
    foreach ($text as $key => $element) {
      _simplenews_analytics_parse_body($text[$key]);
    }
  }
  else {
    if (!empty($text)) {
      $text = preg_replace_callback("`(https?://[a-zA-Z0-9@:%_+*~#?&=.,/;-]*[a-zA-Z0-9@:%_+*~#&?=/;-])`i", '_simplenews_analytics_parse_full_url', $text);
    }
  }
}

/**
 * preg callback: Add Google Analytics query string to url.
 *
 * @param $match
 *  Preg match array.
 *  
 * @return parsed url
 */
function _simplenews_analytics_parse_full_url($match) {
  // Don't add query string if link is outside of current domain.
  if (variable_get('simplenews_analytics_current_domain', TRUE) && strpos($match[1], _simplenews_analytics_current_domain()) === FALSE) {
    return $match[1];
  }
  
  // Use ? or & prefix depending on existing query string.
  if ($query = _simplenews_analytics_build_query()) {
    $query = strpos($match[1],'?') ? '&'. $query : '?'. $query;
  }

  // Add query string to url.
  return $match[1] . $query;
}

/**
 * Build query from Google Analytics settings
 *
 * @return query string containing Google Analytics query.
 */
function _simplenews_analytics_build_query() {
  global $language;
  $query[] = 'utm_source='.  drupal_urlencode(variable_get('simplenews_analytics_utm_source', 'newsletter'));
  $query[] = 'utm_medium='.  drupal_urlencode(variable_get('simplenews_analytics_utm_medium', 'email'));

  $context = _simplenews_analytics_get_context();
  $tokens = simplenews_mail_tokens($context['account'], $context, $language);
  $campain = strtr(variable_get('simplenews_analytics_utm_campaign', '!newsletter_name'), $tokens);
  $query[] = 'utm_campaign='.  drupal_urlencode($campain);

  return implode('&', $query);
}

/**
 * Return the base URL without the protocol.
 */
function _simplenews_analytics_current_domain() {
  global $base_url;
  return preg_replace('@https?://(.*)@i', '\1', $base_url);
}

/**
 * Store and reproduce context variables.
 *
 * @param $context
 *  Array of data to store. If NULL
 */
function _simplenews_analytics_get_context($context = NULL) {
  static $data = array();
  
  if (isset($context)) {
    $data = array_merge($data, $context);
  }
  return $data;
}