<?php

/**
 * @file
 * Provides integration with Mailgun's email sending API.
 */

use Mailgun\Mailgun;

define('MAILGUN_DOCUMENTATION_LINK', 'https://www.drupal.org/node/2547591');
define('MAILGUN_DASHBOARD_LINK', 'https://mailgun.com/app/dashboard');
define('MAILGUN_ADMIN_PAGE', 'admin/config/services/mailgun');

/**
 * Implements hook_menu().
 */
function mailgun_menu() {
  $items = array();

  $items[MAILGUN_ADMIN_PAGE] = array(
    'title' => 'Mailgun',
    'description' => 'Configure Mailgun settings.',
    'page callback' => 'drupal_get_form',
    'page arguments' => array('mailgun_admin_settings'),
    'access arguments' => array('administer mailgun'),
    'file' => 'mailgun.admin.inc',
  );
  $items[MAILGUN_ADMIN_PAGE . '/settings'] = array(
    'title' => 'Settings',
    'type' => MENU_DEFAULT_LOCAL_TASK,
    'weight' => 0,
  );
  $items[MAILGUN_ADMIN_PAGE . '/test'] = array(
    'title' => 'Send test email',
    'page callback' => 'drupal_get_form',
    'page arguments' => array('mailgun_test_form'),
    'access arguments' => array('administer mailgun'),
    'description' => 'Send a test e-mail using the Mailgun API.',
    'file' => 'mailgun.admin.inc',
    'type' => MENU_LOCAL_TASK,
    'weight' => 1,
  );

  return $items;
}

/**
 * Implements hook_permission().
 */
function mailgun_permission() {
  return array(
    'administer mailgun' => array(
      'title' => t('Administer Mailgun'),
      'description' => t('Perform administration tasks for the Mailgun e-mail sending service.'),
      'restrict access' => TRUE,
    ),
  );
}

/**
 * Implements hook_theme().
 */
function mailgun_theme($existing, $type, $theme, $path) {
  return array(
    'mailgun_message' => array(
      'variables' => array(
        'subject' => NULL,
        'body' => NULL,
        'message' => array(),
      ),
      'template' => 'mailgun-message',
      'path' => drupal_get_path('module', 'mailgun') . '/templates',
      'mail theme' => TRUE,
    ),
  );
}

/**
 * Implements hook_help().
 */
function mailgun_help($path, $arg) {
  switch ($path) {
    case MAILGUN_ADMIN_PAGE:
      return '<p>' . t('See !link for instructions on installing and configuring Mailgun.', array(
        '!link' => l(t('documentation'), MAILGUN_DOCUMENTATION_LINK),
      )) . '</p>';

    case MAILGUN_ADMIN_PAGE . '/test':
      return '<p>' . t('Use this form to send a test e-mail to ensure you have correctly configured Mailgun.') . '</p>';
  }
}

/**
 * Implements hook_cron_queue_info().
 */
function mailgun_cron_queue_info() {
  $queues = array();
  $queues['mailgun_queue'] = array(
    'worker callback' => 'mailgun_send',
    'time' => 60,
  );
  return $queues;
}

/**
 * Implements hook_mail().
 */
function mailgun_mail($key, &$message, $params) {
  switch ($key) {
    case 'test':
      $message['subject'] = t('Mailgun test email');
      $message['body'] = $params['message'];
      if ($params['attachment']) {
        $message['params']['attachments'] = array(drupal_realpath('misc/druplicon.png'));
      }
      break;
  }
}

/**
 * Implements hook_libraries_info().
 */
function mailgun_libraries_info() {
  $libraries['mailgun'] = array(
    'name' => 'Mailgun PHP library',

    'vendor url' => 'https://documentation.mailgun.com/en/latest/libraries.html#php',
    'download url' => 'https://github.com/mailgun/mailgun-php',

    'version arguments' => array(
      'file' => 'vendor/mailgun/mailgun-php/CHANGELOG.md',
      'pattern' => '/##\W+((\d+)\.(\d+))/',
    ),

    // Path to the 'autoload.php' created by Composer.
    'path' => 'vendor',
    'files' => array(
      'php' => array('autoload.php'),
    ),
  );

  return $libraries;
}

/**
 * Implements hook_form_FORM_ID_alter().
 */
function mailgun_form_libraries_admin_library_status_form_alter(&$form, &$form_state, $form_id) {
  $library = drupal_array_get_nested_value($form_state, array(
    'build_info', 'args', 0,
  ));
  if (empty($library['machine name']) || $library['machine name'] !== 'mailgun') {
    return;
  }
  // Libraries module provides own instruction "How to install the library".
  // We override it because this instruction is not correct and may confuse.
  $form['instructions'] = array(
    '#markup' => t('The Mailgun PHP library is not installed. Please see Installation section in the !link.', array(
      '!link' => l(t('documentation'), MAILGUN_DOCUMENTATION_LINK),
    )),
  );
}

/**
 * Get the Mailgun client to access Mailgun's endpoints.
 *
 * @param string $key
 *   The Mailgun API key. Leave empty to use the API key saved in database.
 *
 * @return \Mailgun\Mailgun
 *   Mailgun object.
 */
function mailgun_get_client($key = '') {
  // Check if the Mailgun PHP library is installed.
  if (!mailgun_check_library()) {
    watchdog('mailgun', 'Mailgun client initialization failed: Unable to load the Mailgun PHP library.', array(), WATCHDOG_ERROR);
    return FALSE;
  }

  $key = (empty($key)) ? variable_get('mailgun_api_key', '') : $key;
  if (empty($key)) {
    watchdog('mailgun', 'Mailgun client initialization failed: Missing API key.', array(), WATCHDOG_ERROR);
    return FALSE;
  }

  return Mailgun::create($key);
}

/**
 * Detect if Mailgun library is installed.
 *
 * @return bool
 *   TRUE if library is installed, FALSE otherwise.
 */
function mailgun_check_library() {
  if (module_exists('libraries')) {
    libraries_load('mailgun');
  }
  if (method_exists('\Mailgun\Mailgun', 'create')) {
    return TRUE;
  }
  return FALSE;
}

/**
 * Prepares variables for mailgun-message.tpl.php.
 *
 * Adds id/module/key-specific hook suggestions.
 *
 * @see templates/mailgun-message.tpl.php
 */
function template_preprocess_mailgun_message(&$variables) {
  $variables['theme_hook_suggestions'][] = 'mailgun_message__' . $variables['message']['id'];
  $variables['theme_hook_suggestions'][] = 'mailgun_message__' . $variables['message']['module'];
  $variables['theme_hook_suggestions'][] = 'mailgun_message__' . $variables['message']['key'];
}

/**
 * Send an e-mail using the Mailgun API.
 *
 * @param array $mailgun_message
 *   A Mailgun message array. Contains the following keys:
 *   - from: The e-mail addressthe message will be sent from.
 *   - to: The e-mail addressthe message will be sent to.
 *   - subject: The subject of the message.
 *   - text: The plain-text version of the message. Processed using
 *    drupal_html_to_text().
 *   - html: The original message content. May contain HTML tags.
 *   - cc: One or more carbon copy recipients. If multiple, separate with
 *    commas.
 *   - bcc: One or more blind carbon copy recipients. If multiple, separate
 *    with commas.
 *   - o:tag: An array containing the tags to add to the message.
 *    See: https://documentation.mailgun.com/user_manual.html#tagging.
 *   - o:campaign: The campaign ID this message belongs to.
 *    https://documentation.mailgun.com/user_manual.html#um-campaign-analytics
 *   - o:deliverytime: Desired time of delivery. Messages can be scheduled for
 *    a maximum of 3 days in the future.
 *    See: https://documentation.mailgun.com/api-intro.html#date-format.
 *   - o:dkim: Boolean indicating whether or not to enable DKIM signatures on
 *    per-message basis.
 *   - o:testmode: Boolean indicating whether or not to enable test mode.
 *    See: https://documentation.mailgun.com/user_manual.html#manual-testmode.
 *   - o:tracking: Boolean indicating whether or not to toggle tracking on a
 *    per-message basis.
 *    See: https://documentation.mailgun.com/user_manual.html#tracking-messages.
 *   - o:tracking-clicks: Boolean or string "htmlonly" indicating whether or
 *    not to toggle clicks tracking on a per-message basis. Has higher
 *    priority than domain-level setting.
 *   - o:tracking-opens: Boolean indicating whether or not to toggle clicks
 *    tracking on a per-message basis. Has higher priority than domain-level
 *    setting.
 *   - h:X-My-Header: h: prefix followed by an arbitrary value allows to append
 *    a custom MIME header to the message (X-My-Header in this case).
 *    For example, h:Reply-To to specify Reply-To address.
 *   - v:my-var: v: prefix followed by an arbitrary name allows to attach a
 *    custom JSON data to the message.
 *    See: https://documentation.mailgun.com/user_manual.html#manual-customdata.
 *
 * @return bool
 *   TRUE if the mail was successfully accepted, FALSE otherwise.
 */
function mailgun_send(array $mailgun_message) {
  $client = mailgun_get_client();
  if (!$client) {
    return FALSE;
  }

  // Test mode. Mailgun will accept the message but will not send it.
  if (variable_get('mailgun_test', FALSE)) {
    $mailgun_message['o:testmode'] = 'yes';
  }

  // Merge the $mailgun_message array with options.
  $mailgun_message += $mailgun_message['params'];
  unset($mailgun_message['params']);

  if (variable_get('mailgun_domain', '_sender') === '_sender') {
    // Extract the domain from the sender's email address.
    // Use regular expression to check since it could be either a plain email
    // address or in the form "Name <example@example.com>".
    $tokens = (preg_match('/^\s*(.+?)\s*<\s*([^>]+)\s*>$/', $mailgun_message['from'], $matches) === 1) ? explode('@', $matches[2]) : explode('@', $mailgun_message['from']);
    $mail_domain = array_pop($tokens);

    // Retrieve a list of available domains first.
    $domains = array();
    try {
      $result = $client->domains()->index();
      if (!empty($result)) {
        foreach ($result->getDomains() as $domain) {
          $domains[$domain->getName()] = $domain->getName();
        }
      }
      else {
        watchdog('mailgun', 'Could not retrieve domain list.', array(), WATCHDOG_ERROR);
      }
    }
    catch (Exception $e) {
      watchdog('mailgun', 'An exception occurred while retrieving domains. @code: @message', array(
        '@code' => $e->getCode(),
        '@message' => $e->getMessage(),
      ), WATCHDOG_ERROR);
    }

    if (empty($domains)) {
      // No domain available.
      // Although this shouldn't happen, doesn't hurt to check.
      return FALSE;
    }

    // Now, we need to get the working domain. This is generally the domain the
    // From address is on or the root domain of it.
    $working_domain = '';
    if (in_array($mail_domain, $domains, TRUE)) {
      // Great. Found it.
      $working_domain = $mail_domain;
    }
    else {
      // Oops. No match. Perhaps it's a subdomain instead.
      foreach ($domains as $domain) {
        if (strpos($domain, $mail_domain) !== FALSE) {
          // Got it.
          $working_domain = $domain;
          break;
        }
      }
    }

    // There is a chance that the user is attempting to send from an email
    // address that's on a domain not yet added to the Mailgun account.
    // In that case, abort sending and report error.
    if (empty($working_domain)) {
      watchdog('mailgun', 'Unable to locate a working domain for From address %mail. Aborting sending.', array(
        '%mail' => $mailgun_message['from'],
      ), WATCHDOG_ERROR);
      return FALSE;
    }
  }
  else {
    $working_domain = variable_get('mailgun_domain', '');
  }

  // Send message with attachments.
  if (!empty($mailgun_message['attachment'])) {
    foreach ($mailgun_message['attachment'] as &$attachment) {
      // Ignore array constructions. Not sure what values can be here.
      if (is_array($attachment)) {
        continue;
      }
      $attachment = array('filePath' => $attachment);
    }
  }

  try {
    $result = $client->messages()->send($working_domain, $mailgun_message);

    if (!empty($result)) {
      if (variable_get('mailgun_log', FALSE)) {
        watchdog('mailgun', 'Successfully sent message from %from to %to. %message.', array(
          '%from' => $mailgun_message['from'],
          '%to' => $mailgun_message['to'],
          '%message' => $result->getMessage(),
        ));
      }
      return TRUE;
    }
    else {
      watchdog('mailgun', 'Failed to send message from %from to %to. %message.', array(
        '%from' => $mailgun_message['from'],
        '%to' => $mailgun_message['to'],
        '%message' => $result->getMessage(),
      ), WATCHDOG_ERROR);
      return FALSE;
    }
  }
  catch (Exception $e) {
    watchdog('mailgun', 'Exception occurred while trying to send test email from %from to %to. @code: @message.', array(
      '%from' => $mailgun_message['from'],
      '%to' => $mailgun_message['to'],
      '@code' => $e->getCode(),
      '@message' => $e->getMessage(),
    ));
    return FALSE;
  }
}