<?php
// $Id: email_example.module,v 1.4 2010-03-03 15:48:59 rfay Exp $

/**
 * @file
 * Example of how to use Drupal's mail API.
 *
 * This example module provides two different examples of the Drupal email API.
 *  - defines a simple contact form and shows how to use drupal_mail()
 *    to send an e-mail (defined in hook_mail()) when the form is submitted.
 *  - shows how modules can alter emails defined by other Drupal modules or
 *    Core using hook_mail_alter by attaching a custom signature before
 *    they are sent.
 */

/**
 * Implement hook_mail().
 *
 * This hook defines a list of possible e-mail templates that this module can
 * send. Each e-mail is given a unique identifier, or 'key'.
 *
 * $message comes in with some standard properties already set: 'to' address,
 * 'from' address, and a set of default 'headers' from drupal_mail(). The goal
 * of hook_mail() is to set the message's 'subject' and 'body' properties, as
 * well as make any adjustments to the headers that are necessary.
 *
 * The $params argument is an array which can hold any additional data required
 * to build the mail subject and body; for example, user-entered form data, or
 * some context information as to where the mail request came from.
 *
 * Note that hook_mail() is not actually a hook. It is only called for a single
 * module, the module named in the first argument of drupal_mail(). So it's
 * a callback of a type, but not a hook.
 */
function email_example_mail($key, &$message, $params) {
  global $user;

  // Each message is associated with a language, which may or may not be the
  // current user's selected language, depending on the type of e-mail being
  // sent. This $options array is used later in the t() calls for subject
  // and body to ensure the proper translation takes effect.
  $options = array(
    'langcode' => $message['language']->language,
  );

  switch ($key) {
    // Send a simple message from the contact form.
    case 'contact_message':
      $message['subject'] = t('E-mail sent from @site-name', array('@site-name' => variable_get('site_name', 'Drupal')), $options);
      // Note that the message body is an array, not a string.
      $message['body'][] = t('@name sent you the following message:', array('@name' => $user->name), $options);
      // Because this is just user-entered text, we do not need to translate it.

      // Since user-entered text may have unintentional HTML entities in it like
      // '<' or '>', we need to make sure these entities are properly escaped,
      // as the body will later be transformed from HTML to text, meaning
      // that a normal use of '<' will result in truncation of the message.
      $message['body'][] = check_plain($params['message']);
      break;
  }
}

/**
 * Send an e-mail.
 *
 * @param $form_values
 *   An array of values from the contact form fields that were submitted.
 *   There are just two relevant items: $form_values['email'] and
 *   $form_values['message'].
 */
function email_example_mail_send($form_values) {
  // All system mails need to specify the module and template key (mirrored from
  // hook_mail()) that the message they want to send comes from.
  $module = 'email_example';
  $key = 'contact_message';

  // Specify 'to' and 'from' addresses.
  $to = $form_values['email'];
  $from = variable_get('site_mail', 'admin@example.com');

  // "params" loads in additional context for email content completion in
  // hook_mail(). In this case, we want to pass in the values the user entered
  // into the form, which include the message body in $form_values['message'].
  $params = $form_values;

  // The language of the e-mail. This will one of three values:
  // * user_preferred_language(): Used for sending mail to a particular website
  //   user, so that the mail appears in their preferred language.
  // * global $language: Used when sending a mail back to the user currently
  //   viewing the site. This will send it in the language they're currently
  //   using.
  // * language_default(): Used when sending mail to a pre-existing, 'neutral'
  //   address, such as the system e-mail address, or when you're unsure of the
  //   language preferences of the intended recipient.
  //
  // Since in our case, we are sending a message to a random e-mail address that
  // is not necessarily tied to a user account, we will use the site's default
  // language.
  $language = language_default();

  // Whether or not to automatically send the mail when drupal_mail() is
  // called. This defaults to TRUE, and is normally what you want unless you
  // need to do additional processing before drupal_mail_send() is called.
  $send = TRUE;
  // Send the mail, and check for success. Note that this does not guarantee
  // message delivery; only that there were no PHP-related issues encountered
  // while sending.
  $result = drupal_mail($module, $key, $to, $language, $params, $from, $send);
  if ($result['result'] == TRUE) {
    drupal_set_message(t('Your message has been sent.'));
  }
  else {
    drupal_set_message(t('There was a problem sending your message and it was not sent.'), 'error');
  }

}

/**
 * Implement hook_mail_alter().
 *
 * This function is not required to send an email using Drupal's mail system.
 *
 * Hook_mail_alter() provides an interface to alter any aspect of email sent by
 * Drupal. You can use this hook to add a common site footer to all outgoing
 * email, add extra header fields, and/or modify the email in anyway. HTML-izing
 * the outgoing email is one possibility.
 */
function email_example_mail_alter(&$message) {
  // For the purpose of this example, modify all the outgoing messages and
  // attach a site signature. The signature will be translated to the language
  // in which message was built.
  $options = array(
    'langcode' => $message['language']->language,
  );

  $signature = t("\n--\nMail altered by email_example module.", array(), $options);
  if (is_array($message['body'])) {
    $message['body'][] = $signature;
  }
  else {  // Some modules use the body as a string, erroneously.
    $message['body'] .= $signature;
  }
}

///// Supporting functions ////

/**
 * Implement hook_menu().
 *
 * Set up a page with an e-mail contact form on it.
 */
function email_example_menu() {
  $items['example/email_example'] = array(
    'title' => 'E-mail Example: contact form',
    'page callback' => 'drupal_get_form',
    'page arguments' => array('email_example_form'),
    'access arguments' => array('access content'),
  );

  return $items;
}

/**
 * The contact form.
 */
function email_example_form() {
  $form['intro'] = array(
    '#markup' => t('Use this form to send a message to an e-mail address. No spamming!'),
  );
  $form['email'] = array(
    '#type' => 'textfield',
    '#title' => t('E-mail address'),
    '#required' => TRUE,
  );
  $form['message'] = array(
    '#type' => 'textarea',
    '#title' => t('Message'),
    '#required' => TRUE,
  );
  $form['submit'] = array(
    '#type' => 'submit',
    '#value' => t('Submit'),
  );

  return $form;
}

/**
 * Form validation logic for the contact form.
 */
function email_example_form_validate($form, &$form_state) {
  if (!valid_email_address($form_state['values']['email'])) {
    form_set_error('email', t('That e-mail address is not valid.'));
  }
}

/**
 * Form submission logic for the contact form.
 */
function email_example_form_submit($form, &$form_state) {
  email_example_mail_send($form_state['values']);
}