<?php
// $Id$

/**
 * @file
 *   Builds links to post pages to twitter.
 */

/**
 * Implementation of hook_help().
 */
function tweet_help($path, $arg) {
  $output = '';
  switch ($path) {
    case "admin/help#tweet":
      $output = '<p>'. t("This module builds links to post pages to twitter.") .'</p>';
      break;
  }
  return $output;
}

/**
 * Implementation of hook_link().
 */
function tweet_link($type, $node = NULL, $teaser = FALSE) {
  if ($type == 'node' && in_array($node->type, variable_get('tweet_types', _tweet_node_types())) && !_tweet_exclude($node->nid)) {
    $title = variable_get('tweet_title', 1);
    if (!$teaser) {
      $link_type = variable_get('tweet_node', 'icon');
      if ($link_type != 'none') {
        $links['tweet'] = _tweet_to_twitter($link_type, '', $node->nid);
        return $links;
      }
    }
    else {
      $link_type = variable_get('tweet_teaser', 'none');
      if ($link_type != 'none') {
        $links['tweet'] = _tweet_to_twitter($link_type, '', $node->nid);
        return $links;
      }
    }
  }
}

/**
 * Implementation of hook_menu().
 */
function tweet_menu() {
  $items = array();
  $items['admin/settings/tweet'] = array(
    'title' => 'Tweet settings',
    'description' => 'Adjust certain display settings for Tweet.',
    'page callback' => 'drupal_get_form',
    'page arguments' => array('tweet_admin'),
    'access arguments' => array('access administration pages'),
    'file' => 'tweet.admin.inc',
  );
  return $items;
}

/**
 * Returns a link from _tweet_to_twitter().
 * @see _tweet_to_twitter()
 */
function tweet_to_twitter($type = 'icon', $title = TRUE, $nid = '') {
  $array = _tweet_to_twitter($type, $title, $nid);
  return l($array['title'], $array['href'], array('attributes' => $array['attributes'], 'query' => $array['query'], 'absolute' => TRUE, 'html' => $array['html']));
}

/**
 * Creates a link to post a URL and optionally title to twitter.  Uses the
 * current page by default.
 *
 * @param $type
 *   Specifies what will show up in the link: the twitter icon, the twitter icon
 *   and text, or just text. Pass 'icon' to show just the icon, 'icon_text' to
 *   show the icon and text, and 'text' to show just the text. Required if
 *   display options for nodes are set to 'none' on the settings page.
 * @param $format
 *   A string representing the tweet text, optionally with the case-insensitive
 *   tokens [url] and [title]. If not passed, the format from the settings page
 *   will be used.
 * @param $nid
 *   The NID of the node for which the twitter link should be constructed, or
 *   the absolute URL of the page for which the twitter link should be
 *   constructed. If the URL given is not the current URL, and if $nid is not a
 *   NID, the title must be set manually (instead of using the [title] token) or
 *   it will be incorrect.
 * @return
 *   A themed link to post the specified or current page to twitter.
 */
function _tweet_to_twitter($type = '', $format = '', $nid = '') {
  $q = '';
  if (is_numeric($nid)) {
    $q = url('node/'. $nid, array('absolute' => TRUE));
  }
  $url = $q;
  if (module_exists('shorten')) {
    $url = shorten_url($q);
  }
  $title = _tweet_get_title($nid);

  if (!$format) {
    $format = variable_get('tweet_format', '[url] [title]');
  }
  $tweet = _tweet_process($format, array('[url]' => $url, '[title]' => $title));

  $path = 'http://twitter.com/home';
  $text = t('Post to Twitter');
  $image_location = drupal_get_path('module', 'tweet') .'/icon.png';
  global $base_url;
  $image = '<img src="'. $base_url . base_path() . check_plain(variable_get('tweet_image', $image_location)) .'" alt="'. $text .'" title="'. $text .'" />';
  if (!$type) {
    //Note that $type can be 'none', in which case nothing shows up.
    $type = variable_get('tweet_node', 'icon');
  }
  if ($type == 'icon') {
    $show = $image;
  }
  else if ($type == 'icon_text') {
    $show = $image .' '. $text;
  }
  else if ($type == 'text') {
    $show = $text;
  }
  $attributes = array('class' => 'tweet', 'rel' => 'nofollow');
  if (variable_get('tweet_new_window', 'target') == 'target') {
    $attributes['target'] = '_blank';
  }
  else if (variable_get('tweet_new_window', 'target') == 'js') {
    $attributes['onclick'] = "window.open('$path?status=$tweet','twitter','')";
    $path = $_GET['q'];
    $tweet = 'sent';
  }
  return array('title' => $show, 'href' => $path, 'attributes' => $attributes, 'query' => 'status='. $tweet, 'html' => TRUE);
}

/**
 * Determines what will be in the tweet itself.
 *
 * @param $format
 *   A string containing the text of the tweet before it gets processed.
 * @param $tokens
 *   An associative array where keys represent text that will be replaced by
 *   their value in $format.
 * @return
 *   The URL-ready tweet text.
 */
function _tweet_process($format = '', $tokens = array()) {
  if (!$format) {
    $format = variable_get('tweet_format', '[url] [title]');
  }
  foreach ($tokens as $search => $replace) {
    $format = str_ireplace($search, $replace, $format);
  }
  $format = drupal_urlencode($format);
  //The #, &, and / characters get double-encoded by drupal_urlencode, but they must appear single-encoded for Twitter to recognize them.
  //Spaces are manually encoded to plus signs for clarity of whitespace at the end of the tweet.
  $format = str_replace(array('%2523', '%2526', '%252F', '%20'), array('%23', '%26', '%2F', '+'), $format);
  return $format;
}

/**
 * Returns the title of the node for which the NID was passed or the current
 * page. Note that there is no good way to get the page title for a page that is
 * not the current page. We assume the title is the same as the title of the
 * node if a node is being viewed, but this is often not the case when certain
 * modules are being used. In this case, it is recommended that you manually
 * pass the title to tweet_to_twitter().
 *
 * @param $nid
 *   The NID of the node for which to return the title.  If not passed, uses the
 *   current page.
 * @return
 *   The title of the node for the NID passed or the title of the current page.
 */
function _tweet_get_title($nid = '') {
  if (is_numeric($nid)) {
    $node = node_load(array('nid' => $nid));
    $title = $node->title;
  }
  else {
    $title = drupal_get_title();
  }
  if (drupal_strlen($title) > 120) {
    $title = drupal_substr($title, 0, 119) .'…';
  }
  return $title;
}

/**
 * Excludes certain Node IDs from displaying links.
 *
 * @param $nid
 *   The NID to check for exclusion.
 * @return
 *   TRUE if the node should be excluded, or FALSE if it should not.
 */
function _tweet_exclude($nid) {
  $exclude = explode(',', variable_get('tweet_exclude', ''));
  $excludes = array();
  foreach ($exclude as $check) {
    $excludes[] = trim($check);
  }
  if (!empty($excludes)) {
    if (in_array($nid, $excludes)) {
      return TRUE;
    }
  }
  return FALSE;
}

/**
 * Helper function to provide node types in the format array(TYPE => TYPE).
 */
function _tweet_node_types() {
  $a = array_keys(node_get_types());
  $return = drupal_map_assoc($a);
  return $return;
}