<?php
/*
  This module looks for <img> tags of the class 'image-left', 'image-right' or 'standalone-image'
  with a title attibute set.  It then places the <img> tag in a <div> with the width and class
  attributes set. A <div> tag of class "caption" is also added with the caption text obtained
  from the title.  It removes the class attribute from the <img> tag.
  <img> tags missing alt attributes are also marked with warning text to draw attention to
   this fact.
  @info
  http://drupal.org/node/264932
  @author
  John Fletcher
  @contact
  http://drupal.org/user/236219/contact
*/

/**
* Display help and module information
* @param path which path of the site we're displaying help
* @param arg array that holds the current path as would be returned from arg() function
* @return help text for the path
*/
function image_caption_filter_help($path, $arg) {
  $output = '';
  switch ($path) {
    case "admin/help#image_caption_filter":
      $output = '<p>' .  t("Adds captions to images") . '</p>';
      break;
  }
  return $output;
} //function image_caption_filter_help


function image_caption_filter_admin() {
  $form = array();

  $form['image_caption_filter_classes'] = array(
    '#type' => 'textfield',
    '#title' => t('Classes to be searched for image captions'),
    '#default_value' => variable_get('image_caption_filter_classes', 'image-left,image-right'),
    '#size' => 80,
    '#description' => t('Enter a comma-separated list of classes. The filter will only operate on images which have one of these CSS classes and have a title attribute and a width set.'),
    '#required' => TRUE,
  );

  return system_settings_form($form);
}

function image_caption_filter_menu() {
  $items = array();

  $items['admin/settings/image_caption_filter'] = array(
    'title' => 'Image caption filter',
    'description' => t('Configure image caption filter settings.'),
    'page callback' => 'drupal_get_form',
    'page arguments' => array('image_caption_filter_admin'),
    'access arguments' => array('administer site configuration'),
    'type' => MENU_NORMAL_ITEM,
   );

  return $items;
}

//filter hook implementation
function image_caption_filter_filter($op, $delta = 0, $format = -1, $text = '') {
  switch ($op) {
    case 'list':
      return array(0 => t('Image caption filter'));

    case 'description':
      return t('Adds captions to images via a filter.');

    case 'prepare':
      // Nothing to prepare
      return $text;

    case "process":
      //Look for <img> tags and run the do_img_titles function on the <img> tag
      $text = preg_replace_callback('|(<img.*?>)|s', 'do_img_titles', $text);
      return $text;

    default:
      return $text;
  }
} //function image_caption_filter_filter


//helper function to do the actual manipulation
function do_img_titles($img_tag_matches) {
  // code changes:
  // - to prevent Undefined offset: 1 notices
  // - minor optimizations (this code gets executed for each image tag in each node and block): bail out on any negative condition
  // other possible optimization: make $active_class_array static and process the list of variables only once
	$img_tag = $img_tag_matches[0];
  $return_text = $img_tag;

  //the classes we will operate on
  $active_classes = variable_get("image_caption_filter_classes", 'image-left,image-right');

  //clean out whitespace and create array
  $active_classes_cleaned = str_replace(' ', '', $active_classes);
  $active_class_array = explode(',', $active_classes_cleaned);

  // only execute this filter on img tags with (at least) one of the classes we are interested in
  $has_class = preg_match ('/class=\"(.+?)\"/i', $img_tag, $matches) > 0;
  if ($has_class) {
    $class = $matches[1];
    // formally, class is a space separated list of classes, but we allow all horizontal whitespace in any quantity
    // that's why we use preg_split instead of explode
    $classes = preg_split('/\h+/', $class, null, PREG_SPLIT_NO_EMPTY);
    if (count(array_intersect($classes, $active_class_array)) > 0) {
      // only execute this filter on img tags that have a title attribute
      $has_title = preg_match ('/title=\"(.+?)\"/i', $img_tag, $matches) > 0;
      if ($has_title) {
        $title = $matches[1];

        // search for width specified as an inline style or width attribute,
        // if no width specified, don't output it on the outer span, assume width will be handled with css external to this module/filter
        $width = '';
        if (preg_match ('/width:\s*(\d+)px/i', $img_tag, $matches) == 1 || preg_match ('/width=\"(\d+?)\"/i', $img_tag, $matches) == 1) {
          $width = $matches[1];
          $width = " style=\"width: {$width}px\"";
        }

        // remove the class from the image tag
        $img_tag = preg_replace ('/class=\"(.+?)\"/i', '', $img_tag);

        // add the outer and caption span
        $return_text = "<span class=\"$class\"$width>$img_tag<span class=\"caption\">$title</span></span>";
      }
    }
  }
  return $return_text;
} //function do_img_titles

?>