<?php
// $Id: captcha.module,v 1.1 2004/07/11 14:50:57 jseng Exp $

/**
 * Implementation of hook_init().
 */
function captcha_init() {
  global $_captcha_default_format, $_captcha_formats;

  $_captcha_imagetypes = imagetypes();
  $_captcha_formats = array();
  
  if ($_captcha_imagetypes & IMG_JPG) {
    $_captcha_default_format = 2;
    $_captcha_formats = array_merge(array(2 => 'JPG'), $_captcha_formats);
  } 
  
  if ($_captcha_imagetypes & IMG_GIF) {
    $_captcha_default_format = 1;
    $_captcha_formats = array_merge(array(1 => 'GIF'), $_captcha_formats);
  } 
  
  if ($_captcha_imagetypes & IMG_PNG) {
    $_captcha_default_format = 0;
    $_captcha_formats = array_merge(array(0 => 'PNG'), $_captcha_formats);
  } 
}

/**
 * Implementation of hook_help().
 */
function captcha_help($section = "admin/help#captcha") {
  $output = "";

  switch ($section) {
    case 'admin/help#captcha':
      $output = t('Users would be shown a graphic image with some text which they will have to enter manually to verify they are not a bot. CAPTCHA requires PHP to be compiled with GD support.');
      break;
    case 'admin/modules#description':
      $output = t("Adds a Captcha to specified forms.");
      if (!function_exists('imagecreate')) {
        $output .= " ".t("GD support is not detected. This module requires PHP to be compiled with GD support.");
      }
      break;
  }
  return $output;
}

/**
 * Implementation of hook_settings().
 */
function captcha_settings() {
  global $_captcha_default_format, $_captcha_formats;

  $group .= form_select(t('Image format'), 'captcha_format', variable_get('captcha_format', $_captcha_default_format), $_captcha_formats, t("Output captcha image format. These are the formats supported in your PHP so if you can't see the image, try another one."));
  $output .= form_group(t('Image Options'),$group);

  if (function_exists('imagecreate')) {
    $group = form_radios(t('user registration'), 'captcha_newuser', variable_get('captcha_newuser', 0), array(0 => t('No CAPTCHA support'), 1 => t('CAPTCHA support')));
    $group .= form_radios(t('comments'), 'captcha_comment', variable_get('captcha_comment', 0), array(0 => t('No CAPTCHA support'), 1 => t('CAPTCHA support'), 2 => t('CAPTCHA support only for anonymous user')));
    foreach (node_list() as $type) {
      $group .= form_radios(t(node_invoke($type,'node_name')), "captcha_node_$type", variable_get("captcha_node_$type", 0), array(0 => t('No CAPTCHA support'), 1 => t('CAPTCHA support'), 2 => t('CAPTCHA support only for anonymous user')));
    }
    $output .= form_group(t('Form Options'),$group);
  }
  return $output;
}

/**
 * Implementation of hook_menu().
 */
function captcha_menu($may_cache) {
  $items = array();

  $items[] = array('path' => 'captcha/image', 'title' => t('captcha image'),
    'callback' => '_captcha_image', 'access' => user_access('access content'),
    'type' => MENU_CALLBACK);

  return $items;
}

/**
 * Implementation of hook_link().
 */
function captcha_link($type, $node = 0, $main) {
  if ($type  == 'system') {
    menu('captcha', t('captcha image'), 'captcha_image', 0, MENU_HIDE);
  }
}

/**
 * Implementation of hook_nodeapi().
 */
function captcha_nodeapi(&$node, $op, $arg) {
  global $user;

  $type = $node->type;
  
  // check if captcha is enabled for form type
  if (variable_get("captcha_node_$type",0) != 1 && !(variable_get("captcha_node_$type",0) == 2 && !$user->uid))
    return;

  // check for GD support
  if (!function_exists('imagecreate')) return;


  switch ($op) {
    case 'validate':
      $node->captcha = trim($node->captcha);
      if (isset($node->captcha) && $node->captcha != variable_get('captcha_code','') || variable_get('captcha_code','') == '') {
        form_set_error('captcha', t('The user verification code you entered is not correct.'));
      }
      break;
    case 'form post':
      variable_set('captcha_code', _captcha_generate_code());
      $group = form_item('','<img src="'.url('captcha/image').'" alt="'.t('captcha image').'" />');
      $group .= form_textfield(t('Code'), 'captcha', NULL, 15, 15, t('Enter the characters shown in the image above.'), NULL, TRUE);
      $output = form_group(t('Human user verification'),$group);
      return $output;
  }
}

/**
 * User callback; adds captcha field to new user form.
 */
function captcha_user($type, &$edit, &$user, $category = NULL) {
  global $user;

  // check if user is logged in
  if ($user->uid) return;
  
  // check if captcha is enabled for form type
  if (variable_get('captcha_newuser',0) == 0) return;

  // check for GD support
  if (!function_exists('imagecreate')) return;

  switch ($type) {
    case 'validate':
      if ($edit['captcha'] == '' || variable_get('captcha_code','') == '' || $edit['captcha'] != variable_get('captcha_code','')) {
        form_set_error('captcha', t('The user verification code you entered is not correct.'));
//        variable_set('captcha_code', _captcha_generate_code());
      } 
      break;
    case 'register':
      variable_set('captcha_code', _captcha_generate_code());
      $group = form_item('','<img src="'.url('captcha/image').'" alt="'.t('captcha image').'" />');
      $group .= form_textfield(t('Code'), 'captcha', NULL, 15, 15, t('Enter the characters shown in the image above.'), NULL, TRUE);
      return array(array('title' => t('Human user verification'), 'data'=>$group));
  }
}

/**
 * Comment callback; adds captcha field to new comment form.
 */
function captcha_comment($op,$edit) {
  global $user;

  // check if captcha is enabled for form type
  if (variable_get('captcha_comment',0) != 1 && !(variable_get('captcha_comment',0) == 2 && !$user->uid))
    return;

  // check for GD support
  if (!function_exists('imagecreate')) return;

  switch ($op) {
    case 'validate':
      // only validate captcha if "Post comment" button is used
      if ($_POST['op'] == t('Post comment') && (variable_get('captcha_code','') == '' || $edit['captcha'] != variable_get('captcha_code',''))) {
        form_set_error('captcha', t('The user verification code you entered is not correct.'));
      }
      break;
    case 'form':
      // only show captcha form if the "Post comment" button is visible
      if (!variable_get('comment_preview', 1) || ($_POST['op'] == t('Preview comment')) || ($_POST['op'] == t('Post comment'))) {
        variable_set('captcha_code', _captcha_generate_code());
        $group = form_item('','<img src="'.url('captcha/image').'" alt="'.t('captcha image').'" />');
        $group .= form_textfield(t('Code'), 'captcha', NULL, 15, 15, t('Enter the characters shown in the image above.'), NULL, TRUE);
        $output = form_group(t('Human user verification'),$group);
        return $output;
      }
  }
}

/**
 * Prints an image containing a captcha code.
 */
function _captcha_image() {
  global $_captcha_default_format, $_captcha_formats;

  // Check for captcha code and exit if not existant to prevent abuse
  $captchaCode = variable_get('captcha_code','');
  if ($captchaCode == '')
    return drupal_goto();

  // Check for GD support
  if (!function_exists('imagecreate')) 
    return drupal_goto();

  // define the image dimensions
  $imageWidth = 280;
  $imageHeight = 60;
  $img = imagecreate($imageWidth,$imageHeight);

  // draw image
  $img = _captcha_image_arcs($img,$captchaCode);

  // Set headers
  header('Expires: Mon, 01 Jan 1997 05:00:00 GMT');
  header('Cache-Control: no-store, no-cache, must-revalidate');
  header('Cache-Control: post-check=0, pre-check=0', false);
  header('Pragma: no-cache');

  switch (variable_get('captcha_format',$_captcha_default_format)) {
    case 2:
      header('Content-type: image/jpg');
      break;
    case 1:
      header('Content-type: image/gif');
      break;
    default:
      header('Content-type: image/png');
      break;
  }

  // output the image
  switch (variable_get('captcha_format',$_captcha_default_format)) {
    case 2:
      imagejpeg($img);
      break;
    case 1:
      imagegif($img);
      break;
    default:
      imagepng($img);
      break;
  }

  // destroy the image
  imagedestroy($img);
}

/**
 * Returns a captcha code.
 */
function _captcha_generate_code() {
  $charlist = 'QWERTYUPLKJHGFDSAZXCVBNM23456789';
  $length = rand(6,8);
  $code = '';

  srand((double) microtime() * 1000000);
  for ($i=0;$i<$length;$i++) {
    $char = substr($charlist, rand() % strlen($charlist), 1);
    if (preg_match("/".$char."/",$code) == 0) {
      $code .= $char;
    } else {
      $i--;
    }
  }

  return $code;
}

/**
 * Returns an array of files with TTF extensions in the specified directory.
 */
function _captcha_font_list($dir) {
  $filelist = array();
  if ($handle = opendir($dir)) {
    while ($file = readdir($handle)) {
      if (preg_match("/\.ttf$/i",$file) == 1)
        $filelist[] = $file;
    }
    closedir($handle);
  }

  return $filelist;
}

/**
 * Draws a captcha image
 */
function _captcha_image_arcs($img,$code) {

  // define colors
  $backgroundColor = imagecolorallocate($img,224,224,224);
  $borderColor = imagecolorallocate($img,0,0,0);
  $textColor = imagecolorallocate($img,0,0,0);
  $noiseColor = imagecolorallocate($img,0,0,0);

  // define number of noise elements
  $noiseCount = rand(imagesx($img)/30,imagesx($img)/10);

  // draw image background
  imagefill($img,0,0,$backgroundColor);

  // draw image noise
  for ($i=0;$i<$noiseCount;$i++) {
    $segmentCount = rand(1,4);
    $x = rand(10,imagesx($img)-10);
    $y = rand(4,imagesy($img)-10);
    $angle = rand(0,180);
    for ($j=0;$j<$segmentCount;$j++) {
      // randomly draw an arc or a line
      if (rand(0,3) == 1) {
        imagearc($img,$x,$y,rand(10,15),rand(10,15),rand(0,224),rand(180,360),$noiseColor);
        $x += rand(-20,20);
        $y += rand(-20,20);
      } else {
        $segmentAngle = $angle + rand(-2,2);
        $segmentLength = rand(3,10);
        $xLength = round($segmentLength * cos($segmentAngle));
        $yLength = round($segmentLength * sin($segmentAngle));
        imageline($img,$x,$y,$x+$xLength,$y+$yLength,$noiseColor);
        $x += $xLength;
        $y += $yLength;
      }
    }
  }

  // Get truetype font list
  $fontDir = 'modules/captcha';
  $fonts = _captcha_font_list($fontDir);

  if (count($fonts) > 0) {
    // write text using a truetype font

    $charSize = 20;		// font size
    $charWidth = 0;		// width of previous character
    $x = 20;			// initial x position

    // iterate over characters
    for ($i=0;$i<strlen($code);$i++) {

      // define angle and position of character based on previous character dimension
      $x += $charWidth * rand(1.6,1.8);
      $y = rand(30,50);
      $charAngle = rand(-25,25);
      $char = substr($code,$i,1);

      // select random font
      $font = $fontDir.'/'.$fonts[rand(0,count($fonts)-1)];

      // draw character
      imagettftext($img,$charSize,$charAngle,$x,$y,$textColor,$font,$char);

      // capture character dimensions to increment x position
      $bbox = imagettfbbox($charSize,$charAngle,$font,$char);
      $charWidth = max($bbox[0],$bbox[2],$bbox[4],$bbox[6]) - min($bbox[0],$bbox[2],$bbox[4],$bbox[6]);
    }
  } else {
    // write text using a built-in font

    $x = 40;
    $y = 25;

    for ($i=0;$i<strlen($code);$i++) {
      imagestring($img,5,$x,$y,substr($code,$i,1),$textColor);
      $x += 30;
    }
  }

  // draw image border
  imagerectangle($img,0,0,imagesx($img)-1,imagesy($img)-1,$borderColor);

  return $img;
}

?>