<?php
// $Id:  $

/**
 * Implementation of hook_help().
 */
function captcha_help($section = "admin/help#captcha") {
  switch ($section) {
    case 'admin/help#captcha':
      $output = t('A challenge/response will be added to forms to prevent automated submissions.');
      break;
    case 'admin/modules#description':
      $output = t("Adds a Captcha to specified forms.");
      break;
    default:
      $output = '';
  }
  return $output;
}

/**
 * Implementation of hook_settings().
 */
function captcha_settings() {
  $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_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;

  switch ($op) {
    case 'validate':
      $node->captcha = trim($node->captcha);
      // only validate captcha if "Submit" button is used
      if ($_POST['op'] == t('Preview') && (variable_get('captcha_code','') == '' || $node->captcha != variable_get('captcha_code',''))) {
        form_set_error('captcha', t('The submission verification response you entered is not correct.'));
      }
      break;
    case 'form post':
      // only show captcha form if the "Submit" button is visible
      if (!variable_get('node_preview', 0) || ($_POST['op'] == t('Preview')) || ($_POST['op'] == t('Submit'))) {
        $qa = _captcha_qa();
        variable_set('captcha_code', $qa['answer']);
        $group = form_item(t('Question'), $qa['question']);
        $group .= form_textfield(t('Answer'), 'captcha', NULL, 15, 15, t('This helps prevent automated submissions.'), NULL, TRUE);
        $output = form_group(t('Verify your submission'),$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;

  switch ($type) {
    case 'validate':
      if ($edit['captcha'] == '' || variable_get('captcha_code','') == '' || $edit['captcha'] != variable_get('captcha_code','')) {
        form_set_error('captcha', t('The submission verification response you entered is not correct.'));
      } 
      break;
    case 'register':
      $qa = _captcha_qa();
      variable_set('captcha_code', $qa['answer']);
      $group = form_item(t('Question'), $qa['question']);
      $group .= form_textfield(t('Answer'), 'captcha', NULL, 15, 15, t('This helps prevent automated submissions.'), NULL, TRUE);
      return array(array('title' => t('Verify your submission'), '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;

  switch ($op) {
    case 'validate':
      // only validate captcha if "Post comment" button is used
      if ($_POST['op'] == t('Post comment') && (variable_get('captcha_code','') == '' || $edit['captcha'] != variable_get('captcha_code',''))) {
        form_set_error('captcha', t('The submission verification response you entered is not correct.'));
      }
      break;
    case 'form':
      // only show captcha form if the "Post comment" button is visible
      if (!variable_get('comment_preview', 1) || ($_POST['op'] == t('Preview comment')) || ($_POST['op'] == t('Post comment'))) {
        $qa = _captcha_qa();
        variable_set('captcha_code', $qa['answer']);
        $group = form_item(t('Question'), $qa['question']);
        $group .= form_textfield(t('Answer'), 'captcha', NULL, 15, 15, t('This helps prevent automated submissions.'), NULL, TRUE);
        $output = form_group(t('Verify your submission'),$group);
        return $output;
      }
  }
}

/**
 * Returns a question and answer.
 */
function _captcha_qa() {
  $numbers = array(
    1 => t('one'),
    2 => t('two'),
    3 => t('three'),
    4 => t('four'),
    5 => t('five'),
    6 => t('six'),
    7 => t('seven'),
    8 => t('eight'),
    9 => t('nine'),
    10 => t('ten'),
    11 => t('eleven'),
    12 => t('twelve')
  );

  $operators = array(
    0 => array(name => t('plus'), symbol => '+'),
    1 => array(name => t('minus'), symbol => '-'),
    2 => array(name => t('multiplied by'), symbol => '*'),
    3 => array(name => t('divided by'), symbol => '/')
  );

  $operator = rand(0,count($operators)-1);

  // choose numbers based on operator to keep the math simple
  switch($operator) {
    case 0:
      // do addition logic
      $firstNumber = rand(1,count($numbers)-1);
      $secondNumber = rand(1,count($numbers)-1);
      $result = $firstNumber + $secondNumber;
      break;
    case 1:
      // do subtraction logic
      $firstNumber = rand(6,count($numbers)-1);
      $secondNumber = rand(1,5);
      $result = $firstNumber - $secondNumber;
      break;
    case 2:
      // do multiplication logic
      $firstNumber = rand(1,8);
      $secondNumber = rand(1,8);
      $result = $firstNumber * $secondNumber;
      break;
    case 3:
      // do division logic
      $secondNumber = rand(2,4);
      $firstNumber = $secondNumber * rand(1,4);
      $result = $firstNumber / $secondNumber;
      break;
  }

  $equation = $numbers[$firstNumber].' '.$operators[$operator]['name'].' '.$numbers[$secondNumber];
  $output = array('question' => t('What is ') . $equation . '?', t('answer') => $result);

  return $output;
}

?>