<?php
// $Id: captcha.module,v 1.25 2006/07/26 19:32:02 wundo Exp $

/**
* Implementation of hook_help().
*/
function captcha_help($section = 'admin/help#captcha') {
  switch ($section) {
    case 'admin/help#captcha':
      return '<p>'. t('Adds a Captcha to the registration form.') .'</p>';
  }
}

/**
 * Implementation of hook_menu()
 */
function captcha_menu($may_cache) {
  $items = array();
  if ($may_cache) {
    $items[] = array(
      'path' => 'admin/settings/captcha',
      'callback' => 'drupal_get_form',
      'callback arguments' => array('captcha_settings_form'),
      'title' => t('CAPTCHA settings'),
      'description' => t('Adds a CAPTCHA to forms to prevent spam.'),
      'access' => user_access('administer site configuration')
    );
  }
  return $items;
}

/**
 * Form builder for the captcha settings.
 */
function captcha_settings_form() {
  //this is where you can add more captcha points
  $captcha_points = array(
    'comment_form' => t('Comment Form'),
    'user_login' => t('User Login Form'),
    'user_login_block' => t('User Login Form Block'),
    'user_edit' => t('User Edit Form'),
    'user_register' => t('User Registration Form'),
    'user_pass' => t('User Forgot Password Form'),
    'contact_mail_user' => t('User Contact Form'),
    'contact_mail_page' => t('Sitewide Contact Form'),
    'node_form' => t('Create a node'),
  );

  $roles = user_roles();

  foreach ($roles as $role) {
    $varsuffix = strtr($role, ' ', '_') .'_captcha';
    $form[$varsuffix] = array(
      '#type' => 'fieldset',
      '#title' => t('Captcha Points for the role %role', array('%role' => $role)),
      '#collapsible' => TRUE,
      '#collapsed' => TRUE
    );
    foreach ($captcha_points as $captcha_point => $captcha_point_description) {
      $varname = $captcha_point .'_'. $varsuffix;
      $form[$varsuffix][$varname] = array(
        '#type' => 'checkbox',
        '#title' => $captcha_point_description,
        '#default_value' => variable_get($varname, NULL)
      );
    }
  }

  // preprocess array into a map
  foreach (module_implements('captchachallenge') as $module) {
    $captchamodules[$module] = $module;
  }

  $form['captcha_type'] = array(
    '#type' => 'select',
    '#title' => t('Type of captcha to use'),
    '#default_value' => variable_get('captcha_type', 'captcha'),
    '#options' => $captchamodules,
    '#description' => t('Select what kind of challenge you want to pose to the user')
  );

  return system_settings_form($form);
}



/**
* Implementation of hook_form_alter().
*/
function captcha_form_alter($formid, &$form) {
  global $user;
  $captcha_type = variable_get('captcha_type', NULL);

  if (!$captcha_type) {
    return;
  }

  $flag = TRUE;
  $trigger = NULL;

  foreach ($user->roles as $role) {
    $candidate_trigger = $formid .'_'. strtr($role, ' ', '_') .'_captcha';
    if (variable_get($candidate_trigger, NULL)) {
      $trigger = $candidate_trigger;
    }
    else {
      $flag = FALSE;
      break;
    }
  }
  if ($flag && isset($trigger)) {
    $form['#submit'] = array('captcha_submit' => array()) + $form['#submit'];
    if (!_captcha_validate($_POST['edit']['captcha_response'])) {
      //use call_func because module_invoke does not allow call by reference.
      if (module_hook($captcha_type, 'captchachallenge')) {
        call_user_func_array($captcha_type.'_captchachallenge', array(&$form, &$_SESSION['captcha']));
      }
    }
  }
}

/**
* On submit, captcha is reset
*/
function captcha_submit() {
  if ($_SESSION['captcha_correct']) {
    unset($_SESSION['captcha_correct']);
    unset($_SESSION['captcha']);
  }
}


function _captcha_validate($captcha_response) {
  global $user;

  if ($_SESSION['captcha_correct']) {
    return TRUE;
  }
  if (is_array($captcha_response)) {
    $captcha_response = $captcha_response['#value'];
  }
  if (trim($captcha_response) == '') {
    return FALSE;
  }
  $captcha_type = variable_get('captcha_type', NULL);
  $trigger = NULL;

  if (module_hook($captcha_type, 'captchavalidate')) {
    call_user_func_array($captcha_type.'_captchavalidate', array(&$captcha_response, &$_SESSION['captcha_correct']));
  }

  return $_SESSION['captcha_correct'];
}

/*
 * Default implementation of the captcha challenge & validation
 */
function captcha_captchachallenge(&$form, &$captcha) {
  $x = rand(1, 10);
  $y = rand(1, 10);

  $captcha = $x + $y;

  $form['captcha_response'] = array(
    '#type' => 'textfield',
    '#title' => t('Math Question: What is %problem?', array('%problem' => $x .' + '. $y)),
    '#defaultvalue' => '',
    '#size' => 10,
    '#description' => t('Please solve the math problem above and type in the result. e.g. for 1 + 1, type 2'),
    '#required' => TRUE,
    '#validate' => array('_captcha_validate' => array()),
    '#weight' => -1,
  );
}

function captcha_captchavalidate(&$captcha_word, &$correct) {
  $captcha_word = drupal_strtolower($captcha_word);
  if ($captcha_word == $_SESSION['captcha']) {
    $correct = TRUE;
  }
  else {
    $correct = FALSE;
    form_set_error('captcha_response', t('The answer you entered to the math problem is incorrect.'));
  }
}