<?php
// $Id: captcha.module,v 1.39 2007-04-02 19:35:27 wundo Exp $

/**
 * Implementation of hook_help(). 
 */
function captcha_help($section = 'admin/help#captcha') {
  $output = '';

  switch ($section) {
  case 'admin/help#captcha':
    $output .= '<p>'. t('Adds a Captcha to various forms to help prevent spam submissions.') .'</p>';
    // TODO: More help needed here.
    break;
  }
  return $output;
}

/**
 * Implementation of hook_menu().
 */
function captcha_menu($may_cache) {
  $items = array();
  if ($may_cache) {
    $items[] = array(
      'path' => 'admin/settings/captcha',
      'title' => t('Captcha'),
      'description' => t('Administer how and where Captchas are used.'),
      'callback' => 'drupal_get_form',
      'callback arguments' => array('captcha_admin_settings'),
      'access' => user_access('administer site configuration'),
      'type' => MENU_NORMAL_ITEM,
    );
    $items[] = array(
      'path' => 'admin/settings/captcha/captcha',
      'title' => t('Captcha'),
      'description' => t('Administer how and where Captchas are used.'),
      'access' => user_access('administer site configuration'),
      'type' => MENU_DEFAULT_LOCAL_TASK,
    );
    $items[] = array(
      'path' => 'admin/settings/captcha/points',
      'title' => t('Captcha Points'),
      'description' => t('Administer in what forms Captchas are applied.'),
      'callback' => 'drupal_get_form',
      'callback arguments' => array('captcha_admin_points'),
      'access' => user_access('administer site configuration'),
      'type' => MENU_LOCAL_TASK,
    );
  }
  return $items;
}


function _captcha_supported_challenges_types(){
  static $captcha_challenges = NULL;
  
  if($captcha_challenges != NULL) {
  	return $captcha_challenges; 
  }	
  
  $captcha_challenges['none'] = 'none';
  
  foreach(module_implements('captcha') as $module) {
    $result = call_user_func_array($module .'_captcha', 'list');
    if (isset($result)) { //&& is_array($result)) {
      foreach($result as $challenge) {
      	$captcha_challenges[$module.'/'.$challenge] = $module.'/'.$challenge;
      }
    }
  }
  
  
  return $captcha_challenges;
}

function _captcha_points() {
  $captcha_points = variable_get('captcha_points',NULL);
  if($captcha_points == NULL) {
    $captcha_points = array(
      'comment_form' => t('Comment form'),
      'contact_mail_user' => t('User contact form'),
      'contact_mail_page' => t('Sitewide contact form'),
    );
    variable_set('captcha_points',serialize($captcha_points));
  }
  else {
    $captcha_points = unserialize($captcha_points);
  }
  return $captcha_points;
}

function captcha_admin_points() {
  $captcha_points = _captcha_points();
  $output = '';
  
  if(function_exists('form_store_get_all')) {
    $form = array('#description' => t('Enable/Disable captcha points.'));
    $known_forms = form_store_get_all();
    $form['captcha_points']['#tree'] = true;
    foreach($known_forms as $item) {
      $form['captcha_points'][$item->form_id] = array(
        '#type' => 'checkbox',
        '#title' => $item->form_id.' - '.$item->description,
        '#default_value' => isset($captcha_points[$item->form_id]),
      );
    }
    $output = system_settings_form($form);
  }

  return $output;
}

function captcha_admin_points_submit($form_id, $form_values) {
  if($form_id == 'captcha_admin_points') {
    $known_forms = form_store_get_all();
    $captcha_points = array();
    foreach($form_values['captcha_points'] as $key => $selected) {
      if($selected)
        $captcha_points[$key] = $known_forms[$key]->description;
    }
    variable_set('captcha_points',serialize($captcha_points));
    drupal_set_message(t('Your captcha points were sucessful updated, please configure the challenge options in the other tab.'),'status');
  }
}

/**
 * Helper function generates admin settings page.
 */
function captcha_admin_settings() {
  $captcha_points = _captcha_points();
  $roles = variable_get('captcha_roles',user_roles());
  $captcha_challenges = _captcha_supported_challenges_types();
  
  foreach($roles as $role) {
    $varsuffix = strtr($role, ' ', '_') .'_captcha';
    $form[$varsuffix] = array(
      '#type' => 'fieldset',
      '#title' => t('Captcha points for the role @role', array('@role' => $role)),
      '#description' => t('Select what kind of challenge you want to pose to the user in each captcha point.'),
      '#collapsible' => TRUE,
      '#collapsed' => TRUE,
    );
    foreach($captcha_points as $captcha_point => $captcha_point_description) {
      $varname = $captcha_point .'_'. $varsuffix;
      $form[$varsuffix][$varname] = array(
        '#type' => 'select',
        '#title' => t('@point', array('@point' => $captcha_point_description)),
        '#default_value' => variable_get($varname, 'captcha/Math'),
        '#options' => $captcha_challenges,
      );
    }
  }
  
  return system_settings_form($form);
}

/**
 * Implementation of hook_form_alter().
 */
function captcha_form_alter($form_id, &$form) {
  global $captcha;
  global $user;

  $seed = $form['form_token']['#default_value'];
  if($_SESSION['captcha'][$seed]['success'] === TRUE)
    return;

  foreach($user->roles as $role) {	
  	$candidate_trigger = $form_id .'_'. strtr($role, ' ', '_') .'_captcha';
  	$captcha_type = variable_get($candidate_trigger,NULL);

  	if($captcha_type != NULL) {
  	  //Found one valid captcha challenge for this point.
  	  break;
  	}
  }

  if($captcha_type == 'none') {
    //One of the user roles doesn't have captcha challenge for this point, aborting.
    return;
  }
  elseif($captcha_type == NULL) {
  	//captcha_type null;
  	return;
  }
     
  $challenge = explode('/',$captcha_type);
   
  $result = module_invoke($challenge[0], 'captcha', 'generate', $challenge[1]);
  
  $form = array_merge($form,$result['form']);
  
  $form['#validate'] += array('captcha_validate' => array());
  $form['#pre_render'] = array('captcha_prerender');

  $_SESSION['captcha'][$seed]['success'] = FALSE;
  $_SESSION['captcha'][$seed]['form_id'] = $form_id;
  $_SESSION['captcha'][$seed]['form'] = $result['form'];
  $_SESSION['captcha'][$seed]['new_value'] = $result['value'];
  $_SESSION['captcha'][$seed]['preprocess'] = isset($result['preprocess'])? $result['preprocess'] : FALSE;
  $_SESSION['captcha'][$seed]['module'] = $challenge[0];
  $_SESSION['captcha'][$seed]['type'] = $challenge[1];
}

function captcha_validate($form_id, $form_item) {
  $seed = $form_item['form_token'];

  if($_SESSION['captcha'][$seed]['preprocess']) {
    $value = module_invoke($_SESSION['captcha'][$seed]['module'],'captcha','process',$_SESSION['captcha'][$seed]['type'],$form_item['captcha_challenge']);
  }
  else {
  	$value = $form_item['captcha_challenge'];
  } 

  if($value == $_SESSION['captcha'][$seed]['value']) {
  	$_SESSION['captcha'][$seed]['success'] = TRUE;
    return;
  }
  form_set_error('captcha_response', t('The answer you entered to the captcha challenge is incorrect.'));  
}

/**
 * Implementation of form #pre_render.
 *
 */
function captcha_prerender($form_id, $form) {
  $seed = $form['#post']['form_token'];
  $_SESSION['captcha'][$seed]['value'] = $_SESSION['captcha'][$seed]['new_value'];
  if($_SESSION['captcha'][$seed]['success']) {
    unset($form['captcha_challenge']);
    unset($_SESSION['captcha'][$seed]);
  }
}


/**
 * Default implementation of hook_captcha
 */
function captcha_captcha() {
  $args = func_get_args();
  $op = array_shift($args); 
  switch($op) {
    case 'list':
      return array("Math");
    case 'generate':
      $captcha_type = array_shift($args);
      $result = array();
      if($captcha_type == "Math") {
        $answer = mt_rand(1, 20);
        $x = mt_rand(1, $answer);
        $y = $answer - $x;
 
        $result['value'] = (string)($answer);
        $result['form']['captcha_challenge'] = array (
          '#type' => 'textfield',
          '#title' => t('Math Question: What is %problem?', array('%problem' => $x .' + '. $y)),
          '#description' => t('Please solve the math problem above and type in the result. e.g. for 1+1, type 2.'),
          '#weight' => 0,
          '#required' => TRUE,
        );
      }
      return $result;
  }
}