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math_captcha.module in CAPTCHA Pack 5

Same filename and directory in other branches
  1. 8 math_captcha/math_captcha.module
  2. 6 math_captcha/math_captcha.module
  3. 7 math_captcha/math_captcha.module

File

math_captcha/math_captcha.module
View source 
<?php

/**
 * Implementation of a math CAPTCHA, for use with the CAPTCHA module
 */

/**
 * Implementation of hook_menu().
 */
function math_captcha_menu($may_cache) {
  $items = array();
  if ($may_cache) {
    $items[] = array(
      'path' => 'admin/user/captcha/math_captcha',
      'title' => t('Math CAPTCHA'),
      'callback' => 'drupal_get_form',
      'callback arguments' => array(
        'math_captcha_settings_form',
      ),
      'type' => MENU_LOCAL_TASK,
    );
  }
  return $items;
}

/**
 * Function for getting the enabled challenges (e.g. for use as checkboxes default_value)
 */
function _math_captcha_enabled_challenges() {
  $enabled = variable_get('math_captcha_enabled_challenges', array(
    'addition' => 'addition',
    'subtraction' => 'subtraction',
    'multiplication' => 'multiplication',
  ));
  return $enabled;
}

/**
 * Math CAPTCHA settings form
 */
function math_captcha_settings_form() {
  $form = array();
  $enabled_challenges = _math_captcha_enabled_challenges();
  $form['math_captcha_enabled_challenges'] = array(
    '#type' => 'checkboxes',
    '#title' => t('Enabled math challenges'),
    '#options' => array(
      'addition' => t('Addition: x + y = z'),
      'subtraction' => t('Subtraction: x - y = z'),
      'multiplication' => t('Multiplication: x * y = z'),
    ),
    '#default_value' => $enabled_challenges,
    '#description' => t('Select the math challenges you want to enable.'),
  );
  $form['math_captcha_textual_numbers'] = array(
    '#type' => 'checkbox',
    '#title' => 'Textual representation of numbers',
    '#default_value' => variable_get('math_captcha_textual_numbers', TRUE),
    '#description' => t('When enabled, the numbers in the challenge will get a textual representation if available. E.g. "four" instead of "4".'),
  );
  $form['math_captcha_textual_operators'] = array(
    '#type' => 'checkbox',
    '#title' => 'Textual representation of operators',
    '#default_value' => variable_get('math_captcha_textual_operators', FALSE),
    '#description' => t('When enabled, the operators in the challenge will get a textual representation if available. E.g. "plus" instead of "+".'),
  );

  // Addition challenge
  $form['math_captcha_addition'] = array(
    '#type' => 'fieldset',
    '#title' => t('Addition challenge: x + y = z'),
  );
  $form['math_captcha_addition']['math_captcha_addition_argmax'] = array(
    '#type' => 'textfield',
    '#title' => t('Maximum value for x and y'),
    '#default_value' => variable_get('math_captcha_addition_argmax', 10),
    '#maxlength' => 3,
    '#size' => 3,
  );
  $form['math_captcha_addition']['math_captcha_addition_allow_negative'] = array(
    '#type' => 'checkbox',
    '#title' => t('Allow negative values for x and y'),
    '#default_value' => variable_get('math_captcha_addition_allow_negative', FALSE),
  );

  // subtraction challenge
  $form['math_captcha_subtraction'] = array(
    '#type' => 'fieldset',
    '#title' => t('Subtraction challenge: x - y = z'),
  );
  $form['math_captcha_subtraction']['math_captcha_subtraction_argmax'] = array(
    '#type' => 'textfield',
    '#title' => t('Maximum value for x and y'),
    '#default_value' => variable_get('math_captcha_subtraction_argmax', 10),
    '#maxlength' => 3,
    '#size' => 3,
  );
  $form['math_captcha_subtraction']['math_captcha_subtraction_allow_negative'] = array(
    '#type' => 'checkbox',
    '#title' => t('Allow negative values for x, y and z'),
    '#default_value' => variable_get('math_captcha_subtraction_allow_negative', FALSE),
  );

  // multiplication challenge
  $form['math_captcha_multiplication'] = array(
    '#type' => 'fieldset',
    '#title' => t('Multiplication challenge: x * y = z'),
  );
  $form['math_captcha_multiplication']['math_captcha_multiplication_argmax'] = array(
    '#type' => 'textfield',
    '#title' => t('Maximum value for x and y'),
    '#default_value' => variable_get('math_captcha_multiplication_argmax', 5),
    '#maxlength' => 3,
    '#size' => 3,
  );
  $form['math_captcha_multiplication']['math_captcha_multiplication_allow_negative'] = array(
    '#type' => 'checkbox',
    '#title' => t('Allow negative values for x, y'),
    '#default_value' => variable_get('math_captcha_multiplication_allow_negative', FALSE),
  );

  // add buttons and return
  return system_settings_form($form);
}

/**
 * Validation function for Math CAPTCHA settings form
 */
function math_captcha_settings_form_validate($form_id, $form_values) {
  if ($form_id == 'math_captcha_settings_form') {

    // check enabled challenges
    if ($form_values['math_captcha_enabled_challenges'][0]) {
      form_set_error('math_captcha_enabled_challenges', t('You should select at least one type of math challenges.'));
    }

    // check argmax's
    $argmaxs = array(
      'math_captcha_addition_argmax',
      'math_captcha_subtraction_argmax',
      'math_captcha_multiplication_argmax',
    );
    foreach ($argmaxs as $argmax) {
      if (!is_numeric($form_values[$argmax])) {
        form_set_error($argmax, t('Maximum value should be an integer.'));
      }
      else {
        if (intval($form_values[$argmax]) < 2) {
          form_set_error($argmax, t('Maximum value should be an integer and at least 2'));
        }
      }
    }
  }
}

/**
 * Helper function for transforming a number to a textual representation
 */
function _math_captcha_repr($n, $add_paratheses_when_negative = FALSE) {

  // start with no textual representation
  $t = "{$n}";

  // if enabled and available: do textual representation
  if (variable_get('math_captcha_textual_numbers', TRUE)) {
    $repr_map = array(
      0 => t('zero'),
      1 => t('one'),
      2 => t('two'),
      3 => t('three'),
      4 => t('four'),
      5 => t('five'),
      6 => t('six'),
      7 => t('seven'),
      8 => t('eight'),
      9 => t('nine'),
      10 => t('ten'),
      11 => t('eleven'),
      12 => t('twelve'),
      13 => t('thirteen'),
      14 => t('fourteen'),
      15 => t('fifteen'),
    );
    if (array_key_exists(abs($n), $repr_map)) {
      $t = $repr_map[abs($n)];
      if ($n < 0) {
        $t = t('minus !number', array(
          '!number' => $t,
        ));
      }
    }
  }
  if ($add_paratheses_when_negative && $n < 0) {
    $t = "({$t})";
  }
  return $t;
}
function _math_captcha_repr_op($op) {

  // start with no textual representation
  $t = "{$op}";

  // if enabled and available: do textual representation
  if (variable_get('math_captcha_textual_operators', FALSE)) {
    $repr_map = array(
      '+' => t('plus'),
      '-' => t('minus'),
      '*' => t('times'),
      '=' => t('equals'),
    );
    if (array_key_exists($op, $repr_map)) {
      $t = $repr_map[$op];
    }
  }
  return $t;
}

/**
 * helper function to build a math CAPTCHA form item
 */
function _math_captcha_build_captcha($x, $y, $operator, $result, $maxlength = 3) {
  $form_item = array();
  $form_item['form']['captcha_response'] = array(
    '#type' => 'textfield',
    '#title' => t('Math question'),
    '#required' => TRUE,
    '#size' => $maxlength + 2,
    '#maxlength' => $maxlength,
    '#description' => t('Solve this math question and enter the solution with digits. E.g. for "two plus four = ?" enter "6".'),
  );
  switch (mt_rand(0, 2)) {
    case 0:

      // question like "x + y = ?"
      $form_item['solution'] = "{$result}";
      $form_item['form']['captcha_response']['#field_prefix'] = _math_captcha_repr($x, TRUE) . ' ' . _math_captcha_repr_op($operator) . ' ' . _math_captcha_repr($y, TRUE) . ' ' . _math_captcha_repr_op('=');
      break;
    case 1:

      // question like "x + ? = z"
      $form_item['solution'] = "{$y}";
      $form_item['form']['captcha_response']['#field_prefix'] = _math_captcha_repr($x, TRUE) . ' ' . _math_captcha_repr_op($operator) . ' ';
      $form_item['form']['captcha_response']['#field_suffix'] = ' ' . _math_captcha_repr_op('=') . ' ' . _math_captcha_repr($result);
      break;
    case 2:

      // question like "? + y = z"
      $form_item['solution'] = "{$x}";
      $form_item['form']['captcha_response']['#field_suffix'] = ' ' . _math_captcha_repr_op($operator) . ' ' . _math_captcha_repr($y, TRUE) . ' ' . _math_captcha_repr_op('=') . ' ' . _math_captcha_repr($result);
      break;
  }
  return $form_item;
}

/**
 * function for addition challenges
 */
function _math_captcha_addition_challenge() {
  $argmax = intval(variable_get('math_captcha_addition_argmax', 10));
  if (variable_get('math_captcha_addition_allow_negative', FALSE)) {
    $x = mt_rand(-$argmax, $argmax);
    $y = mt_rand(-$argmax, $argmax);
  }
  else {
    $x = mt_rand(0, $argmax);
    $y = mt_rand(0, $argmax);
  }
  $solution = $x + $y;
  $maxlength = strlen(strval($argmax + $argmax)) + intval(variable_get('math_captcha_addition_allow_negative', FALSE));
  return _math_captcha_build_captcha($x, $y, '+', $solution, $maxlength);
}

/**
 * function for subtraction challenges
 */
function _math_captcha_subtraction_challenge() {
  $argmax = intval(variable_get('math_captcha_subtraction_argmax', 10));
  if (variable_get('math_captcha_subtraction_allow_negative', FALSE)) {
    $x = mt_rand(-$argmax, $argmax);
    $y = mt_rand(-$argmax, $argmax);
  }
  else {
    $y = mt_rand(0, $argmax);
    $x = mt_rand($y, $argmax);
  }
  $solution = $x - $y;
  $maxlength = strlen(strval($argmax + $argmax)) + intval(variable_get('math_captcha_subtraction_allow_negative', FALSE));
  return _math_captcha_build_captcha($x, $y, '-', $solution, $maxlength);
}

/**
 * function for multiplication challenges
 */
function _math_captcha_multiplication_challenge() {
  $argmax = intval(variable_get('math_captcha_multiplication_argmax', 5));
  $x = mt_rand(1, $argmax);
  $y = mt_rand(1, $argmax);
  if (variable_get('math_captcha_multiplication_allow_negative', FALSE)) {
    $x = $x * (mt_rand(0, 1) * 2 - 1);
    $y = $y * (mt_rand(0, 1) * 2 - 1);
  }
  $solution = $x * $y;
  $maxlength = strlen(strval($argmax * $argmax)) + intval(variable_get('math_captcha_multiplication_allow_negative', FALSE));
  return _math_captcha_build_captcha($x, $y, '*', $solution, $maxlength);
}

/**
 * Implementation of hook_captcha().
 */
function math_captcha_captcha($op, $captcha_type = '') {
  switch ($op) {
    case 'list':
      return array(
        'Math CAPTCHA',
      );
    case 'generate':
      if ($captcha_type == 'Math CAPTCHA') {

        // get the available challenges
        $challenges = array_filter(_math_captcha_enabled_challenges());
        $challenge = $challenges[array_rand($challenges)];
        $form_item = call_user_func("_math_captcha_{$challenge}_challenge");
        return $form_item;
      }
  }
}

Functions

Namesort descending Description
math_captcha_captcha Implementation of hook_captcha().
math_captcha_menu Implementation of hook_menu().
math_captcha_settings_form Math CAPTCHA settings form
math_captcha_settings_form_validate Validation function for Math CAPTCHA settings form
_math_captcha_addition_challenge function for addition challenges
_math_captcha_build_captcha helper function to build a math CAPTCHA form item
_math_captcha_enabled_challenges Function for getting the enabled challenges (e.g. for use as checkboxes default_value)
_math_captcha_multiplication_challenge function for multiplication challenges
_math_captcha_repr Helper function for transforming a number to a textual representation
_math_captcha_repr_op
_math_captcha_subtraction_challenge function for subtraction challenges