MathSpamProtectorField.php

<?php

/**
 * {@link FormField} for adding an optional maths protection question to a form.
 *
 * @package mathspamprotection
 */

class MathSpamProtectorField extends TextField {

	/**
	 * @config
	 *
	 * @var bool $enabled
	 */
	private static $enabled = true;
	
	public function Field($properties = array()) {
		if(Config::inst()->get('MathSpamProtectorField', 'enabled')) {
			return parent::Field($properties);
		}

		return null;
	}

	public function FieldHolder($properties = array()) {
		if(Config::inst()->get('MathSpamProtectorField', 'enabled')) {
			return parent::FieldHolder($properties);
		}

		return null;
	}

	/**
	 * Returns the spam question
	 *
	 * @return string
	 */
	public function Title() {
		return sprintf(
			_t('MathSpamProtectionField.SPAMQUESTION', "Spam protection question: %s"), 
			self::get_math_question()
		);
	}

	/**
	 * Validates the value submitted by the user with the one saved into the 
	 * {@link Session} and then notify callback object with the spam checking 
	 * result.
	 *
	 * @return bool
	 */
	public function validate($validator) {
		if(!Config::inst()->get('MathSpamProtectorField', 'enabled')) {
			return true;
		}

		if(!self::correct_answer($this->Value())) {
			$validator->validationError(
				$this->name,
				_t(
					'MathSpamProtectionField.INCORRECTSOLUTION',
					"Incorrect solution to the spam protection question, please try again."
				),
				"error"
			);

			return false;
		}

		return true;
	}


	/**
	 * Creates the question from random variables, which are also saved to the session.
	 *
	 * @return string
	 */
	public static function get_math_question() {
		if(!Session::get("mathQuestionV1") && !Session::get("mathQuestionV2")) {
			$v1 = rand(1,9);
			$v2 = rand(1,9);

			Session::set("mathQuestionV1",$v1);
			Session::set("mathQuestionV2",$v2);
		} else {
			$v1 = Session::get("mathQuestionV1");
			$v2 = Session::get("mathQuestionV2");
		}

		return sprintf(
			_t('MathSpamProtection.WHATIS',"What is %s plus %s?"),
			MathSpamProtectorField::digit_to_word($v1),
			MathSpamProtectorField::digit_to_word($v2)
		);
	}

	/**
	 * Checks the given answer if it matches the addition of the saved session 
	 * variables.
	 *
	 * Users can answer using words or digits.
	 *
	 * @return bool
	 */
	public static function correct_answer($answer){
		$v1 = Session::get("mathQuestionV1");
		$v2 = Session::get("mathQuestionV2");

		Session::clear('mathQuestionV1');
		Session::clear('mathQuestionV2');

		$word = MathSpamProtectorField::digit_to_word($v1 + $v2);

		return ($word == strtolower($answer) || ($v1 + $v2) == $answer);
	}

	/**
	 * Helper method for converting digits to their equivalent english words
	 *
	 * @return string
	 */
	public static function digit_to_word($num){
		$numbers = array(_t('MathSpamProtection.ZERO', 'zero'),
			_t('MathSpamProtection.ONE', 'one'),
			_t('MathSpamProtection.TWO', 'two'),
			_t('MathSpamProtection.THREE', 'three'),
			_t('MathSpamProtection.FOUR', 'four'),
			_t('MathSpamProtection.FIVE', 'five'),
			_t('MathSpamProtection.SIX', 'six'),
			_t('MathSpamProtection.SEVEN', 'seven'),
			_t('MathSpamProtection.EIGHT', 'eight'),
			_t('MathSpamProtection.NINE', 'nine'),
			_t('MathSpamProtection.TEN', 'ten'),
			_t('MathSpamProtection.ELEVEN', 'eleven'),
			_t('MathSpamProtection.TWELVE', 'twelve'),
			_t('MathSpamProtection.THIRTEEN', 'thirteen'),
			_t('MathSpamProtection.FOURTEEN', 'fourteen'),
			_t('MathSpamProtection.FIFTEEN', 'fifteen'),
			_t('MathSpamProtection.SIXTEEN', 'sixteen'),
			_t('MathSpamProtection.SEVENTEEN', 'seventeen'),
			_t('MathSpamProtection.EIGHTEEN', 'eighteen'));

			if($num < 0) return "minus ".($numbers[-1*$num]);

		return $numbers[$num];
	}
}