<?php
namespace newznab;

use ReCaptcha\ReCaptcha;

class Captcha {
	/**
	 * Smarty $page
	 *
	 * @var \Page
	 */
	private $page;

	/**
	 * ReCaptcha Site Key from the
	 * settings database.
	 *
	 * @var bool|string
	 */
	private $sitekey;

	/**
	 * ReCaptcha Secret Key from the
	 * settings database.
	 *
	 * @var bool|string
	 */
	private $secretkey;

	/**
	 * ReCaptcha instance if enabled.
	 *
	 * @var \ReCaptcha\ReCaptcha
	 */
	private $recaptcha;


	/**
	 * Contains the error output if ReCaptcha
	 * validation fails.
	 *
	 * @var string|bool
	 */
	private $error = false;


	/**
	 * $_POST key for the user-supplied ReCaptcha response.
	 */
	const RECAPTCHA_POSTKEY = 'g-recaptcha-response';

	/**
	 * Error key literals.
	 */
	const RECAPTCHA_ERROR_MISSING_SECRET 	= 'missing-input-secret';
	const RECAPTCHA_ERROR_INVALID_SECRET 	= 'invalid-input-secret';
	const RECAPTCHA_ERROR_MISSING_RESPONSE 	= 'missing-input-response';
	const RECAPTCHA_ERROR_INVALID_RESPONSE 	= 'invalid-input-response';

	/**
	 * Settings key literals
	 */
	const RECAPTCHA_SETTING_SITEKEY		= 'recaptchapublickey';
	const RECAPTCHA_SETTING_SECRETKEY 	= 'recaptchaprivatekey';

	/**
	 * Construct and decide whether to show the captcha or not.
	 *
	 * @note Passing $page by reference to setup smarty vars easily.
	 * @param \Page $page
	 */
	public function __construct(&$page) {
		if (!$page instanceof \Page) {
			throw new \InvalidArgumentException('Invalid Page variable provided');
		}

		$this->page = $page;

		if ($this->shouldDisplay()) {
			$this->page->smarty->assign('showCaptcha', true);
			$this->page->smarty->assign('sitekey', $this->sitekey);

			if ($this->page->isPostBack()) {
				if (!$this->processCaptcha($_POST, $_SERVER['REMOTE_ADDR'])) {
					$this->page->smarty->assign('error', $this->getError());
				}
				//Delete this key after using so it doesn't interfere with normal $_POST
				//processing. (i.e. contact-us)
				unset($_POST[Captcha::RECAPTCHA_POSTKEY]);
			}
		} else {
			$this->page->smarty->assign('showCaptcha', false);
		}
	}

	/**
	 * If site admin setup keys properly,
	 * allow display of recaptcha.
	 *
	 * @return bool
	 */
	public function shouldDisplay() {
		if ($this->_bootstrapCaptcha()) {
			return true;
		}

		return false;
	}

	/**
	 * Return formatted error messages.
	 *
	 * @return string
	 */
	public function getError() {
		return $this->error;
	}

	/**
	 * Process the submitted captcha and validate.
	 *
	 * @param array $response
	 * @param string $ip
	 * @return bool
	 */
	public function processCaptcha($response, $ip) {
		if (isset($response[self::RECAPTCHA_POSTKEY])) {
			$post_response = $response[self::RECAPTCHA_POSTKEY];
		} else {
			$post_response = '';
		}

		$verify_response = $this->recaptcha->verify($post_response, $ip);

		if (!$verify_response->isSuccess()) {
			$this->_handleErrors($verify_response->getErrorCodes());
			return false;
		}

		return true;
	}

	/**
	 * Build formatted error string for output using
	 * Google's reCaptcha error codes.
	 *
	 * @param array $codes
	 */
	private function _handleErrors($codes) {
		$rc_error = 'ReCaptcha Failed: ';

		foreach ($codes as $c) {
			switch($c) {
				case self::RECAPTCHA_ERROR_MISSING_SECRET:
					$rc_error .= 'Missing Secret Key';
					break;
				case self::RECAPTCHA_ERROR_INVALID_SECRET:
					$rc_error .= 'Invalid Secret Key';
					break;
				case self::RECAPTCHA_ERROR_MISSING_RESPONSE:
					$rc_error .= 'No Response!';
					break;
				case self::RECAPTCHA_ERROR_INVALID_RESPONSE:
					$rc_error .= 'Invalid response! You are a bot!';
					break;
				default:
					$rc_error .= 'Unknown Error!';
			}
		}

		$this->error = $rc_error;
	}

	/**
	 * Instantiate the ReCaptcha library and store it.
	 * Return bool on success/failure.
	 *
	 * @return bool
	 */
	private function _bootstrapCaptcha() {
		if ($this->recaptcha instanceof ReCaptcha) {
			return true;
		}

		$this->sitekey = $this->page->settings->getSetting(self::RECAPTCHA_SETTING_SITEKEY);
		$this->secretkey = $this->page->settings->getSetting(self::RECAPTCHA_SETTING_SECRETKEY);

		if ($this->sitekey != false && $this->sitekey != '') {
			if ($this->secretkey != false && $this->secretkey != '') {
				$this->recaptcha = new ReCaptcha($this->secretkey);
				return true;
			}
		}

		return false;
	}
}