<?php

class Qs_Validate_YoutubeUrl extends Zend_Validate_Abstract
{
    const INVALID       = 'invalid';
    const INVALID_ID    = 'invalidId';

    /**
     * @var array
     */
    protected $_messageTemplates = [
        self::INVALID       => 'Url is in wrong format',
        self::INVALID_ID    => 'Wrong video id',
    ];

    /**
     * Pattern for youtube url validation
     * @link http://stackoverflow.com/questions/2964678/jquery-youtube-url-validation-with-regex
     * @var string
     */
    protected $_pattern = '/^(?:https?:\/\/)?(?:www\.)?(?:youtu\.be\/|youtube\.com\/(?:embed\/|v\/|watch\?v=|watch\?.+&v=))((\w|-){11})(?:\S+)?$/';

    /**
     * Url pattern used to validate videoId
     * @var string
     */
    protected $_dataUrlPattern = 'http://gdata.youtube.com/feeds/api/videos/%s';

    public function __construct(array $options = [])
    {
        if (isset($options['messages'])) {
            $this->setMessages($options['messages']);
        }
    }

    protected function _validateVideoId($videoId)
    {
        $url = sprintf($this->_dataUrlPattern, $videoId);
        if (ini_get('allow_url_fopen')) {
            if (($handle = fopen($url, 'rb')) && ($data = fread($handle, 256)) && ('<?xml' === substr($data, 0, 5))) {
                return true;
            }
        }
        return false;
    }

    /**
     * Returns true if and only if $value meets the validation requirements
     *
     * If $value fails validation, then this method returns false, and
     * getMessages() will return an array of messages that explain why the
     * validation failed.
     *
     * @param  mixed $value
     *
     * @return boolean
     * @throws Zend_Validate_Exception If validation of $value is impossible
     */
    public function isValid($value)
    {
        $value = (string) $value;
        $this->_setValue($value);

        if (false == preg_match($this->_pattern, $value, $match)) {
            $this->_error(self::INVALID);
            return false;
        }

        if (false == $this->_validateVideoId($match[1])) {
            $this->_error(self::INVALID_ID);
            return false;
        }

        return true;
    }

}