<?php
/**
 * Video Url Parser
 *
 * Parses URLs from major cloud video providers. Capable of returning
 * keys from various video embed and link urls to manipulate and
 * access videos in various ways.
 */
class video_url_parser
{
	/**
	 * Determines which cloud video provider is being used based on the passed url.
	 *
	 * @param string $url The url
	 * @return null|string Null on failure to match, the service's name on success
	 */
	public static function identify_service($url)
	{
		if (preg_match('%youtube|youtu\.be%i', $url)) {
			return 'youtube';
		}
		elseif (preg_match('%vimeo%i', $url)) {
			return 'vimeo';
		}
		return null;
	}

	/**
	 * Determines which cloud video provider is being used based on the passed url,
	 * and extracts the video id from the url.
	 *
	 * @param string $url The url
	 * @return null|string Null on failure, the video's id on success
	 */
	public static function get_url_id($url)
	{
		$service = self::identify_service($url);

		if ($service == 'youtube') {
			return self::get_youtube_id($url);
		}
		elseif ($service == 'vimeo') {
			return self::get_vimeo_id($url);
		}
		return null;
	}

	/**
	 * Determines which cloud video provider is being used based on the passed url,
	 * extracts the video id from the url, and builds an embed url.
	 *
	 * @param string $url The url
	 * @return null|string Null on failure, the video's embed url on success
	 */
	public static function get_url_embed($url)
	{
		$service = self::identify_service($url);

		$id = self::get_url_id($url);

		if ($service == 'youtube') {
			return self::get_youtube_embed($id);
		}
		elseif ($service == 'vimeo') {
			return self::get_vimeo_embed($id);
		}
		return null;
	}

	/**
	 * Parses various youtube urls and returns video identifier.
	 *
	 * @param string $url The url
	 * @return string the url's id
	 */
	public static function get_youtube_id($url)
	{
		$youtube_url_keys = array('v','vi');

		// Try to get ID from url parameters
		$key_from_params = self::parse_url_for_params($url, $youtube_url_keys);
		if ($key_from_params) return $key_from_params;

		// Try to get ID from last portion of url
		return self::parse_url_for_last_element($url);
	}

	/**
	 * Builds a Youtube embed url from a video id.
	 *
	 * @param string $youtube_video_id The video's id
	 * @return string the embed url
	 */
	public static function get_youtube_embed($youtube_video_id, $autoplay = 0)
	{
		$embed = "http://youtube.com/embed/$youtube_video_id";

		return $embed;
	}

	/**
	 * Parses various vimeo urls and returns video identifier.
	 *
	 * @param string $url The url
	 * @return string The url's id
	 */
	public static function get_vimeo_id($url)
	{
		// Try to get ID from last portion of url
		return self::parse_url_for_last_element($url);
	}

	/**
	 * Builds a Vimeo embed url from a video id.
	 *
	 * @param string $vimeo_video_id The video's id
	 * @return string the embed url
	 */
	public static function get_vimeo_embed($vimeo_video_id, $autoplay = 0)
	{
		$embed = "http://player.vimeo.com/video/$vimeo_video_id";

		return $embed;
	}

	/**
	 * Find the first matching parameter value in a url from the passed params array.
	 *
	 * @access private
	 *
	 * @param string $url The url
	 * @param array $target_params Any parameter keys that may contain the id
	 * @return null|string Null on failure to match a target param, the url's id on success
	 */
	private static function parse_url_for_params($url, $target_params)
	{
		parse_str( parse_url( $url, PHP_URL_QUERY ), $my_array_of_params );
		foreach ($target_params as $target) {
			if (array_key_exists ($target, $my_array_of_params)) {
				return $my_array_of_params[$target];
			}
		}
		return null;
	}

	/**
	 * Find the last element in a url, without any trailing parameters
	 *
	 * @access private
	 *
	 * @param string $url The url
	 * @return string The last element of the url
	 */
	private static function parse_url_for_last_element($url)
	{
		$url_parts = explode("/", $url);
		$prospect = end($url_parts);
		$prospect_and_params = preg_split("/(\?|\=|\&)/", $prospect);
		if ($prospect_and_params) {
			return $prospect_and_params[0];
		} else {
			return $prospect;
		}
		return $url;
	}
}
 ?>