<?php

/*
Plugin Name: YouTube API
Description: Check links to YouTube videos and playlists using the YouTube API.
Version: 3
Author: Janis Elsts

ModuleID: youtube-checker
ModuleCategory: checker
ModuleContext: on-demand
ModuleLazyInit: true
ModuleClassName: blcYouTubeChecker
ModulePriority: 100

ModuleCheckerUrlPattern: @^https?://(?:([\w\d]+\.)*youtube\.[^/]+/watch\?.*v=[^/#]|youtu\.be/[^/#\?]+|(?:[\w\d]+\.)*?youtube\.[^/]+/(playlist|view_play_list)\?[^/#]{15,}?)@i
*/

class blcYouTubeChecker extends blcChecker {
	var $api_grace_period      = 0.3; //How long to wait between YouTube API requests.
	var $last_api_request      = 0;   //Timestamp of the last request.

	function can_check( $url, $parsed ) {
		return true;
	}

	function check( $url ) {
		//Throttle API requests to avoid getting blocked due to quota violation.
		$delta = microtime_float() - $this->last_api_request;
		if ( $delta < $this->api_grace_period ) {
			usleep( ( $this->api_grace_period - $delta ) * 1000000 );
		}

		$result = array(
			'final_url'      => $url,
			'redirect_count' => 0,
			'timeout'        => false,
			'broken'         => false,
			'log'            => "<em>(Using YouTube API)</em>\n\n",
			'result_hash'    => '',
		);

		$components = @parse_url( $url );
		if ( isset( $components['query'] ) ) {
			parse_str( $components['query'], $query );
		} else {
			$query = array();
		}

		//Extract the video or playlist ID from the URL
		$video_id = null;
		$playlist_id = null;
		if ( strtolower( $components['host'] ) === 'youtu.be' ) {
			$video_id = trim( $components['path'], '/' );
		} elseif ( ( strpos( $components['path'], 'watch' ) !== false ) && isset( $query['v'] ) ) {
			$video_id = $query['v'];
		} elseif ( '/playlist' == $components['path'] ) {
			$playlist_id = $query['list'];
		} elseif ( '/view_play_list' == $components['path'] ) {
			$playlist_id = $query['p'];
		}

		if ( empty( $playlist_id ) && empty( $video_id ) ) {
			$result['status_text'] = 'Unsupported URL Syntax';
			$result['status_code'] = BLC_LINK_STATUS_UNKNOWN;
			return $result;
		}

		//Fetch video or playlist from the YouTube API
		if ( ! empty( $video_id ) ) {
			$api_url = $this->get_video_resource_url( $video_id );
		} else {
			$api_url = $this->get_playlist_resource_url( $playlist_id );
		}

		$conf = blc_get_configuration();
		$args = array( 'timeout' => $conf->options['timeout'] );

		$start                      = microtime_float();
		$response                   = wp_remote_get( $api_url, $args );
		$result['request_duration'] = microtime_float() - $start;
		$this->last_api_request     = $start;

		//Got anything?
		if ( is_wp_error( $response ) ) {
			$result['log'] .= "Error.\n" . $response->get_error_message();
			//WP doesn't make it easy to distinguish between different internal errors.
			$result['broken']    = true;
			$result['http_code'] = 0;
		} else {
			$result['http_code'] = intval( $response['response']['code'] );

			if ( ! empty( $video_id ) ) {
				$result = $this->check_video( $response, $result );
			} else {
				$result = $this->check_playlist( $response, $result );
			}
		}


		//The hash should contain info about all pieces of data that pertain to determining if the
		//link is working.
		$result['result_hash'] = implode(
			'|',
			array(
				'youtube',
				$result['http_code'],
				$result['broken'] ? 'broken' : '0',
				$result['timeout'] ? 'timeout' : '0',
				isset( $result['state_name'] ) ? $result['state_name'] : '-',
				isset( $result['state_reason'] ) ? $result['state_reason'] : '-',
			)
		);

		return $result;
	}

	/**
	 * Check API response for a single video.
	 *
	 * @param array $response WP HTTP API response.
	 * @param array $result Current result array.
	 * @return array New result array.
	 */
	protected function check_video( $response, $result ) {
		$api        = json_decode( $response['body'], true );
		$videoFound = ( 200 == $result['http_code'] ) && isset( $api['items'], $api['items'][0] );

		if ( isset( $api['error'] ) && ( 404 !== $result['http_code'] ) ) { //404's are handled later.
			$result['status_code'] = BLC_LINK_STATUS_WARNING;
			$result['warning']     = true;
			if ( isset( $api['error']['errors'] ) ) {
				$result['status_text'] = $api['error']['errors'][0]['reason'];
			} else {
				$result['status_text'] = __( 'Unknown Error', 'broken-link-checker' );
			}
			$result['log'] .= $this->format_api_error( $response, $api );

		} elseif ( $videoFound ) {
			$result['log']        .= __( 'Video OK', 'broken-link-checker' );
			$result['status_text'] = _x( 'OK', 'link status', 'broken-link-checker' );
			$result['status_code'] = BLC_LINK_STATUS_OK;
			$result['http_code']   = 0;

			//Add the video title to the log, purely for information.
			if ( isset( $api['items'][0]['snippet']['title'] ) ) {
				$title          = $api['items'][0]['snippet']['title'];
				$result['log'] .= "\n\nTitle : \"" . htmlentities( $title ) . '"';
			}
		} else {
			$result['log']        .= __( 'Video Not Found', 'broken-link-checker' );
			$result['broken']      = true;
			$result['http_code']   = 0;
			$result['status_text'] = __( 'Video Not Found', 'broken-link-checker' );
			$result['status_code'] = BLC_LINK_STATUS_ERROR;
		}

		return $result;
	}

	/**
	 * Check a YouTube API response that contains a single playlist.
	 *
	 * @param array $response
	 * @param array $result
	 * @return array
	 */
	protected function check_playlist( $response, $result ) {
		$api = json_decode( $response['body'], true );

		if ( 404 === $result['http_code'] ) {
			//Not found.
			$result['log']        .= __( 'Playlist Not Found', 'broken-link-checker' );
			$result['broken']      = true;
			$result['http_code']   = 0;
			$result['status_text'] = __( 'Playlist Not Found', 'broken-link-checker' );
			$result['status_code'] = BLC_LINK_STATUS_ERROR;

		} elseif ( 403 === $result['http_code'] ) {
			//Forbidden. We're unlikely to see this code for playlists, but lets allow it.
			$result['log']        .= htmlentities( $response['body'] );
			$result['broken']      = true;
			$result['status_text'] = __( 'Playlist Restricted', 'broken-link-checker' );
			$result['status_code'] = BLC_LINK_STATUS_ERROR;

		} elseif ( ( 200 === $result['http_code'] ) && isset( $api['items'] ) && is_array( $api['items'] ) ) {
			//The playlist exists.
			if ( empty( $api['items'] ) ) {
				//An empty playlist. It is possible that all of the videos have been deleted.
				$result['log']        .= __( 'This playlist has no entries or all entries have been deleted.', 'broken-link-checker' );
				$result['status_text'] = _x( 'Empty Playlist', 'link status', 'broken-link-checker' );
				$result['status_code'] = BLC_LINK_STATUS_WARNING;
				$result['http_code']   = 0;
				$result['broken']      = true;
			} else {
				//Treat the playlist as broken if at least one video is inaccessible.
				foreach ( $api['items'] as $video ) {
					$is_private = isset( $video['status']['privacyStatus'] ) && ( 'private' == $video['status']['privacyStatus'] );
					if ( $is_private ) {
						$result['log'] .= sprintf(
							__( 'Video status : %1$s%2$s', 'broken-link-checker' ),
							$video['status']['privacyStatus'],
							''
						);

						$result['broken']      = true;
						$result['status_text'] = __( 'Video Restricted', 'broken-link-checker' );
						$result['status_code'] = BLC_LINK_STATUS_WARNING;
						$result['http_code']   = 0;
						break;
					}
				}

				if ( ! $result['broken'] ) {
					//All is well.
					$result['log']        .= __( 'Playlist OK', 'broken-link-checker' );
					$result['status_text'] = _x( 'OK', 'link status', 'broken-link-checker' );
					$result['status_code'] = BLC_LINK_STATUS_OK;
					$result['http_code']   = 0;
				}
			}
		} else {
			//Some other error.
			$result['status_code'] = BLC_LINK_STATUS_WARNING;
			$result['warning']     = true;

			if ( isset( $api['error']['message'] ) ) {
				$result['status_text'] = $api['error']['message'];
			} else {
				$result['status_text'] = __( 'Unknown Error', 'broken-link-checker' );
			}
			$result['log'] .= $this->format_api_error( $response, $api );
		}

		return $result;
	}

	protected function get_video_resource_url( $video_id ) {
		$params = array(
			'part' => 'status,snippet',
			'id'   => $video_id,
			'key'  => $this->get_youtube_api_key(),
		);
		$params = array_map( 'urlencode', $params );
		return 'https://www.googleapis.com/youtube/v3/videos?' . build_query( $params );
	}

	protected function get_playlist_resource_url( $playlist_id ) {
		if ( strpos( $playlist_id, 'PL' ) === 0 ) {
			$playlist_id = substr( $playlist_id, 2 );
		}
		$params = array(
			'key'        => $this->get_youtube_api_key(),
			'playlistId' => $playlist_id,
			'part'       => 'snippet,status',
			'maxResults' => 10, //Playlists can be big. Lets just check the first few videos.
		);
		$query  = build_query( array_map( 'urlencode', $params ) );
		return 'https://www.googleapis.com/youtube/v3/playlistItems?' . $query;
	}

	protected function format_api_error( $response, $api ) {
		$log  = $response['response']['code'] . ' ' . $response['response']['message'];
		$log .= "\n" . __( 'Unknown YouTube API response received.' );

		//Log error details.
		if ( isset( $api['error']['errors'] ) && is_array( $api['error']['errors'] ) ) {
			foreach ( $api['error']['errors'] as $error ) {
				$log .= "\n---\n";

				if ( is_array( $error ) ) {
					foreach ( $error as $key => $value ) {
						$log .= sprintf(
							"%s: %s\n",
							htmlentities( $key ),
							htmlentities( $value )
						);
					}
				}
			}
		}

		return $log;
	}

	public function get_youtube_api_key() {
		$conf = blc_get_configuration();

		$api_key = ! empty( $conf->options['youtube_api_key'] ) ? $conf->options['youtube_api_key'] : '';

		return apply_filters( 'blc_youtube_api_key', $conf->options['youtube_api_key'] );
	}

}