<?php
/**
 * YouTube Data API v3 client with caching.
 *
 * Only playlistItems, videos and channels are used (1 quota unit each), never
 * search.list (100 units). Shorts come from the channel's "UUSH" playlist and
 * long videos from its "UULF" playlist, which YouTube keeps for every channel.
 *
 * @package YouWall
 */

defined( 'ABSPATH' ) || exit;

/**
 * YouTube API client.
 */
class YouWall_API {

	const BASE = 'https://www.googleapis.com/youtube/v3/';

	/**
	 * API key.
	 *
	 * @var string
	 */
	private $api_key;

	/**
	 * Constructor.
	 *
	 * @param string|null $api_key Key to use; defaults to the saved key.
	 */
	public function __construct( $api_key = null ) {
		$this->api_key = null === $api_key ? (string) YouWall_Settings::get( 'api_key' ) : (string) $api_key;
	}

	/* ── IDs ─────────────────────────────────────────────────────────── */

	/**
	 * Whether a string is a channel ID (UC + 22 characters).
	 *
	 * @param string $id Value.
	 * @return bool
	 */
	public static function is_channel_id( $id ) {
		return (bool) preg_match( '/^UC[A-Za-z0-9_-]{22}$/', (string) $id );
	}

	/**
	 * Channel ID → its Shorts (UUSH…) or long videos (UULF…) playlist.
	 *
	 * @param string $kind       'shorts' or 'videos'.
	 * @param string $channel_id Channel ID.
	 * @return string
	 */
	public static function channel_playlist( $kind, $channel_id ) {
		return ( 'shorts' === $kind ? 'UUSH' : 'UULF' ) . substr( $channel_id, 2 );
	}

	/**
	 * Turn a channel ID, @handle or channel URL into a channel ID.
	 *
	 * @param string $input What the user typed.
	 * @return string|WP_Error Channel ID.
	 */
	public function resolve_channel( $input ) {
		$input = trim( (string) $input );

		if ( preg_match( '#youtube\.com/(channel/|@|c/|user/)?([^/?\#]+)#i', $input, $m ) ) {
			$type  = strtolower( $m[1] );
			$input = ( '@' === $type ) ? '@' . $m[2] : rawurldecode( $m[2] );
			if ( 'user/' === $type ) {
				return $this->lookup_channel( array( 'forUsername' => $input ), $input );
			}
		}

		if ( self::is_channel_id( $input ) ) {
			return $input;
		}

		$handle = ltrim( $input, '@' );
		if ( ! preg_match( '/^[\p{L}\p{N}._-]{3,100}$/u', $handle ) ) {
			return new WP_Error(
				'youwall_bad_channel',
				__( 'Enter a channel ID (starts with UC), a handle like @yourchannel, or the channel’s YouTube address.', 'youwall' )
			);
		}

		return $this->lookup_channel( array( 'forHandle' => '@' . $handle ), '@' . $handle );
	}

	/**
	 * Look up a channel ID by handle or legacy username (cached for a week).
	 *
	 * @param array  $args  channels.list arguments.
	 * @param string $label Shown in the error message.
	 * @return string|WP_Error
	 */
	private function lookup_channel( $args, $label ) {
		$key    = 'youwall_ch_' . md5( wp_json_encode( $args ) );
		$cached = get_transient( $key );
		if ( is_string( $cached ) && self::is_channel_id( $cached ) ) {
			return $cached;
		}

		$body = $this->request( 'channels', array_merge( array( 'part' => 'id' ), $args ) );
		if ( is_wp_error( $body ) ) {
			return $body;
		}
		if ( empty( $body['items'][0]['id'] ) ) {
			return new WP_Error(
				'youwall_channel_not_found',
				/* translators: %s: channel handle or name the user entered. */
				sprintf( __( 'No YouTube channel found for “%s”.', 'youwall' ), $label )
			);
		}

		set_transient( $key, $body['items'][0]['id'], WEEK_IN_SECONDS );
		return $body['items'][0]['id'];
	}

	/* ── Feeds ───────────────────────────────────────────────────────── */

	/**
	 * One page of a playlist, newest first (cached per page).
	 *
	 * @param string $playlist_id Playlist ID.
	 * @param string $kind        'shorts' or 'videos' (controls thumbnails).
	 * @param int    $per_page    1 to 50.
	 * @param string $token       YouTube page token, '' for the first page.
	 * @return array|WP_Error { items: array, next: string }
	 */
	public function get_page( $playlist_id, $kind, $per_page, $token = '' ) {
		$per_page = max( 1, min( 50, absint( $per_page ) ) );
		$key      = $this->cache_key( 'page', $playlist_id, $kind, $per_page, $token );
		$cached   = get_transient( $key );
		if ( is_array( $cached ) ) {
			return $cached;
		}

		$args = array(
			'part'       => 'snippet,status',
			'playlistId' => $playlist_id,
			'maxResults' => $per_page,
		);
		if ( '' !== $token ) {
			$args['pageToken'] = $token;
		}

		$body = $this->request( 'playlistItems', $args );

		if ( is_wp_error( $body ) ) {
			$data = $body->get_error_data();
			// A channel with no Shorts (or no long videos) has no UUSH/UULF playlist yet.
			$derived = 0 === strpos( $playlist_id, 'UUSH' ) || 0 === strpos( $playlist_id, 'UULF' );
			if ( $derived && isset( $data['status'] ) && 404 === $data['status'] ) {
				$result = array(
					'items' => array(),
					'next'  => '',
				);
				set_transient( $key, $result, YouWall_Settings::cache_seconds() );
				return $result;
			}
			return $body;
		}

		$items = array();
		foreach ( isset( $body['items'] ) ? $body['items'] : array() as $row ) {
			if ( isset( $row['status']['privacyStatus'] ) && 'public' !== $row['status']['privacyStatus'] ) {
				continue;
			}
			$id = isset( $row['snippet']['resourceId']['videoId'] ) ? (string) $row['snippet']['resourceId']['videoId'] : '';
			if ( ! preg_match( '/^[A-Za-z0-9_-]{11}$/', $id ) ) {
				continue;
			}
			$items[ $id ] = array(
				'id'        => $id,
				'title'     => isset( $row['snippet']['title'] ) ? (string) $row['snippet']['title'] : '',
				'published' => isset( $row['snippet']['publishedAt'] ) ? (string) $row['snippet']['publishedAt'] : '',
				'thumbnail' => self::thumbnail( $kind, $id, isset( $row['snippet']['thumbnails'] ) ? $row['snippet']['thumbnails'] : array() ),
				'views'     => null,
				'duration'  => 0,
			);
		}

		$items  = $this->add_stats( $items );
		$result = array(
			'items' => array_values( $items ),
			'next'  => isset( $body['nextPageToken'] ) ? (string) $body['nextPageToken'] : '',
		);

		set_transient( $key, $result, YouWall_Settings::cache_seconds() );
		return $result;
	}

	/**
	 * Check a key and channel before saving.
	 *
	 * @param string $channel Channel ID, handle or URL.
	 * @return array|WP_Error { channel_id, title }
	 */
	public function test_connection( $channel ) {
		$channel_id = $this->resolve_channel( $channel );
		if ( is_wp_error( $channel_id ) ) {
			return $channel_id;
		}
		$body = $this->request(
			'channels',
			array(
				'part' => 'snippet',
				'id'   => $channel_id,
			)
		);
		if ( is_wp_error( $body ) ) {
			return $body;
		}
		if ( empty( $body['items'][0] ) ) {
			return new WP_Error( 'youwall_channel_not_found', __( 'The API key works, but this channel was not found.', 'youwall' ) );
		}
		return array(
			'channel_id' => $channel_id,
			'title'      => isset( $body['items'][0]['snippet']['title'] ) ? (string) $body['items'][0]['snippet']['title'] : $channel_id,
		);
	}

	/* ── Helpers ─────────────────────────────────────────────────────── */

	/**
	 * Add view counts and durations (one videos.list call per page).
	 *
	 * @param array $items Items keyed by video ID.
	 * @return array
	 */
	private function add_stats( $items ) {
		if ( empty( $items ) ) {
			return $items;
		}
		$body = $this->request(
			'videos',
			array(
				'part' => 'statistics,contentDetails',
				'id'   => implode( ',', array_keys( $items ) ),
			)
		);
		if ( is_wp_error( $body ) || empty( $body['items'] ) ) {
			return $items;
		}
		foreach ( $body['items'] as $row ) {
			$id = isset( $row['id'] ) ? $row['id'] : '';
			if ( ! isset( $items[ $id ] ) ) {
				continue;
			}
			if ( isset( $row['statistics']['viewCount'] ) ) {
				$items[ $id ]['views'] = (int) $row['statistics']['viewCount'];
			}
			if ( isset( $row['contentDetails']['duration'] ) ) {
				$items[ $id ]['duration'] = self::duration_seconds( $row['contentDetails']['duration'] );
			}
		}
		return $items;
	}

	/**
	 * Thumbnail URL. Shorts use YouTube's portrait cover; videos use the largest
	 * size the API says exists (maxresdefault is missing for many videos).
	 *
	 * @param string $kind       'shorts' or 'videos'.
	 * @param string $id         Video ID.
	 * @param array  $thumbnails snippet.thumbnails.
	 * @return string
	 */
	private static function thumbnail( $kind, $id, $thumbnails ) {
		if ( 'shorts' === $kind ) {
			return 'https://i.ytimg.com/vi/' . $id . '/oar2.jpg';
		}
		foreach ( array( 'maxres', 'standard', 'high', 'medium', 'default' ) as $size ) {
			if ( ! empty( $thumbnails[ $size ]['url'] ) ) {
				return (string) $thumbnails[ $size ]['url'];
			}
		}
		return 'https://i.ytimg.com/vi/' . $id . '/hqdefault.jpg';
	}

	/**
	 * Call the API.
	 *
	 * @param string $endpoint API endpoint, e.g. 'playlistItems'.
	 * @param array  $args     Query arguments.
	 * @return array|WP_Error Decoded body.
	 */
	private function request( $endpoint, $args ) {
		if ( '' === $this->api_key ) {
			return new WP_Error( 'youwall_no_key', __( 'Add your YouTube API key in YouWall > Connect.', 'youwall' ) );
		}

		$args['key'] = $this->api_key;
		$response    = wp_remote_get(
			add_query_arg( array_map( 'rawurlencode', $args ), self::BASE . $endpoint ),
			array( 'timeout' => 15 )
		);

		if ( is_wp_error( $response ) ) {
			return new WP_Error(
				'youwall_http',
				/* translators: %s: technical error message. */
				sprintf( __( 'Could not reach YouTube: %s', 'youwall' ), $response->get_error_message() )
			);
		}

		$code = (int) wp_remote_retrieve_response_code( $response );
		$body = json_decode( wp_remote_retrieve_body( $response ), true );

		if ( 200 === $code && is_array( $body ) ) {
			return $body;
		}

		$reason = isset( $body['error']['errors'][0]['reason'] ) ? (string) $body['error']['errors'][0]['reason'] : '';
		$known  = array(
			'keyInvalid'          => __( 'The YouTube API key is not valid. Check it in YouWall > Connect.', 'youwall' ),
			'badRequest'          => __( 'The YouTube API key is not valid. Check it in YouWall > Connect.', 'youwall' ),
			'quotaExceeded'       => __( 'Today’s YouTube API quota is used up. The feed will work again after it resets (midnight Pacific Time).', 'youwall' ),
			'accessNotConfigured' => __( 'YouTube Data API v3 is not enabled for this key. Enable it in Google Cloud Console.', 'youwall' ),
			'forbidden'           => __( 'YouTube refused the request. Check the key’s restrictions in Google Cloud Console.', 'youwall' ),
			'playlistNotFound'    => __( 'This playlist was not found, or it is private.', 'youwall' ),
		);

		if ( isset( $known[ $reason ] ) ) {
			$message = $known[ $reason ];
		} elseif ( ! empty( $body['error']['message'] ) ) {
			$message = wp_strip_all_tags( (string) $body['error']['message'] );
		} else {
			/* translators: %d: HTTP status code. */
			$message = sprintf( __( 'YouTube returned error %d.', 'youwall' ), $code );
		}

		return new WP_Error(
			'youwall_api',
			$message,
			array(
				'status' => $code,
				'reason' => $reason,
			)
		);
	}

	/**
	 * Cache key that includes the cache version, so "Clear cache" is one option update.
	 *
	 * @param mixed ...$parts Key parts.
	 * @return string
	 */
	private function cache_key( ...$parts ) {
		return 'youwall_' . md5( YouWall_Settings::cache_version() . '|' . wp_json_encode( $parts ) );
	}

	/**
	 * ISO 8601 duration (e.g. P1DT2H3M4S) → seconds.
	 *
	 * @param string $iso Duration.
	 * @return int
	 */
	public static function duration_seconds( $iso ) {
		if ( ! preg_match( '/^P(?:(\d+)D)?(?:T(?:(\d+)H)?(?:(\d+)M)?(?:(\d+)S)?)?$/', (string) $iso, $m ) ) {
			return 0;
		}
		$m = array_map( 'intval', array_pad( $m, 5, 0 ) );
		return $m[1] * DAY_IN_SECONDS + $m[2] * HOUR_IN_SECONDS + $m[3] * MINUTE_IN_SECONDS + $m[4];
	}

	/**
	 * Seconds → "4:05" or "1:02:03".
	 *
	 * @param int $seconds Seconds.
	 * @return string
	 */
	public static function format_duration( $seconds ) {
		$seconds = absint( $seconds );
		if ( ! $seconds ) {
			return '';
		}
		$h = intdiv( $seconds, 3600 );
		$m = intdiv( $seconds % 3600, 60 );
		$s = $seconds % 60;
		return $h ? sprintf( '%d:%02d:%02d', $h, $m, $s ) : sprintf( '%d:%02d', $m, $s );
	}

	/**
	 * View count → "1.2K views".
	 *
	 * @param int|null $views View count.
	 * @return string
	 */
	public static function format_views( $views ) {
		if ( null === $views ) {
			return '';
		}
		$n = (int) $views;
		if ( $n >= 1000000 ) {
			$short = rtrim( rtrim( number_format_i18n( $n / 1000000, 1 ), '0' ), '.,' ) . 'M';
		} elseif ( $n >= 1000 ) {
			$short = rtrim( rtrim( number_format_i18n( $n / 1000, 1 ), '0' ), '.,' ) . 'K';
		} else {
			$short = number_format_i18n( $n );
		}
		/* translators: %s: view count, for example "1.2K". */
		return sprintf( _n( '%s view', '%s views', $n, 'youwall' ), $short );
	}

	/**
	 * Publish date → "3 days ago".
	 *
	 * @param string $iso ISO date.
	 * @return string
	 */
	public static function time_ago( $iso ) {
		$ts = $iso ? strtotime( $iso ) : false;
		if ( ! $ts ) {
			return '';
		}
		/* translators: %s: time span, for example "3 days". */
		return sprintf( __( '%s ago', 'youwall' ), human_time_diff( $ts ) );
	}
}