<?php
/**
 * In-stream ICY metadata provider.
 *
 * Many hosts (Zeno, SurferNetwork, Radio.co relays, plain Icecast/Shoutcast behind a CDN) publish
 * no status page, but send the current title inside the audio stream when the client asks for it
 * with `Icy-MetaData: 1`: every `icy-metaint` bytes of audio come one length byte and a block like
 * `StreamTitle='Artist - Title';`. This provider opens the stream, reads up to the first block and
 * disconnects (a few kB, about a second at 128 kbps).
 *
 * @package StreamSera
 */

namespace StreamSera\Metadata;

if ( ! defined( 'ABSPATH' ) ) {
	exit;
}

/**
 * ICY in-stream metadata.
 */
class Icy implements Provider, Describable {

	/**
	 * {@inheritdoc}
	 */
	public function id() {
		return 'icy';
	}

	/**
	 * {@inheritdoc}
	 */
	public function definition() {
		return array(
			'label'       => __( 'In-stream (ICY) metadata', 'streamsera' ),
			'description' => __( 'Reads the title the stream itself carries (Zeno and most hosted streams). No status page needed.', 'streamsera' ),
			'usesUrl'     => false,
			'usesMount'   => false,
		);
	}

	/**
	 * {@inheritdoc}
	 *
	 * @param array $source Source definition (url, mount, stream_url).
	 */
	public function fetch( array $source ) {
		$url = ! empty( $source['stream_url'] ) ? (string) $source['stream_url'] : '';
		if ( ! $url ) {
			return null;
		}
		/**
		 * Seconds allowed for reading the first in-stream metadata block.
		 *
		 * @param int $timeout Default 6.
		 */
		$response = Resolver::probe_headers( $url, (int) apply_filters( 'streamsera_icy_timeout', 6 ), true );
		if ( ! is_array( $response ) || empty( $response['icy_meta'] ) ) {
			return null;
		}
		$raw = self::stream_title( (string) $response['icy_meta'] );
		if ( null === $raw ) {
			return null;
		}
		// Hosts often send "- Title" or "Artist -" when one part is missing.
		// trim() works on bytes, which would cut multibyte dashes (and any title ending in a
		// character that shares their bytes) apart: strip them as characters.
		$raw   = (string) preg_replace( '/^[\s\-–—]+|[\s\-–—]+$/u', '', $raw );
		$parts = Resolver::split_title( $raw );
		$h     = (array) $response['headers'];
		return array(
			'title'       => $parts['title'],
			'artist'      => $parts['artist'],
			'raw'         => $raw,
			'listeners'   => null,
			'live'        => true,
			'server'      => 'icy',
			'server_name' => isset( $h['icy-name'] ) ? (string) $h['icy-name'] : '',
			'bitrate'     => isset( $h['icy-br'] ) ? (int) $h['icy-br'] : null,
		);
	}

	/**
	 * Convert a Latin-1 (ISO-8859-1) string to UTF-8.
	 *
	 * @param string $text Latin-1 text.
	 * @return string
	 */
	private static function latin1_to_utf8( $text ) {
		if ( function_exists( 'mb_convert_encoding' ) ) {
			return (string) mb_convert_encoding( $text, 'UTF-8', 'ISO-8859-1' );
		}
		// Every Latin-1 byte is the Unicode code point of the same value.
		return (string) preg_replace_callback(
			'/[\x80-\xFF]/',
			static function ( $m ) {
				$b = ord( $m[0] );
				return chr( 0xC0 | ( $b >> 6 ) ) . chr( 0x80 | ( $b & 0x3F ) );
			},
			$text
		);
	}

	/**
	 * StreamTitle from a metadata block (`StreamTitle='…';StreamUrl='…';`).
	 *
	 * @param string $meta Raw block.
	 * @return string|null Title (may be empty when the station sends none), null if absent.
	 */
	public static function stream_title( $meta ) {
		if ( ! preg_match( "/StreamTitle='(.*?)';(?:Stream|$)/s", $meta, $m ) ) {
			return null;
		}
		$title = $m[1];
		if ( ! preg_match( '//u', $title ) ) {
			// Not valid UTF-8: older encoders send Latin-1.
			$title = self::latin1_to_utf8( $title );
		}
		return trim( wp_strip_all_tags( $title ) );
	}
}