<?php
/*
 * ffmpeg.php
 * A barebones ffmpeg based webm implementation for vichan.
 */

function get_webm_info($filename) {
	global $config;

	$filename = escapeshellarg($filename);
	$ffprobe = $config['webm']['ffprobe_path'];
	$ffprobe_out = [];
	$webminfo = [];

	exec("$ffprobe -v quiet -print_format json -show_format -show_streams $filename", $ffprobe_out);
	$ffprobe_out = json_decode(implode("\n", $ffprobe_out), 1);
	$validcheck = is_valid_webm($ffprobe_out);
	$webminfo['error'] = $validcheck['error'];
	if (empty($webminfo['error'])) {
		$trackmap = $validcheck['trackmap'];
		$videoidx = $trackmap['videoat'][0];
		$webminfo['width'] = $ffprobe_out['streams'][$videoidx]['width'];
		$webminfo['height'] = $ffprobe_out['streams'][$videoidx]['height'];
		$webminfo['duration'] = $ffprobe_out['format']['duration'];
	}
	return $webminfo;
}

function locate_webm_tracks($ffprobe_out) {
	$streams = $ffprobe_out['streams'];
	$streamcount = count($streams);
	$video_at = [];
	$audio_at = [];
	$others = [];

	for ($k = 0; $k < $streamcount; $k++) {
		$stream = $streams[$k];
		$codec_type = $stream['codec_type'];

		if ($codec_type === 'video') {
			$video_at[] = $k;
		} elseif ($codec_type === 'audio') {
			$audio_at[] = $k;
		} else {
			if (isset($others[$codec_type])) {
				$others[$codec_type][] = $k;
			} else {
				$others[$codec_type] = [$k];
			}
		}
	}

	return [ 'videoat' => $video_at, 'audioat' => $audio_at, 'others' => $others ];
}

function is_valid_webm($ffprobe_out) {
	global $config;

	if (empty($ffprobe_out)) {
		return [ 'error' => [ 'code' => 1, 'msg' => $config['error']['genwebmerror'] ] ];
	}
	$trackmap = locate_webm_tracks($ffprobe_out);

	// one video track
	if (count($trackmap['videoat']) != 1) {
		return [
			'error' => [
				'code' => 2,
				'msg' => $config['error']['invalidwebm'] . ' [video track count]'
			]
		];
	}
	$videoidx = $trackmap['videoat'][0];

	$extension = pathinfo($ffprobe_out['format']['filename'], PATHINFO_EXTENSION);
	if ($extension === 'webm' && !stristr($ffprobe_out['format']['format_name'], 'mp4')) {
		if ($ffprobe_out['format']['format_name'] != 'matroska,webm') {
			return [
				'error' => [
					'code' => 2,
					'msg' => $config['error']['invalidwebm'] . 'error 1'
				]
			];
		}
	} elseif ($extension === 'mp4' || stristr($ffprobe_out['format']['format_name'], 'mp4')) {
		// If the video is not h264 or (there is audio but it's not aac).
		if ($ffprobe_out['streams'][$videoidx]['codec_name'] != 'h264') {
			if (!isset($ffprobe_out['streams'][0]['codec_name'])) {
				return [
					'error' => [
						'code' => 2,
						'msg' => $config['error']['invalidwebm']
					]
				];
			}

			$video_codec = $ffprobe_out['streams'][0]['codec_name'];

			$audio_codec = $ffprobe_out['streams'][1]['codec_name'] ?? null;

			if ($video_codec !== 'h264' || ($audio_codec && $audio_codec !== 'aac')) {
				return [
					'error' => [
						'code' => 2,
						'msg' => $config['error']['invalidwebm']
					]
				];
			}
		}
	} else {
		return [
			'error' => [
				'code' => 1,
				'msg' => $config['error']['genwebmerror'] . 'error 3'
			]
		];
	}
	if ((count($ffprobe_out['streams']) > 1) && (!$config['webm']['allow_audio'])) {
		return [
			'error' => [
				'code' => 3,
				'msg' => $config['error']['webmhasaudio'] . 'error 4'
			]
		];
	}
	if ((count($trackmap['audioat']) > 0) && !$config['webm']['allow_audio']) {
		return [
			'error' => [
				'code' => 3,
				'msg' => $config['error']['webmhasaudio'] . 'error 5'
			]
		];
	}
	if ($ffprobe_out['format']['duration'] > $config['webm']['max_length']) {
		return [
			'error' => [
				'code' => 4,
				'msg' => sprintf($config['error']['webmtoolong'], $config['webm']['max_length']) . 'error 6'
			]
		];
	}
	return [
		'error' => [],
		'trackmap' => $trackmap
	];
}

function make_webm_thumbnail($filename, $thumbnail, $width, $height, $duration) {
	global $config;

	$filename = escapeshellarg($filename);
	// Should be safe by default but you can never be too safe.
	$thumbnailfc = escapeshellarg($thumbnail);

	// Same as above.
	$width = escapeshellarg($width);
	$height = escapeshellarg($height);
	$ffmpeg = $config['webm']['ffmpeg_path'];
	$ret = 0;
	$ffmpeg_out = [];

	exec("$ffmpeg -strict -2 -ss " . floor($duration / 2) . " -i $filename -v quiet -an -vframes 1 -f mjpeg -vf scale=$width:$height $thumbnailfc 2>&1", $ffmpeg_out, $ret);

	// Work around for https://trac.ffmpeg.org/ticket/4362.
	if (filesize($thumbnail) === 0) {
		// Try again with first frame.
		exec("$ffmpeg -y -strict -2 -ss 0 -i $filename -v quiet -an -vframes 1 -f mjpeg -vf scale=$width:$height $thumbnailfc 2>&1", $ffmpeg_out, $ret);
		clearstatcache();
		// Failed if no thumbnail size even if ret code 0, ffmpeg is buggy.
		if (filesize($thumbnail) === 0) {
			$ret = 1;
		}
	}
	return $ret;
}