netfelix-audio-fix/server/services/ffmpeg.ts

import type { MediaItem, MediaStream, StreamDecision } from '../types';
import { normalizeLanguage } from './jellyfin';

// ─── Subtitle extraction helpers ──────────────────────────────────────────────

/** ISO 639-2/B → ISO 639-1 two-letter codes for subtitle filenames. */
const ISO639_1: Record<string, string> = {
	eng: 'en', deu: 'de', spa: 'es', fra: 'fr', ita: 'it',
	por: 'pt', jpn: 'ja', kor: 'ko', zho: 'zh', ara: 'ar',
	rus: 'ru', nld: 'nl', swe: 'sv', nor: 'no', dan: 'da',
	fin: 'fi', pol: 'pl', tur: 'tr', tha: 'th', hin: 'hi',
	hun: 'hu', ces: 'cs', ron: 'ro', ell: 'el', heb: 'he',
	fas: 'fa', ukr: 'uk', ind: 'id', cat: 'ca', nob: 'nb',
	nno: 'nn', isl: 'is', hrv: 'hr', slk: 'sk', bul: 'bg',
	srp: 'sr', slv: 'sl', lav: 'lv', lit: 'lt', est: 'et',
};

/** Subtitle codec → external file extension. */
const SUBTITLE_EXT: Record<string, string> = {
	subrip: 'srt', srt: 'srt', ass: 'ass', ssa: 'ssa',
	webvtt: 'vtt', vtt: 'vtt',
	hdmv_pgs_subtitle: 'sup', pgssub: 'sup',
	dvd_subtitle: 'sub', dvbsub: 'sub',
	mov_text: 'srt', text: 'srt',
};

function subtitleLang2(lang: string | null): string {
	if (!lang) return 'und';
	const n = normalizeLanguage(lang);
	return ISO639_1[n] ?? n;
}

/** Returns the ffmpeg codec name to use when extracting this subtitle stream. */
function subtitleCodecArg(codec: string | null): string {
	if (!codec) return 'copy';
	return codec.toLowerCase() === 'mov_text' ? 'subrip' : 'copy';
}

function subtitleExtForCodec(codec: string | null): string {
	if (!codec) return 'srt';
	return SUBTITLE_EXT[codec.toLowerCase()] ?? 'srt';
}

/**
 * Build ffmpeg output args for extracting ALL subtitle streams
 * to external sidecar files next to the video.
 *
 * Returns a flat array of args to append after the main output in the
 * command. Each subtitle becomes a separate ffmpeg output:
 *   -map 0:s:N -c:s copy 'basename.en.srt'
 *
 * @param allStreams  All streams for the item (needed to compute type-relative indices)
 * @param basePath   Video file path without extension (host or /work path)
 */
interface ExtractionEntry {
	stream: MediaStream;
	typeIdx: number;
	outPath: string;
	codecArg: string;
}

/** Compute extraction metadata for all subtitle streams. Shared by buildExtractionOutputs and predictExtractedFiles. */
function computeExtractionEntries(
	allStreams: MediaStream[],
	basePath: string
): ExtractionEntry[] {
	const subTypeIdx = new Map<number, number>();
	let subCount = 0;
	for (const s of [...allStreams].sort((a, b) => a.stream_index - b.stream_index)) {
		if (s.type === 'Subtitle') subTypeIdx.set(s.id, subCount++);
	}

	const allSubs = allStreams
		.filter((s) => s.type === 'Subtitle')
		.sort((a, b) => a.stream_index - b.stream_index);

	if (allSubs.length === 0) return [];

	const usedNames = new Set<string>();
	const entries: ExtractionEntry[] = [];

	for (const s of allSubs) {
		const typeIdx = subTypeIdx.get(s.id) ?? 0;
		const langCode = subtitleLang2(s.language);
		const ext = subtitleExtForCodec(s.codec);
		const codecArg = subtitleCodecArg(s.codec);

		const nameParts = [langCode];
		if (s.is_forced) nameParts.push('forced');
		if (s.is_hearing_impaired) nameParts.push('hi');

		let outPath = `${basePath}.${nameParts.join('.')}.${ext}`;
		let counter = 2;
		while (usedNames.has(outPath)) {
			outPath = `${basePath}.${nameParts.join('.')}.${counter}.${ext}`;
			counter++;
		}
		usedNames.add(outPath);

		entries.push({ stream: s, typeIdx, outPath, codecArg });
	}

	return entries;
}

function buildExtractionOutputs(
	allStreams: MediaStream[],
	basePath: string
): string[] {
	const entries = computeExtractionEntries(allStreams, basePath);
	const args: string[] = [];
	for (const e of entries) {
		args.push(`-map 0:s:${e.typeIdx}`, `-c:s ${e.codecArg}`, shellQuote(e.outPath));
	}
	return args;
}

/**
 * Predict the sidecar files that subtitle extraction will create.
 * Used to populate the subtitle_files table after a successful job.
 */
export function predictExtractedFiles(
	item: MediaItem,
	streams: MediaStream[]
): Array<{ file_path: string; language: string | null; codec: string | null; is_forced: boolean; is_hearing_impaired: boolean }> {
	const basePath = item.file_path.replace(/\.[^.]+$/, '');
	const entries = computeExtractionEntries(streams, basePath);
	return entries.map((e) => ({
		file_path: e.outPath,
		language: e.stream.language,
		codec: e.stream.codec,
		is_forced: !!e.stream.is_forced,
		is_hearing_impaired: !!e.stream.is_hearing_impaired,
	}));
}

// ─────────────────────────────────────────────────────────────────────────────

const LANG_NAMES: Record<string, string> = {
	eng: 'English', deu: 'German', spa: 'Spanish', fra: 'French',
	ita: 'Italian', por: 'Portuguese', jpn: 'Japanese', kor: 'Korean',
	zho: 'Chinese', ara: 'Arabic', rus: 'Russian', nld: 'Dutch',
	swe: 'Swedish', nor: 'Norwegian', dan: 'Danish', fin: 'Finnish',
	pol: 'Polish', tur: 'Turkish', tha: 'Thai', hin: 'Hindi',
	hun: 'Hungarian', ces: 'Czech', ron: 'Romanian', ell: 'Greek',
	heb: 'Hebrew', fas: 'Persian', ukr: 'Ukrainian', ind: 'Indonesian',
	cat: 'Catalan', nob: 'Norwegian Bokmål', nno: 'Norwegian Nynorsk',
	isl: 'Icelandic', slk: 'Slovak', hrv: 'Croatian', bul: 'Bulgarian',
	srp: 'Serbian', slv: 'Slovenian', lav: 'Latvian', lit: 'Lithuanian',
	est: 'Estonian',
};

function trackTitle(stream: MediaStream): string | null {
	if (stream.type === 'Subtitle') {
		// Subtitles always get a clean language-based title so Jellyfin displays
		// "German", "English (Forced)", etc. regardless of the original file title.
		// The review UI shows a ⚠ badge when the original title looks like a
		// different language, so users can spot and remove mislabeled tracks.
		if (!stream.language) return null;
		const lang = normalizeLanguage(stream.language);
		const base = LANG_NAMES[lang] ?? lang.toUpperCase();
		if (stream.is_forced) return `${base} (Forced)`;
		if (stream.is_hearing_impaired) return `${base} (CC)`;
		return base;
	}
	// For audio and other stream types: preserve any existing title
	// (e.g. "Director's Commentary") and fall back to language name.
	if (stream.title) return stream.title;
	if (!stream.language) return null;
	const lang = normalizeLanguage(stream.language);
	return LANG_NAMES[lang] ?? lang.toUpperCase();
}

const TYPE_SPEC: Record<string, string> = { Video: 'v', Audio: 'a', Subtitle: 's' };

/**
 * Build -map flags using type-relative specifiers (0:v:N, 0:a:N, 0:s:N).
 *
 * Jellyfin's stream_index is an absolute index that can include EmbeddedImage
 * and Data streams which ffmpeg may count differently (e.g. cover art stored
 * as attachments). Using the stream's position within its own type group
 * matches ffmpeg's 0:a:N convention exactly and avoids silent mismatches.
 */
function buildMaps(
	allStreams: MediaStream[],
	kept: { stream: MediaStream; dec: StreamDecision }[]
): string[] {
	// Map each stream id → its 0-based position among streams of the same type,
	// sorted by stream_index (the order ffmpeg sees them in the input).
	const typePos = new Map<number, number>();
	const counts: Record<string, number> = {};
	for (const s of [...allStreams].sort((a, b) => a.stream_index - b.stream_index)) {
		if (!TYPE_SPEC[s.type]) continue;
		const n = counts[s.type] ?? 0;
		typePos.set(s.id, n);
		counts[s.type] = n + 1;
	}

	return kept
		.filter((k) => !!TYPE_SPEC[k.stream.type])
		.map((k) => `-map 0:${TYPE_SPEC[k.stream.type]}:${typePos.get(k.stream.id) ?? 0}`);
}

/**
 * Build disposition and metadata flags for kept audio streams.
 * - Marks the first kept audio stream as default, clears all others.
 * - Sets harmonized language-name titles on all kept audio streams.
 */
function buildStreamFlags(
	kept: { stream: MediaStream; dec: StreamDecision }[]
): string[] {
	const audioKept = kept.filter((k) => k.stream.type === 'Audio');
	const args: string[] = [];

	// Disposition: first audio = default, rest = clear
	audioKept.forEach((_, i) => {
		args.push(`-disposition:a:${i}`, i === 0 ? 'default' : '0');
	});

	// Titles for audio streams (custom_title overrides generated title)
	audioKept.forEach((k, i) => {
		const title = k.dec.custom_title ?? trackTitle(k.stream);
		if (title) args.push(`-metadata:s:a:${i}`, `title=${shellQuote(title)}`);
	});

	return args;
}

/**
 * Build the full shell command to remux a media file, keeping only the
 * streams specified by the decisions and in the target order.
 *
 * Returns null if all streams are kept and ordering is unchanged (noop).
 */
export function buildCommand(
	item: MediaItem,
	streams: MediaStream[],
	decisions: StreamDecision[]
): string {
	// Sort kept streams by type priority then target_index
	const kept = streams
		.map((s) => {
			const dec = decisions.find((d) => d.stream_id === s.id);
			return dec?.action === 'keep' ? { stream: s, dec } : null;
		})
		.filter(Boolean) as { stream: MediaStream; dec: StreamDecision }[];

	// Sort: Video first, Audio second, Subtitle third, Data last
	const typeOrder: Record<string, number> = { Video: 0, Audio: 1, Subtitle: 2, Data: 3, EmbeddedImage: 4 };
	kept.sort((a, b) => {
		const ta = typeOrder[a.stream.type] ?? 9;
		const tb = typeOrder[b.stream.type] ?? 9;
		if (ta !== tb) return ta - tb;
		return (a.dec.target_index ?? 0) - (b.dec.target_index ?? 0);
	});

	const inputPath = item.file_path;
	const ext = inputPath.match(/\.([^.]+)$/)?.[1] ?? 'mkv';
	const tmpPath = inputPath.replace(/\.[^.]+$/, `.tmp.${ext}`);

	const maps = buildMaps(streams, kept);
	const streamFlags = buildStreamFlags(kept);

	const parts: string[] = [
		'ffmpeg',
		'-y',
		'-i', shellQuote(inputPath),
		...maps,
		...streamFlags,
		'-c copy',
		shellQuote(tmpPath),
		'&&',
		'mv', shellQuote(tmpPath), shellQuote(inputPath),
	];

	return parts.join(' ');
}

/**
 * Build a command that also changes the container to MKV.
 * Used when MP4 container can't hold certain subtitle codecs.
 */
export function buildMkvConvertCommand(
	item: MediaItem,
	streams: MediaStream[],
	decisions: StreamDecision[]
): string {
	const inputPath = item.file_path;
	const outputPath = inputPath.replace(/\.[^.]+$/, '.mkv');
	const tmpPath = inputPath.replace(/\.[^.]+$/, '.tmp.mkv');

	const kept = streams
		.map((s) => {
			const dec = decisions.find((d) => d.stream_id === s.id);
			return dec?.action === 'keep' ? { stream: s, dec } : null;
		})
		.filter(Boolean) as { stream: MediaStream; dec: StreamDecision }[];

	const typeOrder: Record<string, number> = { Video: 0, Audio: 1, Subtitle: 2, Data: 3 };
	kept.sort((a, b) => {
		const ta = typeOrder[a.stream.type] ?? 9;
		const tb = typeOrder[b.stream.type] ?? 9;
		if (ta !== tb) return ta - tb;
		return (a.dec.target_index ?? 0) - (b.dec.target_index ?? 0);
	});

	const maps = buildMaps(streams, kept);
	const streamFlags = buildStreamFlags(kept);

	return [
		'ffmpeg', '-y',
		'-i', shellQuote(inputPath),
		...maps,
		...streamFlags,
		'-c copy',
		'-f matroska',
		shellQuote(tmpPath),
		'&&',
		'mv', shellQuote(tmpPath), shellQuote(outputPath),
	].join(' ');
}

/**
 * Build a command that ONLY extracts subtitles to sidecar files
 * without modifying the container. Useful when the item is otherwise
 * a noop but the user wants sidecar subtitle files.
 */
export function buildExtractOnlyCommand(
	item: MediaItem,
	streams: MediaStream[]
): string | null {
	const basePath = item.file_path.replace(/\.[^.]+$/, '');
	const extractionOutputs = buildExtractionOutputs(streams, basePath);
	if (extractionOutputs.length === 0) return null;
	return ['ffmpeg', '-y', '-i', shellQuote(item.file_path), ...extractionOutputs].join(' ');
}

/** Safely quote a path for shell usage. */
export function shellQuote(s: string): string {
	return `'${s.replace(/'/g, "'\\''")}'`;
}

/** Returns a human-readable summary of what will change. */
export function summarizeChanges(
	streams: MediaStream[],
	decisions: StreamDecision[]
): { removed: MediaStream[]; kept: MediaStream[] } {
	const removed: MediaStream[] = [];
	const kept: MediaStream[] = [];
	for (const s of streams) {
		const dec = decisions.find((d) => d.stream_id === s.id);
		if (!dec || dec.action === 'remove') removed.push(s);
		else kept.push(s);
	}
	return { removed, kept };
}

/** Format a stream for display. */
export function streamLabel(s: MediaStream): string {
	const parts: string[] = [s.type];
	if (s.codec) parts.push(s.codec);
	if (s.language_display || s.language) parts.push(s.language_display ?? s.language!);
	if (s.title) parts.push(`"${s.title}"`);
	if (s.type === 'Audio' && s.channels) parts.push(`${s.channels}ch`);
	if (s.is_forced) parts.push('forced');
	if (s.is_hearing_impaired) parts.push('CC');
	return parts.join(' · ');
}