import 'dart:async';
import 'dart:convert';
import 'dart:io';

import 'package:path/path.dart' as p;

import '../../core/download_detect.dart';
import '../../services/downloader.dart';

/// 실행 파일 찾기: 앱 옆 tools\ → 앱 폴더 → PATH
String locateTool(String name) {
  final exe = Platform.isWindows ? '$name.exe' : name;
  final appDir = p.dirname(Platform.resolvedExecutable);
  for (final dir in [p.join(appDir, 'tools'), appDir]) {
    final f = p.join(dir, exe);
    if (File(f).existsSync()) return f;
  }
  return name;
}

/// yt-dlp 로 동영상 다운로드 (작업마다 프로세스 하나)
///
/// 일시정지 = 프로세스 중지, 다시 시작하면 yt-dlp 가 .part 파일에서 이어 받는다.
class YtDlpBackend implements DownloadBackend {
  final String ytdlp;

  /// yt-dlp 가 영상·음성을 합칠 때 쓰는 ffmpeg 폴더
  final String? ffmpegDir;

  /// YouTube 추출용 JavaScript 실행기 (없으면 일부 화질이 빠질 수 있음)
  final String? deno;

  final _procs = <String, Process>{};
  final _stopping = <String>{};

  /// 형식 · 화질 인수 (환경 설정에서 읽음). 없으면 MP4 최고 화질.
  final List<String> Function() formatArgs;

  /// 쿠키 인수 (YouTube 로봇 확인 대응, 환경 설정에서 읽음)
  final List<String> Function() cookieArgs;

  YtDlpBackend({
    String? ytdlp,
    this.ffmpegDir,
    String? deno,
    List<String> Function()? formatArgs,
    List<String> Function()? cookieArgs,
  })  : ytdlp = ytdlp ?? locateTool('yt-dlp'),
        deno = deno ?? _existing(locateTool('deno')),
        formatArgs = formatArgs ?? (() => ytDlpFormatArgs(YtContainer.mp4, YtQuality.best)),
        cookieArgs = cookieArgs ?? (() => const []);

  static const _env = {'PYTHONIOENCODING': 'utf-8', 'PYTHONUTF8': '1'};

  @override
  Future<(String, List<PlaylistEntry>)?> expandPlaylist(String url) async {
    final listId = youtubePlaylistId(url);
    if (listId == null) return null;
    // 영상은 받지 않고 목록만 빠르게 읽는다
    final r = await Process.run(
      ytdlp,
      [
        '--flat-playlist', '-J', '--no-warnings', '--encoding', 'utf-8',
        if (deno != null) ...['--js-runtimes', 'deno:$deno'],
        ...cookieArgs(),
        'https://www.youtube.com/playlist?list=$listId',
      ],
      environment: _env,
      stdoutEncoding: utf8,
      stderrEncoding: utf8,
    );
    if (r.exitCode != 0) {
      throw ProcessException(
          ytdlp, [url], '재생목록을 읽을 수 없습니다: ${friendlyYtDlpError((r.stderr as String).trim())}', r.exitCode);
    }
    final j = jsonDecode(r.stdout as String) as Map<String, dynamic>;
    final entries = <PlaylistEntry>[];
    for (final e in (j['entries'] as List? ?? const [])) {
      final m = e as Map;
      final id = m['id'] as String?;
      final title = (m['title'] as String?) ?? id ?? '';
      // 삭제 · 비공개 영상은 건너뜀
      if (id == null || title == '[Deleted video]' || title == '[Private video]') continue;
      entries.add(PlaylistEntry('https://www.youtube.com/watch?v=$id', title));
    }
    return ((j['title'] as String?) ?? listId, entries);
  }

  static String? _existing(String path) => File(path).existsSync() ? path : null;

  @override
  DownloadKind get kind => DownloadKind.video;

  List<String> _args(DownloadTask t) => [
        '--newline', '--no-colors', '--encoding', 'utf-8',
        '--no-playlist', '--windows-filenames', '--no-mtime',
        '--progress-template',
        'download:[JJ]%(progress._percent_str)s|%(progress._speed_str)s|%(progress._eta_str)s',
        '--print', 'before_dl:[JJT]%(title)s',
        '--print', 'after_move:[JJF]%(filepath)s',
        '-P', t.dir,
        '-o', '%(title).150B [%(id)s].%(ext)s',
        ...formatArgs(),
        ...cookieArgs(),
        if (ffmpegDir != null) ...['--ffmpeg-location', ffmpegDir!],
        if (deno != null) ...['--js-runtimes', 'deno:$deno'],
        t.source,
      ];

  @override
  Future<void> start(DownloadTask t, void Function() changed) async {
    if (_procs.containsKey(t.id)) return;
    await Directory(t.dir).create(recursive: true);
    t
      ..state = DownloadState.downloading
      ..error = null;
    changed();

    final Process proc;
    try {
      proc = await Process.start(ytdlp, _args(t), environment: _env);
    } on ProcessException catch (e) {
      t
        ..state = DownloadState.failed
        ..error = 'yt-dlp 를 실행할 수 없습니다: ${e.message}';
      changed();
      return;
    }
    _procs[t.id] = proc;

    final errTail = <String>[];
    void onLine(String line) {
      final prog = parseYtDlpProgress(line);
      if (prog != null) {
        t
          ..progress = prog.percent ?? t.progress
          ..speed = prog.speed
          ..eta = prog.eta;
        changed();
      } else if (line.startsWith('[JJT]')) {
        t.title = line.substring(5).trim();
        changed();
      } else if (line.startsWith('[JJF]')) {
        t.files.add(line.substring(5).trim());
      } else if (line.startsWith('[download] Destination: ')) {
        t.files.add(line.substring('[download] Destination: '.length).trim());
      } else if (line.startsWith('[Merger] Merging formats into "')) {
        t.files.add(line.substring('[Merger] Merging formats into "'.length).replaceFirst(RegExp(r'"$'), ''));
      }
    }

    final outDone = proc.stdout
        .transform(const Utf8Decoder(allowMalformed: true))
        .transform(const LineSplitter())
        .forEach(onLine);
    final errDone = proc.stderr
        .transform(const Utf8Decoder(allowMalformed: true))
        .transform(const LineSplitter())
        .forEach((l) {
      errTail.add(l);
      if (errTail.length > 8) errTail.removeAt(0);
    });

    final code = await proc.exitCode;
    await Future.wait([outDone, errDone]);
    _procs.remove(t.id);
    if (_stopping.remove(t.id)) return; // 일시정지·취소는 호출한 쪽에서 상태 설정
    if (code == 0) {
      t
        ..state = DownloadState.done
        ..progress = 1
        ..speed = ''
        ..eta = '';
    } else {
      t
        ..state = DownloadState.failed
        ..error = friendlyYtDlpError(
            errTail.where((l) => l.contains('ERROR')).join('\n').ifEmpty(errTail.join('\n')));
    }
    changed();
  }

  Future<void> _stop(DownloadTask t) async {
    final proc = _procs[t.id];
    if (proc == null) return;
    _stopping.add(t.id);
    // yt-dlp 가 띄운 ffmpeg 까지 함께 종료
    if (Platform.isWindows) {
      await Process.run('taskkill', ['/PID', '${proc.pid}', '/T', '/F']);
    } else {
      proc.kill();
    }
    await proc.exitCode.timeout(const Duration(seconds: 5), onTimeout: () => -1);
  }

  @override
  Future<void> pause(DownloadTask t) async {
    await _stop(t);
    t
      ..state = DownloadState.paused
      ..speed = ''
      ..eta = '';
  }

  @override
  Future<void> cancel(DownloadTask t) async {
    await _stop(t);
    t.state = DownloadState.cancelled;
    for (final f in t.files) {
      for (final path in [f, '$f.part', '$f.ytdl']) {
        try {
          final file = File(path);
          if (await file.exists()) await file.delete();
        } catch (_) {}
      }
    }
    // 조각 파일 (영상.f137.mp4.part 등)
    try {
      final dir = Directory(t.dir);
      if (await dir.exists()) {
        await for (final e in dir.list()) {
          final n = p.basename(e.path);
          if (e is File && (n.endsWith('.part') || n.endsWith('.ytdl')) &&
              t.files.any((f) => n.startsWith(p.basenameWithoutExtension(f)))) {
            await e.delete();
          }
        }
      }
    } catch (_) {}
  }

  @override
  Future<void> shutdown() async {
    for (final id in _procs.keys.toList()) {
      final proc = _procs[id]!;
      _stopping.add(id);
      if (Platform.isWindows) {
        await Process.run('taskkill', ['/PID', '${proc.pid}', '/T', '/F']);
      } else {
        proc.kill();
      }
    }
    _procs.clear();
  }
}

extension on String {
  String ifEmpty(String other) => isEmpty ? other : this;
}