// Author: fruit.com.cn

import 'package:flutter/foundation.dart';
import 'package:flutter/material.dart';
import 'package:video_player/video_player.dart';

import '../../../core/theme/app_colors.dart';

const double _errorHorizontal = 32;
const int _errorMaxLines = 3;

/// 黑色底层与视频层共用同一控制器。清晰度切换时用仍在播放的旧画面盖住新纹理的黑帧。
class PlayerVideoSurface extends StatefulWidget {
  const PlayerVideoSurface({
    super.key,
    required this.controller,
    required this.videoUrl,
    required this.theater,
    this.handoff,
    this.openingFrame,
    this.holdOpeningUntilFirstFrame = false,
    this.preparedFrameAvailable = false,
  });

  final VideoPlayerController? controller;
  final VideoPlayerController? handoff;

  /// 解码出第一帧之前垫上的视频首帧，没有则为空。
  final Widget? openingFrame;

  /// 播放中的新片源在位置首次前进前继续显示封面，避免混入未出帧纹理。
  final bool holdOpeningUntilFirstFrame;

  /// 相邻集预热槽已持有可用画面，进入页面时不需要封面兜底。
  final bool preparedFrameAvailable;
  final String videoUrl;
  final bool theater;

  @override
  State<PlayerVideoSurface> createState() => _PlayerVideoSurfaceState();
}

class _PlayerVideoSurfaceState extends State<PlayerVideoSurface> {
  String? _lastDebugState;
  String? _lastLayerState;
  VideoPlayerController? _firstFrameController;
  bool _playbackStarted = false;
  bool _firstFrameSeen = false;

  @override
  void didUpdateWidget(covariant PlayerVideoSurface oldWidget) {
    super.didUpdateWidget(oldWidget);
    if (oldWidget.controller != widget.controller) {
      _lastDebugState = null;
      _lastLayerState = null;
      _firstFrameController = null;
      _playbackStarted = false;
      _firstFrameSeen = false;
    }
  }

  @override
  Widget build(BuildContext context) {
    final controller = widget.controller;
    if (controller == null) return _frame(null);
    return ValueListenableBuilder<VideoPlayerValue>(
      valueListenable: controller,
      builder: (context, value, _) => _frame(value),
    );
  }

  Widget _frame(VideoPlayerValue? value) {
    final controller = widget.controller;
    final handoff = _liveHandoff(controller);
    final firstFrameSeen = _trackFrameState(controller, value);
    final firstFrameReady =
        widget.preparedFrameAvailable || firstFrameSeen;
    final textureReady = _shouldReveal(value, handoff != null);
    final reveal = textureReady &&
        (!widget.holdOpeningUntilFirstFrame ||
            widget.preparedFrameAvailable ||
            firstFrameReady ||
            _playbackStarted &&
                value?.isPlaying == false &&
                value?.isBuffering != true);
    final showOpening =
        widget.openingFrame != null && handoff == null && !reveal;
    _logStateChange(value);
    _logLayerState(
      value,
      handoff,
      reveal,
      firstFrameReady,
      showOpening,
    );
    return Stack(
      fit: StackFit.expand,
      children: [
        const ColoredBox(
          key: Key('player-fallback-background'),
          color: AppColors.mediaBlack,
        ),
        if (showOpening)
          KeyedSubtree(
            key: const Key('player-opening-frame'),
            child: widget.openingFrame!,
          ),
        AnimatedOpacity(
          key: const Key('player-video-opacity'),
          opacity: reveal ? 1 : 0,
          duration: Duration.zero,
          child: reveal && controller != null
              ? _VideoLayer(
                  controller: controller,
                  value: value!,
                  theater: widget.theater,
                )
              : const SizedBox.expand(),
        ),
        if (handoff != null)
          _VideoLayer(
            key: const Key('player-video-handoff'),
            controller: handoff,
            value: handoff.value,
            theater: widget.theater,
          ),
        if (kDebugMode && value?.hasError == true)
          Center(
            child: Padding(
              padding: const EdgeInsets.symmetric(horizontal: _errorHorizontal),
              child: Text(
                value?.errorDescription ?? 'unknown video error',
                key: const Key('player-video-error'),
                maxLines: _errorMaxLines,
                overflow: TextOverflow.ellipsis,
                textAlign: TextAlign.center,
                style: const TextStyle(color: AppColors.muted, fontSize: 13),
              ),
            ),
          ),
      ],
    );
  }

  bool _shouldReveal(VideoPlayerValue? value, bool covered) {
    if (covered) return value?.isInitialized ?? false;
    if (value == null || value.hasError || !value.isInitialized) return false;
    return value.size.width > 0 && value.size.height > 0;
  }

  bool _trackFrameState(
    VideoPlayerController? controller,
    VideoPlayerValue? value,
  ) {
    if (!identical(_firstFrameController, controller)) {
      _firstFrameController = controller;
      _playbackStarted = false;
      _firstFrameSeen = false;
    }
    if (value == null) return false;
    _playbackStarted = _playbackStarted || value.isPlaying;
    _firstFrameSeen =
        _firstFrameSeen || value.position > Duration.zero || value.isCompleted;
    return _firstFrameSeen;
  }

  /// 只画会话仍持有的旧画面，控制器一旦被换掉就不再引用。
  VideoPlayerController? _liveHandoff(VideoPlayerController? controller) {
    final handoff = widget.handoff;
    if (handoff == null || identical(handoff, controller)) return null;
    return handoff;
  }

  void _logStateChange(VideoPlayerValue? value) {
    if (!kDebugMode) return;
    final status = _debugStatus(value);
    final signature =
        '$status|${value?.isInitialized ?? false}|'
        '${value?.errorDescription ?? 'none'}';
    if (signature == _lastDebugState) return;
    _lastDebugState = signature;
    final source = widget.controller?.dataSource ?? widget.videoUrl;
    debugPrint(
      '[video] init=${value?.isInitialized ?? false} '
      'err=${value?.errorDescription ?? 'none'} host=${_host(source)}',
    );
  }

  void _logLayerState(
    VideoPlayerValue? value,
    VideoPlayerController? handoff,
    bool reveal,
    bool firstFrameReady,
    bool showOpening,
  ) {
    if (!kDebugMode) return;
    final reason = handoff != null
        ? 'handoff'
        : !_shouldReveal(value, handoff != null)
        ? 'uninitialized'
        : widget.preparedFrameAvailable
        ? 'warm-frame'
        : !firstFrameReady && widget.holdOpeningUntilFirstFrame
        ? 'awaiting-first-frame'
        : 'reveal';
    final signature =
        'warm=${widget.preparedFrameAvailable ? 1 : 0} '
        'frame=${firstFrameReady ? 1 : 0} '
        'cover=${showOpening ? 1 : 0} '
        'video=${reveal ? 1 : 0} handoff=${handoff == null ? 0 : 1} '
        'init=${value?.isInitialized == true ? 1 : 0} '
        'playing=${value?.isPlaying == true ? 1 : 0} '
        'buffering=${value?.isBuffering == true ? 1 : 0} '
        'reason=$reason';
    if (signature == _lastLayerState) return;
    _lastLayerState = signature;
    debugPrint('[player-layer] $signature');
  }

  String _debugStatus(VideoPlayerValue? value) {
    if (value == null) return 'loading';
    if (value.hasError) {
      return 'error: ${value.errorDescription ?? 'unknown'}';
    }
    if (value.isBuffering) return 'buffering';
    if (value.isInitialized) return 'initialized';
    return 'loading';
  }

  String _host(String source) {
    final uri = Uri.tryParse(source);
    if (uri == null || uri.host.isEmpty) return 'unknown';
    final port = uri.hasPort
        ? uri.port
        : uri.scheme == 'https'
        ? 443
        : 80;
    return '${uri.host}:$port';
  }
}

class _VideoLayer extends StatelessWidget {
  const _VideoLayer({
    super.key,
    required this.controller,
    required this.value,
    required this.theater,
  });

  final VideoPlayerController controller;
  final VideoPlayerValue value;
  final bool theater;

  @override
  Widget build(BuildContext context) {
    return FittedBox(
      fit: theater ? BoxFit.contain : BoxFit.cover,
      child: SizedBox(
        width: value.size.width,
        height: value.size.height,
        child: VideoPlayer(controller, key: ValueKey(controller)),
      ),
    );
  }
}