// Author: fruit.com.cn

part of 'home_feed_overlay.dart';

const double _thumbSize = 6;
const double _thumbActiveSize = 14;
const double _trackActiveHeight = 6;
const double _lineCenterFromBottom = 8;

/// 整集条底部的进度线：20px 手势区内可点按/拖动 seek。
class _FeedProgressBar extends StatefulWidget {
  const _FeedProgressBar({
    required this.controller,
    required this.height,
    required this.hitHeight,
    this.onScrubStart,
    this.onSeek,
  });

  final ValueListenable<VideoPlayerValue>? controller;
  final double height;
  final double hitHeight;
  final VoidCallback? onScrubStart;
  final ValueChanged<Duration>? onSeek;

  @override
  State<_FeedProgressBar> createState() => _FeedProgressBarState();
}

class _FeedProgressBarState extends State<_FeedProgressBar> {
  static const _bufferDebounce = Duration(milliseconds: 350);

  double? _preview;
  Timer? _bufferTimer;
  bool _buffering = false;

  @override
  void initState() {
    super.initState();
    _attachSource();
  }

  @override
  void didUpdateWidget(covariant _FeedProgressBar oldWidget) {
    super.didUpdateWidget(oldWidget);
    if (oldWidget.controller != widget.controller) {
      _detachSource(oldWidget.controller);
      _bufferTimer?.cancel();
      _bufferTimer = null;
      _buffering = false;
      _attachSource();
    }
  }

  @override
  void dispose() {
    _detachSource(widget.controller);
    _bufferTimer?.cancel();
    super.dispose();
  }

  @override
  Widget build(BuildContext context) {
    return LayoutBuilder(
      builder: (context, constraints) {
        final width = constraints.maxWidth;
        final source = widget.controller;
        final scrubbing = _preview != null;
        final loading =
            source == null ||
            (!scrubbing && (!source.value.isInitialized || _buffering));
        final track = source == null
            ? _loadingTrack()
            : ValueListenableBuilder<VideoPlayerValue>(
                valueListenable: source,
                builder: (context, value, _) {
                  if (!scrubbing && (!value.isInitialized || _buffering)) {
                    return _loadingTrack();
                  }
                  final total = value.duration.inMilliseconds;
                  final played = total <= 0
                      ? 0.0
                      : (value.position.inMilliseconds / total)
                            .clamp(0.0, 1.0)
                            .toDouble();
                  return _track(_preview ?? played, width);
                },
              );
        return GestureDetector(
          key: const Key('home-feed-progress'),
          behavior: HitTestBehavior.opaque,
          onHorizontalDragStart: loading
              ? null
              : (details) {
                  widget.onScrubStart?.call();
                  _update(details.localPosition.dx / width);
                },
          onHorizontalDragUpdate: loading
              ? null
              : (details) => _update(details.localPosition.dx / width),
          onHorizontalDragEnd: loading ? null : (_) => _commit(_preview),
          onHorizontalDragCancel: loading
              ? null
              : () => setState(() => _preview = null),
          child: track,
        );
      },
    );
  }

  void _attachSource() {
    widget.controller?.addListener(_handleSourceChanged);
    _syncBufferState(notify: false);
  }

  void _detachSource(ValueListenable<VideoPlayerValue>? source) {
    source?.removeListener(_handleSourceChanged);
  }

  void _handleSourceChanged() => _syncBufferState();

  void _syncBufferState({bool notify = true}) {
    final source = widget.controller;
    if (source == null) {
      _bufferTimer?.cancel();
      _bufferTimer = null;
      _setBuffering(false, notify: notify);
      return;
    }
    final value = source.value;
    if (!value.isInitialized) {
      _bufferTimer?.cancel();
      _bufferTimer = null;
      _setBuffering(true, notify: notify);
      return;
    }
    if (!value.isBuffering) {
      _bufferTimer?.cancel();
      _bufferTimer = null;
      _setBuffering(false, notify: notify);
      return;
    }
    if (_buffering || _bufferTimer != null) return;
    _bufferTimer = Timer(_bufferDebounce, () {
      _bufferTimer = null;
      final current = widget.controller;
      if (!mounted ||
          current != source ||
          !current!.value.isInitialized ||
          !current.value.isBuffering) {
        return;
      }
      _setBuffering(true);
    });
  }

  void _setBuffering(bool buffering, {bool notify = true}) {
    if (_buffering == buffering) return;
    if (!notify || !mounted) {
      _buffering = buffering;
      return;
    }
    setState(() => _buffering = buffering);
  }

  Widget _loadingTrack() {
    final bottom = _lineCenterFromBottom - widget.height / 2;
    return SizedBox(
      height: widget.hitHeight,
      child: Stack(
        children: [
          Positioned(
            left: 0,
            right: 0,
            bottom: bottom,
            child: LoadingProgressTrack(height: widget.height),
          ),
        ],
      ),
    );
  }

  void _update(double fraction) {
    setState(() => _preview = fraction.clamp(0.0, 1.0).toDouble());
  }

  void _commit(double? fraction) {
    if (fraction == null) return;
    final total = widget.controller?.value.duration.inMilliseconds ?? 0;
    if (total > 0) {
      widget.onSeek?.call(
        Duration(milliseconds: (total * fraction.clamp(0.0, 1.0)).round()),
      );
    }
    setState(() => _preview = null);
  }

  Widget _track(double fraction, double width) {
    final dragging = _preview != null;
    final trackHeight = dragging ? _trackActiveHeight : widget.height;
    final size = dragging ? _thumbActiveSize : _thumbSize;
    final left = (width * fraction - size / 2)
        .clamp(0.0, width - size)
        .toDouble();
    final lineBottom = _lineCenterFromBottom - trackHeight / 2;
    final thumbBottom = _lineCenterFromBottom - size / 2;
    return SizedBox(
      height: widget.hitHeight,
      child: Stack(
        clipBehavior: Clip.none,
        children: [
          Positioned(
            left: 0,
            right: 0,
            bottom: lineBottom,
            child: Container(
              key: const Key('home-feed-progress-track'),
              height: trackHeight,
              color: Colors.white24,
            ),
          ),
          Positioned(
            left: 0,
            bottom: lineBottom,
            child: Container(
              width: width * fraction,
              height: trackHeight,
              color: AppColors.blue,
            ),
          ),
          Positioned(
            left: left,
            bottom: thumbBottom,
            child: Container(
              key: const Key('home-feed-progress-thumb'),
              width: size,
              height: size,
              decoration: const BoxDecoration(
                color: Colors.white,
                shape: BoxShape.circle,
              ),
            ),
          ),
        ],
      ),
    );
  }
}