ReelShort/lib/pages/player/widgets/player_render_stack.dart

// 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';
import 'player_opening_frame.dart';
import 'player_video_surface.dart';

enum PlayerRenderSlotRole { previous, current, next }

class PlayerRenderSlotData {
  const PlayerRenderSlotData({
    required this.role,
    this.index,
    this.pagePosition,
    this.controller,
    this.videoUrl = '',
    this.theater = false,
    this.placeholder,
    this.warmFrameAvailable = false,
    this.thumbnailReady = false,
    this.posterReady = false,
    this.fallback = PlayerOpeningFallback.black,
    this.warmSlotReused = false,
    this.waitForPlaybackFrame = false,
  });

  final PlayerRenderSlotRole role;
  final int? index;
  final double? pagePosition;
  final VideoPlayerController? controller;
  final String videoUrl;
  final bool theater;
  final Widget? placeholder;
  final bool warmFrameAvailable;
  final bool thumbnailReady;
  final bool posterReady;
  final PlayerOpeningFallback fallback;
  final bool warmSlotReused;
  final bool waitForPlaybackFrame;

  factory PlayerRenderSlotData.empty(PlayerRenderSlotRole role) {
    return PlayerRenderSlotData(role: role);
  }
}

/// 播放画面不随 PageView 生命周期销毁，三个固定槽位只更新控制器和位置。
class PlayerRenderStack extends StatefulWidget {
  const PlayerRenderStack({
    super.key,
    required this.pageController,
    required this.slots,
    this.onCurrentVideoVisible,
    this.showNeighbors = true,
  });

  final PageController pageController;
  final Map<PlayerRenderSlotRole, PlayerRenderSlotData> slots;
  final ValueChanged<int?>? onCurrentVideoVisible;
  final bool showNeighbors;

  @override
  State<PlayerRenderStack> createState() => _PlayerRenderStackState();
}

class _PlayerRenderStackState extends State<PlayerRenderStack> {
  int? _lastCurrentIndex;

  @override
  void initState() {
    super.initState();
    _lastCurrentIndex = _currentSlot.index;
    _log(
      'init current=${_lastCurrentIndex ?? '-'} '
      'pageController=${identityHashCode(widget.pageController)}',
    );
  }

  @override
  void didUpdateWidget(covariant PlayerRenderStack oldWidget) {
    super.didUpdateWidget(oldWidget);
    final currentIndex = _currentSlot.index;
    if (_lastCurrentIndex != currentIndex) {
      _log(
        'session-index previous=${_lastCurrentIndex ?? '-'} '
        'current=${currentIndex ?? '-'}',
      );
      _lastCurrentIndex = currentIndex;
    }
  }

  @override
  void dispose() {
    _log(
      'dispose current=${_lastCurrentIndex ?? '-'} '
      'pageController=${identityHashCode(widget.pageController)}',
    );
    super.dispose();
  }

  PlayerRenderSlotData get _currentSlot =>
      widget.slots[PlayerRenderSlotRole.current] ??
      PlayerRenderSlotData.empty(PlayerRenderSlotRole.current);

  @override
  Widget build(BuildContext context) {
    return IgnorePointer(
      child: AnimatedBuilder(
        animation: widget.pageController,
        builder: (context, _) {
          return LayoutBuilder(
            builder: (context, constraints) {
              final viewportHeight = constraints.maxHeight.isFinite
                  ? constraints.maxHeight
                  : MediaQuery.sizeOf(context).height;
              final pageOffset = _pageOffset();
              final currentPage = _currentSlot.pagePosition ?? pageOffset;
              final slots = widget.showNeighbors
                  ? [
                      _slotData(PlayerRenderSlotRole.previous),
                      _slotData(PlayerRenderSlotRole.current),
                      _slotData(PlayerRenderSlotRole.next),
                    ]
                  : [_slotData(PlayerRenderSlotRole.current)];
              return Stack(
                key: const Key('player-render-stack'),
                fit: StackFit.expand,
                clipBehavior: Clip.hardEdge,
                children: [
                  const ColoredBox(
                    key: Key('player-fallback-background'),
                    color: AppColors.mediaBlack,
                  ),
                  for (final slot in slots)
                    _positionedSurface(
                      slot,
                      pageOffset: pageOffset,
                      viewportHeight: viewportHeight,
                      fallbackPage: _fallbackPage(slot.role, currentPage),
                    ),
                ],
              );
            },
          );
        },
      ),
    );
  }

  PlayerRenderSlotData _slotData(PlayerRenderSlotRole role) {
    return widget.slots[role] ?? PlayerRenderSlotData.empty(role);
  }

  double _pageOffset() {
    if (!widget.pageController.hasClients) {
      return widget.pageController.initialPage.toDouble();
    }
    final position = widget.pageController.position;
    if (!position.hasPixels ||
        !position.hasViewportDimension ||
        position.viewportDimension <= 0) {
      return widget.pageController.initialPage.toDouble();
    }
    return position.pixels / position.viewportDimension;
  }

  double _fallbackPage(PlayerRenderSlotRole role, double currentPage) {
    return switch (role) {
      PlayerRenderSlotRole.previous => currentPage - 1,
      PlayerRenderSlotRole.current => currentPage,
      PlayerRenderSlotRole.next => currentPage + 1,
    };
  }

  Widget _positionedSurface(
    PlayerRenderSlotData slot, {
    required double pageOffset,
    required double viewportHeight,
    required double fallbackPage,
  }) {
    final slotPage = slot.pagePosition ?? fallbackPage;
    final offset = (slotPage - pageOffset) * viewportHeight;
    return Positioned.fill(
      child: Transform.translate(
        key: Key('player-render-transform-${slot.role.name}'),
        offset: Offset(0, offset),
        child: PlayerVideoSurface(
          key: ValueKey('player-render-slot-${slot.role.name}'),
          debugSlot: slot.role.name,
          debugIndex: slot.index,
          showFallbackBackground: false,
          controller: slot.controller,
          videoUrl: slot.videoUrl,
          theater: slot.theater,
          placeholder: slot.placeholder,
          warmFrameAvailable: slot.warmFrameAvailable,
          thumbnailReady: slot.thumbnailReady,
          posterReady: slot.posterReady,
          fallback: slot.fallback,
          warmSlotReused: slot.warmSlotReused,
          waitForPlaybackFrame: slot.waitForPlaybackFrame,
          onVideoVisible: slot.role == PlayerRenderSlotRole.current
              ? () => widget.onCurrentVideoVisible?.call(slot.index)
              : null,
        ),
      ),
    );
  }

  void _log(String message) {
    if (!kDebugMode) return;
    debugPrint(
      '[player-render] ts=${DateTime.now().millisecondsSinceEpoch} $message',
    );
  }
}