import 'dart:async';

import 'package:flutter/material.dart';

import 'dart:ui' as ui;

import 'package:flutter/services.dart';

class SpeedControlledGif extends StatefulWidget {
  final String assetPath;
  final double speedFactor;
  final BoxFit? fit;

  /// [speedFactor] 播放速度倍数，默认1.0，
  /// 大于1表示加速播放，小于1表示减速播放
  const SpeedControlledGif(
    this.assetPath, {
    Key? key,
    this.speedFactor = 1.0,
    this.fit,
  }) : super(key: key);

  @override
  _SpeedControlledGifState createState() => _SpeedControlledGifState();
}

class _SpeedControlledGifState extends State<SpeedControlledGif> {
  ui.Codec? _codec;
  ui.FrameInfo? _currentFrame;
  Timer? _timer;
  bool _isDisposed = false;

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

  Future<void> _loadGif() async {
    final data = await rootBundle.load(widget.assetPath);
    _codec = await ui.instantiateImageCodec(data.buffer.asUint8List());

    if (_isDisposed) return;

    _showNextFrame();
  }

  Future<void> _showNextFrame() async {
    if (_isDisposed || _codec == null) return;

    _currentFrame = await _codec!.getNextFrame();

    if (_isDisposed) return;

    if (mounted) {
      setState(() {});
    }

    // 取当前帧持续时间，单位毫秒
    final baseDuration = _currentFrame?.duration.inMilliseconds ?? 100;

    // 限制最小帧间隔，防止刷新过快
    const minFrameDuration = 50;

    // 计算实际播放帧间隔，speedFactor越大速度越快
    final adjustedDuration = (baseDuration / widget.speedFactor)
        .round()
        .clamp(minFrameDuration, 10000);

    _timer = Timer(Duration(milliseconds: adjustedDuration), _showNextFrame);
  }

  @override
  void dispose() {
    _isDisposed = true;
    _timer?.cancel();
    _codec?.dispose();
    super.dispose();
  }

  @override
  Widget build(BuildContext context) {
    if (_currentFrame == null) {
      // 加载中或无帧时显示空容器或占位
      return Container();
    }
    return RawImage(
      image: _currentFrame!.image,
      fit: widget.fit,
    );
  }
}