nomo/lib/app/widgets/country_icon.dart

import 'package:flutter/material.dart';
import 'package:flutter/services.dart';
import 'package:flutter_svg/flutter_svg.dart';
import 'package:nomo/app/extensions/widget_extension.dart';
import 'ix_image.dart';

/// 国旗/图标组件
///
/// 智能查找逻辑：
/// 1. 优先从 assets/flags/{countryCode}.svg 查找
/// 2. 找不到则从 assets/images/streaming/{countryCode}.png 查找
/// 3. 都找不到则显示默认图标 assets/flags/xx.svg
class CountryIcon extends StatefulWidget {
  /// 国家/地区代码（如: us, cn, netflix 等）
  final String countryCode;

  /// 宽度
  final double width;

  /// 高度
  final double height;

  /// 圆角
  final double? borderRadius;

  /// 适配方式
  final BoxFit? fit;

  const CountryIcon({
    super.key,
    required this.countryCode,
    required this.width,
    required this.height,
    this.borderRadius,
    this.fit,
  });

  @override
  State<CountryIcon> createState() => _CountryIconState();
}

class _CountryIconState extends State<CountryIcon> {
  /// 静态缓存：存储已查找过的图片路径，避免重复异步检查
  static final Map<String, _ImageInfo> _imageCache = {};

  /// 图片路径
  String? _imagePath;

  /// 图片类型：svg 或 png
  String? _imageType;

  /// 是否首次加载（仅首次加载时显示占位符）
  bool _isFirstLoad = true;

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

  @override
  void didUpdateWidget(CountryIcon oldWidget) {
    super.didUpdateWidget(oldWidget);
    if (oldWidget.countryCode != widget.countryCode) {
      _findImage();
    }
  }

  /// 智能查找图片
  Future<void> _findImage() async {
    if (!mounted) return;

    final code = widget.countryCode.toLowerCase().trim();

    // 如果为空，直接使用默认图标
    if (code.isEmpty) {
      _updateImage('assets/flags/xx.svg', 'svg');
      return;
    }

    // 检查缓存，如果有缓存则直接使用，避免异步等待
    if (_imageCache.containsKey(code)) {
      final cached = _imageCache[code]!;
      _updateImage(cached.path, cached.type);
      return;
    }

    // 异步查找图片（不设置 loading 状态，保持旧图片显示）
    String? foundPath;
    String? foundType;

    // 1. 先检查 flags 目录的 svg
    final flagPath = 'assets/flags/$code.svg';
    if (await _assetExists(flagPath)) {
      foundPath = flagPath;
      foundType = 'svg';
    } else {
      // 2. 检查 streaming 目录的 png
      final streamingPath = 'assets/images/streaming/$code.png';
      if (await _assetExists(streamingPath)) {
        foundPath = streamingPath;
        foundType = 'png';
      } else {
        // 3. 使用默认图标
        foundPath = 'assets/flags/xx.svg';
        foundType = 'svg';
      }
    }

    // 缓存结果
    _imageCache[code] = _ImageInfo(foundPath, foundType);

    // 检查 widget 是否仍然需要这个 code 的图片（防止快速切换时的竞态）
    if (!mounted || widget.countryCode.toLowerCase().trim() != code) return;

    _updateImage(foundPath, foundType);
  }

  /// 更新图片状态
  void _updateImage(String path, String type) {
    if (!mounted) return;
    setState(() {
      _imagePath = path;
      _imageType = type;
      _isFirstLoad = false;
    });
  }

  /// 检查资源文件是否存在
  Future<bool> _assetExists(String path) async {
    try {
      await rootBundle.load(path);
      return true;
    } catch (e) {
      return false;
    }
  }

  @override
  Widget build(BuildContext context) {
    // 仅首次加载时显示占位符，切换时保持旧图片
    if (_isFirstLoad || _imagePath == null || _imageType == null) {
      return _buildPlaceholder().withShadow(
        borderRadius: widget.borderRadius ?? 0,
      );
    }

    // 根据图片类型返回不同的组件
    if (_imageType == 'svg') {
      return ClipRRect(
        borderRadius: BorderRadius.circular(widget.borderRadius ?? 0),
        child: SvgPicture.asset(
          _imagePath!,
          width: widget.width,
          height: widget.height,
          fit: widget.fit ?? BoxFit.cover,
          placeholderBuilder: (context) => _buildPlaceholder(),
        ),
      ).withShadow(borderRadius: widget.borderRadius ?? 0);
    } else {
      // png 类型使用 IXImage
      return IXImage(
        source: _imagePath!,
        sourceType: ImageSourceType.asset,
        width: widget.width,
        height: widget.height,
        borderRadius: widget.borderRadius,
        fit: widget.fit,
      ).withShadow(borderRadius: widget.borderRadius ?? 0);
    }
  }

  /// 构建占位符
  Widget _buildPlaceholder() {
    return Container(
      width: widget.width,
      height: widget.height,
      decoration: BoxDecoration(
        color: Colors.grey.withValues(alpha: 0.2),
        borderRadius: BorderRadius.circular(widget.borderRadius ?? 0),
      ),
    );
  }
}

/// 国旗/图标组件的简化版本（同步加载，不检查文件是否存在）
///
/// 性能更好，但可能在资源不存在时显示错误
class CountryIconFast extends StatelessWidget {
  /// 国家/地区代码
  final String countryCode;

  /// 宽度
  final double width;

  /// 高度
  final double height;

  /// 圆角
  final double? borderRadius;

  /// 适配方式
  final BoxFit? fit;

  /// 是否优先使用 streaming 目录
  final bool preferStreaming;

  const CountryIconFast({
    super.key,
    required this.countryCode,
    required this.width,
    required this.height,
    this.borderRadius,
    this.fit,
    this.preferStreaming = false,
  });

  @override
  Widget build(BuildContext context) {
    final code = countryCode.toLowerCase().trim();

    if (code.isEmpty) {
      return _buildSvg('assets/flags/xx.svg');
    }

    // 如果优先使用 streaming
    if (preferStreaming) {
      return _buildPng('assets/images/streaming/$code.png');
    }

    // 默认优先使用 flags
    return _buildSvg('assets/flags/$code.svg');
  }

  Widget _buildSvg(String path) {
    return ClipRRect(
      borderRadius: BorderRadius.circular(borderRadius ?? 0),
      child: SvgPicture.asset(
        path,
        width: width,
        height: height,
        fit: fit ?? BoxFit.cover,
        placeholderBuilder: (context) => _buildFallback(),
      ),
    );
  }

  Widget _buildPng(String path) {
    return IXImage(
      source: path,
      sourceType: ImageSourceType.asset,
      width: width,
      height: height,
      borderRadius: borderRadius,
      fit: fit,
    );
  }

  Widget _buildFallback() {
    // 降级到默认图标
    return SvgPicture.asset(
      'assets/flags/xx.svg',
      width: width,
      height: height,
      fit: fit ?? BoxFit.cover,
    );
  }
}

/// 图片信息缓存类
class _ImageInfo {
  final String path;
  final String type;

  _ImageInfo(this.path, this.type);
}