import 'package:flutter/material.dart';

/// 数字货币图标组件
/// 
/// 支持离线图标和兜底显示
class CoinIcon extends StatelessWidget {
    final String symbol;  // 币种代码，如 'BTC', 'ETH'
    final double size;    // 图标大小，默认 40
    final bool isCircle;  // 是否圆形背景，默认 false
    
    const CoinIcon({
        super.key,
        required this.symbol,
        this.size = 40,
        this.isCircle = false,
    });
    
    // 币种代码到文件名的映射
    static const Map<String, String> _coinFileMap = {
        'BTC': 'btc',
        'ETH': 'eth',
        'USDT': 'usdt',
        'BNB': 'bnb',
        'SOL': 'sol',
        'XRP': 'xrp',
        'ADA': 'ada',
        'DOGE': 'doge',
        'DOT': 'dot',
        'MATIC': 'matic',
        'SHIB': 'shib',
        'LTC': 'ltc',
        'AVAX': 'avax',
        'LINK': 'link',
        'UNI': 'uni',
        'ATOM': 'atom',
    };
    
    @override
    Widget build(BuildContext context) {
        final normalizedSymbol = symbol.toUpperCase();
        final fileName = _coinFileMap[normalizedSymbol];
        
        Widget icon;
        
        if (fileName != null) {
            // 尝试加载本地图标
            icon = Image.asset(
                'assets/icons/crypto/$fileName.png',
                width: size,
                height: size,
                fit: BoxFit.contain,
                errorBuilder: (context, error, stackTrace) {
                    // 加载失败，显示兜底UI
                    return _buildFallback(context, normalizedSymbol);
                },
            );
        } else {
            // 没有对应的图标，显示兜底UI
            icon = _buildFallback(context, normalizedSymbol);
        }
        
        if (isCircle) {
            return Container(
                width: size,
                height: size,
                decoration: BoxDecoration(
                    shape: BoxShape.circle,
                    color: Theme.of(context).colorScheme.surfaceContainerHigh,
                ),
                child: Center(child: icon),
            );
        }
        
        return icon;
    }
    
    /// 构建兜底UI（显示币种代码）
    Widget _buildFallback(BuildContext context, String symbol) {
        return Container(
            width: size,
            height: size,
            decoration: BoxDecoration(
                shape: BoxShape.circle,
                gradient: LinearGradient(
                    begin: Alignment.topLeft,
                    end: Alignment.bottomRight,
                    colors: [
                        Theme.of(context).colorScheme.primary,
                        Theme.of(context).colorScheme.secondary,
                    ],
                ),
            ),
            child: Center(
                child: Text(
                    symbol.length > 3 ? symbol.substring(0, 3) : symbol,
                    style: TextStyle(
                        color: Colors.white,
                        fontSize: size * 0.35,
                        fontWeight: FontWeight.bold,
                    ),
                ),
            ),
        );
    }
}