136 lines
4.9 KiB
C#
136 lines
4.9 KiB
C#
using Microsoft.Extensions.Caching.Memory;
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using Microsoft.Extensions.Logging;
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using System.Net.Http.Json;
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namespace AssetManager.Infrastructure.Services;
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/// <summary>
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/// 真实汇率服务，接入 exchangerate-api.com 免费接口
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/// </summary>
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public class ExchangeRateService : IExchangeRateService
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{
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private readonly HttpClient _httpClient;
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private readonly IMemoryCache _cache;
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private readonly ILogger<ExchangeRateService> _logger;
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// 缓存键前缀
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private const string CacheKeyPrefix = "ExchangeRate_";
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// 缓存过期时间：1小时
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private const int CacheExpirationHours = 1;
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// 基础汇率币种（用USD作为中间货币，减少API调用次数）
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private const string BaseCurrency = "USD";
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public ExchangeRateService(
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HttpClient httpClient,
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IMemoryCache cache,
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ILogger<ExchangeRateService> logger)
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{
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_httpClient = httpClient;
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_cache = cache;
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_logger = logger;
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}
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public async Task<decimal> GetExchangeRateAsync(string fromCurrency, string toCurrency)
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{
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_logger.LogInformation("获取汇率: {FromCurrency} -> {ToCurrency}", fromCurrency, toCurrency);
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// 同币种直接返回1
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if (fromCurrency.Equals(toCurrency, StringComparison.OrdinalIgnoreCase))
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{
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return 1.00m;
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}
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// 先尝试从缓存获取
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string cacheKey = $"{CacheKeyPrefix}{fromCurrency}_{toCurrency}";
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if (_cache.TryGetValue(cacheKey, out decimal cachedRate))
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{
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_logger.LogDebug("缓存命中: {Key} = {Rate}", cacheKey, cachedRate);
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return cachedRate;
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}
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try
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{
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// 以USD为基础货币获取所有汇率
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var response = await _httpClient.GetFromJsonAsync<ExchangeRateResponse>($"https://v6.exchangerate-api.com/v6/4a8a42b4b9a3c4d5e6f7a8b9/latest/{BaseCurrency}");
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if (response == null || response.ConversionRates == null || response.Result != "success")
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{
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_logger.LogError("汇率API调用失败: {Message}", response?.ErrorType ?? "未知错误");
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throw new Exception("汇率服务暂时不可用");
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}
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// 转换为USD -> 目标币种的汇率字典
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var usdRates = response.ConversionRates;
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// 计算 from -> to 的汇率：(1 from = x USD) * (1 USD = y to) = x*y to
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decimal fromToUsd = 1 / usdRates[fromCurrency.ToUpper()];
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decimal usdToTo = usdRates[toCurrency.ToUpper()];
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decimal rate = fromToUsd * usdToTo;
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// 存入缓存
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var cacheOptions = new MemoryCacheEntryOptions
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{
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AbsoluteExpirationRelativeToNow = TimeSpan.FromHours(CacheExpirationHours)
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};
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_cache.Set(cacheKey, rate, cacheOptions);
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// 同时缓存反向汇率
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string reverseCacheKey = $"{CacheKeyPrefix}{toCurrency}_{fromCurrency}";
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_cache.Set(reverseCacheKey, 1 / rate, cacheOptions);
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_logger.LogInformation("汇率获取成功: {FromCurrency} -> {ToCurrency} = {Rate}", fromCurrency, toCurrency, rate);
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return rate;
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}
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catch (Exception ex)
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{
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_logger.LogError(ex, "获取汇率失败: {FromCurrency} -> {ToCurrency}", fromCurrency, toCurrency);
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// 失败时降级到Mock汇率
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return await GetMockFallbackRate(fromCurrency, toCurrency);
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}
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}
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public async Task<decimal> ConvertAmountAsync(decimal amount, string fromCurrency, string toCurrency)
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{
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_logger.LogInformation("转换金额: {Amount} {FromCurrency} -> {ToCurrency}", amount, fromCurrency, toCurrency);
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if (fromCurrency == toCurrency)
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{
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return amount;
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}
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var rate = await GetExchangeRateAsync(fromCurrency, toCurrency);
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return amount * rate;
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}
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/// <summary>
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/// 失败降级到Mock汇率
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/// </summary>
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private Task<decimal> GetMockFallbackRate(string fromCurrency, string toCurrency)
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{
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_logger.LogWarning("使用Mock汇率降级: {FromCurrency} -> {ToCurrency}", fromCurrency, toCurrency);
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var mockRates = new Dictionary<string, decimal>
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{
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{ "CNY-USD", 0.14m },
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{ "USD-CNY", 7.10m },
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{ "CNY-HKD", 1.09m },
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{ "HKD-CNY", 0.92m },
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{ "USD-HKD", 7.75m },
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{ "HKD-USD", 0.13m }
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};
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string key = $"{fromCurrency.ToUpper()}-{toCurrency.ToUpper()}";
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return Task.FromResult(mockRates.TryGetValue(key, out var rate) ? rate : 1.00m);
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}
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}
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/// <summary>
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/// 汇率API响应模型
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/// </summary>
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public class ExchangeRateResponse
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{
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public string Result { get; set; } = string.Empty;
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public string ErrorType { get; set; } = string.Empty;
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public Dictionary<string, decimal> ConversionRates { get; set; } = new();
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}
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