zszq-trs/YLErpDAL/Modules/DataProviderModule/Fr007FixingCache.cs

using YLErp.Modules;

namespace YLErp.Modules.DataProviderModule
{
    /// <summary>
    /// FR007 定盘快照缓存。定盘是"每工作日一个数、发布后不变"的小表（一年约 250 行，全历史数千行），
    /// 故采用整表快照而非逐键缓存：
    ///
    /// <para>① <b>预载</b>：首次访问一次性 SELECT 全历史进字典，此后读取 O(1)、零查询；</para>
    /// <para>② <b>miss 不进快照</b>（负缓存防线）：当日定盘 ~11:15 后才出现、历史可补录——
    /// 字典查不到必须回退直查库，绝不能把"查不到"缓存住，否则发布后仍沿用旧利率；</para>
    /// <para>③ <b>写侧版本失效</b>：经应用的 FR007 写入（SwapFlowService 新增/修改/删除）立即失效，
    /// 下次访问整表重载一次；</para>
    /// <para>④ <b>TTL 1 分钟兜底</b>：覆盖直改库与其他通用价格写入口（导入/复制/合成等），
    /// 可见性窗口 ≤1 分钟，重启无需。</para>
    ///
    /// <para>快照以引用替换发布（Volatile.Write），读侧要么看到旧快照要么看到新快照，无撕裂；
    /// 重载加锁去抖，避免并发下重复整表查询。</para>
    /// </summary>
    public static class Fr007FixingCache
    {
        public const string UnderlyingCode = "FR007";

        /// <summary>TTL：兜底"直接改库/通用写入口"的可见性窗口（FR007 专属写入口走版本失效，不受此限）。</summary>
        internal static TimeSpan Ttl = TimeSpan.FromMinutes(1);

        /// <summary>测试接缝：时钟（默认 UtcNow Ticks）。</summary>
        internal static Func<long> NowTicks = () => DateTime.UtcNow.Ticks;

        /// <summary>测试接缝：快照装载器（默认直查库）。返回 日期→ReferencePrice 全量映射。</summary>
        internal static Func<Dictionary<DateTime, double>> LoadSnapshot = LoadFromDb;

        private static Dictionary<DateTime, double> _snapshot = new();
        private static bool _loaded;        // 是否已完成首次装载
        private static long _loadedAt;     // 快照装载时刻（NowTicks 口径）
        private static long _writeVersion; // 写侧版本（Invalidate 递增）
        private static long _snapVersion;  // 装载时的写侧版本
        private static readonly object _reloadLock = new();

        private static Dictionary<DateTime, double> LoadFromDb()
        {
            using var db = DbContextFactory.GetYLDbContext();
            return db.eod_commodity_future_price
                .Where(x => x.UnderlyingCode == UnderlyingCode && x.ReferencePrice != null)
                .Select(x => new { x.ValueDate, Price = x.ReferencePrice!.Value })
                .AsEnumerable()
                .GroupBy(x => x.ValueDate.Date)
                .ToDictionary(g => g.Key, g => g.First().Price);
        }

        /// <summary>命中返回 true。miss 仅代表"快照里没有"，调用方须直查库兜底（当日新发布/补录）。</summary>
        public static bool TryGet(DateTime valueDate, out double price)
        {
            EnsureFresh();
            return Volatile.Read(ref _snapshot).TryGetValue(valueDate.Date, out price);
        }

        /// <summary>写侧失效：FR007 行经应用新增/修改/删除后调用，下次访问整表重载。</summary>
        public static void Invalidate() => Interlocked.Increment(ref _writeVersion);

        /// <summary>重置为未装载状态并恢复默认接缝（仅测试用）。</summary>
        internal static void ResetForTest()
        {
            lock (_reloadLock)
            {
                _snapshot = new Dictionary<DateTime, double>();
                _loaded = false;
                _loadedAt = 0;
                _writeVersion = 0;
                _snapVersion = 0;
                Ttl = TimeSpan.FromMinutes(1);
                NowTicks = () => DateTime.UtcNow.Ticks;
                LoadSnapshot = LoadFromDb;
            }
        }

        private static void EnsureFresh()
        {
            if (IsFresh()) return;
            lock (_reloadLock)
            {
                if (IsFresh()) return;
                var snap = LoadSnapshot();
                Volatile.Write(ref _snapshot, snap);
                Volatile.Write(ref _loaded, true);
                Volatile.Write(ref _loadedAt, NowTicks());
                Volatile.Write(ref _snapVersion, Volatile.Read(ref _writeVersion));
            }
        }

        private static bool IsFresh()
            => Volatile.Read(ref _loaded)
               && Volatile.Read(ref _snapVersion) == Volatile.Read(ref _writeVersion)
               && NowTicks() - Volatile.Read(ref _loadedAt) <= Ttl.Ticks;
    }
}