namespace MoShiro.Backend.Analysis;

public sealed record PresetDef(string Id, string Label, IReadOnlyList<string> MetricIds);

/// <summary>
/// 指标注册表：存储、降采样、API、目录都由它驱动。新增指标时，在对应的 Metrics 文件里加一行声明，
/// 再把它放进这里的 <see cref="All"/>（显式注册，AOT 安全，不使用反射）。
/// </summary>
public static class MetricRegistry
{
    public static readonly IReadOnlyList<MetricDef> All =
    [
        LinkMetrics.Rtt, LinkMetrics.LossUp, LinkMetrics.LossDown, LinkMetrics.LossTotal,
        LinkMetrics.JitterUp, LinkMetrics.JitterDown, LinkMetrics.LossRun, LinkMetrics.Reorder, LinkMetrics.Dup, LinkMetrics.SamplesUdp,
        TcpMetrics.Rtt, TcpMetrics.Slow, TcpMetrics.Stall, TcpMetrics.StallMax, TcpMetrics.Retrans, TcpMetrics.Srtt, TcpMetrics.BulkRate, TcpMetrics.BulkPeak, TcpMetrics.SamplesTcp,
        SessionMetrics.ConnectSuccess, SessionMetrics.ConnectTcp, SessionMetrics.ConnectTls,
        SessionMetrics.FailTimeout, SessionMetrics.FailReset, SessionMetrics.FailTls,
        SessionMetrics.HoldResets, SessionMetrics.HoldLifetime,
        SessionMetrics.TrainLoss, SessionMetrics.TrainJitter, SessionMetrics.TrainRate, SessionMetrics.SamplesConnect,
    ];

    /// <summary>指标分组：前端按分组展示，新增指标只需要把它加进分组。</summary>
    public static readonly IReadOnlyList<PresetDef> Presets =
    [
        new("udp", "UDP", ["loss.up", "loss.down", "loss.total", "rtt.p50", "rtt.p95", "rtt.p99", "jitter.up.p95", "jitter.down.p95", "loss.run_max", "reorder", "dup"]),
        new("tcp", "TCP", ["tcp.rtt.p50", "tcp.rtt.p95", "tcp.rtt.p99", "tcp.rtt.p999", "tcp.rtt.max", "tcp.rtt.tail", "tcp.slow", "tcp.stall.per_min", "tcp.stall_max", "tcp.retrans", "tcp.srtt.p95"]),
        new("connect", "Connect", ["connect.success", "connect.tcp_ms.p95", "connect.tls_ms.p95", "connect.fail.timeout", "connect.fail.rst", "connect.fail.tls"]),
        new("session", "Session", ["hold.resets.per_h", "hold.lifetime_max"]),
        new("scores", "Scores", ["score.base", "score.mc", "score.hy2", "score.reality"]),
    ];

    private static readonly Dictionary<string, MetricDef> s_byId = All.ToDictionary(m => m.Id, StringComparer.Ordinal);

    private static readonly Dictionary<string, (MetricDef Def, MetricExport Export)> s_byExport = BuildExportIndex();

    public static MetricDef? Find(string metricId) => s_byId.GetValueOrDefault(metricId);

    /// <summary>按导出 id（例如 <c>rtt.p95</c>）查找。</summary>
    public static bool TryFindExport(string exportId, out MetricDef def, out MetricExport export)
    {
        if (s_byExport.TryGetValue(exportId, out (MetricDef Def, MetricExport Export) found))
        {
            def = found.Def;
            export = found.Export;
            return true;
        }

        def = null!;
        export = null!;
        return false;
    }

    public static PresetDef? FindPreset(string id) => Presets.FirstOrDefault(p => p.Id == id);

    public static IEnumerable<(MetricDef Def, MetricExport Export)> AllExports() =>
        All.SelectMany(def => def.Exports.Select(export => (def, export)));

    private static Dictionary<string, (MetricDef, MetricExport)> BuildExportIndex()
    {
        var index = new Dictionary<string, (MetricDef, MetricExport)>(StringComparer.Ordinal);
        foreach (MetricDef def in All)
        {
            foreach (MetricExport export in def.Exports)
            {
                if (!index.TryAdd(export.Id, (def, export)))
                {
                    throw new InvalidOperationException($"duplicate export id {export.Id}");
                }
            }
        }

        return index;
    }
}