using ExperionCrawler.Core.Application.Feedforward;

namespace ExperionCrawler.Infrastructure.Control;

public sealed class StreamState
{
    public DeadTimeBuffer Dead { get; } = new();
    public FirstOrderLag  Lag  { get; } = new();
    public RateLimiter    Rate { get; } = new();
    public double LastRec { get; set; } = double.NaN;
}

public sealed class ColumnState
{
    public FirstOrderLag FeedFilter  { get; } = new();
    public FirstOrderLag PressFilter { get; } = new();
    public Derivative    FeedDeriv   { get; } = new();
    public double        SettleTimerSec { get; set; }
    public bool          Initialized { get; set; }
    public Dictionary<string, StreamState> Streams { get; } = new();

    public StreamState Stream(string key)
    {
        if (!Streams.TryGetValue(key, out var s)) { s = new StreamState(); Streams[key] = s; }
        return s;
    }
}

public sealed class FeedforwardEngine
{
    public AdvisoryResult Tick(ColumnConfig cfg, PvSnapshot pv, ColumnState st, DateTime now)
    {
        var ts = cfg.ScanSec;

        if (!pv.Feed.Good || !Num.IsFinite(pv.Feed.Value))
            return Hold(cfg, st, now, "FEED BAD");

        var ff = st.FeedFilter.Step(pv.Feed.Value, cfg.FeedFilterTauSec, ts);

        if (!st.Initialized) { SeedAll(cfg, pv, st, ff); st.Initialized = true; }

        var  dF       = st.FeedDeriv.Update(ff, ts);
        bool moving   = cfg.FeedMoveThresholdPerMin > 0
                        && Math.Abs(dF) * 60.0 > cfg.FeedMoveThresholdPerMin;
        bool pUnstable = false;
        if (pv.Pressure is { Good: true } pp && Num.IsFinite(pp.Value))
        {
            var pf = st.PressFilter.Step(pp.Value, cfg.PressFilterTauSec, ts);
            pUnstable = Math.Abs(pp.Value - pf) > cfg.PressureBand;
        }
        if (moving || pUnstable) st.SettleTimerSec = cfg.SettleSec;
        else                     st.SettleTimerSec = Math.Max(0.0, st.SettleTimerSec - ts);
        bool   transient = moving || pUnstable || st.SettleTimerSec > 0.0;
        string treason   = moving ? "FEED 이동"
                         : pUnstable ? "압력 불안정"
                         : st.SettleTimerSec > 0.0 ? $"정착 대기 {st.SettleTimerSec:F0}s" : "";

        var outs       = new List<StreamAdvisory>(cfg.Streams.Count);
        double? prodRec = null;

        foreach (var s in cfg.Streams)
        {
            if (s.RefluxFromProduct) continue;
            var (rec, note) = ComputeStream(s, ff, dF, ts, st.Stream(s.Key));
            if (s.Key == cfg.ProductKey) prodRec = rec;
            outs.Add(BuildAdvisory(s, pv, rec, note, transient, st.Stream(s.Key)));
        }
        foreach (var s in cfg.Streams)
        {
            if (!s.RefluxFromProduct) continue;
            var stt = st.Stream(s.Key);
            double? rec = null;
            if (prodRec is double p)
            {
                var raw = Num.Clamp(s.TargetCoeff * p, s.SpMin, s.SpMax);
                rec = stt.Rate.Step(raw, s.RateUpPerMin, s.RateDnPerMin, ts);
            }
            outs.Add(BuildAdvisory(s, pv, rec, "외부환류 R=R_f×P (P 지연 상속)", transient, stt));
        }

        double? vloss = null, yield = null;
        string  mbState;
        if (transient)
            mbState = $"정착 대기 ({st.SettleTimerSec:F0}s)";
        else if (TryStreamPv(pv, "D", out var d) && TryStreamPv(pv, "P", out var pp2)
              && TryStreamPv(pv, "B", out var b) && ff > 1e-6)
        {
            vloss   = ff - (d + pp2 + b);
            yield   = 100.0 * pp2 / ff;
            mbState = Math.Abs(vloss.Value) > 0.03 * ff ? "물질수지 불일치(계측 점검)"
                    : vloss.Value < 0                   ? "음의 손실(스팬 오류 의심)"
                    : "정상";
        }
        else mbState = "입력 부족";

        return new AdvisoryResult(cfg.Id, cfg.Name, now, cfg.Enabled,
            transient, treason, ff, outs, vloss, yield, mbState);
    }

    private static (double? rec, string note) ComputeStream(
        StreamConfig s, double ff, double dF, double ts, StreamState stt)
    {
        switch (s.Role)
        {
            case StreamRole.Commanded:
                double theta = dF >= 0 ? s.ThetaUpSec : s.ThetaDnSec;
                double fd    = stt.Dead.Through(ff, theta, ts);
                fd           = stt.Lag.Step(fd, s.TauSec, ts);
                double raw   = Num.Clamp(s.TargetCoeff * fd, s.SpMin, s.SpMax);
                double rec   = stt.Rate.Step(raw, s.RateUpPerMin, s.RateDnPerMin, ts);
                return (rec, "");
            case StreamRole.LevelDriven:
                return (s.TargetCoeff * ff, "레벨 제어 구동 — 기대치(deadtime 미적용)");
            default:
                return (null, "모니터(SP 없음)");
        }
    }

    private static StreamAdvisory BuildAdvisory(
        StreamConfig s, PvSnapshot pv, double? rec, string note, bool transient, StreamState stt)
    {
        double curPv = pv.Streams.TryGetValue(s.Key, out var smp) && smp.Good ? smp.Value : double.NaN;
        int    trend = rec is double r && Num.IsFinite(stt.LastRec)
                       ? Math.Sign(r - stt.LastRec) : 0;
        if (rec is double rr) stt.LastRec = rr;
        double? gap = (rec is double g && Num.IsFinite(curPv)) ? g - curPv : null;
        return new StreamAdvisory(s.Key, s.FlowTag, s.Role, curPv, rec, gap, trend,
            !transient && s.Role != StreamRole.Monitor, s.Grade, s.LevelTag, note);
    }

    private static bool TryStreamPv(PvSnapshot pv, string key, out double v)
    {
        v = double.NaN;
        if (pv.Streams.TryGetValue(key, out var s) && s.Good && Num.IsFinite(s.Value)) { v = s.Value; return true; }
        return false;
    }

    private static void SeedAll(ColumnConfig cfg, PvSnapshot pv, ColumnState st, double ff)
    {
        st.FeedDeriv.Update(ff, cfg.ScanSec);
        foreach (var s in cfg.Streams)
        {
            var stt = st.Stream(s.Key);
            double seed = pv.Streams.TryGetValue(s.Key, out var smp) && smp.Good ? smp.Value : ff * s.TargetCoeff;
            stt.Lag.Seed(seed);
            stt.Rate.Seed(seed);
            stt.LastRec = seed;
        }
    }

    private AdvisoryResult Hold(ColumnConfig cfg, ColumnState st, DateTime now, string reason)
    {
        var outs = cfg.Streams.Select(s =>
        {
            var stt = st.Stream(s.Key);
            double? rec = Num.IsFinite(stt.LastRec) ? stt.LastRec : (double?)null;
            return new StreamAdvisory(s.Key, s.FlowTag, s.Role, double.NaN, rec, null, 0,
                false, s.Grade, s.LevelTag, $"홀드: {reason}");
        }).ToList();
        return new AdvisoryResult(cfg.Id, cfg.Name, now, cfg.Enabled, true, reason,
            st.FeedFilter.Value, outs, null, null, $"홀드: {reason}");
    }
}