using System;
using System.Collections.Generic;
using System.Globalization;
using System.IO;
using System.Linq;
using System.Text.RegularExpressions;
using AcDream.Core.Physics;
using Xunit;

namespace AcDream.Core.Tests.Physics;

/// <summary>
/// L.2g S2 conformance harness, layer 1: golden fixtures parsed from a LIVE
/// cdb trace of a RETAIL observer client
/// (Fixtures/l2g-observer-trace.log, captured 2026-07-02 with
/// tools/cdb/l2g-observer.cdb while a retail actor ran the structured
/// motion protocol through ACE).
///
/// Each [MTIS] block is an exact INPUT (the InterpretedMotionState retail
/// received, dumped field-by-field) and the [DIM] lines that follow on the
/// same minterp are retail's exact OUTPUT (every DoInterpretedMotion
/// dispatch, in order). We replay every input through acdream's funnel and
/// assert an identical dispatch sequence — retail's actual runtime is the
/// oracle, not anyone's reading of the decomp.
///
/// Exclusions (documented, not silent):
///  - Action-class dispatches (0x10000000 bit) come from the UM's action
///    LIST, which the [MTIS] struct dump doesn't include (LList pointer
///    only) — filtered from both sides; covered by the synthetic action
///    tests in MotionInterpreterFunnelTests instead.
///  - motion==0x80000000 entries (the unpack-level DoMotion(command_ids[0])
///    style call for wire style index 0) — outside
///    move_to_interpreted_state; S3 wires the unpack-level style-on-change.
/// </summary>
public class RetailObserverTraceConformanceTests
{
    private sealed record TraceCase(
        int Line, string Minterp, InboundInterpretedState Ims, List<uint> Dims);

    private sealed class RecordingSink : IInterpretedMotionSink
    {
        public readonly List<uint> Applied = new();
        public bool ApplyMotion(uint motion, float speed)
        {
            Applied.Add(motion);
            // R3-W5: style/stance ids (>= 0x80000000) have no dat MotionData
            // entry — retail's real motion-table lookup fails for them
            // (see MotionInterpreterDoMotionFamilyTests / the interface
            // doc on IInterpretedMotionSink.ApplyMotion for the full
            // rationale). The fake sink mirrors that so the style dispatch
            // doesn't clobber ForwardCommand before the next read.
            return motion < 0x80000000u;
        }
        public bool StopMotion(uint motion) => true;
    }

    private static string TracePath()
    {
        var dir = AppContext.BaseDirectory;
        while (dir is not null && !File.Exists(Path.Combine(dir, "AcDream.slnx")))
            dir = Directory.GetParent(dir)?.FullName;
        Assert.NotNull(dir);
        return Path.Combine(dir!, "tests", "AcDream.Core.Tests", "Fixtures", "l2g-observer-trace.log");
    }

    private static List<TraceCase> ParseTrace()
    {
        var lines = File.ReadAllLines(TracePath());
        var cases = new List<TraceCase>();
        var mtisRe  = new Regex(@"\[MTIS\] minterp=(\w+)");
        var fieldRe = new Regex(@"\+0x(\w+) (\w+)\s+: (\S+)");
        var dimRe   = new Regex(@"\[DIM\] minterp=(\w+) motion=(\w+)");

        for (int i = 0; i < lines.Length; i++)
        {
            var m = mtisRe.Match(lines[i]);
            if (!m.Success) continue;
            string minterp = m.Groups[1].Value;

            var ims = InboundInterpretedState.Default();
            int j = i + 1;
            for (; j < lines.Length; j++)
            {
                var f = fieldRe.Match(lines[j]);
                if (!f.Success) break;
                string name = f.Groups[2].Value;
                string val = f.Groups[3].Value;
                uint ParseHex() => Convert.ToUInt32(val, 16);
                float ParseF() => float.Parse(val, CultureInfo.InvariantCulture);
                switch (name)
                {
                    case "current_style":    ims.CurrentStyle    = ParseHex(); break;
                    case "forward_command":  ims.ForwardCommand  = ParseHex(); break;
                    case "forward_speed":    ims.ForwardSpeed    = ParseF();   break;
                    case "sidestep_command": ims.SideStepCommand = ParseHex(); break;
                    case "sidestep_speed":   ims.SideStepSpeed   = ParseF();   break;
                    case "turn_command":     ims.TurnCommand     = ParseHex(); break;
                    case "turn_speed":       ims.TurnSpeed       = ParseF();   break;
                }
            }

            // Collect this minterp's DIMs until the next UNPACK/MTIS event.
            var dims = new List<uint>();
            for (; j < lines.Length; j++)
            {
                if (lines[j].Contains("[UNPACK]") || lines[j].Contains("[MTIS]")) break;
                var d = dimRe.Match(lines[j]);
                if (d.Success && d.Groups[1].Value == minterp)
                    dims.Add(Convert.ToUInt32(d.Groups[2].Value, 16));
            }

            // A SECOND style dispatch marks a second apply_current_movement
            // pass fired by the physics tick (HitGround / LeaveGround
            // re-apply, CMotionInterp::HitGround 0x00528ac0) — not by this
            // UM. Keep only the first pass as this UM's output. (2 cases in
            // the capture — the actor's jump/land moments.)
            int secondStyle = -1;
            for (int k = 1; k < dims.Count; k++)
                if (dims[k] == ims.CurrentStyle) { secondStyle = k; break; }
            if (secondStyle > 0) dims = dims.Take(secondStyle).ToList();

            cases.Add(new TraceCase(i + 1, minterp, ims, dims));
        }
        return cases;
    }

    private static bool IsExcluded(uint motion)
        => (motion & 0x10000000u) != 0   // action-list dispatches, not in the dump
        || motion == 0x80000000u;        // unpack-level style-index-0 call

    [Fact]
    public void EveryTracedUm_ProducesRetailsExactDispatchSequence()
    {
        var cases = ParseTrace();
        Assert.True(cases.Count > 100, $"expected >100 traced UMs, parsed {cases.Count}");

        int verified = 0;
        var failures = new List<string>();
        foreach (var c in cases)
        {
            // The trace breakpoint sits at DoInterpretedMotion ENTRY
            // (pre-gate); the sink records POST-gate (GetObjectSequence)
            // calls. For grounded bodies they coincide. A Falling dispatch
            // for a non-Falling forward command marks the traced body as
            // AIRBORNE at that moment (the actor's jump) — replay those
            // with contact cleared, and drop the traced style entry from
            // the expectation (called pre-gate, blocked post-gate).
            bool airborne = c.Ims.ForwardCommand != 0x40000015u
                         && c.Dims.Contains(0x40000015u);

            var body = new PhysicsBody();
            body.State |= PhysicsStateFlags.Gravity;
            body.TransientState |= TransientStateFlags.Active;
            if (!airborne)
                body.TransientState |= TransientStateFlags.Contact
                                     | TransientStateFlags.OnWalkable;
            var mi = new MotionInterpreter(body);
            var sink = new RecordingSink();

            mi.MoveToInterpretedState(c.Ims, sink);

            var expected = c.Dims.Where(d => !IsExcluded(d)
                                          && (!airborne || d != c.Ims.CurrentStyle)).ToList();
            var actual   = sink.Applied.Where(d => !IsExcluded(d)).ToList();
            if (!expected.SequenceEqual(actual))
            {
                failures.Add(
                    $"line {c.Line} minterp {c.Minterp}: " +
                    $"fwd=0x{c.Ims.ForwardCommand:X8}@{c.Ims.ForwardSpeed:F2} " +
                    $"side=0x{c.Ims.SideStepCommand:X8} turn=0x{c.Ims.TurnCommand:X8} — " +
                    $"retail [{string.Join(",", expected.Select(d => d.ToString("X8")))}] " +
                    $"vs acdream [{string.Join(",", actual.Select(d => d.ToString("X8")))}]");
            }
            else
            {
                verified++;
            }
        }

        Assert.True(failures.Count == 0,
            $"{failures.Count} of {cases.Count} traced UMs diverged "
            + $"({verified} conformant):\n" + string.Join("\n", failures.Take(12)));
    }
}