using System.Collections.Generic;
using AcDream.Core.Physics;
using Xunit;

namespace AcDream.Core.Tests.Physics;

/// <summary>
/// L.2g S2 — the inbound CMotionInterp funnel (deviation DEV-1).
///
/// Oracle: docs/research/2026-07-02-s2-inbound-funnel-pseudocode.md
/// (decomp: move_to_interpreted_state 0x005289c0 @305936,
/// apply_interpreted_movement 0x00528600 @305713) — validated against the
/// LIVE retail-observer cdb trace (l2g-observer-trace.log), which showed the
/// per-UM dispatch order verbatim: style → forward → sidestep(-stop) →
/// turn(-stop).
/// </summary>
public class MotionInterpreterFunnelTests
{
    private sealed class RecordingSink : IInterpretedMotionSink
    {
        public readonly List<string> Calls = new();
        public bool ApplyMotion(uint motion, float speed)
        {
            Calls.Add($"DIM {motion:x8}@{speed:F2}");
            // R3-W5: a style/stance id (>= 0x80000000, i.e. negative as
            // int32) has no locomotion MotionData entry in the dat — retail's
            // real CMotionTable::DoObjectMotion genuinely fails for it
            // (MotionTableManagerError.MotionFailed). The fake sink mirrors
            // that so InterpretedMotionState.ForwardCommand isn't clobbered
            // by ApplyMotion's negative-motion branch before the very next
            // dispatch reads it — matches the live retail-observer trace.
            return motion < 0x80000000u;
        }
        public bool StopMotion(uint motion)
        {
            Calls.Add($"STOP {motion:x8}");
            return true;
        }
    }

    private static MotionInterpreter GroundedInterp()
    {
        var body = new PhysicsBody();
        body.State |= PhysicsStateFlags.Gravity;
        body.TransientState |= TransientStateFlags.Contact
                             | TransientStateFlags.OnWalkable
                             | TransientStateFlags.Active;
        return new MotionInterpreter(body);
    }

    private static InboundInterpretedState Ims(
        uint style = 0x8000003Du,
        uint fwd = 0x41000003u, float fwdSpd = 1.0f,
        uint side = 0u, float sideSpd = 1.0f,
        uint turn = 0u, float turnSpd = 1.0f,
        IReadOnlyList<InboundMotionAction>? actions = null)
        => new()
        {
            CurrentStyle = style,
            ForwardCommand = fwd, ForwardSpeed = fwdSpd,
            SideStepCommand = side, SideStepSpeed = sideSpd,
            TurnCommand = turn, TurnSpeed = turnSpd,
            Actions = actions,
        };

    [Fact]
    public void EmptyUm_DispatchesStyleThenReadyThenStops_RetailOrder()
    {
        // The flags=0 "empty" UM: all defaults → a wholesale stop. Live-trace
        // golden (actor minterp 18e8b0f8): DIM style, DIM Ready, then the
        // sidestep + turn stop notifications.
        var mi = GroundedInterp();
        var sink = new RecordingSink();

        mi.MoveToInterpretedState(Ims(), sink);

        Assert.Equal(new[]
        {
            "DIM 8000003d@1.00",
            "DIM 41000003@1.00",
            "STOP 6500000f",
            "STOP 6500000d",
        }, sink.Calls);
        Assert.Equal(0x41000003u, mi.InterpretedState.ForwardCommand);
        Assert.Equal(1.0f, mi.InterpretedState.ForwardSpeed);
    }

    [Fact]
    public void RunUm_DispatchesRunAtWireSpeed_AndCachesMyRunRate()
    {
        // fwd=RunForward@2.85 — apply_interpreted_movement caches
        // my_run_rate from forward_speed BEFORE dispatching (305718).
        var mi = GroundedInterp();
        var sink = new RecordingSink();

        mi.MoveToInterpretedState(Ims(fwd: 0x44000007u, fwdSpd: 2.85f), sink);

        Assert.Equal(new[]
        {
            "DIM 8000003d@1.00",
            "DIM 44000007@2.85",
            "STOP 6500000f",
            "STOP 6500000d",
        }, sink.Calls);
        Assert.Equal(2.85f, mi.MyRunRate);
        Assert.Equal(0x44000007u, mi.InterpretedState.ForwardCommand);
        Assert.Equal(2.85f, mi.InterpretedState.ForwardSpeed);
    }

    [Fact]
    public void WalkUm_DoesNotTouchMyRunRate()
    {
        var mi = GroundedInterp();
        mi.MyRunRate = 2.5f;

        mi.MoveToInterpretedState(Ims(fwd: 0x45000005u), new RecordingSink());

        Assert.Equal(2.5f, mi.MyRunRate); // only RunForward caches
    }

    [Fact]
    public void RunPlusTurnUm_TurnDispatched_NoTurnStop_NoIdleEnqueue()
    {
        // turn_command != 0 → DIM(turn) then EARLY RETURN — no turn-stop,
        // no idle bookkeeping (305711-305713 early return).
        var mi = GroundedInterp();
        var sink = new RecordingSink();

        mi.MoveToInterpretedState(
            Ims(fwd: 0x44000007u, fwdSpd: 2.85f, turn: 0x6500000Du, turnSpd: 1.5f), sink);

        Assert.Equal(new[]
        {
            "DIM 8000003d@1.00",
            "DIM 44000007@2.85",
            "STOP 6500000f",
            "DIM 6500000d@1.50",
        }, sink.Calls);
    }

    [Fact]
    public void SidestepUm_DispatchedInsteadOfSidestepStop()
    {
        var mi = GroundedInterp();
        var sink = new RecordingSink();

        mi.MoveToInterpretedState(Ims(side: 0x6500000Fu, sideSpd: -1.2f), sink);

        Assert.Equal(new[]
        {
            "DIM 8000003d@1.00",
            "DIM 41000003@1.00",
            "DIM 6500000f@-1.20",
            "STOP 6500000d",
        }, sink.Calls);
    }

    [Fact]
    public void AirborneBody_NoCycleDispatches_OnlyTurnStop()
    {
        // Airborne (gravity on, no Contact): apply_interpreted_movement
        // substitutes DIM(Falling 0x40000015) for the forward block
        // (305723-305727), but DoInterpretedMotion's OWN contact gate
        // (0x00528360) then takes the apply-only path for style + Falling —
        // GetObjectSequence never fires. This is retail's real mechanism
        // behind the K-fix17 "preserve the Falling cycle while airborne"
        // empirical guard: airborne remotes simply don't re-cycle from UMs.
        // Only the unconditional turn-stop notification comes through.
        var body = new PhysicsBody(); // no Contact flag
        body.State |= PhysicsStateFlags.Gravity;
        var mi = new MotionInterpreter(body);
        var sink = new RecordingSink();

        mi.MoveToInterpretedState(Ims(fwd: 0x44000007u, fwdSpd: 2.85f), sink);

        // Falling (0x40000015) is ALWAYS allowed by contact_allows_move
        // (0x00528240 early-accept), so it reaches the sink; the style and
        // forward dispatches are gate-blocked (apply-only path).
        Assert.Equal(new[] { "DIM 40000015@1.00", "STOP 6500000d" }, sink.Calls);
        // R3-W5 correction: DoInterpretedMotion's verbatim body (raw
        // 305575-305631) writes InterpretedState via
        // InterpretedMotionState::ApplyMotion on BOTH the success path
        // (raw 305609-305610, gated on the sink's own result) AND the
        // blocked/apply-only `label_528440` path (raw 305616-305618,
        // UNCONDITIONAL on the ModifyInterpretedState bit — no sink
        // involved at all). This W5 slice is the first port to actually
        // WIRE that state-write (the pre-W5 funnel never called
        // InterpretedMotionState.ApplyMotion from dispatch at all — state
        // was set only by MoveToInterpretedState's flat copy at the top of
        // the call), so the blocked style dispatch DOES flip
        // ForwardCommand to Ready (0x41000003) at step 1, which then makes
        // the Falling substitution dispatch (step 2) ITself write
        // ForwardCommand = Falling (0x40000015) via the SAME mechanism —
        // this replaces the assertion this comment used to make ("state
        // still flat-copies") with the verbatim end state. Only
        // sink.Calls (dispatch ORDER) was ever cdb-verified by this file's
        // module doc; this resulting-state assertion was an untested
        // assumption from the pre-W5 architecture.
        Assert.Equal(0x40000015u, mi.InterpretedState.ForwardCommand);
    }

    [Fact]
    public void FlatCopy_OverwritesEveryAxis()
    {
        // copy_movement_from (0x0051e750) is a FLAT overwrite — a fresh UM
        // with defaults clears a previously-set sidestep/turn.
        var mi = GroundedInterp();
        mi.MoveToInterpretedState(
            Ims(fwd: 0x44000007u, fwdSpd: 2.85f, side: 0x6500000Fu, turn: 0x6500000Du),
            new RecordingSink());

        mi.MoveToInterpretedState(Ims(), new RecordingSink());

        Assert.Equal(0x41000003u, mi.InterpretedState.ForwardCommand);
        Assert.Equal(0u, mi.InterpretedState.SideStepCommand);
        Assert.Equal(0u, mi.InterpretedState.TurnCommand);
    }

    [Fact]
    public void RawStateStyle_AdoptedFromIms()
    {
        // move_to_interpreted_state head: raw_state.current_style =
        // ims.current_style (305944).
        var mi = GroundedInterp();
        mi.MoveToInterpretedState(Ims(style: 0x8000003Cu), new RecordingSink());
        Assert.Equal(0x8000003Cu, mi.RawState.CurrentStyle);
    }

    // ── action list: 15-bit server_action_stamp gate (305953-305989) ──────

    [Fact]
    public void Actions_FreshStamp_DispatchedAfterMovement_AndStampAdopted()
    {
        var mi = GroundedInterp();
        var sink = new RecordingSink();
        var actions = new[] { new InboundMotionAction(0x10000062u, Stamp: 5, Autonomous: false, Speed: 1.25f) };

        mi.MoveToInterpretedState(Ims(actions: actions), sink);

        Assert.Equal("DIM 10000062@1.25", sink.Calls[^1]); // after the movement dispatches
        Assert.Equal(5, mi.ServerActionStamp);
    }

    [Fact]
    public void Actions_StaleStamp_Skipped()
    {
        var mi = GroundedInterp();
        mi.ServerActionStamp = 10;
        var sink = new RecordingSink();

        mi.MoveToInterpretedState(
            Ims(actions: new[] { new InboundMotionAction(0x10000062u, 9, false, 1f) }), sink);

        Assert.DoesNotContain(sink.Calls, c => c.StartsWith("DIM 10000062"));
        Assert.Equal(10, mi.ServerActionStamp);
    }

    [Fact]
    public void Actions_StampWrapsAt15Bits()
    {
        // The compare is 15-bit wraparound (mask 0x7fff, threshold 0x3fff).
        var mi = GroundedInterp();
        mi.ServerActionStamp = 0x7FFE;
        var sink = new RecordingSink();

        mi.MoveToInterpretedState(
            Ims(actions: new[] { new InboundMotionAction(0x10000062u, 2, false, 1f) }), sink);

        Assert.Contains(sink.Calls, c => c.StartsWith("DIM 10000062")); // 2 is newer than 0x7ffe
        Assert.Equal(2, mi.ServerActionStamp);
    }

    [Fact]
    public void Actions_AutonomousOnLocalPlayer_Skipped()
    {
        // Retail skips autonomous action replay on the LOCAL player (its own
        // echo); remotes always apply (305977-305987).
        var body = new PhysicsBody();
        body.TransientState |= TransientStateFlags.Contact | TransientStateFlags.OnWalkable;
        var mi = new MotionInterpreter(body) { IsLocalPlayer = true };
        var sink = new RecordingSink();

        mi.MoveToInterpretedState(
            Ims(actions: new[] { new InboundMotionAction(0x10000062u, 5, Autonomous: true, 1f) }), sink);

        Assert.DoesNotContain(sink.Calls, c => c.StartsWith("DIM 10000062"));
    }

    [Fact]
    public void InboundState_Defaults_MatchRetailUnPack()
    {
        // InterpretedMotionState::UnPack absent-field defaults (0x0051f400):
        // style NonCombat, fwd Ready, speeds 1.0, side/turn 0.
        var d = InboundInterpretedState.Default();
        Assert.Equal(0x8000003Du, d.CurrentStyle);
        Assert.Equal(0x41000003u, d.ForwardCommand);
        Assert.Equal(1.0f, d.ForwardSpeed);
        Assert.Equal(0u, d.SideStepCommand);
        Assert.Equal(1.0f, d.SideStepSpeed);
        Assert.Equal(0u, d.TurnCommand);
        Assert.Equal(1.0f, d.TurnSpeed);
    }
}