using System;
using System.Numerics;
using AcDream.Core.Physics;
using Xunit;

namespace AcDream.Core.Tests.Physics;

// ─────────────────────────────────────────────────────────────────────────────
// MotionInterpreterTests — covers the 10 ported methods.
//
// Source addresses tested:
//   FUN_00529a90  PerformMovement
//   FUN_00529930  DoMotion
//   FUN_00528a50  StopCompletely
//   FUN_00528960  get_state_velocity
//   FUN_00529390  jump
//   FUN_005286b0  get_jump_v_z
//   FUN_00528cd0  get_leave_ground_velocity
//   FUN_00528ec0  jump_is_allowed
//   FUN_00528dd0  contact_allows_move
//   FUN_00529210  apply_current_movement
// ─────────────────────────────────────────────────────────────────────────────

/// <summary>
/// Fake WeenieObject for test isolation — all methods return configurable values.
/// </summary>
file sealed class FakeWeenie : IWeenieObject
{
    public float RunRate  = 1.0f;
    public float JumpVz   = 10.0f;
    public bool  CanJumpResult = true;
    public bool  InqRunRateResult = true;
    public bool  InqJumpVelocityResult = true;

    public bool InqJumpVelocity(float extent, out float vz)
    {
        vz = JumpVz * extent;
        return InqJumpVelocityResult;
    }

    public bool InqRunRate(out float rate)
    {
        rate = RunRate;
        return InqRunRateResult;
    }

    public bool CanJump(float extent) => CanJumpResult;
}

public sealed class MotionInterpreterTests
{
    // ── helpers ───────────────────────────────────────────────────────────────

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

    private static PhysicsBody MakeAirborne()
    {
        var body = new PhysicsBody
        {
            State = PhysicsStateFlags.Gravity | PhysicsStateFlags.ReportCollisions,
        };
        body.TransientState = TransientStateFlags.Active;
        return body;
    }

    private static MotionInterpreter MakeInterp(PhysicsBody? body = null, IWeenieObject? weenie = null)
    {
        body ??= MakeGrounded();
        return new MotionInterpreter(body, weenie);
    }

    // =========================================================================
    // PerformMovement (FUN_00529a90) — dispatcher
    // =========================================================================

    [Theory]
    [InlineData(MovementType.RawCommand)]
    [InlineData(MovementType.InterpretedCommand)]
    [InlineData(MovementType.StopRawCommand)]
    [InlineData(MovementType.StopInterpretedCommand)]
    [InlineData(MovementType.StopCompletely)]
    public void PerformMovement_ValidTypes_ReturnNone(MovementType type)
    {
        var interp = MakeInterp();
        var mvs = new MovementStruct
        {
            Type              = type,
            Motion            = MotionCommand.WalkForward,
            Speed             = 1.0f,
            ModifyInterpretedState = true,
            ModifyRawState    = false,
        };

        var result = interp.PerformMovement(mvs);

        Assert.Equal(WeenieError.None, result);
    }

    [Fact]
    public void PerformMovement_InvalidType_ReturnsGeneralFailure()
    {
        var interp = MakeInterp();
        var mvs = new MovementStruct { Type = (MovementType)99, Motion = MotionCommand.WalkForward };

        var result = interp.PerformMovement(mvs);

        Assert.Equal(WeenieError.GeneralMovementFailure, result);
    }

    [Fact]
    public void PerformMovement_StopCompletely_ResetsToReady()
    {
        var interp = MakeInterp();
        interp.RawState.ForwardCommand         = MotionCommand.WalkForward;
        interp.InterpretedState.ForwardCommand = MotionCommand.WalkForward;

        var mvs = new MovementStruct { Type = MovementType.StopCompletely };
        interp.PerformMovement(mvs);

        Assert.Equal(MotionCommand.Ready, interp.RawState.ForwardCommand);
        Assert.Equal(MotionCommand.Ready, interp.InterpretedState.ForwardCommand);
    }

    [Fact]
    public void PerformMovement_NullPhysicsObj_ReturnsNoPhysicsObject()
    {
        var interp = new MotionInterpreter(); // no PhysicsObj
        var mvs = new MovementStruct { Type = MovementType.RawCommand, Motion = MotionCommand.WalkForward };

        var result = interp.PerformMovement(mvs);

        Assert.Equal(WeenieError.NoPhysicsObject, result);
    }

    // =========================================================================
    // DoMotion (FUN_00529930) — raw motion command sets RawState
    // =========================================================================

    [Fact]
    public void DoMotion_WalkForward_SetsRawForwardCommand()
    {
        var interp = MakeInterp();

        interp.DoMotion(MotionCommand.WalkForward, 0.8f);

        Assert.Equal(MotionCommand.WalkForward, interp.RawState.ForwardCommand);
        Assert.Equal(0.8f, interp.RawState.ForwardSpeed, precision: 5);
    }

    [Fact]
    public void DoMotion_NullPhysicsObj_ReturnsNoPhysicsObject()
    {
        var interp = new MotionInterpreter();

        var result = interp.DoMotion(MotionCommand.WalkForward);

        Assert.Equal(WeenieError.NoPhysicsObject, result);
    }

    // =========================================================================
    // StopCompletely (FUN_00528a50)
    // =========================================================================

    [Fact]
    public void StopCompletely_ResetsRawAndInterpretedToReady()
    {
        var interp = MakeInterp();
        interp.RawState.ForwardCommand         = MotionCommand.WalkForward;
        interp.RawState.SideStepCommand        = MotionCommand.SideStepRight;
        interp.RawState.TurnCommand            = MotionCommand.TurnRight;
        interp.InterpretedState.ForwardCommand = MotionCommand.RunForward;
        interp.InterpretedState.TurnCommand    = MotionCommand.TurnLeft;

        var result = interp.StopCompletely();

        Assert.Equal(WeenieError.None, result);
        Assert.Equal(MotionCommand.Ready, interp.RawState.ForwardCommand);
        Assert.Equal(1.0f, interp.RawState.ForwardSpeed, precision: 5);
        Assert.Equal(0u, interp.RawState.SideStepCommand);
        Assert.Equal(0u, interp.RawState.TurnCommand);
        Assert.Equal(MotionCommand.Ready, interp.InterpretedState.ForwardCommand);
        Assert.Equal(1.0f, interp.InterpretedState.ForwardSpeed, precision: 5);
        Assert.Equal(0u, interp.InterpretedState.SideStepCommand);
        Assert.Equal(0u, interp.InterpretedState.TurnCommand);
    }

    [Fact]
    public void StopCompletely_ZerosPhysicsBodyVelocity()
    {
        var body   = MakeGrounded();
        body.set_velocity(new Vector3(5f, 3f, 0f));
        var interp = MakeInterp(body);

        interp.StopCompletely();

        Assert.Equal(Vector3.Zero, body.Velocity);
    }

    [Fact]
    public void StopCompletely_NullPhysicsObj_ReturnsNoPhysicsObject()
    {
        var interp = new MotionInterpreter();

        var result = interp.StopCompletely();

        Assert.Equal(WeenieError.NoPhysicsObject, result);
    }

    // =========================================================================
    // get_state_velocity (FUN_00528960)
    // =========================================================================

    [Fact]
    public void GetStateVelocity_Idle_ReturnsZero()
    {
        var interp = MakeInterp();
        // Default interpreted state = Ready, no sidestep, no turn

        var vel = interp.get_state_velocity();

        Assert.Equal(Vector3.Zero, vel);
    }

    [Fact]
    public void GetStateVelocity_WalkForward_ReturnsWalkSpeed()
    {
        var interp = MakeInterp();
        interp.InterpretedState.ForwardCommand = MotionCommand.WalkForward;
        interp.InterpretedState.ForwardSpeed   = 1.0f;

        var vel = interp.get_state_velocity();

        // Y = WalkAnimSpeed * 1.0 = 3.12
        Assert.Equal(0f, vel.X, precision: 5);
        Assert.Equal(MotionInterpreter.WalkAnimSpeed, vel.Y, precision: 4);
        Assert.Equal(0f, vel.Z, precision: 5);
    }

    [Fact]
    public void GetStateVelocity_RunForward_ReturnsRunSpeed()
    {
        var interp = MakeInterp();
        interp.InterpretedState.ForwardCommand = MotionCommand.RunForward;
        interp.InterpretedState.ForwardSpeed   = 1.0f;

        var vel = interp.get_state_velocity();

        // Y = RunAnimSpeed * 1.0 = 4.0
        Assert.Equal(MotionInterpreter.RunAnimSpeed, vel.Y, precision: 4);
    }

    [Fact]
    public void GetStateVelocity_SidestepRight_ReturnsPositiveX()
    {
        var interp = MakeInterp();
        interp.InterpretedState.SideStepCommand = MotionCommand.SideStepRight;
        interp.InterpretedState.SideStepSpeed   = 1.0f;

        var vel = interp.get_state_velocity();

        Assert.Equal(MotionInterpreter.SidestepAnimSpeed, vel.X, precision: 4);
        Assert.Equal(0f, vel.Y, precision: 5);
    }

    [Fact]
    public void GetStateVelocity_ClampsToMaxSpeed_WhenExceedRunRate()
    {
        // Speed=10 for walk would produce velocity.Y = 3.12*10 = 31.2, well over
        // RunAnimSpeed * runRate = 4.0 * 1.0 = 4.0; must be clamped.
        var interp = MakeInterp();
        interp.InterpretedState.ForwardCommand = MotionCommand.WalkForward;
        interp.InterpretedState.ForwardSpeed   = 10.0f;

        var vel = interp.get_state_velocity();

        float maxSpeed = MotionInterpreter.RunAnimSpeed * interp.MyRunRate;
        Assert.True(vel.Length() <= maxSpeed + 1e-4f, $"velocity {vel.Length()} exceeds maxSpeed {maxSpeed}");
    }

    [Fact]
    public void GetStateVelocity_UsesWeenieRunRate()
    {
        var weenie = new FakeWeenie { RunRate = 2.0f };
        var interp = MakeInterp(weenie: weenie);
        interp.InterpretedState.ForwardCommand = MotionCommand.RunForward;
        interp.InterpretedState.ForwardSpeed   = 1.0f;

        var vel = interp.get_state_velocity();

        // maxSpeed = 4.0 * 2.0 = 8.0; velocity.Y = RunAnimSpeed * 1.0 = 4.0 ≤ 8.0
        Assert.Equal(MotionInterpreter.RunAnimSpeed, vel.Y, precision: 4);
    }

    // =========================================================================
    // get_state_velocity + GetCycleVelocity accessor (Option B — r03 §1.3)
    //
    // When the accessor is wired (AnimationSequencer.CurrentVelocity =
    // MotionData.Velocity * speedMod), get_state_velocity prefers that value
    // over the decompiled constant path. Keeps legs-per-meter invariant.
    // =========================================================================

    [Fact]
    public void GetStateVelocity_CycleAccessor_OverridesRunAnimSpeed()
    {
        // Sequencer's CurrentVelocity represents MotionData.Velocity * speedMod.
        // With speedMod=2.0 and MotionData.Velocity.Y=3.0, the sequencer reports
        // 6.0 — which should override the decompiled `RunAnimSpeed * ForwardSpeed`
        // path (= 4.0 * 2.0 = 8.0).
        //
        // maxSpeed clamp (RunAnimSpeed * runRate = 4.0 * 2.0 = 8.0) allows 6.0.
        var weenie = new FakeWeenie { RunRate = 2.0f };
        var interp = MakeInterp(weenie: weenie);
        interp.InterpretedState.ForwardCommand = MotionCommand.RunForward;
        interp.InterpretedState.ForwardSpeed   = 2.0f;
        interp.GetCycleVelocity = () => new Vector3(0f, 6.0f, 0f);

        var vel = interp.get_state_velocity();

        Assert.Equal(6.0f, vel.Y, precision: 4);
    }

    [Fact]
    public void GetStateVelocity_CycleAccessor_OverridesWalkAnimSpeed()
    {
        // Walk with MotionData.Velocity.Y=2.5 + speedMod=1.0 → sequencer reports 2.5.
        // Without accessor, get_state_velocity would return WalkAnimSpeed (3.12).
        var interp = MakeInterp();
        interp.InterpretedState.ForwardCommand = MotionCommand.WalkForward;
        interp.InterpretedState.ForwardSpeed   = 1.0f;
        interp.GetCycleVelocity = () => new Vector3(0f, 2.5f, 0f);

        var vel = interp.get_state_velocity();

        Assert.Equal(2.5f, vel.Y, precision: 4);
    }

    [Fact]
    public void GetStateVelocity_CycleAccessor_ZeroY_FallsBackToConstant()
    {
        // During a zero-velocity link transition the sequencer's CurrentVelocity
        // temporarily goes to (0,0,0). The constant path remains the safe default
        // so the body keeps moving at ForwardSpeed's expected rate.
        var interp = MakeInterp();
        interp.InterpretedState.ForwardCommand = MotionCommand.RunForward;
        interp.InterpretedState.ForwardSpeed   = 1.0f;
        interp.GetCycleVelocity = () => Vector3.Zero;

        var vel = interp.get_state_velocity();

        Assert.Equal(MotionInterpreter.RunAnimSpeed, vel.Y, precision: 4);
    }

    [Fact]
    public void GetStateVelocity_CycleAccessor_ClampStillApplies()
    {
        // Runaway MotionData.Velocity (20 m/s) must still be clamped to
        // RunAnimSpeed * runRate (4.0 * 1.0 = 4.0). This preserves the
        // decompiled `if (|velocity| > maxSpeed)` guard at the bottom of
        // FUN_00528960 — the accessor only replaces the *drive*, not the clamp.
        var interp = MakeInterp();
        interp.InterpretedState.ForwardCommand = MotionCommand.RunForward;
        interp.InterpretedState.ForwardSpeed   = 1.0f;
        interp.GetCycleVelocity = () => new Vector3(0f, 20.0f, 0f);

        var vel = interp.get_state_velocity();

        float maxSpeed = MotionInterpreter.RunAnimSpeed * interp.MyRunRate;
        Assert.True(vel.Length() <= maxSpeed + 1e-4f,
            $"velocity {vel.Length()} exceeds maxSpeed {maxSpeed}");
    }

    [Fact]
    public void GetStateVelocity_CycleAccessor_OnlyAffectsForwardAxis()
    {
        // Sidestep uses its own constant path — the sequencer only tracks the
        // forward cycle's velocity, so strafe must ignore the accessor's X.
        // Even if the accessor returned a bogus X, SideStepAnimSpeed wins.
        var interp = MakeInterp();
        interp.InterpretedState.ForwardCommand  = MotionCommand.Ready;
        interp.InterpretedState.SideStepCommand = MotionCommand.SideStepRight;
        interp.InterpretedState.SideStepSpeed   = 1.0f;
        interp.GetCycleVelocity = () => new Vector3(99f, 0f, 0f);

        var vel = interp.get_state_velocity();

        // velocity.X must equal SidestepAnimSpeed (1.25), NOT 99.
        Assert.Equal(MotionInterpreter.SidestepAnimSpeed, vel.X, precision: 4);
    }

    [Fact]
    public void GetStateVelocity_CycleAccessor_NotCalledWhenIdle()
    {
        // When ForwardCommand == Ready, the decompiled path never reads the
        // forward-axis; the accessor shouldn't be invoked either (avoid
        // misleading zero readings when stationary).
        int invocations = 0;
        var interp = MakeInterp();
        interp.InterpretedState.ForwardCommand = MotionCommand.Ready;
        interp.GetCycleVelocity = () =>
        {
            invocations++;
            return new Vector3(0f, 5f, 0f);
        };

        var vel = interp.get_state_velocity();

        // Velocity must be zero; accessor must not have supplied the 5.0f.
        Assert.Equal(0f, vel.Y, precision: 4);
        // Implementation detail: it's OK to call the accessor once (we do),
        // but it must never leak its value into velocity when ForwardCommand
        // is Ready. The assertion above guarantees that without over-pinning
        // the exact call count.
    }

    // =========================================================================
    // jump (FUN_00529390)
    // =========================================================================

    [Fact]
    public void Jump_Grounded_SetsJumpExtentAndLeavesWalkable()
    {
        var body   = MakeGrounded();
        var interp = MakeInterp(body);

        var result = interp.jump(0.5f);

        Assert.Equal(WeenieError.None, result);
        Assert.Equal(0.5f, interp.JumpExtent, precision: 5);
        Assert.False(body.OnWalkable, "Body should no longer be on walkable after jump");
    }

    [Fact]
    public void Jump_Airborne_ReturnsYouCantJumpWhileInTheAir()
    {
        var body   = MakeAirborne();
        var interp = MakeInterp(body);

        var result = interp.jump(0.5f);

        Assert.Equal(WeenieError.YouCantJumpWhileInTheAir, result);
    }

    [Fact]
    public void Jump_WeenieBlocksJump_ClearStandingLongJump()
    {
        var weenie = new FakeWeenie { CanJumpResult = false };
        var body   = MakeGrounded();
        var interp = MakeInterp(body, weenie);
        interp.StandingLongJump = true;

        var result = interp.jump(0.5f);

        Assert.Equal(WeenieError.CantJumpLoadedDown, result);
        Assert.False(interp.StandingLongJump);
    }

    [Fact]
    public void Jump_NullPhysicsObj_ReturnsNoPhysicsObject()
    {
        var interp = new MotionInterpreter();

        var result = interp.jump(0.5f);

        Assert.Equal(WeenieError.NoPhysicsObject, result);
    }

    // =========================================================================
    // get_jump_v_z (FUN_005286b0)
    // =========================================================================

    [Fact]
    public void GetJumpVz_ZeroExtent_ReturnsZero()
    {
        var interp     = MakeInterp();
        interp.JumpExtent = 0f;

        Assert.Equal(0f, interp.get_jump_v_z(), precision: 5);
    }

    [Fact]
    public void GetJumpVz_NoWeenie_ReturnsDefault()
    {
        var interp     = MakeInterp();
        interp.JumpExtent = 0.5f;

        Assert.Equal(MotionInterpreter.DefaultJumpVz, interp.get_jump_v_z(), precision: 4);
    }

    [Fact]
    public void GetJumpVz_WithWeenie_DelegatesToInqJumpVelocity()
    {
        var weenie     = new FakeWeenie { JumpVz = 8.0f };
        var interp     = MakeInterp(weenie: weenie);
        interp.JumpExtent = 1.0f;

        float vz = interp.get_jump_v_z();

        // FakeWeenie returns JumpVz * extent = 8.0 * 1.0 = 8.0
        Assert.Equal(8.0f, vz, precision: 4);
    }

    [Fact]
    public void GetJumpVz_ExtentClampsAt1()
    {
        var weenie     = new FakeWeenie { JumpVz = 10.0f };
        var interp     = MakeInterp(weenie: weenie);
        interp.JumpExtent = 5.0f; // over-clamped

        float vz = interp.get_jump_v_z();

        // Should clamp extent to 1.0: FakeWeenie returns 10.0 * 1.0 = 10.0
        Assert.Equal(10.0f, vz, precision: 4);
    }

    [Fact]
    public void GetJumpVz_WeenieReturnsFailure_ReturnsZero()
    {
        var weenie = new FakeWeenie { InqJumpVelocityResult = false };
        var interp = MakeInterp(weenie: weenie);
        interp.JumpExtent = 0.5f;

        Assert.Equal(0f, interp.get_jump_v_z(), precision: 5);
    }

    // =========================================================================
    // get_leave_ground_velocity (FUN_00528cd0)
    // =========================================================================

    [Fact]
    public void GetLeaveGroundVelocity_WalkingForward_HasPositiveYAndZ()
    {
        var weenie = new FakeWeenie { JumpVz = 10.0f };
        var body   = MakeGrounded();
        var interp = new MotionInterpreter(body, weenie)
        {
            JumpExtent = 1.0f,
        };
        interp.InterpretedState.ForwardCommand = MotionCommand.WalkForward;
        interp.InterpretedState.ForwardSpeed   = 1.0f;

        var vel = interp.get_leave_ground_velocity();

        Assert.True(vel.Y > 0f, "Y velocity should be positive when walking forward");
        Assert.True(vel.Z > 0f, "Z (jump) velocity should be positive");
    }

    [Fact]
    public void GetLeaveGroundVelocity_Standing_ZeroExtent_ReturnsZeroXY()
    {
        var body   = MakeGrounded();
        var interp = new MotionInterpreter(body)
        {
            JumpExtent = 0f, // below epsilon
        };
        // Default interpreted state = Ready (no walk/run command)

        var vel = interp.get_leave_ground_velocity();

        Assert.Equal(0f, vel.X, precision: 5);
        Assert.Equal(0f, vel.Y, precision: 5);
        Assert.Equal(0f, vel.Z, precision: 5);
    }

    // =========================================================================
    // jump_is_allowed (FUN_00528ec0)
    // =========================================================================

    [Fact]
    public void JumpIsAllowed_Grounded_ReturnsNone()
    {
        var interp = MakeInterp(MakeGrounded());

        var result = interp.jump_is_allowed(0.5f, 0);

        Assert.Equal(WeenieError.None, result);
    }

    [Fact]
    public void JumpIsAllowed_Airborne_ReturnsYouCantJumpWhileInTheAir()
    {
        var interp = MakeInterp(MakeAirborne());

        var result = interp.jump_is_allowed(0.5f, 0);

        Assert.Equal(WeenieError.YouCantJumpWhileInTheAir, result);
    }

    [Fact]
    public void JumpIsAllowed_WeenieBlocks_ReturnsCantJumpLoadedDown()
    {
        var weenie = new FakeWeenie { CanJumpResult = false };
        var interp = MakeInterp(MakeGrounded(), weenie);

        var result = interp.jump_is_allowed(0.5f, 0);

        Assert.Equal(WeenieError.CantJumpLoadedDown, result);
    }

    [Fact]
    public void JumpIsAllowed_NoGravityFlag_ReturnsYouCantJumpWhileInTheAir()
    {
        var body = new PhysicsBody
        {
            State         = PhysicsStateFlags.None, // no gravity
            TransientState = TransientStateFlags.Contact | TransientStateFlags.OnWalkable,
        };
        var interp = MakeInterp(body);

        // No gravity → must be airborne-style
        var result = interp.jump_is_allowed(0.5f, 0);

        Assert.Equal(WeenieError.YouCantJumpWhileInTheAir, result);
    }

    [Fact]
    public void JumpIsAllowed_NullPhysicsObj_ReturnsGeneralFailure()
    {
        var interp = new MotionInterpreter();

        var result = interp.jump_is_allowed(0.5f, 0);

        Assert.Equal(WeenieError.GeneralMovementFailure, result);
    }

    // =========================================================================
    // contact_allows_move (FUN_00528dd0)
    // =========================================================================

    [Fact]
    public void ContactAllowsMove_Grounded_Ready_AllowsMove()
    {
        var body   = MakeGrounded();
        var interp = MakeInterp(body);
        // InterpretedState.ForwardCommand defaults to Ready

        bool allowed = interp.contact_allows_move(MotionCommand.WalkForward);

        Assert.True(allowed);
    }

    [Fact]
    public void ContactAllowsMove_Airborne_RejectsMove()
    {
        var body   = MakeAirborne();
        var interp = MakeInterp(body);

        bool allowed = interp.contact_allows_move(MotionCommand.WalkForward);

        Assert.False(allowed);
    }

    [Fact]
    public void ContactAllowsMove_TurnCommand_AlwaysAllowed_EvenAirborne()
    {
        var body   = MakeAirborne();
        var interp = MakeInterp(body);

        // Turn commands bypass the ground-contact check.
        bool allowRight = interp.contact_allows_move(MotionCommand.TurnRight);
        bool allowLeft  = interp.contact_allows_move(MotionCommand.TurnLeft);

        Assert.True(allowRight);
        Assert.True(allowLeft);
    }

    [Fact]
    public void ContactAllowsMove_FallenState_RejectsMove()
    {
        var body   = MakeGrounded();
        var interp = MakeInterp(body);
        interp.InterpretedState.ForwardCommand = MotionCommand.Fallen;

        bool allowed = interp.contact_allows_move(MotionCommand.WalkForward);

        Assert.False(allowed);
    }

    [Fact]
    public void ContactAllowsMove_DeadState_RejectsMove()
    {
        var body   = MakeGrounded();
        var interp = MakeInterp(body);
        interp.InterpretedState.ForwardCommand = MotionCommand.Dead;

        bool allowed = interp.contact_allows_move(MotionCommand.WalkForward);

        Assert.False(allowed);
    }

    [Theory]
    [InlineData(MotionCommand.Crouch)]
    [InlineData(MotionCommand.Sitting)]
    [InlineData(MotionCommand.Sleeping)]
    public void ContactAllowsMove_PostureState_RejectsMove(uint postureCommand)
    {
        var body   = MakeGrounded();
        var interp = MakeInterp(body);
        interp.InterpretedState.ForwardCommand = postureCommand;

        bool allowed = interp.contact_allows_move(MotionCommand.WalkForward);

        Assert.False(allowed);
    }

    [Fact]
    public void ContactAllowsMove_CrouchRange_RejectsMove()
    {
        var body   = MakeGrounded();
        var interp = MakeInterp(body);
        // 0x41000012 is inside (0x41000011, 0x41000015) — crouch state
        interp.InterpretedState.ForwardCommand = 0x41000012u;

        bool allowed = interp.contact_allows_move(MotionCommand.WalkForward);

        Assert.False(allowed);
    }

    [Fact]
    public void ContactAllowsMove_NoGravity_AlwaysAllows()
    {
        // E.g. flying or swimming object
        var body = new PhysicsBody
        {
            State         = PhysicsStateFlags.None,
            TransientState = TransientStateFlags.None,
        };
        var interp = MakeInterp(body);

        bool allowed = interp.contact_allows_move(MotionCommand.WalkForward);

        Assert.True(allowed);
    }

    [Fact]
    public void ContactAllowsMove_GroundedAndIdle_SetsStandingLongJump()
    {
        var body   = MakeGrounded();
        var interp = MakeInterp(body);
        // All interpreted commands at default (Ready, no sidestep, no turn)
        interp.StandingLongJump = false;

        interp.contact_allows_move(MotionCommand.WalkForward);

        Assert.True(interp.StandingLongJump, "Should set StandingLongJump when grounded and idle");
    }

    // =========================================================================
    // apply_current_movement (FUN_00529210)
    // =========================================================================

    [Fact]
    public void ApplyCurrentMovement_WalkForward_PushesNonZeroVelocity()
    {
        var body   = MakeGrounded();
        var interp = MakeInterp(body);
        interp.InterpretedState.ForwardCommand = MotionCommand.WalkForward;
        interp.InterpretedState.ForwardSpeed   = 1.0f;

        interp.apply_current_movement(cancelMoveTo: false, allowJump: false);

        // The body's local-space velocity should have been set to some non-zero forward component.
        // We can't easily test world-space (depends on orientation = Identity), but with
        // Identity orientation the local Y becomes world Y.
        Assert.True(body.Velocity.Length() > 0f, "Velocity should be non-zero when walking");
    }

    [Fact]
    public void ApplyCurrentMovement_Idle_PushesZeroVelocity()
    {
        var body   = MakeGrounded();
        var interp = MakeInterp(body);
        // Default state = Ready

        interp.apply_current_movement(cancelMoveTo: false, allowJump: false);

        Assert.Equal(Vector3.Zero, body.Velocity);
    }

    [Fact]
    public void ApplyCurrentMovement_Run_UpdatesMyRunRate()
    {
        var body   = MakeGrounded();
        var interp = MakeInterp(body);
        interp.MyRunRate = 1.0f;
        interp.InterpretedState.ForwardCommand = MotionCommand.RunForward;
        interp.InterpretedState.ForwardSpeed   = 2.0f;  // e.g. speed-buff

        interp.apply_current_movement(cancelMoveTo: false, allowJump: false);

        Assert.Equal(2.0f, interp.MyRunRate, precision: 5);
    }

    [Fact]
    public void ApplyCurrentMovement_RunForward_SetsMyRunRate()
    {
        // Verifies that wiring a server-echoed ForwardSpeed (from UpdateMotion
        // 0xF74C InterpretedMotionState flag 0x10) into the MotionInterpreter
        // produces the correct MyRunRate and get_state_velocity result.
        var body = new PhysicsBody();
        var mi = new MotionInterpreter(body);
        mi.InterpretedState.ForwardCommand = MotionCommand.RunForward;
        mi.InterpretedState.ForwardSpeed = 2.375f;

        mi.apply_current_movement(cancelMoveTo: false, allowJump: true);

        Assert.Equal(2.375f, mi.MyRunRate, precision: 3);
        var vel = mi.get_state_velocity();
        Assert.Equal(4.0f * 2.375f, vel.Y, precision: 2);
    }

    // =========================================================================
    // GetMaxSpeed (CMotionInterp::get_max_speed @ 0x00527cb0)
    // L.3.1 Task 2 — InterpolationManager catch-up speed source
    // =========================================================================

    [Fact]
    public void GetMaxSpeed_RunForward_ReturnsRunAnimSpeedTimesRunRate()
    {
        // Retail: get_max_speed returns run rate from InqRunRate; callers
        // multiply by 2 to get catch-up speed. For RunForward the per-m/s
        // speed is RunAnimSpeed × rate = 4.0 × 1.5 = 6.0.
        var weenie = new FakeWeenie { RunRate = 1.5f };
        var interp = MakeInterp(weenie: weenie);
        interp.InterpretedState.ForwardCommand = MotionCommand.RunForward;

        float speed = interp.GetMaxSpeed();

        Assert.Equal(MotionInterpreter.RunAnimSpeed * 1.5f, speed, precision: 4); // 6.0
    }

    [Fact]
    public void GetMaxSpeed_WalkForward_ReturnsWalkAnimSpeed()
    {
        // WalkForward max speed is always WalkAnimSpeed (3.12) — no run-rate scaling.
        var interp = MakeInterp();
        interp.InterpretedState.ForwardCommand = MotionCommand.WalkForward;

        float speed = interp.GetMaxSpeed();

        Assert.Equal(MotionInterpreter.WalkAnimSpeed, speed, precision: 4);
    }

    [Fact]
    public void GetMaxSpeed_WalkBackward_ReturnsWalkAnimSpeedTimesBackwardsFactor()
    {
        // BackwardsFactor = 0.65, from adjust_motion @ 0x00528010 in the named retail decomp.
        var interp = MakeInterp();
        interp.InterpretedState.ForwardCommand = MotionCommand.WalkBackward;

        float speed = interp.GetMaxSpeed();

        Assert.Equal(MotionInterpreter.WalkAnimSpeed * 0.65f, speed, precision: 4);
    }

    [Fact]
    public void GetMaxSpeed_Idle_ReturnsZero()
    {
        // Ready / non-locomotion commands → 0 (no movement speed).
        var interp = MakeInterp();
        interp.InterpretedState.ForwardCommand = MotionCommand.Ready;

        float speed = interp.GetMaxSpeed();

        Assert.Equal(0f, speed, precision: 4);
    }

    [Fact]
    public void GetMaxSpeed_RunForward_NoWeenie_FallsBackToMyRunRate()
    {
        // WeenieObj is null (MakeInterp with no weenie argument); MyRunRate
        // is set explicitly. GetMaxSpeed must use MyRunRate as the run-rate
        // source when InqRunRate is unavailable.
        var interp = MakeInterp();
        interp.MyRunRate = 1.75f;
        interp.InterpretedState.ForwardCommand = MotionCommand.RunForward;

        float speed = interp.GetMaxSpeed();

        Assert.Equal(MotionInterpreter.RunAnimSpeed * 1.75f, speed, precision: 4);
    }
}