acdream/tests/AcDream.Core.Tests/Physics/MotionInterpreterTests.cs

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_ReturnsNotGrounded()
    {
        // R3-W1 renumber (A10): airborne is 0x24 (NotGrounded), not 0x48
        // (0x48 is now reserved for the motion_allows_jump blocklist).
        var body   = MakeAirborne();
        var interp = MakeInterp(body);

        var result = interp.jump(0.5f);

        Assert.Equal(WeenieError.NotGrounded, 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_ReturnsNotGrounded()
    {
        var interp = MakeInterp(MakeAirborne());

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

        Assert.Equal(WeenieError.NotGrounded, 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_ReturnsNotGrounded()
    {
        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.NotGrounded, result);
    }

    [Fact]
    public void JumpIsAllowed_NullPhysicsObj_ReturnsNotGrounded()
    {
        // A10 note: jump_is_allowed returns 0x24 (NotGrounded), NOT 8, when
        // physics_obj == null — the "8 = no physics obj" convention that
        // holds everywhere else in CMotionInterp does not hold here.
        var interp = new MotionInterpreter();

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

        Assert.Equal(WeenieError.NotGrounded, 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);
    }

    // L.2g S2 (2026-07-02): the posture-rejection tests that used to live
    // here pinned a MISATTRIBUTED port — the Fallen/Dead/crouch-range checks
    // belong to jump_charge_is_allowed (0x00527a50) / motion_allows_jump
    // (0x005279e0), NOT to contact_allows_move. The real contact_allows_move
    // (0x00528240, pseudo-C 305471) never reads the forward-command posture:
    // a grounded creature in ANY posture may receive motion
    // (GetObjectSequence handles the posture→locomotion transition via
    // links). Verified against the live retail-observer trace
    // (RetailObserverTraceConformanceTests, 183/183 dispatch conformant).

    [Theory]
    [InlineData(MotionCommand.Fallen)]
    [InlineData(MotionCommand.Dead)]
    [InlineData(MotionCommand.Crouch)]
    [InlineData(MotionCommand.Sitting)]
    [InlineData(MotionCommand.Sleeping)]
    [InlineData(0x41000012u)] // inside the crouch range (0x41000011, 0x41000015)
    public void ContactAllowsMove_GroundedPosture_StillAllowsMove(uint postureCommand)
    {
        var body   = MakeGrounded();
        var interp = MakeInterp(body);
        interp.InterpretedState.ForwardCommand = postureCommand;

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

        Assert.True(allowed);
    }

    [Fact]
    public void ContactAllowsMove_AirborneCreature_AcceptsFallingAndTurns_BlocksWalk()
    {
        // Verbatim 0x00528240: Falling (0x40000015) / Dead-class (0x40000011)
        // and TurnLeft/TurnRight are ALWAYS allowed; a gravity-bound creature
        // without Contact+OnWalkable is blocked for everything else
        // (including the style command, which falls through to the gate).
        var body = new PhysicsBody { State = PhysicsStateFlags.Gravity };
        var interp = MakeInterp(body);

        Assert.True(interp.contact_allows_move(MotionCommand.Falling));
        Assert.True(interp.contact_allows_move(0x40000011u));
        Assert.True(interp.contact_allows_move(MotionCommand.TurnRight));
        Assert.True(interp.contact_allows_move(MotionCommand.TurnLeft));
        Assert.False(interp.contact_allows_move(MotionCommand.WalkForward));
        Assert.False(interp.contact_allows_move(0x8000003Du));
    }

    [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
    }

    [Theory]
    [InlineData(MotionCommand.WalkForward)]
    [InlineData(MotionCommand.WalkBackward)]
    [InlineData(MotionCommand.Ready)]
    [InlineData(MotionCommand.RunForward)]
    public void GetMaxSpeed_IgnoresForwardCommand_AlwaysReturnsRunRate(uint command)
    {
        // GetMaxSpeed is the InterpolationManager.AdjustOffset catch-up speed — it
        // returns RunAnimSpeed × run-rate REGARDLESS of the current ForwardCommand
        // (retail 0x00527cb0 never reads interpreted_state; UN-2 byte verification
        // 2026-06-12, tools/verify_un2_fmul.py). These previously asserted a REMOVED
        // command-branching design (WalkForward → WalkAnimSpeed, WalkBackward →
        // ×0.65, Idle → 0); they PIN the no-branch contract across commands.
        var weenie = new FakeWeenie { RunRate = 1.75f };
        var interp = MakeInterp(weenie: weenie);
        interp.InterpretedState.ForwardCommand = command;

        float speed = interp.GetMaxSpeed();

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

    [Fact]
    public void GetMaxSpeed_NoWeenie_ReturnsLiteralOneTimesRunAnimSpeed()
    {
        // Retail 0x00527cb0 weenie_obj == null path: fld 1.0 (.rdata 0x007928B0),
        // fmul 4.0 (.rdata 0x007C8918) — the LITERAL 1.0, NOT my_run_rate (UN-2
        // byte verification 2026-06-12). MyRunRate is set to a different value to
        // prove it is not consulted on this path.
        var interp = MakeInterp();
        interp.MyRunRate = 1.75f;
        interp.InterpretedState.ForwardCommand = MotionCommand.RunForward;

        float speed = interp.GetMaxSpeed();

        Assert.Equal(MotionInterpreter.RunAnimSpeed * 1.0f, speed, precision: 4);
    }

    [Fact]
    public void GetMaxSpeed_InqRunRateFails_FallsBackToMyRunRate()
    {
        // Retail 0x00527cb0 InqRunRate-failure path: fld [esi+0x7c] (my_run_rate),
        // fmul 4.0. The InqRunRate out-value is discarded on failure.
        var weenie = new FakeWeenie { RunRate = 9.9f, InqRunRateResult = false };
        var interp = MakeInterp(weenie: weenie);
        interp.MyRunRate = 1.75f;
        interp.InterpretedState.ForwardCommand = MotionCommand.RunForward;

        float speed = interp.GetMaxSpeed();

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