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

namespace AcDream.Core.Tests.Physics.Motion;

/// <summary>
/// R4-V2 — <c>MoveToManager::BeginMoveForward</c> (<c>00529a00</c>, raw
/// 306957-307042) per r4-moveto-decomp.md §4c: dispatched motion id / hold
/// key, the write-back to the STORED params, and the progress-clock seed.
/// Also exercises the run→walk demote inside <c>WalkRunThreshhold</c> (the
/// R3 visual-pass expected-diff this closes).
/// </summary>
public sealed class MoveToManagerBeginMoveForwardTests
{
    [Fact]
    public void FarFromTarget_CanRunCanWalk_DispatchesRunForward()
    {
        var h = new MoveToManagerHarness();
        h.WorldPosition = new Position(1u, Vector3.Zero, Quaternion.Identity);
        h.Heading = 90f; // already facing target — no aux turn needed

        var p = new MovementParameters { DistanceToObject = 0.6f, WalkRunThreshhold = 15f };
        // Distance far beyond threshold+dto -> Run.
        h.Manager.MoveToPosition(new Position(1u, new Vector3(100f, 0f, 0f), Quaternion.Identity), p);

        // MoveToPosition's node plan queues [TurnToHeading(face)] first since
        // heading(0->target)=90 != current heading is not tested here (we
        // set Heading=90 already so diff=0, GetCommand still picks motion
        // because distance is huge, so a turn node is queued anyway — but
        // since diff==0 the queued turn will complete immediately in
        // BeginNextNode's synchronous dispatch, landing directly on
        // BeginMoveForward).
        // ForwardCommand (post-adjust_motion, dispatched to the interp) is
        // RunForward; CurrentCommand (the manager's OWN field) stores the
        // PRE-adjust command GetCommand chose — get_command's own body only
        // ever returns WalkForward/WalkBackward/0 (§5c) — the Run promotion
        // happens downstream, inside adjust_motion (_DoMotion §7a), and is
        // never written back into CurrentCommand.
        Assert.Equal(MotionCommand.RunForward, h.ForwardCommand);
        Assert.Equal(HoldKey.Run, h.Manager.Params.HoldKeyToApply);
        Assert.Equal(MotionCommand.WalkForward, h.Manager.CurrentCommand);
    }

    [Fact]
    public void WithinWalkRunThreshold_DemotesToWalk()
    {
        var h = new MoveToManagerHarness();
        h.WorldPosition = new Position(1u, Vector3.Zero, Quaternion.Identity);
        h.Heading = 90f;

        var p = new MovementParameters { DistanceToObject = 0.6f, WalkRunThreshhold = 15f };
        // dist - dto = 10 - 0.6 = 9.4 <= 15 -> walk.
        h.Manager.MoveToPosition(new Position(1u, new Vector3(10f, 0f, 0f), Quaternion.Identity), p);

        Assert.Equal(MotionCommand.WalkForward, h.ForwardCommand);
        Assert.Equal(HoldKey.None, h.Manager.Params.HoldKeyToApply);
    }

    [Fact]
    public void CanCharge_FastPathWins_RunsEvenWhenClose()
    {
        var h = new MoveToManagerHarness();
        h.WorldPosition = new Position(1u, Vector3.Zero, Quaternion.Identity);
        h.Heading = 90f;

        var p = new MovementParameters { DistanceToObject = 0.6f, WalkRunThreshhold = 15f, CanCharge = true };
        h.Manager.MoveToPosition(new Position(1u, new Vector3(2f, 0f, 0f), Quaternion.Identity), p);

        Assert.Equal(MotionCommand.RunForward, h.ForwardCommand);
        Assert.Equal(HoldKey.Run, h.Manager.Params.HoldKeyToApply);
    }

    [Fact]
    public void HoldKeyWriteBack_ToStoredParams_NotJustLocalCopy()
    {
        var h = new MoveToManagerHarness();
        h.WorldPosition = new Position(1u, Vector3.Zero, Quaternion.Identity);
        h.Heading = 90f;

        var p = new MovementParameters { DistanceToObject = 0.6f, WalkRunThreshhold = 15f, HoldKeyToApply = HoldKey.Invalid };
        h.Manager.MoveToPosition(new Position(1u, new Vector3(100f, 0f, 0f), Quaternion.Identity), p);

        Assert.Equal(HoldKey.Run, h.Manager.Params.HoldKeyToApply);
    }

    [Fact]
    public void ProgressClockSeeded_PreviousAndOriginalEqualCurrentDistance()
    {
        var h = new MoveToManagerHarness();
        h.WorldPosition = new Position(1u, Vector3.Zero, Quaternion.Identity);
        h.Heading = 90f;
        h.CurTime = 5.0;

        // UseSpheres defaults true on a fresh MovementParameters, and
        // MoveToPosition's own params (copied into Params BEFORE
        // BeginMoveForward runs) drive GetCurrentDistance's use_spheres
        // branch: cylinder distance = center distance - ownRadius(0.5) -
        // targetRadius(0, position moves always zero SoughtObjectRadius).
        var p = new MovementParameters { DistanceToObject = 0.6f, UseSpheres = false };
        h.Manager.MoveToPosition(new Position(1u, new Vector3(20f, 0f, 0f), Quaternion.Identity), p);

        Assert.Equal(20f, h.Manager.PreviousDistance, 2);
        Assert.Equal(20f, h.Manager.OriginalDistance, 2);
        Assert.Equal(5.0, h.Manager.PreviousDistanceTime, 3);
        Assert.Equal(5.0, h.Manager.OriginalDistanceTime, 3);
    }

    [Fact]
    public void ProgressClockSeeded_UseSpheresDefault_UsesCylinderDistance()
    {
        var h = new MoveToManagerHarness { OwnRadius = 0.5f };
        h.WorldPosition = new Position(1u, Vector3.Zero, Quaternion.Identity);
        h.Heading = 90f;
        h.CurTime = 5.0;

        var p = new MovementParameters { DistanceToObject = 0.6f }; // UseSpheres=true (default)
        h.Manager.MoveToPosition(new Position(1u, new Vector3(20f, 0f, 0f), Quaternion.Identity), p);

        // center distance 20 - ownRadius 0.5 - targetRadius 0 (position
        // moves zero SoughtObjectRadius, §3c) = 19.5.
        Assert.Equal(19.5f, h.Manager.PreviousDistance, 2);
        Assert.Equal(19.5f, h.Manager.OriginalDistance, 2);
    }

    [Fact]
    public void CancelMoveToBit_ClearedOnLocalParams_DoesNotSelfCancel()
    {
        // If the 0x8000 CancelMoveTo bit were NOT cleared on the local
        // params passed into _DoMotion, InterruptCurrentMovement-style
        // cancellation logic downstream could tear down THIS moveto before
        // it starts. We assert the observable effect: the manager is still
        // MovingTo after BeginMoveForward dispatches.
        var h = new MoveToManagerHarness();
        h.WorldPosition = new Position(1u, Vector3.Zero, Quaternion.Identity);
        h.Heading = 90f;

        h.Manager.MoveToPosition(new Position(1u, new Vector3(20f, 0f, 0f), Quaternion.Identity), new MovementParameters());

        Assert.True(h.Manager.IsMovingTo());
    }

    [Fact]
    public void NoPhysicsObj_CancelsWithNoPhysicsObjectCode()
    {
        var h = new MoveToManagerHarness();
        h.WorldPosition = new Position(1u, Vector3.Zero, Quaternion.Identity);
        h.Manager.MoveToPosition(new Position(1u, new Vector3(20f, 0f, 0f), Quaternion.Identity), new MovementParameters());
        Assert.True(h.Manager.IsMovingTo());

        h.Manager.HasPhysicsObj = false;
        h.Manager.BeginMoveForward();

        Assert.False(h.Manager.IsMovingTo());
    }
}