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

namespace AcDream.Core.Tests.Physics.Motion;

/// <summary>
/// R4-V2 — <c>BeginNextNode</c>'s sticky handoff (<c>00529cb0</c>, raw
/// 307123-307171, decomp §4b) and <c>CancelMoveTo</c>
/// (<c>00529930</c>, raw 306886-306940, decomp §7c) including the
/// reentrancy invariant (r4-port-plan.md §4: CancelMoveTo →
/// CleanUpAndCallWeenie → StopCompletely → InterruptCurrentMovement →
/// CancelMoveTo no-ops on Invalid).
/// </summary>
public sealed class MoveToManagerStickyAndCancelTests
{
    // ── Sticky handoff (§4b) — read BEFORE CleanUp, then StickTo ───────────

    [Fact]
    public void StickyArrival_ReadsRadiusHeightTlidBeforeCleanUp_ThenCallsStickTo()
    {
        var h = new MoveToManagerHarness();
        h.WorldPosition = new Position(1u, Vector3.Zero, Quaternion.Identity);
        h.Heading = 0f;

        var p = new MovementParameters { Sticky = true };
        h.Manager.MoveToObject(0x50005555u, 0x50005555u, radius: 1.5f, height: 2.5f, p);
        Assert.True(h.Manager.Params.Sticky); // preserved by MoveToObject (§3b)

        var target = new Position(1u, new Vector3(0.1f, 0f, 0f), Quaternion.Identity); // inside default dto -> arrives instantly
        h.Manager.HandleUpdateTarget(new TargetInfo(0x50005555u, TargetStatus.Ok, target, target));

        Assert.Single(h.StickToCalls);
        Assert.Equal((0x50005555u, 1.5f, 2.5f), h.StickToCalls[0]);
        Assert.Equal(MovementType.Invalid, h.Manager.MovementTypeState); // CleanUp ran
    }

    [Fact]
    public void NonStickyArrival_NoStickToCall_JustCleanUpAndStop()
    {
        var h = new MoveToManagerHarness();
        h.WorldPosition = new Position(1u, Vector3.Zero, Quaternion.Identity);
        h.Heading = 0f;

        var p = new MovementParameters { Sticky = false };
        h.Manager.MoveToObject(0x50005555u, 0x50005555u, radius: 1.5f, height: 2.5f, p);

        var target = new Position(1u, new Vector3(0.1f, 0f, 0f), Quaternion.Identity);
        h.Manager.HandleUpdateTarget(new TargetInfo(0x50005555u, TargetStatus.Ok, target, target));

        Assert.Empty(h.StickToCalls);
        Assert.Equal(MovementType.Invalid, h.Manager.MovementTypeState);
    }

    [Fact]
    public void MoveToPosition_NeverSticks_EvenIfRequested()
    {
        // §3c: MoveToPosition force-clears the sticky bit — so even an
        // arrival that WOULD have stuck (had it been an object move) just
        // completes plainly.
        var h = new MoveToManagerHarness();
        h.WorldPosition = new Position(1u, Vector3.Zero, Quaternion.Identity);
        h.Heading = 0f;

        var p = new MovementParameters { Sticky = true, DistanceToObject = 0.6f, UseSpheres = false };
        h.Manager.MoveToPosition(new Position(1u, new Vector3(0.1f, 0f, 0f), Quaternion.Identity), p); // already in range -> instant complete

        Assert.Empty(h.StickToCalls);
        Assert.Equal(MovementType.Invalid, h.Manager.MovementTypeState);
    }

    [Fact]
    public void StickyHandoff_UsesSoughtRadiusHeight_NotOwnRadiusHeight()
    {
        var h = new MoveToManagerHarness { OwnRadius = 99f, OwnHeight = 99f };
        h.WorldPosition = new Position(1u, Vector3.Zero, Quaternion.Identity);

        var p = new MovementParameters { Sticky = true };
        h.Manager.MoveToObject(0x50006666u, 0x50006666u, radius: 3f, height: 4f, p);

        var target = new Position(1u, new Vector3(0.1f, 0f, 0f), Quaternion.Identity);
        h.Manager.HandleUpdateTarget(new TargetInfo(0x50006666u, TargetStatus.Ok, target, target));

        Assert.Equal((0x50006666u, 3f, 4f), h.StickToCalls[0]); // the TARGET's radius/height, not the mover's own.
    }

    // ── CancelMoveTo (§7c) — drain + CleanUp + Stop; reentrancy ────────────

    [Fact]
    public void CancelMoveTo_OnInvalidState_IsANoOp()
    {
        var h = new MoveToManagerHarness();
        Assert.Equal(MovementType.Invalid, h.Manager.MovementTypeState);

        h.Manager.CancelMoveTo(WeenieError.ActionCancelled);

        Assert.Equal(0, h.StopCompletelyCalls); // no-op: never even called StopCompletely
        Assert.Equal(0, h.ClearTargetCalls);
    }

    [Fact]
    public void CancelMoveTo_DrainsPendingActions()
    {
        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.NotEmpty(h.Manager.PendingActions);

        h.Manager.CancelMoveTo(WeenieError.ActionCancelled);

        Assert.Empty(h.Manager.PendingActions);
        Assert.Equal(MovementType.Invalid, h.Manager.MovementTypeState);
    }

    [Fact]
    public void CancelMoveTo_ErrorArgument_NeverReadInBody_SameBehaviorForAnyCode()
    {
        // §7c: the WeenieError arg is NEVER read — every code produces
        // identical observable behavior (drain + CleanUp + Stop).
        var h1 = new MoveToManagerHarness();
        h1.WorldPosition = new Position(1u, Vector3.Zero, Quaternion.Identity);
        h1.Manager.MoveToPosition(new Position(1u, new Vector3(20f, 0f, 0f), Quaternion.Identity), new MovementParameters());
        h1.Manager.CancelMoveTo(WeenieError.YouChargedTooFar);

        var h2 = new MoveToManagerHarness();
        h2.WorldPosition = new Position(1u, Vector3.Zero, Quaternion.Identity);
        h2.Manager.MoveToPosition(new Position(1u, new Vector3(20f, 0f, 0f), Quaternion.Identity), new MovementParameters());
        h2.Manager.CancelMoveTo(WeenieError.NoObject);

        Assert.Equal(h1.Manager.MovementTypeState, h2.Manager.MovementTypeState);
        Assert.Equal(h1.StopCompletelyCalls, h2.StopCompletelyCalls);
    }

    [Fact]
    public void CancelMoveTo_ClearsTarget_ForObjectMoves()
    {
        var h = new MoveToManagerHarness();
        h.WorldPosition = new Position(1u, Vector3.Zero, Quaternion.Identity);
        h.Manager.MoveToObject(0x50007777u, 0x50007777u, 1f, 2f, new MovementParameters());
        Assert.Single(h.SetTargetCalls);

        h.Manager.CancelMoveTo(WeenieError.ActionCancelled);

        Assert.Equal(1, h.ClearTargetCalls);
    }

    [Fact]
    public void CancelMoveTo_DoesNotClearTarget_ForPositionMoves()
    {
        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());

        h.Manager.CancelMoveTo(WeenieError.ActionCancelled);

        Assert.Equal(0, h.ClearTargetCalls); // TopLevelObjectId is 0 for a position move -> the clear_target gate never fires.
    }

    [Fact]
    public void Reentrancy_StopCompletelyCallback_ReenteringCancelMoveTo_NoOps()
    {
        // r4-port-plan.md §4 reentrancy invariant: the StopCompletely tail
        // of CancelMoveTo/CleanUpAndCallWeenie can re-enter
        // InterruptCurrentMovement -> CancelMoveTo (this is exactly what
        // happens in production: MotionInterpreter.StopCompletely()
        // invokes InterruptCurrentMovement, which V5 binds to
        // entity.MoveTo.CancelMoveTo). This must no-op because CleanUp
        // already reset movement_type to Invalid BEFORE StopCompletely
        // runs. Wire the reentrant callback DIRECTLY (bypassing the shared
        // harness, which doesn't expose this seam post-construction) to
        // prove the invariant against the real CancelMoveTo/CleanUp
        // ordering.
        var interp = new MotionInterpreter();
        var body = new PhysicsBody { TransientState = TransientStateFlags.Contact | TransientStateFlags.OnWalkable | TransientStateFlags.Active };
        interp.PhysicsObj = body;

        Position worldPosition = new(1u, Vector3.Zero, Quaternion.Identity);
        int stopCompletelyCalls = 0;
        int reentrantCancelCalls = 0;
        MoveToManager? mgr = null;

        mgr = new MoveToManager(
            interp,
            stopCompletely: () =>
            {
                stopCompletely_body();
            },
            getPosition: () => worldPosition,
            getHeading: () => 0f,
            setHeading: (h, send) => { },
            getOwnRadius: () => 0.5f,
            getOwnHeight: () => 2f,
            contact: () => true,
            isInterpolating: () => false,
            getVelocity: () => Vector3.Zero,
            getSelfId: () => 0x50000001u,
            setTarget: (a, b, c, d) => { },
            clearTarget: () => { },
            getTargetQuantum: () => 0.0,
            setTargetQuantum: q => { });

        void stopCompletely_body()
        {
            stopCompletelyCalls++;
            // Re-enter: exactly the retail chain
            // interp.StopCompletely() -> InterruptCurrentMovement?.Invoke()
            // -> entity.MoveTo.CancelMoveTo(ActionCancelled) (V5 binding).
            reentrantCancelCalls++;
            mgr!.CancelMoveTo(WeenieError.ActionCancelled);
        }

        mgr.MoveToPosition(new Position(1u, new Vector3(20f, 0f, 0f), Quaternion.Identity), new MovementParameters());
        int stopCallsAfterArm = stopCompletelyCalls; // MoveToPosition's own unconditional stop (§3c) — 1 call, no reentrancy (MovementTypeState was already Invalid before this call started, so its OWN reentrant CancelMoveTo-from-StopCompletely no-ops too).

        mgr.CancelMoveTo(WeenieError.ActionCancelled);

        // CancelMoveTo's own StopCompletely fires exactly once more (its
        // reentrant CancelMoveTo call finds MovementTypeState already
        // Invalid — CleanUp ran first — so it no-ops and does NOT trigger a
        // THIRD StopCompletely call).
        Assert.Equal(stopCallsAfterArm + 1, stopCompletelyCalls);
        Assert.Equal(2, reentrantCancelCalls); // one from MoveToPosition's own stop, one from CancelMoveTo's stop
        Assert.Equal(MovementType.Invalid, mgr.MovementTypeState);
    }

    [Fact]
    public void CleanUpAndCallWeenie_FiresMoveToComplete_WithGivenError()
    {
        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());

        h.Manager.CleanUpAndCallWeenie(WeenieError.None);

        Assert.Single(h.MoveToCompleteCalls);
        Assert.Equal(WeenieError.None, h.MoveToCompleteCalls[0]);
        Assert.Equal(MovementType.Invalid, h.Manager.MovementTypeState);
    }

    [Fact]
    public void CleanUpAndCallWeenie_Ordering_MovementTypeAlreadyInvalid_WhenStopCompletelyFires()
    {
        // §7e: CleanUpAndCallWeenie = CleanUp() THEN StopCompletely() —
        // reentrancy-safe ordering (the same ordering CancelMoveTo uses).
        // Directly observe MovementTypeState AT THE MOMENT StopCompletely
        // is invoked by wiring a probe into the seam.
        var interp = new MotionInterpreter();
        var body = new PhysicsBody { TransientState = TransientStateFlags.Contact | TransientStateFlags.OnWalkable | TransientStateFlags.Active };
        interp.PhysicsObj = body;
        Position worldPosition = new(1u, Vector3.Zero, Quaternion.Identity);
        MovementType? stateDuringStopCompletely = null;
        MoveToManager? mgr = null;

        mgr = new MoveToManager(
            interp,
            stopCompletely: () => stateDuringStopCompletely = mgr!.MovementTypeState,
            getPosition: () => worldPosition,
            getHeading: () => 0f,
            setHeading: (h, send) => { },
            getOwnRadius: () => 0.5f,
            getOwnHeight: () => 2f,
            contact: () => true,
            isInterpolating: () => false,
            getVelocity: () => Vector3.Zero,
            getSelfId: () => 0x50000001u,
            setTarget: (a, b, c, d) => { },
            clearTarget: () => { },
            getTargetQuantum: () => 0.0,
            setTargetQuantum: q => { });

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

        mgr.CleanUpAndCallWeenie(WeenieError.None);

        Assert.Equal(MovementType.Invalid, stateDuringStopCompletely);
    }

    [Fact]
    public void CleanUp_StopsCurrentAndAuxCommands_ClearsTargetForObjectMoves_ThenReinitializes()
    {
        var h = new MoveToManagerHarness();
        h.WorldPosition = new Position(1u, Vector3.Zero, Quaternion.Identity);
        h.Manager.MoveToObject(0x50008888u, 0x50008888u, 1f, 2f, new MovementParameters());
        var target = new Position(1u, new Vector3(20f, 0f, 0f), Quaternion.Identity);
        h.Manager.HandleUpdateTarget(new TargetInfo(0x50008888u, TargetStatus.Ok, target, target));
        Assert.NotEqual(0u, h.Manager.CurrentCommand);

        h.Manager.CleanUp();

        Assert.Equal(MovementType.Invalid, h.Manager.MovementTypeState);
        Assert.Equal(1, h.ClearTargetCalls);
        Assert.Equal(0u, h.Manager.CurrentCommand);
    }
}