using System.Numerics;
using AcDream.Core.Net.Messages;
using AcDream.Core.Physics;
using AcDream.Runtime.Entities;
using AcDream.Runtime.Physics;
using AcDream.Runtime.Session;

namespace AcDream.Runtime.Tests.Physics;

/// <summary>
/// C4 route 4b-2: the arm-selection half of the remote far snap. Every route
/// here is produced by the REAL classifier from a real request, including the
/// negative cases the classifier genuinely emits from other entry points (a
/// local-player <c>SetPositionSimple</c>, a remote top-level Create) and which
/// the far arm must decline. Exactly ONE route is hand-shaped — the
/// flags/disposition mismatch in
/// <see cref="OwnsFarSnap_IsAStrictSubsetOfThePlacementOwnersPredicate"/>,
/// which no classifier path produces but a caller could express.
///
/// <para>
/// Each test was verified to discriminate by temporarily reverting the
/// corresponding guard in <see cref="RuntimeRemoteFarSnapPosition"/> and
/// confirming the matching test failed, then restoring it.
/// </para>
/// </summary>
public sealed class RuntimeRemoteFarSnapPositionTests
{
    private const uint Cell = 0x0101FFFFu;

    [Fact]
    public void OwnsFarSnap_TrueForTheRemoteFarBranch()
    {
        RuntimeAuthoritativePositionRoute far =
            Classify(hasContact: true, playerDistance: 200f);

        // Retail: player_distance >= 96f -> StopInterpolating @0x005163CB +
        // SetPositionSimple @0x005163D9, whose arg3 != 0 builds flags 0x1012
        // (Teleport|Slide|SendPositionEvent) @0x005162C4.
        Assert.Equal(
            RuntimeAuthoritativePositionDisposition.SetPositionSimple,
            far.Disposition);
        Assert.True(far.StopInterpolating);
        Assert.True(RuntimeRemoteFarSnapPosition.OwnsFarSnap(far));
    }

    [Fact]
    public void OwnsFarSnap_TrueExactlyAtTheRetailBoundary()
    {
        // Retail compares player_distance against 96f and takes the
        // InterpolateTo branch only when strictly LESS (@0x00516393-@0x0051639E,
        // the `x87_r7 < temp1` test). 96.0 itself is the far branch.
        Assert.False(RuntimeRemoteFarSnapPosition.OwnsFarSnap(
            Classify(hasContact: true, playerDistance: 95.99f)));
        Assert.True(RuntimeRemoteFarSnapPosition.OwnsFarSnap(
            Classify(hasContact: true, playerDistance: 96f)));
    }

    [Fact]
    public void OwnsFarSnap_FalseForEveryOtherRemoteClassification()
    {
        // Near InterpolateTo @0x005163AF.
        Assert.False(RuntimeRemoteFarSnapPosition.OwnsFarSnap(
            Classify(hasContact: true, playerDistance: 10f)));
        // Airborne no-op @0x0051636D.
        Assert.False(RuntimeRemoteFarSnapPosition.OwnsFarSnap(
            Classify(hasContact: false, playerDistance: 10f)));
        // Cell-less: retail's `this_1->cell == 0` branch @0x00516386 —
        // SetPosition, NOT the far snap. 4b-3 owns it.
        Assert.False(RuntimeRemoteFarSnapPosition.OwnsFarSnap(
            Classify(hasContact: true, playerDistance: 200f, committedCellId: 0u)));
        // Fresh TELEPORT_TS: the same @0x00516386 branch. 4b-3 owns it.
        Assert.False(RuntimeRemoteFarSnapPosition.OwnsFarSnap(
            Classify(
                hasContact: true,
                playerDistance: 200f,
                previousTeleport: 10,
                acceptedTeleport: 11)));
        // Rejections and "no classification at all".
        Assert.False(RuntimeRemoteFarSnapPosition.OwnsFarSnap(
            Classify(
                hasContact: true,
                playerDistance: 200f,
                disposition: PositionTimestampDisposition.Rejected)));
        Assert.False(RuntimeRemoteFarSnapPosition.OwnsFarSnap(
            Classify(hasContact: true, playerDistance: float.NaN)));
        Assert.False(RuntimeRemoteFarSnapPosition.OwnsFarSnap(null));
    }

    /// <summary>
    /// The disposition alone is not the discriminator: the classifier emits
    /// <c>SetPositionSimple</c> for the LOCAL PLAYER's FORCE_POSITION branch
    /// too (<c>RuntimeAuthoritativePositionRouteClassifier.cs:332</c>). Route
    /// 4b-2 is a remote route; claiming that one would run a remote arm over
    /// route 2's local-player transaction.
    /// </summary>
    [Fact]
    public void OwnsFarSnap_FalseForTheLocalPlayerForcePositionRoute()
    {
        RuntimeAuthoritativePositionRoute force = ClassifyKind(
            RuntimePositionEntityKind.LocalPlayer,
            hasContact: true,
            playerDistance: 200f,
            disposition: PositionTimestampDisposition.ForcePosition);

        Assert.Equal(
            RuntimeAuthoritativePositionDisposition.SetPositionSimple,
            force.Disposition);
        Assert.Equal(
            RuntimeSetPositionOperationKind.LocalAuthoritative,
            force.OperationKind);
        Assert.False(RuntimeRemoteFarSnapPosition.OwnsFarSnap(force));
    }

    /// <summary>
    /// A REMOTE top-level initial Create is also <c>RemoteAuthoritative</c>;
    /// it is excluded here by its disposition (<c>SetPosition</c>), which
    /// route 4b-3 owns.
    /// </summary>
    [Fact]
    public void OwnsFarSnap_FalseForARemoteTopLevelCreateRoute()
    {
        RuntimeAuthoritativePositionRoute create =
            RuntimeAuthoritativePositionRouteClassifier.ClassifyCreate(
                new RuntimeCreatePositionRouteRequest(
                    Authority(PositionTimestampDisposition.Apply, 10, 10),
                    RuntimePositionEntityKind.Remote,
                    RuntimeCreateResidenceKind.TopLevel,
                    new CreateObject.ServerPosition(
                        Cell, 10f, 20f, 30f, 1f, 0f, 0f, 0f),
                    default));

        Assert.Equal(
            RuntimeSetPositionOperationKind.RemoteAuthoritative,
            create.OperationKind);
        Assert.Equal(
            PhysicsSetPositionFlags.Placement | PhysicsSetPositionFlags.Slide,
            create.SetPositionFlags);
        Assert.False(RuntimeRemoteFarSnapPosition.OwnsFarSnap(create));
    }

    /// <summary>
    /// The invariant the <c>Teleport</c>-flag term actually carries:
    /// <see cref="RuntimeRemoteFarSnapPosition.OwnsFarSnap"/> must be a strict
    /// SUBSET of
    /// <see cref="RuntimeRemotePlacementDriveController.OwnsPlacement"/>. The
    /// far arm hands its route straight to that controller, so any route the
    /// arm claims but the controller declines would execute
    /// <c>StopInterpolating</c> and then silently do nothing
    /// (<c>NotApplicable</c>) — a remote that stops tracking the server with
    /// no diagnostic. The flags term is what keeps the two predicates
    /// aligned; without it, the hand-shaped route below is claimed here and
    /// declined there.
    /// </summary>
    [Fact]
    public void OwnsFarSnap_IsAStrictSubsetOfThePlacementOwnersPredicate()
    {
        // Every route the real classifier produces.
        foreach (RuntimeAuthoritativePositionRoute route in new[]
        {
            Classify(hasContact: true, playerDistance: 200f),
            Classify(hasContact: true, playerDistance: 10f),
            Classify(hasContact: false, playerDistance: 10f),
            Classify(hasContact: true, playerDistance: 200f, committedCellId: 0u),
            Classify(hasContact: true, playerDistance: float.NaN),
            ClassifyKind(
                RuntimePositionEntityKind.LocalPlayer,
                hasContact: true,
                playerDistance: 200f,
                disposition: PositionTimestampDisposition.ForcePosition),
        })
        {
            if (RuntimeRemoteFarSnapPosition.OwnsFarSnap(route))
            {
                Assert.True(
                    RuntimeRemotePlacementDriveController.OwnsPlacement(route));
            }
        }

        // …and the shape a caller could construct that the classifier does
        // not: the far disposition and operation kind with a Create's flags.
        RuntimeAuthoritativePositionRoute mismatched =
            Classify(hasContact: true, playerDistance: 200f) with
            {
                SetPositionFlags = PhysicsSetPositionFlags.Placement
                    | PhysicsSetPositionFlags.Slide,
            };
        Assert.False(
            RuntimeRemotePlacementDriveController.OwnsPlacement(mismatched));
        Assert.False(RuntimeRemoteFarSnapPosition.OwnsFarSnap(mismatched));
    }

    // ── Arm selection is total, and the leftovers are named ─────────────────

    [Fact]
    public void ResolveArm_MapsEveryRemoteClassificationToExactlyOneArm()
    {
        Assert.Equal(
            RuntimeRemoteAcceptedPositionArm.AirborneNoOperation,
            RuntimeRemoteFarSnapPosition.ResolveArm(
                Classify(hasContact: false, playerDistance: 10f)));
        Assert.Equal(
            RuntimeRemoteAcceptedPositionArm.NearInterpolate,
            RuntimeRemoteFarSnapPosition.ResolveArm(
                Classify(hasContact: true, playerDistance: 10f)));
        Assert.Equal(
            RuntimeRemoteAcceptedPositionArm.FarSnapPlacement,
            RuntimeRemoteFarSnapPosition.ResolveArm(
                Classify(hasContact: true, playerDistance: 200f)));

        // The acdream-only leftovers left in THIS arm after C4 route 4b-3
        // moved the cell-less/fresh-teleport shapes onto the teleport arm
        // (RuntimeRemoteTeleportPosition.OwnsTeleportPlacement — see that
        // class's own tests). What remains: no classification at all, and
        // the two rejections.
        Assert.Equal(
            RuntimeRemoteAcceptedPositionArm.UnroutedCatchUp,
            RuntimeRemoteFarSnapPosition.ResolveArm(
                Classify(
                    hasContact: true,
                    playerDistance: 10f,
                    disposition: PositionTimestampDisposition.Rejected)));
        Assert.Equal(
            RuntimeRemoteAcceptedPositionArm.UnroutedCatchUp,
            RuntimeRemoteFarSnapPosition.ResolveArm(
                Classify(hasContact: true, playerDistance: float.NaN)));
        Assert.Equal(
            RuntimeRemoteAcceptedPositionArm.UnroutedCatchUp,
            RuntimeRemoteFarSnapPosition.ResolveArm(null));
    }

    private static RuntimeAuthoritativePositionAuthority Authority(
        PositionTimestampDisposition disposition,
        ushort previousTeleport,
        ushort acceptedTeleport) =>
        new(
            new RuntimeGenerationToken(7),
            new RuntimeEntityKey(0x70000001u, 3),
            PositionAuthorityVersion: 11UL,
            AcceptedPositionSequence: 20,
            previousTeleport,
            acceptedTeleport,
            disposition);

    private static RuntimeAuthoritativePositionRoute Classify(
        bool hasContact,
        float playerDistance,
        uint committedCellId = Cell,
        ushort previousTeleport = 10,
        ushort acceptedTeleport = 10,
        PositionTimestampDisposition disposition =
            PositionTimestampDisposition.Apply) =>
        ClassifyKind(
            RuntimePositionEntityKind.Remote,
            hasContact,
            playerDistance,
            committedCellId,
            previousTeleport,
            acceptedTeleport,
            disposition);

    private static RuntimeAuthoritativePositionRoute ClassifyKind(
        RuntimePositionEntityKind kind,
        bool hasContact,
        float playerDistance,
        uint committedCellId = Cell,
        ushort previousTeleport = 10,
        ushort acceptedTeleport = 10,
        PositionTimestampDisposition disposition =
            PositionTimestampDisposition.Apply) =>
        RuntimeAuthoritativePositionRouteClassifier.ClassifyAcceptedPosition(
            new RuntimeAcceptedPositionRouteRequest(
                Authority(disposition, previousTeleport, acceptedTeleport),
                kind,
                RuntimeAcceptedPositionSource.PositionEvent,
                new CreateObject.ServerPosition(
                    Cell, 10f, 20f, 30f, 1f, 0f, 0f, 0f),
                PlacementFrame: 0u,
                PositionPackVelocity: Vector3.Zero,
                committedCellId,
                hasContact,
                playerDistance,
                UsePositionFromServer: false,
                HasAnimations: false,
                default));
}