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

namespace AcDream.Core.Tests.Physics;

public class PhysicsBodyCellSyncTests
{
    [Fact]
    public void SnapToCell_SeedsCellPosition_AndWorldPosition()
    {
        var body = new PhysicsBody();
        body.SnapToCell(0xC95B0001u, worldPos: new Vector3(1000f, 2000f, 12f), cellLocal: new Vector3(14.8f, 0.3f, 12f));
        Assert.Equal(0xC95B0001u, body.CellPosition.ObjCellId);
        Assert.Equal(new Vector3(14.8f, 0.3f, 12f), body.CellPosition.Frame.Origin);
        Assert.Equal(new Vector3(1000f, 2000f, 12f), body.Position);
    }

    [Fact]
    public void PositionDelta_MirrorsIntoCellPosition_WithinLandblock()
    {
        var body = new PhysicsBody();
        body.SnapToCell(0xC95B0001u, new Vector3(1000f, 2000f, 12f), new Vector3(100f, 50f, 12f));
        body.Position += new Vector3(5f, 3f, 0f);   // move within the landblock
        Assert.Equal(new Vector3(105f, 53f, 12f), body.CellPosition.Frame.Origin);
        Assert.Equal(0xC95B0001u, body.CellPosition.ObjCellId);   // no [0,192) crossing → same cell
        Assert.Equal(new Vector3(1005f, 2003f, 12f), body.Position); // world still authoritative + moved
    }

    [Fact]
    public void PositionDelta_AcrossSouthLandblockEdge_BumpsCellAndRewraps()
    {
        var body = new PhysicsBody();
        // local Y just above 0 in 0xC95B (lbY=0x5B); move south past 0 → south neighbour 0xC95A, local Y near 192.
        body.SnapToCell(0xC95B0001u, new Vector3(1000f, 2000f, 12f), new Vector3(100f, 0.3f, 12f));
        body.Position += new Vector3(0f, -1f, 0f);
        int lbY = (int)((body.CellPosition.ObjCellId >> 16) & 0xFFu);
        Assert.Equal(0x5A, lbY);                                     // bumped to south neighbour
        Assert.InRange(body.CellPosition.Frame.Origin.Y, 190f, 192f); // re-wrapped near top of southern block
    }

    [Fact]
    public void PositionDelta_WithoutSeed_LeavesCellPositionDefault()
    {
        // A body that was never SnapToCell'd (e.g. a remote entity) must NOT get
        // a synthesized cell — CellPosition stays default, no AdjustToOutside.
        var body = new PhysicsBody();
        body.Position += new Vector3(10f, 10f, 0f);
        Assert.Equal(0u, body.CellPosition.ObjCellId);
    }
}