using System.Numerics;
using AcDream.App.Rendering;
using Xunit;

namespace AcDream.App.Tests.Rendering;

public class OutdoorCellNodeTests
{
    // A building cell at world-translate (10,0,0) with one exit portal (OtherCellId=0xFFFF)
    // whose local plane faces +X (InsideSide=0). The outdoor node must expose ONE portal
    // back into that building cell, with the entrance polygon moved to world space and the
    // inside-side flipped (so the outdoor half-space is "inside" the node).
    private static LoadedCell BuildingWithOneExit(uint cellId)
    {
        var cell = new LoadedCell { CellId = cellId };
        cell.WorldTransform = Matrix4x4.CreateTranslation(10f, 0f, 0f);
        cell.InverseWorldTransform = Matrix4x4.CreateTranslation(-10f, 0f, 0f);
        cell.Portals.Add(new CellPortalInfo(OtherCellId: 0xFFFF, PolygonId: 0, Flags: 0, OtherPortalId: 0));
        cell.ClipPlanes.Add(new PortalClipPlane { Normal = new Vector3(1, 0, 0), D = 0f, InsideSide = 0 });
        cell.PortalPolygons.Add(new[]
        {
            new Vector3(0, -1, 0), new Vector3(0, 1, 0), new Vector3(0, 1, 2), new Vector3(0, -1, 2)
        });
        return cell;
    }

    [Fact]
    public void Build_FromBuildingExit_AddsReversePortalIntoBuilding()
    {
        uint outdoorId = 0xA9B40031;
        var building = BuildingWithOneExit(0xA9B40170);
        var node = OutdoorCellNode.Build(outdoorId, new[] { building });

        Assert.Equal(outdoorId, node.CellId);
        Assert.True(node.SeenOutside);
        Assert.True(node.IsOutdoorNode); // the flag PortalVisibilityBuilder keys the full-screen OutsideView on
        Assert.Equal(Matrix4x4.Identity, node.WorldTransform);
        Assert.Single(node.Portals);
        Assert.Equal((ushort)(0xA9B40170 & 0xFFFF), node.Portals[0].OtherCellId);
        // Reversed inside-side: the building's exit was InsideSide=0, the node's is 1.
        Assert.Equal(1, node.ClipPlanes[0].InsideSide);
        // Entrance polygon moved to world space (building translated +10 X): first vert x≈10.
        Assert.Equal(10f, node.PortalPolygons[0][0].X, 3);
    }

    [Fact]
    public void Build_NoBuildings_ReturnsEmptyPortalNode()
    {
        var node = OutdoorCellNode.Build(0xA9B40031, System.Array.Empty<LoadedCell>());
        Assert.Empty(node.Portals);
        Assert.True(node.SeenOutside);
        Assert.True(node.IsOutdoorNode);
    }
}