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

namespace AcDream.App.Tests.Rendering.Walk;

/// <summary>
/// The FW1 conformance replay harness: reconstructs the camera state from a
/// pose-stamped oracle frame and drives the ported walk over
/// adapter-built world data. Convention notes (adjudicate against the
/// fixtures, loudly, on any mismatch):
/// <list type="bullet">
/// <item>The dumped quaternion is retail Frame storage order w,x,y,z
/// (q0=w) — unit-norm verified on the captures.</item>
/// <item>Retail's frame axes: +Y forward, +Z up (the camera looks along
/// the rotated +Y).</item>
/// <item>Pose origin is landblock-local, the same space the adapter's
/// cell transforms produce.</item>
/// </list>
/// </summary>
public sealed class WalkTraceReplayContext : IWalkFrameContext, IRetailFrameWalkContext
{
    private sealed class BasisRayCaster(
        Vector3 right, Vector3 forward, Vector3 up,
        float halfWidth, float halfHeight, float focal) : IWalkRayCaster
    {
        public Vector3 RayThrough(float screenX, float screenY)
        {
            // Screen origin top-left, y down (the xformStart convention).
            float nx = (screenX - halfWidth) / halfWidth;
            float ny = (halfHeight - screenY) / halfHeight;
            return right * (nx / focal) + forward + up * (ny / focal);
        }
    }

    private readonly Dictionary<uint, WalkCell> _cells;
    private readonly Matrix4x4 _viewProjection;
    private readonly IWalkRayCaster _rays;

    public WalkTraceReplayContext(
        WalkOraclePose pose, Dictionary<uint, WalkCell> cells,
        float viewportWidth = 800f, float viewportHeight = 600f,
        float verticalFovRadians = 1.0f)
    {
        _cells = cells;
        WorldViewpoint = pose.Origin;
        var rotation = new Quaternion(pose.Q1, pose.Q2, pose.Q3, pose.Q0);
        Vector3 forward = Vector3.Transform(Vector3.UnitY, rotation);
        Vector3 up = Vector3.Transform(Vector3.UnitZ, rotation);
        Vector3 right = Vector3.Transform(Vector3.UnitX, rotation);

        Matrix4x4 view = Matrix4x4.CreateLookAt(pose.Origin, pose.Origin + forward, up);
        Matrix4x4 projection = Matrix4x4.CreatePerspectiveFieldOfView(
            verticalFovRadians, viewportWidth / viewportHeight, 0.1f, 5000f);
        _viewProjection = view * projection;

        ViewportWidth = viewportWidth;
        ViewportHeight = viewportHeight;
        float focal = MathF.Tan(verticalFovRadians / 2f);
        _rays = new BasisRayCaster(
            right, forward, up, viewportWidth / 2f, viewportHeight / 2f, focal);

        // The retail CY near plane: N = forward, d = −dot(eye, forward) − znear.
        CyPlane = new WalkPlane(forward, -Vector3.Dot(pose.Origin, forward) - 0.1f);
    }

    public Vector3 ViewpointIn(WalkCell cell)
        => Vector3.Transform(WorldViewpoint, cell.InverseWorldTransform);

    public Matrix4x4 ObjectToClip(WalkCell cell)
        => cell.WorldTransform * _viewProjection;

    public WalkCell? GetVisible(uint cellId) => _cells.GetValueOrDefault(cellId);
    public IWalkRayCaster Rays => _rays;
    public Vector3 WorldViewpoint { get; }
    public float ViewportWidth { get; }
    public float ViewportHeight { get; }
    public WalkPlane CyPlane { get; }
    public IWalkFrameContext CellContext => this;
    public void SetActiveView(WalkPortalView views, int index) { }

    public Vector3 ViewpointInBuilding(WalkBuilding building) => WorldViewpoint;

    public int ClipBuildingPolygon(
        WalkBuilding building, WalkPolygon polygon, int side, Span<WalkScreenPoint> output)
        => 0;   // building look-ins join the conformance surface with the landscape fixtures

    // ---- signatures for comparing walk output to oracle frames ----

    public static string Signature(IEnumerable<WalkEvent> events)
        => string.Join("|", events.Select(e => e.Kind switch
        {
            WalkEventKind.Landscape => "LS",
            WalkEventKind.Building => $"BLD:{e.CellId:x8}",
            WalkEventKind.DrawInside => $"DI:{e.CellId:x8}",
            WalkEventKind.DrawCells =>
                $"DC:ov={e.OutsideViewCount}:{string.Join(',', e.Cells.Select(c => c.ToString("x8")))}",
            _ => "?",
        }));

    public static string Signature(WalkOracleFrame frame)
        => string.Join("|", frame.Events.Select(e => e.Kind switch
        {
            WalkOracleEventKind.Landscape => "LS",
            WalkOracleEventKind.Building => $"BLD:{e.CellId!.Value:x8}",
            WalkOracleEventKind.DrawInside => $"DI:{e.CellId!.Value:x8}",
            WalkOracleEventKind.DrawCells =>
                $"DC:ov={e.OutsideViewCount}:{string.Join(',', e.Cells.Select(c => c.ToString("x8")))}",
            _ => "?",
        }));
}