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
{
    // Retail projection globals, dumped live from the capture client
    // (recon 2026-08-30 evening: Render::bw/bh/xinvscale/yinvscale/tx/ty/vdst).
    public const float RetailViewportWidth = 1024f;
    public const float RetailViewportHeight = 720f;
    public const float RetailXInvScale = 0.00025f;
    public const float RetailYInvScale = 0.00025f;
    public const float RetailTx = 0.127875f;
    public const float RetailTy = 0.089875f;
    public const float RetailVdst = 0.1330766976f;

    private sealed class RetailRayCaster(
        Vector3 right, Vector3 forward, Vector3 up) : IWalkRayCaster
    {
        // Retail's unproject (copy_view's ray path; equal to
        // ScreenToViewTransform for these globals):
        //   u = sx·xinvscale − tx;  w = sy·yinvscale − ty
        //   ray = Xaxis·u + Yaxis·vdst − Zaxis·w
        public Vector3 RayThrough(float screenX, float screenY)
        {
            float u = screenX * RetailXInvScale - RetailTx;
            float w = screenY * RetailYInvScale - RetailTy;
            return right * u + forward * RetailVdst - up * w;
        }
    }

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

    public WalkTraceReplayContext(WalkOraclePose pose, Dictionary<uint, WalkCell> cells)
    {
        _cells = cells;
        WorldViewpoint = pose.Origin;
        var rotation = new Quaternion(pose.Q1, pose.Q2, pose.Q3, pose.Q0);
        // Basis convention RE-pinned 2026-08-30 (second pass): storage
        // w,x,y,z; forward = rotated +Y — the retail Frame convention. The
        // motion sweep briefly favored +X, but the walkabout camera was
        // mouse-turned off the run direction; the terrace-edge fixture's
        // EXTERNAL ground truth (the ledge faces the F518 vista, east)
        // decodes east ONLY under +Y-forward, and +Y makes the street
        // fixture's punch on/off-screen pattern match retail 4-for-4.
        Vector3 forward = Vector3.Transform(Vector3.UnitY, rotation);
        Vector3 up = Vector3.Transform(Vector3.UnitZ, rotation);
        Vector3 right = Vector3.Transform(Vector3.UnitX, rotation);

        // The exact retail frustum: tan(halfFovY) = ty/vdst, aspect = tx/ty.
        float fovY = 2f * MathF.Atan(RetailTy / RetailVdst);
        Matrix4x4 view = Matrix4x4.CreateLookAt(pose.Origin, pose.Origin + forward, up);
        Matrix4x4 projection = Matrix4x4.CreatePerspectiveFieldOfView(
            fovY, RetailTx / RetailTy, 0.1f, 5000f);
        _viewProjection = view * projection;

        ViewportWidth = RetailViewportWidth;
        ViewportHeight = RetailViewportHeight;
        _rays = new RetailRayCaster(right, forward, up);

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

    /// <summary>Building placements (camera-block-local) for the landscape
    /// fixtures; empty for the interior-only ones.</summary>
    public Dictionary<WalkBuilding, WalkWorldDatAdapter.BuildingEntry> Buildings { get; set; }
        = new();

    private Vector2[] _activeViewVerts = new Vector2[32];
    private int _activeViewVertCount;

    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)
    {
        WalkViewPoly poly = views.View.Polys[index];
        if (_activeViewVerts.Length < poly.VertexCount)
            _activeViewVerts = new Vector2[poly.VertexCount];
        for (int k = 0; k < poly.VertexCount; k++)
            _activeViewVerts[k] = views.View.Vertices[poly.VertexIndex + k].Point;
        _activeViewVertCount = poly.VertexCount;
    }

    public Vector3 ViewpointInBuilding(WalkBuilding building)
        => Vector3.Transform(WorldViewpoint, Buildings[building].InverseWorldTransform);

    public float ViewerDistanceTo(WalkBuilding building)
        => Vector3.Distance(
            WorldViewpoint,
            Vector3.Transform(building.SortCenter, Buildings[building].WorldTransform));

    public int ClipBuildingPolygon(
        WalkBuilding building, WalkPolygon polygon, int side, Span<WalkScreenPoint> output)
    {
        Matrix4x4 objectToClip = Buildings[building].WorldTransform * _viewProjection;
        Span<WalkScreenPoint> projected = stackalloc WalkScreenPoint[polygon.Vertices.Length];
        for (int i = 0; i < polygon.Vertices.Length; i++)
            projected[i] = WalkScreenClip.TransformToScreen(
                polygon.Vertices[i], objectToClip, ViewportWidth, ViewportHeight);
        if (side != 0)
            projected.Reverse();
        return WalkScreenClip.ClipAgainstView(
            projected, _activeViewVerts.AsSpan(0, _activeViewVertCount), output);
    }

    // ---- 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")))}",
            _ => "?",
        }));
}