using System.Numerics;
using AcDream.App.Input;
using AcDream.Core.Physics;
using AcDream.Core.Rendering;

namespace AcDream.App.Rendering;

internal readonly record struct WorldSceneDiagnosticOutcome(
    int VisibleLandblocks,
    int TotalLandblocks);

internal interface IWorldSceneDiagnostics
{
    CameraCellResolution CameraCellResolution { get; }

    void EmitPViewInput(
        PortalVisibilityFrame portalFrame,
        Matrix4x4 viewProjection,
        LoadedCell clipRoot,
        Vector3 cameraPosition,
        Vector3 playerPosition);

    void EmitRenderSignature(
        string branch,
        LoadedCell? clipRoot,
        LoadedCell? viewerRoot,
        LoadedCell? playerRoot,
        uint viewerCellId,
        uint playerCellId,
        bool playerIndoorGate,
        bool cameraInsideCell,
        bool renderSky,
        bool drawSkyThisFrame,
        bool terrainDrawn,
        TerrainClipMode terrainClipMode,
        bool skyDrawn,
        bool depthClear,
        bool outdoorSceneryDrawn,
        int liveDynamicDrawnCount,
        string sceneParticles,
        RetailPViewFrameResult? pviewResult,
        Vector3 cameraPosition,
        Vector3 playerPosition);

    WorldSceneDiagnosticOutcome DrawAndPublish(
        in WorldCameraFrame camera,
        IReadOnlyList<(uint LandblockId, Vector3 AabbMin, Vector3 AabbMax)> bounds);
}

/// <summary>
/// Owns world-pass probes, collision wireframes, and the DebugVM facts derived
/// from one completed normal-world draw. None of these diagnostics influence
/// visibility or pass ordering.
/// </summary>
internal sealed class WorldSceneDiagnosticsController : IWorldSceneDiagnostics
{
    private readonly WorldRenderDiagnostics _diagnostics;
    private readonly IWorldScenePViewDiagnosticSource _pview;
    private readonly IWorldSceneDebugStateSource _state;
    private readonly DebugLineRenderer? _lines;
    private readonly PhysicsEngine _physics;
    private readonly ILocalPlayerModeSource _mode;
    private readonly IRuntimeLocalPlayerControllerSource _player;
    private readonly DebugVmRenderFactsPublisher _debugVm;
    private readonly bool _debugVmConsumerActive;
    private int _debugDrawLogCount;
    // #337 (TEMPORARY): built on first use so the ordinary overlay path and
    // every headless/no-window host pay nothing for it.
    private CollisionMeshWireframe? _meshWireframe;
    private CollisionMeshWireframeStats _lastMeshStats = new(-1, -1, -1, -1, false);

    public WorldSceneDiagnosticsController(
        WorldRenderDiagnostics diagnostics,
        IWorldScenePViewDiagnosticSource pview,
        IWorldSceneDebugStateSource state,
        DebugLineRenderer? lines,
        PhysicsEngine physics,
        ILocalPlayerModeSource mode,
        IRuntimeLocalPlayerControllerSource player,
        DebugVmRenderFactsPublisher debugVm,
        bool debugVmConsumerActive)
    {
        _diagnostics = diagnostics ?? throw new ArgumentNullException(nameof(diagnostics));
        _pview = pview ?? throw new ArgumentNullException(nameof(pview));
        _state = state ?? throw new ArgumentNullException(nameof(state));
        _lines = lines;
        _physics = physics ?? throw new ArgumentNullException(nameof(physics));
        _mode = mode ?? throw new ArgumentNullException(nameof(mode));
        _player = player ?? throw new ArgumentNullException(nameof(player));
        _debugVm = debugVm ?? throw new ArgumentNullException(nameof(debugVm));
        _debugVmConsumerActive = debugVmConsumerActive;
    }

    public CameraCellResolution CameraCellResolution => _pview.CameraCellResolution;

    public void EmitPViewInput(
        PortalVisibilityFrame portalFrame,
        Matrix4x4 viewProjection,
        LoadedCell clipRoot,
        Vector3 cameraPosition,
        Vector3 playerPosition)
    {
        if (!RenderingDiagnostics.ProbePvInputEnabled)
            return;

        _diagnostics.EmitPViewInput(
            enabled: true,
            portalFrame,
            viewProjection,
            clipRoot.IsOutdoorNode,
            cameraPosition,
            playerPosition,
            _pview.RawPlayerPositionOr(playerPosition),
            _pview.PlayerYaw,
            _pview.SampleTerrainZ(cameraPosition.X, cameraPosition.Y));
    }

    public void EmitRenderSignature(
        string branch,
        LoadedCell? clipRoot,
        LoadedCell? viewerRoot,
        LoadedCell? playerRoot,
        uint viewerCellId,
        uint playerCellId,
        bool playerIndoorGate,
        bool cameraInsideCell,
        bool renderSky,
        bool drawSkyThisFrame,
        bool terrainDrawn,
        TerrainClipMode terrainClipMode,
        bool skyDrawn,
        bool depthClear,
        bool outdoorSceneryDrawn,
        int liveDynamicDrawnCount,
        string sceneParticles,
        RetailPViewFrameResult? pviewResult,
        Vector3 cameraPosition,
        Vector3 playerPosition)
    {
        _diagnostics.EmitRenderSignatureIfChanged(
            RenderingDiagnostics.ProbeFlapEnabled,
            branch,
            clipRoot,
            viewerRoot,
            playerRoot,
            viewerCellId,
            playerCellId,
            playerIndoorGate,
            cameraInsideCell,
            renderSky,
            drawSkyThisFrame,
            terrainDrawn,
            terrainClipMode,
            skyDrawn,
            depthClear,
            outdoorSceneryDrawn,
            outdoorPortalDrawn: false,
            outdoorRootObjectCount: 0,
            liveDynamicDrawnCount,
            sceneParticles,
            pviewResult?.PortalFrame,
            pviewResult?.ClipAssembly,
            pviewResult?.DrawableCells,
            pviewResult?.DiagnosticPartition,
            exteriorPortalFrame: null,
            exteriorClipAssembly: null,
            exteriorDrawableCells: null,
            exteriorPartition: null,
            cameraPosition,
            playerPosition);
    }

    public WorldSceneDiagnosticOutcome DrawAndPublish(
        in WorldCameraFrame camera,
        IReadOnlyList<(uint LandblockId, Vector3 AabbMin, Vector3 AabbMax)> bounds)
    {
        ArgumentNullException.ThrowIfNull(bounds);
        // Brackets the normal-world phase against the clear-phase tripwire: any
        // GL state the world's geometry drew under but the next frame's clear
        // no longer sees shows up as a difference between the two lines.
        _diagnostics.EmitPostWorldGlStateIfChanged(
            AcDream.Core.Rendering.RenderingDiagnostics.ProbeGlStateEnabled);
        DrawCollisionWireframes(in camera);

        int visible = 0;
        int total = bounds.Count;
        for (int index = 0; index < bounds.Count; index++)
        {
            var entry = bounds[index];
            if (FrustumCuller.IsAabbVisible(
                    camera.Frustum,
                    entry.AabbMin,
                    entry.AabbMax))
            {
                visible++;
            }
        }

        // AllEntriesForDebug is a yield sequence. Do not even construct its
        // iterator unless the developer UI is mounted and consumes the facts.
        if (_debugVmConsumerActive)
        {
            Vector3 nearestOrigin =
                _mode.IsPlayerMode && _player.Controller is { } controller
                    ? controller.Position
                    : camera.Position;
            _debugVm.PublishDebugVmFacts(
                consumerActive: true,
                visible,
                total,
                nearestOrigin,
                _physics.ShadowObjects.AllEntriesForDebug());
        }
        return new WorldSceneDiagnosticOutcome(visible, total);
    }

    private void DrawCollisionWireframes(in WorldCameraFrame camera)
    {
        if (!_state.CollisionWireframesVisible || _lines is null)
            return;

        // #337 (2026-08-06 — TEMPORARY): ACDREAM_WIRE_MESH=1 replaces the
        // broadphase-proxy overlay below with the objects' real physics-BSP
        // polygon edges beside their visual mesh boxes and the terrain surface
        // — see CollisionMeshWireframe for why the proxy cannot answer the
        // question this mode exists for. Default off; F2 keeps its old
        // behaviour otherwise.
        if (RenderingDiagnostics.CollisionMeshWireframeEnabled)
        {
            DrawCollisionMesh(in camera);
            return;
        }

        _lines.Begin();
        int drawn = 0;
        foreach (ShadowEntry shadow in _physics.ShadowObjects.AllEntriesForDebug())
        {
            if (shadow.CollisionType == ShadowCollisionType.Cylinder)
            {
                float height = shadow.CylHeight > 0f
                    ? shadow.CylHeight
                    : shadow.Radius * 2f;
                _lines.AddCylinder(
                    shadow.Position,
                    shadow.Radius,
                    height,
                    new Vector3(0f, 1f, 0f));
            }
            else
            {
                _lines.AddCylinder(
                    shadow.Position - new Vector3(0f, 0f, shadow.Radius),
                    shadow.Radius,
                    shadow.Radius * 2f,
                    new Vector3(1f, 0.5f, 0f));
            }
            drawn++;
        }

        if (_mode.IsPlayerMode && _player.Controller is { } localPlayer)
        {
            Vector3 position = localPlayer.Position;
            _lines.AddCylinder(
                new Vector3(position.X, position.Y, position.Z),
                DebugVmRenderFactsPublisher.PlayerCollisionRadius,
                1.8f,
                new Vector3(1f, 0f, 0f));
            LogNearbyCollisionObjects(position, drawn);
        }

        _lines.Flush(camera.Camera.View, camera.Projection);
    }

    /// <summary>
    /// #337 (2026-08-06 — TEMPORARY, strip with the probe family). Centres on
    /// the player when there is one, else on the camera, so the fly-camera
    /// mode can inspect geometry too.
    /// </summary>
    private void DrawCollisionMesh(in WorldCameraFrame camera)
    {
        Vector3 centre = _mode.IsPlayerMode && _player.Controller is { } controller
            ? controller.Position
            : camera.Position;

        _meshWireframe ??= new CollisionMeshWireframe(_physics);

        _lines!.Begin();
        CollisionMeshWireframeStats stats = _meshWireframe.Draw(_lines, centre);

        if (_mode.IsPlayerMode && _player.Controller is { } player)
        {
            _lines.AddCylinder(
                player.Position,
                DebugVmRenderFactsPublisher.PlayerCollisionRadius,
                1.8f,
                new Vector3(1f, 0f, 0f));
        }

        _lines.Flush(camera.Camera.View, camera.Projection);

        // A capped frame is showing PARTIAL geometry, which would otherwise be
        // indistinguishable from an object that has none — exactly the
        // misreading this overlay exists to prevent. Say so, throttled, rather
        // than letting the picture lie.
        if (stats != _lastMeshStats)
        {
            _lastMeshStats = stats;
            Console.WriteLine(string.Format(
                System.Globalization.CultureInfo.InvariantCulture,
                "[wire-mesh] centre=({0:F2},{1:F2},{2:F2}) objects={3} polys={4} " +
                "noPhysicsGeometry={5} lines={6} capped={7}",
                centre.X, centre.Y, centre.Z,
                stats.ObjectsConsidered, stats.PolygonsDrawn,
                stats.ObjectsWithoutPhysicsGeometry, stats.LinesDrawn, stats.Capped));
        }
    }

    private void LogNearbyCollisionObjects(Vector3 playerPosition, int drawn)
    {
        if (_debugDrawLogCount >= 5)
            return;

        Console.WriteLine(
            $"debug frame {_debugDrawLogCount}: player=({playerPosition.X:F1},{playerPosition.Y:F1},{playerPosition.Z:F1}) drew={drawn} "
            + $"totalReg={_physics.ShadowObjects.TotalRegistered}");
        int logged = 0;
        foreach (ShadowEntry shadow in _physics.ShadowObjects.AllEntriesForDebug())
        {
            float dx = shadow.Position.X - playerPosition.X;
            float dy = shadow.Position.Y - playerPosition.Y;
            float horizontalDistance = MathF.Sqrt(dx * dx + dy * dy);
            if (horizontalDistance >= 10f)
                continue;

            Console.WriteLine(
                $"  near id=0x{shadow.EntityId:X8} type={shadow.CollisionType} "
                + $"pos=({shadow.Position.X:F1},{shadow.Position.Y:F1},{shadow.Position.Z:F1}) "
                + $"r={shadow.Radius:F2} h={shadow.CylHeight:F2} dh={horizontalDistance:F2}");
            if (++logged >= 5)
                break;
        }
        _debugDrawLogCount++;
    }
}