using System.Numerics;
using AcDream.App.Input;
using AcDream.App.Rendering;
using AcDream.App.Streaming;
using AcDream.App.World;
using AcDream.Core.Lighting;
using AcDream.Core.Physics;
using AcDream.Core.Rendering;
using AcDream.Core.World;
using AcDream.Core.World.Cells;

namespace AcDream.App.Tests.Rendering;

public sealed class WorldRenderFrameBuilderTests
{
    [Fact]
    public void Build_orders_world_preparation_and_combines_borrowed_results()
    {
        List<string> calls = [];
        var camera = new FlyCamera { Position = new Vector3(11f, 22f, 33f) };
        var cameraFrame = new WorldCameraFrame(
            camera,
            camera.Projection,
            camera.View * camera.Projection,
            default,
            Matrix4x4.Identity,
            camera.Position);
        WorldRootFrame roots = default;
        var animated = new HashSet<uint> { 41u, 42u };
        var buildings = new List<LoadedCell>();
        var foundation = new RenderFrameFoundation(
            PortalViewportVisible: false,
            Sky: default,
            Atmosphere: default);
        var visibility = new RecordingVisibility(calls);
        var environment = new RecordingEnvironment(calls);
        var builder = new WorldRenderFrameBuilder(
            new RecordingCamera(calls, cameraFrame),
            visibility,
            new RecordingSettings(calls),
            new RecordingRoots(calls, roots),
            environment,
            new RecordingAnimated(calls, animated),
            new RecordingBuildings(calls, new WorldBuildingFrame(null, buildings)));

        WorldRenderFrame result = builder.Build(
            in foundation,
            waitingForLogin: true,
            activeDayGroup: null);
        var drawableCells = new HashSet<uint> { 0x01010001u };
        builder.ObserveDrawableCells(drawableCells);
        builder.ClearDrawableCells();

        Assert.Equal(
            [
                "camera",
                "visibility:begin",
                "settings",
                "roots",
                "environment",
                "visibility:projection",
                "animated",
                "buildings",
            ],
            calls);
        Assert.Same(camera, result.Camera.Camera);
        Assert.Same(animated, result.AnimatedEntityIds);
        Assert.Same(buildings, result.Buildings.NearbyBuildingCells);
        Assert.Null(result.ClipRoot);
        Assert.True(visibility.WaitingForLogin);
        Assert.Equal(foundation, environment.Foundation);
        Assert.Same(drawableCells, environment.DrawableCells);
        Assert.Equal(1, environment.ClearCount);
    }

    [Fact]
    public void Required_sources_fail_fast()
    {
        var camera = new RecordingCamera([], default);
        var visibility = new RecordingVisibility([]);
        var settings = new RecordingSettings([]);
        var roots = new RecordingRoots([], default);
        var environment = new RecordingEnvironment([]);
        var animated = new RecordingAnimated([], []);
        var buildings = new RecordingBuildings([], default);

        Assert.Throws<ArgumentNullException>(() =>
            new WorldRenderFrameBuilder(null!, visibility, settings, roots, environment, animated, buildings));
        Assert.Throws<ArgumentNullException>(() =>
            new WorldRenderFrameBuilder(camera, null!, settings, roots, environment, animated, buildings));
        Assert.Throws<ArgumentNullException>(() =>
            new WorldRenderFrameBuilder(camera, visibility, null!, roots, environment, animated, buildings));
        Assert.Throws<ArgumentNullException>(() =>
            new WorldRenderFrameBuilder(camera, visibility, settings, null!, environment, animated, buildings));
        Assert.Throws<ArgumentNullException>(() =>
            new WorldRenderFrameBuilder(camera, visibility, settings, roots, null!, animated, buildings));
        Assert.Throws<ArgumentNullException>(() =>
            new WorldRenderFrameBuilder(camera, visibility, settings, roots, environment, null!, buildings));
        Assert.Throws<ArgumentNullException>(() =>
            new WorldRenderFrameBuilder(camera, visibility, settings, roots, environment, animated, null!));
    }

    [Fact]
    public void Render_range_state_updates_both_tiers_without_replacing_the_source()
    {
        IWorldRenderRangeSource source = new WorldRenderRangeState(4, 12);
        var mutable = Assert.IsType<WorldRenderRangeState>(source);

        mutable.NearRadius = 7;
        mutable.FarRadius = 19;

        Assert.Equal(7, source.NearRadius);
        Assert.Equal(19, source.FarRadius);
    }

    [Fact]
    public void Runtime_animated_source_reuses_scratch_and_removes_stale_ids()
    {
        var slot = new LiveEntityRuntimeSlot();
        var live = new LiveEntityAnimationRuntimeView<LiveEntityAnimationState>(slot);
        var source = new RuntimeWorldFrameAnimatedEntitySource(
            live,
            statics: null,
            equipped: null);

        HashSet<uint> first = source.Capture();
        first.Add(0xDEADBEEFu);
        HashSet<uint> second = source.Capture();

        Assert.Same(first, second);
        Assert.Empty(second);
    }

    [Fact]
    public void Runtime_building_source_reuses_scratch_and_rebuilds_outdoor_root()
    {
        var pipeline = new LandblockPresentationPipeline(
            publishBeforeSpatialCommit: (_, _) => { },
            state: new GpuWorldState());
        var source = new RuntimeWorldFrameBuildingSource(
            pipeline,
            new CellVisibility());
        FrustumPlanes frustum = default;

        WorldBuildingFrame first = source.Gather(
            viewerRoot: null,
            viewerCellId: 0x01010001u,
            in frustum);
        var scratch = Assert.IsType<List<LoadedCell>>(first.NearbyBuildingCells);
        scratch.Add(new LoadedCell { CellId = 0x01010100u });
        WorldBuildingFrame second = source.Gather(
            viewerRoot: null,
            viewerCellId: 0x02020001u,
            in frustum);

        Assert.Same(scratch, second.NearbyBuildingCells);
        Assert.Empty(second.NearbyBuildingCells);
        Assert.Equal(0x01010001u, first.OutdoorNode?.CellId);
        Assert.Equal(0x02020001u, second.OutdoorNode?.CellId);
    }

    [Fact]
    public void Runtime_root_source_keeps_player_lighting_and_viewer_render_cells_distinct()
    {
        const uint playerCellId = 0x01010100u;
        const uint viewerCellId = 0x01010101u;
        var physics = new PhysicsEngine { DataCache = new PhysicsDataCache() };
        physics.DataCache.CellGraph.Add(CoreCell(playerCellId, seenOutside: false));
        physics.UpdatePlayerCurrCell(playerCellId);
        var cells = new CellVisibility();
        var playerCell = new LoadedCell { CellId = playerCellId, SeenOutside = false };
        var viewerCell = new LoadedCell { CellId = viewerCellId, SeenOutside = true };
        cells.AddCell(playerCell);
        cells.AddCell(viewerCell);
        var retailChase = new RetailChaseCamera();
        retailChase.Update(
            playerPosition: Vector3.Zero,
            playerYaw: 0f,
            playerVelocity: Vector3.Zero,
            isOnGround: true,
            contactPlaneNormal: Vector3.UnitZ,
            dt: 1f / 60f,
            cellId: viewerCellId);
        var mode = new LocalPlayerModeState { IsPlayerMode = true };
        var chase = new ChaseCameraInputState { Retail = retailChase };
        var origin = new LiveWorldOriginState();
        origin.SetPlaceholder(0x01, 0x01);
        var source = new RuntimeWorldFrameRootSource(
            physics,
            cells,
            mode,
            chase,
            new LocalPlayerControllerSlot(),
            origin);
        var camera = new FlyCamera { Position = new Vector3(5f, 6f, 7f) };
        WorldCameraFrame cameraFrame = CameraFrame(camera);
        bool previousRetailCamera = CameraDiagnostics.UseRetailChaseCamera;

        try
        {
            CameraDiagnostics.UseRetailChaseCamera = true;
            WorldRootFrame result = source.Resolve(in cameraFrame);

            Assert.Same(playerCell, result.PlayerRoot);
            Assert.Same(viewerCell, result.ViewerRoot);
            Assert.True(result.PlayerInsideCell);
            Assert.True(result.CameraInsideCell);
            Assert.False(result.PlayerSeenOutside);
            Assert.True(result.RootSeenOutside);
            Assert.True(result.RenderSky);
            Assert.Equal(playerCellId, result.PlayerCellId);
            Assert.Equal(viewerCellId, result.ViewerCellId);
            Assert.Equal(camera.Position, result.ViewerEyePosition);
        }
        finally
        {
            CameraDiagnostics.UseRetailChaseCamera = previousRetailCamera;
        }
    }

    [Fact]
    public void Runtime_root_source_preserves_null_root_fallback_before_player_membership()
    {
        var physics = new PhysicsEngine();
        var source = new RuntimeWorldFrameRootSource(
            physics,
            new CellVisibility(),
            new LocalPlayerModeState(),
            new ChaseCameraInputState(),
            new LocalPlayerControllerSlot(),
            new LiveWorldOriginState());
        WorldCameraFrame camera = CameraFrame(new FlyCamera());

        WorldRootFrame result = source.Resolve(in camera);

        Assert.Null(result.PlayerRoot);
        Assert.Null(result.ViewerRoot);
        Assert.Equal(0u, result.PlayerCellId);
        Assert.Equal(0u, result.ViewerCellId);
        Assert.False(result.PlayerInsideCell);
        Assert.False(result.CameraInsideCell);
        Assert.True(result.RenderSky);
    }

    [Fact]
    public void Runtime_environment_copies_visible_cells_and_clear_restores_unscoped_lights()
    {
        const uint visibleCell = 0x01010100u;
        const uint hiddenCell = 0x01010101u;
        var lighting = new LightManager();
        var visibleLight = new LightSource
        {
            Kind = LightKind.Point,
            CellId = visibleCell,
        };
        var hiddenLight = new LightSource
        {
            Kind = LightKind.Point,
            CellId = hiddenCell,
        };
        lighting.Register(visibleLight);
        lighting.Register(hiddenLight);
        var environment = new RuntimeWorldFrameEnvironmentPreparation(
            RuntimeOptions.Parse("test-dat", _ => null),
            new WorldTimeService(SkyStateProvider.Default()),
            lighting,
            dispatcher: null,
            environmentCells: null,
            lightingUbo: null,
            new WorldRenderRangeState(4, 12),
            skyPes: null);
        var borrowed = new HashSet<uint> { visibleCell };
        environment.ObserveDrawableCells(borrowed);
        borrowed.Clear();
        borrowed.Add(hiddenCell);
        WorldCameraFrame camera = CameraFrame(new FlyCamera());
        WorldRootFrame roots = default;
        RenderFrameFoundation foundation = default;

        environment.Prepare(in camera, in roots, in foundation, activeDayGroup: null);

        Assert.Contains(visibleLight, lighting.PointSnapshot);
        Assert.DoesNotContain(hiddenLight, lighting.PointSnapshot);

        environment.ClearDrawableCells();
        environment.Prepare(in camera, in roots, in foundation, activeDayGroup: null);

        Assert.Contains(visibleLight, lighting.PointSnapshot);
        Assert.Contains(hiddenLight, lighting.PointSnapshot);
    }

    [Fact]
    public void Production_builder_preserves_the_frame_preparation_order()
    {
        string source = BuilderSource();

        AssertAppearsInOrder(
            source,
            "WorldCameraFrame camera = _camera.Resolve();",
            "_visibility.Begin(in camera, waitingForLogin);",
            "_settings.Apply(in camera);",
            "WorldRootFrame roots = _roots.Resolve(in camera);",
            "_environment.Prepare(in camera, in roots, in foundation, activeDayGroup);",
            "_visibility.PublishViewProjection(in camera);",
            "HashSet<uint> animated = _animated.Capture();",
            "WorldBuildingFrame buildings = _buildings.Gather(");
    }

    [Fact]
    public void Environment_preparation_keeps_lighting_snapshot_before_ubo_upload()
    {
        string source = BuilderSource();

        AssertAppearsInOrder(
            source,
            "UpdateSunFromSky(foundation.Sky, roots.PlayerInsideCell);",
            "_lighting.UpdateViewerLight(roots.PlayerViewPosition);",
            "_lighting.Tick(camera.Position);",
            "_lighting.BuildPointLightSnapshot(",
            "_dispatcher?.SetSceneLights(_lighting.PointSnapshot);",
            "_environmentCells?.SetPointSnapshot(_lighting.PointSnapshot);",
            "SceneLightingUbo ubo = SceneLightingUbo.Build(",
            "_lightingUbo?.Upload(ubo);",
            "RenderingDiagnostics.EmitLight(");
    }

    [Fact]
    public void World_scene_uses_the_typed_builder_and_orchestrator_owns_its_local_composition()
    {
        string gameWindow = GameWindowSource();
        string worldScene = File.ReadAllText(Path.Combine(
            FindRepoRoot(),
            "src",
            "AcDream.App",
            "Rendering",
            "WorldSceneRenderer.cs"));

        Assert.Equal(
            1,
            CountOccurrences(worldScene, "_frames.Build("));
        Assert.DoesNotContain("private void UpdateSunFromSky(", gameWindow, StringComparison.Ordinal);
        Assert.DoesNotContain("private void UpdateSkyPes(", gameWindow, StringComparison.Ordinal);
        Assert.DoesNotContain("private static float ParseEnvFloat(", gameWindow, StringComparison.Ordinal);
        Assert.DoesNotContain(
            "private AcDream.App.Rendering.WorldRenderFrameBuilder?",
            gameWindow,
            StringComparison.Ordinal);
        Assert.DoesNotContain(
            "private AcDream.App.Rendering.SkyPesFrameController?",
            gameWindow,
            StringComparison.Ordinal);
        AssertAppearsInOrder(
            worldScene,
            "_alpha.BeginFrame();",
            "_frames.Build(",
            "if (_login.IsWaitingForLogin)",
            "_passes.DrawFlatTerrain(",
            "NormalWorldDrawn: true");
        AssertAppearsInOrder(
            gameWindow,
            "var skyPesFrame = new AcDream.App.Rendering.SkyPesFrameController(",
            "var worldRenderFrameBuilder =",
            "new AcDream.App.Rendering.RenderFrameOrchestrator(",
            "_frameGraphs.Withdraw();",
            "new(\"equipped children\"",
            "new(\"effect network state\"",
            "new(\"audio\"",
            "new(\"mesh draw dispatcher\"",
            "new(\"environment cells\"",
            "new(\"scene lighting\"");
    }

    private static string BuilderSource() => File.ReadAllText(Path.Combine(
        FindRepoRoot(),
        "src",
        "AcDream.App",
        "Rendering",
        "WorldRenderFrameBuilder.cs"));

    private static WorldCameraFrame CameraFrame(FlyCamera camera) => new(
        camera,
        camera.Projection,
        camera.View * camera.Projection,
        default,
        Matrix4x4.Identity,
        camera.Position);

    private static AcDream.Core.World.Cells.EnvCell CoreCell(
        uint id,
        bool seenOutside) => new(
            id,
            Matrix4x4.Identity,
            Matrix4x4.Identity,
            Vector3.Zero,
            Vector3.One,
            Array.Empty<CellPortal>(),
            Array.Empty<uint>(),
            seenOutside,
            containmentBsp: null);

    private static string GameWindowSource() => File.ReadAllText(Path.Combine(
        FindRepoRoot(),
        "src",
        "AcDream.App",
        "Rendering",
        "GameWindow.cs"));

    private static int CountOccurrences(string source, string needle)
    {
        int count = 0;
        int cursor = 0;
        while ((cursor = source.IndexOf(needle, cursor, StringComparison.Ordinal)) >= 0)
        {
            count++;
            cursor += needle.Length;
        }

        return count;
    }

    private static void AssertAppearsInOrder(string source, params string[] needles)
    {
        int cursor = -1;
        foreach (string needle in needles)
        {
            int next = source.IndexOf(needle, cursor + 1, StringComparison.Ordinal);
            Assert.True(next >= 0, $"Missing expected source fragment: {needle}");
            Assert.True(next > cursor, $"Out-of-order source fragment: {needle}");
            cursor = next;
        }
    }

    private static string FindRepoRoot()
    {
        DirectoryInfo? directory = new(AppContext.BaseDirectory);
        while (directory is not null)
        {
            if (File.Exists(Path.Combine(directory.FullName, "AcDream.slnx")))
                return directory.FullName;
            directory = directory.Parent;
        }

        throw new DirectoryNotFoundException("Could not find AcDream.slnx.");
    }

    private sealed class RecordingCamera(
        List<string> calls,
        WorldCameraFrame result) : IWorldFrameCameraSource
    {
        public WorldCameraFrame Resolve()
        {
            calls.Add("camera");
            return result;
        }
    }

    private sealed class RecordingVisibility(List<string> calls)
        : IWorldFrameVisibilityPreparation
    {
        public bool WaitingForLogin { get; private set; }

        public void Begin(in WorldCameraFrame camera, bool waitingForLogin)
        {
            calls.Add("visibility:begin");
            WaitingForLogin = waitingForLogin;
        }

        public void PublishViewProjection(in WorldCameraFrame camera) =>
            calls.Add("visibility:projection");
    }

    private sealed class RecordingSettings(List<string> calls)
        : IWorldFrameSettingsPreview
    {
        public void Apply(in WorldCameraFrame camera) => calls.Add("settings");
    }

    private sealed class RecordingRoots(
        List<string> calls,
        WorldRootFrame result) : IWorldFrameRootSource
    {
        public WorldRootFrame Resolve(in WorldCameraFrame camera)
        {
            calls.Add("roots");
            return result;
        }
    }

    private sealed class RecordingEnvironment(List<string> calls)
        : IWorldFrameEnvironmentPreparation
    {
        public RenderFrameFoundation Foundation { get; private set; }

        public IReadOnlySet<uint>? DrawableCells { get; private set; }

        public int ClearCount { get; private set; }

        public void Prepare(
            in WorldCameraFrame camera,
            in WorldRootFrame roots,
            in RenderFrameFoundation foundation,
            DayGroupData? activeDayGroup)
        {
            calls.Add("environment");
            Foundation = foundation;
        }

        public void ObserveDrawableCells(IReadOnlySet<uint> drawableCells) =>
            DrawableCells = drawableCells;

        public void ClearDrawableCells() => ClearCount++;
    }

    private sealed class RecordingAnimated(
        List<string> calls,
        HashSet<uint> result) : IWorldFrameAnimatedEntitySource
    {
        public HashSet<uint> Capture()
        {
            calls.Add("animated");
            return result;
        }
    }

    private sealed class RecordingBuildings(
        List<string> calls,
        WorldBuildingFrame result) : IWorldFrameBuildingSource
    {
        public WorldBuildingFrame Gather(
            LoadedCell? viewerRoot,
            uint viewerCellId,
            in FrustumPlanes frustum)
        {
            calls.Add("buildings");
            return result;
        }
    }
}