using System.Numerics;
using AcDream.App.Rendering.Gpu;
using AcDream.App.Rendering.Wb;
using AcDream.App.UI;
using AcDream.Core.Lighting;
using AcDream.Core.World;

namespace AcDream.App.Rendering;

/// <summary>
/// Camera contract for retail <c>CreatureMode</c>-style UI viewports. The
/// renderer supplies the authored viewport aspect before each draw and uses
/// <see cref="Eye"/> when it publishes the private scene lighting UBO.
/// </summary>
internal interface IPrivateEntityViewportCamera : ICamera
{
    Vector3 Eye { get; }
}

/// <summary>
/// Shared render-to-texture implementation for the private 3-D creature
/// viewports used by paperdoll and examination UI. Each instance owns one
/// <see cref="IGpuRenderTarget"/>, one synthetic render identity, and one
/// balanced texture-owner lease.
///
/// <para><b>Campaign V slice V6k (V4g's first half).</b> The target used to be a
/// hand-rolled FBO, colour texture and depth renderbuffer, and the resulting GL
/// texture name was published to the retained UI through
/// <c>GlGpuDevice.RegisterExternalColorTexture</c> — the pre-approved
/// transitional seam plan §7.1's final paragraph created, whose stated end was
/// exactly this slice. Both are gone: the device creates the target, the pass
/// DECLARES it, and the colour attachment is registered into the global texture
/// table like any other texture.</para>
///
/// <para>Declaring the target is what discharges §5.4. That section's divergence
/// — GL's <c>BeginPass</c> not binding framebuffer 0 for a null target, so this
/// renderer's own FBO survived — was reverted with V4c and is not on the tree;
/// what remained was the reason it had existed, namely that this renderer bound
/// a framebuffer the RHI knew nothing about. It now names its target, so
/// nothing depends on inheritance and the GL and Vulkan backends agree about
/// what <c>Target: null</c> means.</para>
///
/// <para>The GL arm this renderer used to open an RHI pass and delegate a
/// raw-GL <c>WbDrawDispatcher</c> into (through V10, §5.5.6) was deleted at
/// Campaign V slice V11: <c>WbDrawDispatcher</c> now records into the pass
/// this renderer publishes on both call sites the same way.</para>
/// </summary>
internal sealed class PrivateEntityViewportRenderer :
    IUiViewportRenderer,
    IDisposable
{
    private const uint PrivateLandblockId = 0u;

    private readonly IGpuDevice _device;
    private readonly ICurrentGpuFrameSource _frames;

    /// <summary>
    /// The world pass scope this renderer's own pass publishes into for the
    /// span of the draw. <c>WbDrawDispatcher</c> borrows its pass from the
    /// scope rather than opening one, so this renderer — which opens a pass of
    /// its own to draw into an offscreen target — has to publish it there.
    ///
    /// <para>The raw-GL arm this used to be optional for (the GL dispatcher
    /// recorded against whatever framebuffer was already bound, needing no
    /// publication) was deleted at Campaign V slice V11.</para>
    /// </summary>
    private readonly IWorldPassScope _scope;

    private readonly WbDrawDispatcher _dispatcher;
    private readonly SceneLightingUboBinding _lightUbo;
    private readonly FixedEntityTextureOwnerLease _textureOwnerLease;
    private readonly IWbMeshAdapter _meshAdapter;
    private readonly IPrivateEntityViewportCamera _camera;
    private readonly HashSet<uint> _animatedIds;
    private readonly string _diagnosticName;
    private readonly List<SyntheticEntityMeshReferenceOwner>
        _retiringMeshReferences = [];

    private IGpuRenderTarget? _target;
    private IGpuSampler? _sampler;
    private GpuTextureSlot _slot = GpuTextureSlot.Unassigned;
    private int _fbW;
    private int _fbH;
    private WorldEntity? _entity;
    private SyntheticEntityMeshReferenceOwner? _meshReferences;

    public PrivateEntityViewportRenderer(
        IWorldPassScope scope,
        IGpuDevice device,
        ICurrentGpuFrameSource frames,
        WbDrawDispatcher dispatcher,
        SceneLightingUboBinding lightUbo,
        IEntityTextureLifetime textureLifetime,
        IWbMeshAdapter meshAdapter,
        uint renderId,
        IPrivateEntityViewportCamera camera,
        string diagnosticName)
    {
        if (renderId == 0u)
            throw new ArgumentOutOfRangeException(nameof(renderId));

        _scope = scope ?? throw new ArgumentNullException(
            nameof(scope),
            "The viewport must publish a world pass scope to draw into.");
        _device = device ?? throw new ArgumentNullException(nameof(device));
        _frames = frames ?? throw new ArgumentNullException(nameof(frames));
        _dispatcher = dispatcher ?? throw new ArgumentNullException(nameof(dispatcher));
        _lightUbo = lightUbo ?? throw new ArgumentNullException(nameof(lightUbo));
        _meshAdapter = meshAdapter
            ?? throw new ArgumentNullException(nameof(meshAdapter));
        _camera = camera ?? throw new ArgumentNullException(nameof(camera));
        _diagnosticName = string.IsNullOrWhiteSpace(diagnosticName)
            ? "creature viewport"
            : diagnosticName;
        _animatedIds = [renderId];
        _textureOwnerLease = new FixedEntityTextureOwnerLease(
            textureLifetime ?? throw new ArgumentNullException(nameof(textureLifetime)),
            renderId);
    }

    /// <summary>
    /// A GL framebuffer's colour texture used to sample bottom-up; that arm was
    /// deleted at Campaign V slice V11, and a Vulkan render target's does not.
    /// See <see cref="IUiViewportRenderer.TextureIsBottomUp"/>.
    /// </summary>
    public bool TextureIsBottomUp => false;

    public void SetEntity(WorldEntity? entity)
    {
        ReleaseRetiringMeshReferences();

        if (ReferenceEquals(_entity, entity))
            return;

        SyntheticEntityMeshReferenceOwner? replacement = null;
        if (entity is not null)
        {
            replacement = new SyntheticEntityMeshReferenceOwner(
                _meshAdapter,
                CollectMeshIds(entity));
            replacement.Acquire();
        }

        SyntheticEntityMeshReferenceOwner? previous = _meshReferences;
        try
        {
            _textureOwnerLease.Replace(entity is not null);
        }
        catch (Exception textureFailure)
        {
            if (replacement is null)
                throw;

            try
            {
                replacement.Dispose();
            }
            catch (Exception rollbackFailure)
            {
                throw new AggregateException(
                    $"The {_diagnosticName} texture-owner replacement failed "
                    + "and the replacement mesh-owner rollback did not converge.",
                    textureFailure,
                    rollbackFailure);
            }

            System.Runtime.ExceptionServices.ExceptionDispatchInfo
                .Capture(textureFailure)
                .Throw();
        }

        _meshReferences = replacement;
        _entity = entity;

        if (previous is not null)
        {
            try
            {
                previous.Dispose();
            }
            catch
            {
                _retiringMeshReferences.Add(previous);
                throw;
            }
        }
    }

    /// <summary>
    /// Renders the entity and returns the <see cref="UiTextureTableHandle"/> the
    /// retained UI blits — a one-based index into the device's global texture
    /// table, not a GL texture name. Zero means nothing was rendered.
    /// </summary>
    public uint Render(int width, int height)
    {
        WorldEntity? entity = _entity;
        if (entity is null || entity.MeshRefs.Count == 0 || width <= 0 || height <= 0)
            return 0u;

        EnsureRenderTarget(width, height);
        if (_target is null)
            return 0u;
        _camera.Aspect = width / (float)height;

        IGpuFrame frame = _frames.CurrentFrame
            ?? throw new InvalidOperationException(
                $"The {_diagnosticName} requires an open IGpuFrame (see GpuDeviceFrameLifetime).");

        using IGpuPassEncoder encoder = frame.BeginPass(new GpuPassDescription
        {
            Name = _diagnosticName,
            Color = new GpuColorAttachment(
                Target: _target,
                Load: GpuLoadOp.Clear,
                Store: GpuStoreOp.Store,
                ClearColor: Vector4.Zero),
            Depth = new GpuDepthAttachment(
                Load: GpuLoadOp.Clear,
                Store: GpuStoreOp.DontCare,
                ClearDepth: 1f,
                ClearStencil: 0),
            SampleCount = 1,
        });

        // The dispatcher borrows its pass from the scope, so this pass has to
        // BE the scope's for the span of the draw. Published after the world
        // phase has closed its own, which is why it does not nest; the
        // sections it resets are republished by UploadCreatureLight
        // immediately below, which is the private lighting this view wants
        // rather than the world's.
        using IDisposable publication = _scope.Publish(encoder);

        UploadCreatureLight();

        WorldEntity[] entities = [entity];
        var entries =
            new (uint, Vector3, Vector3, IReadOnlyList<WorldEntity>,
                IReadOnlyDictionary<uint, WorldEntity>?)[]
            {
                (
                    PrivateLandblockId,
                    new Vector3(-1024f),
                    new Vector3(1024f),
                    entities,
                    null),
            };

        _dispatcher.Draw(
            _camera,
            entries,
            frustum: null,
            neverCullLandblockId: PrivateLandblockId,
            visibleCellIds: null,
            animatedEntityIds: _animatedIds);
        return UiTextureTableHandle.FromSlot(_slot);
    }

    /// <summary>
    /// Both retail paperdoll and creature examination call
    /// <c>UIElement_Viewport::SetLight(DISTANT_LIGHT, 2, (0.3,1.9,0.65))</c>.
    /// </summary>
    private void UploadCreatureLight()
    {
        Vector3 direction = Vector3.Normalize(new Vector3(0.3f, 1.9f, 0.65f));
        _lightUbo.Upload(new SceneLightingUbo
        {
            Light0 = new UboLight
            {
                PosAndKind = Vector4.Zero,
                DirAndRange = new Vector4(direction, 1e9f),
                ColorAndIntensity = new Vector4(1f, 1f, 1f, 2f),
                ConeAngleEtc = Vector4.Zero,
            },
            CellAmbient = new Vector4(0.3f, 0.3f, 0.3f, 1f),
            FogParams = new Vector4(1e9f, 1e9f, 0f, 0f),
            FogColor = Vector4.Zero,
            CameraAndTime = new Vector4(_camera.Eye, 0f),
        });
    }

    private void EnsureRenderTarget(int width, int height)
    {
        if (_target is not null && width == _fbW && height == _fbH)
            return;
        ReleaseRenderTarget();

        IGpuRenderTarget target;
        try
        {
            target = _device.CreateRenderTarget(new GpuRenderTargetDescription(
                _diagnosticName,
                width,
                height,
                GpuTextureFormat.Rgba8UnormRenderTarget,
                // Depth24Stencil8, as the hand-rolled renderbuffer was: nothing
                // samples it, and the stencil aspect keeps the attachment shape
                // the depth/stencil renderers already expect.
                GpuTextureFormat.Depth24Stencil8,
                SampleCount: 1));
        }
        catch (Exception failure)
        {
            Console.WriteLine(
                $"[{_diagnosticName}] render target unavailable ({width}x{height}): {failure.Message}");
            return;
        }

        try
        {
            // The retained UI blits this attachment as an ordinary table entry.
            // Linear/clamped is the filtering the hand-rolled colour texture set
            // on itself before the §7.1 seam registered it.
            _sampler = _device.CreateSampler(GpuSamplerDescription.WorldClamp);
            _slot = _device.RegisterTexture(target.ColorTexture, _sampler);
        }
        catch
        {
            target.Dispose();
            _sampler = null;
            _slot = GpuTextureSlot.Unassigned;
            throw;
        }

        _target = target;
        _fbW = width;
        _fbH = height;
    }

    private void ReleaseRenderTarget()
    {
        if (_slot.IsAssigned)
        {
            _device.ReleaseTextureSlot(_slot);
            _slot = GpuTextureSlot.Unassigned;
        }
        _sampler = null;
        _target?.Dispose();
        _target = null;
        _fbW = 0;
        _fbH = 0;
    }

    public void Dispose()
    {
        _entity = null;
        if (_meshReferences is { } current)
        {
            _meshReferences = null;
            _retiringMeshReferences.Add(current);
        }

        List<Exception>? failures = null;
        try
        {
            _textureOwnerLease.Dispose();
        }
        catch (Exception error)
        {
            (failures ??= []).Add(error);
        }
        try
        {
            ReleaseRetiringMeshReferences();
        }
        catch (Exception error)
        {
            (failures ??= []).Add(error);
        }
        try
        {
            ReleaseRenderTarget();
        }
        catch (Exception error)
        {
            (failures ??= []).Add(error);
        }

        if (failures is not null)
        {
            throw new AggregateException(
                $"The {_diagnosticName} resources did not fully release.",
                failures);
        }
    }

    private static IEnumerable<ulong> CollectMeshIds(WorldEntity entity)
    {
        for (int i = 0; i < entity.MeshRefs.Count; i++)
            yield return entity.MeshRefs[i].GfxObjId;
        for (int i = 0; i < entity.PartOverrides.Count; i++)
            yield return entity.PartOverrides[i].GfxObjId;
    }

    private void ReleaseRetiringMeshReferences()
    {
        List<Exception>? failures = null;
        for (int i = _retiringMeshReferences.Count - 1; i >= 0; i--)
        {
            SyntheticEntityMeshReferenceOwner owner =
                _retiringMeshReferences[i];
            try
            {
                owner.Dispose();
                if (owner.IsDisposed)
                    _retiringMeshReferences.RemoveAt(i);
            }
            catch (Exception error)
            {
                (failures ??= []).Add(error);
            }
        }

        if (failures is not null)
        {
            throw new AggregateException(
                $"One or more {_diagnosticName} mesh owners remain pending.",
                failures);
        }
    }
}