using AcDream.App.Rendering.Gpu.Vk;
using Silk.NET.OpenGL;

namespace AcDream.App.Composition;

/// <summary>
/// Campaign V slice V6h: the graphics ownership that platform acquisition
/// publishes, once per backend.
///
/// <para><see cref="GameWindowPlatformAcquisition"/> was already generic over its
/// graphics type; only the call sites pinned <c>GL</c>. This class is what they
/// pin instead, so one composition pipeline drives both backends and the fork
/// lives at the handful of construction sites that genuinely differ rather than
/// in a second copy of the startup topology.</para>
///
/// <para>It is deliberately NOT a capability abstraction. Nothing dispatches on
/// it per frame; phases that still speak raw GL ask for the context by name and
/// take their Vulkan arm when it is absent. The GL arm is deleted at slice V11
/// and this class with it.</para>
/// </summary>
internal abstract class GameWindowGraphics : IDisposable
{
    /// <summary>Which backend this handle owns.</summary>
    public abstract RenderBackendKind Backend { get; }

    /// <summary>
    /// The live GL context, or null on any other backend. Phases whose owners
    /// are still raw GL branch on this; each such branch is a slice of Campaign
    /// V that has not landed yet, and the null arm names which one.
    /// </summary>
    public virtual GL? Gl => null;

    /// <summary>The live Vulkan context, or null on any other backend.</summary>
    public virtual VulkanGraphicsContext? Vulkan => null;

    /// <summary>
    /// The GL context, or a failure naming the caller. Used where the call site
    /// has already established that the GL arm is running, so a null would be a
    /// composition bug rather than a backend difference.
    /// </summary>
    public GL RequireGl(string owner) =>
        Gl ?? throw new InvalidOperationException(
            $"'{owner}' requires the OpenGL context, but the {Backend} backend is active.");

    public abstract void Dispose();
}

/// <summary>OpenGL ownership: the Silk.NET <see cref="GL"/> context itself.</summary>
internal sealed class OpenGlGameWindowGraphics : GameWindowGraphics
{
    public OpenGlGameWindowGraphics(GL gl) =>
        Context = gl ?? throw new ArgumentNullException(nameof(gl));

    /// <summary>The owned context. <see cref="GameWindowGraphics.Gl"/> is the borrowed view.</summary>
    public GL Context { get; }

    public override RenderBackendKind Backend => RenderBackendKind.Gl;

    public override GL? Gl => Context;

    public override void Dispose() => Context.Dispose();
}

/// <summary>
/// Vulkan ownership: the instance, surface, device, swapchain and RHI device
/// that <see cref="VulkanGraphicsContext"/> acquired and gated.
/// </summary>
internal sealed class VulkanGameWindowGraphics : GameWindowGraphics
{
    public VulkanGameWindowGraphics(VulkanGraphicsContext context) =>
        Context = context ?? throw new ArgumentNullException(nameof(context));

    public VulkanGraphicsContext Context { get; }

    public override RenderBackendKind Backend => RenderBackendKind.Vulkan;

    public override VulkanGraphicsContext? Vulkan => Context;

    public override void Dispose() => Context.Dispose();
}