acdream/src/AcDream.App/Rendering/GlResourceCommand.cs

using System.Runtime.ExceptionServices;
using AcDream.App.Rendering.Wb;
using Silk.NET.OpenGL;

namespace AcDream.App.Rendering;

/// <summary>
/// Always-on commit boundary for GL resource commands. OpenGL reports ordinary
/// command failures through its error flag, so an ownership state machine may
/// advance only after the post-command check succeeds.
/// </summary>
internal static class GlResourceCommand
{
    public static void Execute(GL gl, string context, Action command)
    {
        ArgumentNullException.ThrowIfNull(gl);
        ArgumentException.ThrowIfNullOrWhiteSpace(context);
        ArgumentNullException.ThrowIfNull(command);

        GLHelpers.ThrowOnResourceError(gl, $"{context} (precondition)");
        command();
        GLHelpers.ThrowOnResourceError(gl, context);
    }

    public static T Execute<T>(GL gl, string context, Func<T> command)
    {
        ArgumentNullException.ThrowIfNull(gl);
        ArgumentException.ThrowIfNullOrWhiteSpace(context);
        ArgumentNullException.ThrowIfNull(command);

        GLHelpers.ThrowOnResourceError(gl, $"{context} (precondition)");
        T result = command();
        GLHelpers.ThrowOnResourceError(gl, context);
        return result;
    }

    public static uint CreateName(
        GL gl,
        string resourceName,
        Func<uint> create,
        Action<uint> delete)
    {
        ArgumentException.ThrowIfNullOrWhiteSpace(resourceName);
        ArgumentNullException.ThrowIfNull(create);
        ArgumentNullException.ThrowIfNull(delete);

        return CreateNameCore(
            resourceName,
            () => GLHelpers.ThrowOnResourceError(
                gl,
                $"create {resourceName} (precondition)"),
            create,
            () => GLHelpers.ThrowOnResourceError(gl, $"create {resourceName}"),
            ownedName => Execute(
                gl,
                $"rollback {resourceName} name {ownedName}",
                () => delete(ownedName)));
    }

    internal static uint CreateNameCore(
        string resourceName,
        Action precondition,
        Func<uint> create,
        Action postcondition,
        Action<uint> deleteChecked)
    {
        ArgumentException.ThrowIfNullOrWhiteSpace(resourceName);
        ArgumentNullException.ThrowIfNull(precondition);
        ArgumentNullException.ThrowIfNull(create);
        ArgumentNullException.ThrowIfNull(postcondition);
        ArgumentNullException.ThrowIfNull(deleteChecked);

        uint name = 0;
        Exception? creationFailure = null;
        try
        {
            precondition();
            name = create();
            if (name == 0)
                throw new InvalidOperationException($"OpenGL returned no {resourceName} name.");
            postcondition();
            return name;
        }
        catch (Exception failure)
        {
            creationFailure = failure;
        }

        if (name != 0)
        {
            var cleanup = new SingleNameCleanup(name, deleteChecked);
            try
            {
                cleanup.RetryCleanup();
            }
            catch (Exception cleanupFailure)
            {
                throw new GlResourceConstructionException(
                    $"Creating {resourceName} failed and its returned GL name could not be released.",
                    cleanup,
                    [creationFailure, cleanupFailure]);
            }
        }

        ExceptionDispatchInfo.Capture(creationFailure).Throw();
        throw new InvalidOperationException("Unreachable GL resource-creation path.");
    }

    public static uint CreateTexture(GL gl, string context) =>
        CreateName(gl, context, gl.GenTexture, gl.DeleteTexture);

    public static void DeleteTexture(GL gl, uint texture, string context) =>
        Execute(gl, context, () => gl.DeleteTexture(texture));

    public static void DeleteShader(GL gl, uint shader, string context) =>
        Execute(gl, context, () => gl.DeleteShader(shader));

    public static void DeleteProgram(GL gl, uint program, string context) =>
        Execute(gl, context, () => gl.DeleteProgram(program));

    public static void DeleteBuffer(GL gl, uint buffer, string context) =>
        Execute(gl, context, () => gl.DeleteBuffer(buffer));

    public static void DeleteVertexArray(GL gl, uint vertexArray, string context) =>
        Execute(gl, context, () => gl.DeleteVertexArray(vertexArray));

    private sealed class SingleNameCleanup(uint name, Action<uint> delete)
        : IRetryableResourceCleanup
    {
        private uint _name = name;
        private bool _running;

        public bool IsCleanupComplete => _name == 0;

        public void RetryCleanup()
        {
            if (_running || _name == 0)
                return;

            _running = true;
            try
            {
                delete(_name);
                _name = 0;
            }
            finally
            {
                _running = false;
            }
        }
    }
}