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

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

namespace AcDream.App.Rendering;

internal interface IShaderProgramBuildApi
{
    uint CreateShader(ShaderType type);
    void ShaderSource(uint shader, string source);
    void CompileShader(uint shader);
    int GetShaderCompileStatus(uint shader);
    string GetShaderInfoLog(uint shader);
    uint CreateProgram();
    void AttachShader(uint program, uint shader);
    void LinkProgram(uint program);
    int GetProgramLinkStatus(uint program);
    string GetProgramInfoLog(uint program);
    void DetachShader(uint program, uint shader);
    void DeleteShader(uint shader);
    void DeleteProgram(uint program);
}

internal sealed class GlShaderProgramBuildApi(GL gl) : IShaderProgramBuildApi
{
    public uint CreateShader(ShaderType type) =>
        GlResourceCommand.CreateName(
            gl,
            $"{type} shader",
            () => gl.CreateShader(type),
            gl.DeleteShader);

    public void ShaderSource(uint shader, string source) =>
        GlResourceCommand.Execute(
            gl,
            $"upload shader source {shader}",
            () => gl.ShaderSource(shader, source));

    public void CompileShader(uint shader) =>
        GlResourceCommand.Execute(
            gl,
            $"compile shader {shader}",
            () => gl.CompileShader(shader));

    public void GetShader(uint shader, ShaderParameterName name, out int value) =>
        gl.GetShader(shader, name, out value);

    public int GetShaderCompileStatus(uint shader)
    {
        return GlResourceCommand.Execute(
            gl,
            $"read shader {shader} compile status",
            () =>
            {
                gl.GetShader(shader, ShaderParameterName.CompileStatus, out int value);
                return value;
            });
    }

    public string GetShaderInfoLog(uint shader) =>
        GlResourceCommand.Execute(
            gl,
            $"read shader {shader} info log",
            () => gl.GetShaderInfoLog(shader));

    public uint CreateProgram() =>
        GlResourceCommand.CreateName(
            gl,
            "shader program",
            gl.CreateProgram,
            gl.DeleteProgram);

    public void AttachShader(uint program, uint shader) =>
        GlResourceCommand.Execute(
            gl,
            $"attach shader {shader} to program {program}",
            () => gl.AttachShader(program, shader));

    public void LinkProgram(uint program) =>
        GlResourceCommand.Execute(
            gl,
            $"link shader program {program}",
            () => gl.LinkProgram(program));

    public int GetProgramLinkStatus(uint program)
    {
        return GlResourceCommand.Execute(
            gl,
            $"read shader program {program} link status",
            () =>
            {
                gl.GetProgram(program, ProgramPropertyARB.LinkStatus, out int value);
                return value;
            });
    }

    public string GetProgramInfoLog(uint program) =>
        GlResourceCommand.Execute(
            gl,
            $"read shader program {program} info log",
            () => gl.GetProgramInfoLog(program));

    public void DetachShader(uint program, uint shader) =>
        GlResourceCommand.Execute(
            gl,
            $"detach shader {shader} from program {program}",
            () => gl.DetachShader(program, shader));

    public void DeleteShader(uint shader) =>
        GlResourceCommand.DeleteShader(gl, shader, $"delete shader {shader}");

    public void DeleteProgram(uint program) =>
        GlResourceCommand.DeleteProgram(gl, program, $"delete shader program {program}");
}

internal sealed class ShaderProgramCleanup(IShaderProgramBuildApi api)
    : IRetryableResourceCleanup
{
    public uint Vertex { get; set; }
    public uint Fragment { get; set; }
    public uint Program { get; set; }
    public bool VertexAttached { get; set; }
    public bool FragmentAttached { get; set; }

    public bool IsCleanupComplete => Vertex == 0 && Fragment == 0 && Program == 0;

    public uint TransferProgram()
    {
        if (Vertex != 0 || Fragment != 0 || Program == 0)
            throw new InvalidOperationException("The linked program is not ready for ownership transfer.");
        uint program = Program;
        Program = 0;
        return program;
    }

    public List<Exception> Release(bool includeProgram)
    {
        var failures = new List<Exception>();
        Try(
            () =>
            {
                if (Program != 0 && Vertex != 0 && VertexAttached)
                {
                    api.DetachShader(Program, Vertex);
                    VertexAttached = false;
                }
            },
            failures);
        Try(
            () =>
            {
                if (Program != 0 && Fragment != 0 && FragmentAttached)
                {
                    api.DetachShader(Program, Fragment);
                    FragmentAttached = false;
                }
            },
            failures);
        Try(
            () =>
            {
                if (Vertex != 0)
                {
                    api.DeleteShader(Vertex);
                    Vertex = 0;
                    VertexAttached = false;
                }
            },
            failures);
        Try(
            () =>
            {
                if (Fragment != 0)
                {
                    api.DeleteShader(Fragment);
                    Fragment = 0;
                    FragmentAttached = false;
                }
            },
            failures);
        if (includeProgram)
        {
            Try(
                () =>
                {
                    if (Program != 0)
                    {
                        api.DeleteProgram(Program);
                        Program = 0;
                        VertexAttached = false;
                        FragmentAttached = false;
                    }
                },
                failures);
        }

        return failures;
    }

    public List<Exception> ReleaseProgramOnly()
    {
        var failures = new List<Exception>();
        Try(
            () =>
            {
                if (Program != 0)
                {
                    api.DeleteProgram(Program);
                    Program = 0;
                    VertexAttached = false;
                    FragmentAttached = false;
                }
            },
            failures);
        return failures;
    }

    public void RetryCleanup()
    {
        List<Exception> failures = Release(includeProgram: true);
        if (!IsCleanupComplete)
        {
            throw new AggregateException(
                "Shader program cleanup remains incomplete.",
                failures.Count == 0
                    ? [new InvalidOperationException("Shader cleanup retained names without reporting an operation failure.")]
                    : failures);
        }
    }

    private static void Try(Action operation, List<Exception> failures)
    {
        try
        {
            operation();
        }
        catch (Exception failure)
        {
            failures.Add(failure);
        }
    }
}

internal static class ShaderProgramConstruction
{
    public static uint Build(
        IShaderProgramBuildApi api,
        string vertexSource,
        string fragmentSource)
    {
        ArgumentNullException.ThrowIfNull(api);
        ArgumentNullException.ThrowIfNull(vertexSource);
        ArgumentNullException.ThrowIfNull(fragmentSource);

        var cleanup = new ShaderProgramCleanup(api);
        Exception? constructionFailure = null;

        try
        {
            cleanup.Vertex = CreateShader(api, ShaderType.VertexShader);
            Compile(api, cleanup.Vertex, ShaderType.VertexShader, vertexSource);
            cleanup.Fragment = CreateShader(api, ShaderType.FragmentShader);
            Compile(api, cleanup.Fragment, ShaderType.FragmentShader, fragmentSource);
            cleanup.Program = api.CreateProgram();
            if (cleanup.Program == 0)
                throw new InvalidOperationException("OpenGL returned no shader program name.");

            api.AttachShader(cleanup.Program, cleanup.Vertex);
            cleanup.VertexAttached = true;
            api.AttachShader(cleanup.Program, cleanup.Fragment);
            cleanup.FragmentAttached = true;
            api.LinkProgram(cleanup.Program);
            if (api.GetProgramLinkStatus(cleanup.Program) == 0)
                throw new InvalidOperationException(
                    "program link failed: " + api.GetProgramInfoLog(cleanup.Program));
        }
        catch (Exception failure)
        {
            constructionFailure = failure;
        }

        List<Exception> cleanupFailures = cleanup.Release(includeProgram: false);

        if (constructionFailure is null && cleanupFailures.Count == 0)
            return cleanup.TransferProgram();

        cleanupFailures.AddRange(cleanup.ReleaseProgramOnly());

        if (constructionFailure is not null && cleanupFailures.Count == 0)
            ExceptionDispatchInfo.Capture(constructionFailure).Throw();

        var failures = new List<Exception>(cleanupFailures.Count + 1);
        if (constructionFailure is not null)
            failures.Add(constructionFailure);
        failures.AddRange(cleanupFailures);
        const string message =
            "Shader program construction failed and one or more temporary OpenGL names could not be cleanly released.";
        if (!cleanup.IsCleanupComplete)
            throw new GlResourceConstructionException(message, cleanup, failures);
        throw new AggregateException(message, failures);
    }

    private static uint CreateShader(
        IShaderProgramBuildApi api,
        ShaderType type)
    {
        uint shader = api.CreateShader(type);
        if (shader == 0)
            throw new InvalidOperationException($"OpenGL returned no {type} name.");
        return shader;
    }

    private static void Compile(
        IShaderProgramBuildApi api,
        uint shader,
        ShaderType type,
        string source)
    {
        api.ShaderSource(shader, source);
        api.CompileShader(shader);
        if (api.GetShaderCompileStatus(shader) == 0)
            throw new InvalidOperationException(
                $"{type} compile failed: " + api.GetShaderInfoLog(shader));
    }
}