Threading.h

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/** @noop License Comment
 *  @file
 *  @copyright
 *  This Source Code is subject to the terms of the Mozilla Public License, v2.0.
 *  If a copy of the MPL was not distributed with this file You can obtain one at
 *  https://mozilla.org/MPL/2.0/
 *  
 *  @author David Mórász
 *  @date 2025
 */
 
#pragma once
 
#include "CoreMinimal.h"
#include "Mcro/FunctionTraits.h"
#include "Mcro/SharedObjects.h"
 
namespace Mcro::Threading
{
    using namespace Mcro::FunctionTraits;
    using namespace Mcro::SharedObjects;
 
    /**
     *  Returns true when called in the thread which is associated with the given ENamedThreads.
     *  If there's no such a thread or if this function is not called in that thread, return false.
     */
    MCRO_API bool IsInThread(ENamedThreads::Type threadName);
 
    namespace Detail
    {
        MCRO_API auto GetThreadCheck(ENamedThreads::Type threadName) -> bool(*)();
 
        template <CFunctionLike When>
        requires (TFunction_ArgCount<When> == 0)
        void RunInThreadBoilerplate(
            ENamedThreads::Type threadName,
            TUniqueFunction<void()>&& func, When&& when
        ) {
            if (IsInThread(threadName)) func();
            else AsyncTask(threadName, [when = MoveTemp(when), func = MoveTemp(func)]
            {
                if (auto keep = when()) func();
            });
        }
 
        template <CFunctionLike When>
        requires (TFunction_ArgCount<When> == 0)
        void EnqueueRenderCommandBoilerplate(TUniqueFunction<void(FRHICommandListImmediate&)>&& func, When&& when)
        {
            if (IsInRenderingThread()) func(GetImmediateCommandList_ForRenderCommand());
            else
            {
                ENQUEUE_RENDER_COMMAND(FMcroThreading)([when = MoveTemp(when), func = MoveTemp(func)](FRHICommandListImmediate& cmdList)
                {
                    if (auto keep = when()) func(cmdList);
                });
            }
        }
 
        template <CFunctorObject Function, typename Result = TFunction_Return<Function>, CFunctionLike When>
        requires (
            TFunction_ArgCount<Function> == 0
            && TFunction_ArgCount<When> == 0
        )
        TFuture<Result> PromiseInThreadBoilerplate(
            ENamedThreads::Type threadName,
            Function&& func,
            When&& when
        ) {
            if (IsInThread(threadName))
                return MakeFulfilledPromise<Result>(func()).GetFuture();
 
            TPromise<Result> promise;
            auto future = promise.GetFuture();
            
            AsyncTask(threadName, [when = MoveTemp(when), func = MoveTemp(func), promise = MoveTemp(promise)]() mutable 
            {
                if (auto keep = when()) promise.SetValue(func());
                else promise.SetValue({});
            });
            return future;
        }
 
        template <CFunctorObject Function, typename Result = TFunction_Return<Function>, CFunctionLike When>
        requires (
            TFunction_ArgCount<Function> == 1
            && CSameAs<FRHICommandListImmediate&, TFunction_Arg<Function, 0>>
            && TFunction_ArgCount<When> == 0
        )
        TFuture<Result> EnqueueRenderPromiseBoilerplate(
            ENamedThreads::Type threadName,
            Function&& func,
            When&& when
        ) {
            if (IsInRenderingThread())
                return MakeFulfilledPromise<Result>(func(GetImmediateCommandList_ForRenderCommand())).GetFuture();
 
            TPromise<Result> promise;
            auto future = promise.GetFuture();
            
            ENQUEUE_RENDER_COMMAND(FMcroThreading)([when = MoveTemp(when), func = MoveTemp(func), promise = MoveTemp(promise)](FRHICommandListImmediate& cmdList) mutable 
            {
                if (auto keep = when())
                    promise.SetValue(func(cmdList));
                else promise.SetValue({});
            });
            return future;
        }
    }
    
    /** Simply run a lambda function on the selected thread but only use AsyncTask if it's not on the selected thread already */
    MCRO_API void RunInThread(ENamedThreads::Type threadName, TUniqueFunction<void()>&& func);
    
    /**
     *  Simply run a lambda function on the selected thread but only use AsyncTask if it's not on the selected thread
     *  already check the validity of a target object first before running on the selected thread.
     */
    MCRO_API void RunInThread(ENamedThreads::Type threadName, const UObject* boundToObject, TUniqueFunction<void()>&& func);
    
    /**
     * Simply run a lambda function on the selected thread but only use AsyncTask if it's not on the selected thread
     * already check the validity of a target object first before running on the selected thread.
     */
    MCRO_API void RunInThread(ENamedThreads::Type threadName, const FWeakObjectPtr& boundToObject, TUniqueFunction<void()>&& func);
    
    /** Simply run a lambda function on the game thread but only use AsyncTask if it's not on the game thread already */
    MCRO_API void RunInGameThread(TUniqueFunction<void()>&& func);
    
    /**
     * Simply run a lambda function on the game thread but only use AsyncTask if it's not on the game thread already
     * Check the validity of a target object first before running on the game thread.
     */
    MCRO_API void RunInGameThread(const UObject* boundToObject, TUniqueFunction<void()>&& func);
    
    /**
     * Simply run a lambda function on the game thread but only use AsyncTask if it's not on the game thread already
     * Check the validity of a target object first before running on the game thread.
     */
    MCRO_API void RunInGameThread(const FWeakObjectPtr& boundToObject, TUniqueFunction<void()>&& func);
    
    /** Simply run a lambda function on the render thread but only use AsyncTask if it's not on the render thread already */
    MCRO_API void EnqueueRenderCommand(TUniqueFunction<void(FRHICommandListImmediate&)>&& func);
    
    /**
     * Simply run a lambda function on the render thread but only use AsyncTask if it's not on the render thread already
     * Check the validity of a target object first before running on the render thread.
     */
    MCRO_API void EnqueueRenderCommand(const UObject* boundToObject, TUniqueFunction<void(FRHICommandListImmediate&)>&& func);
    
    /**
     * Simply run a lambda function on the render thread but only use AsyncTask if it's not on the render thread already
     * Check the validity of a target object first before running on the render thread.
     */
    MCRO_API void EnqueueRenderCommand(const FWeakObjectPtr& boundToObject, TUniqueFunction<void(FRHICommandListImmediate&)>&& func);
 
    /**
     * Simply run a lambda function on the selected thread but only use AsyncTask if it's not on the selected thread
     * already Check the validity of a target object first before running on the selected thread.
     */
    template <CSharedOrWeak Object>
    void RunInThread(ENamedThreads::Type threadName, const Object& boundToObject, TUniqueFunction<void()>&& func)
    {
        TWeakPtrFrom<Object> weakObject(boundToObject);
        Detail::RunInThreadBoilerplate(threadName, MoveTemp(func), [weakObject = MoveTemp(weakObject)]
        {
            return weakObject.Pin();
        });
    }
 
    /**
     * Simply run a lambda function on the game thread but only use AsyncTask if it's not on the game thread already
     * Check the validity of a target object first before running on the game thread.
     */
    template <CSharedOrWeak Object>
    void RunInGameThread(const Object& boundToObject, TUniqueFunction<void()>&& func)
    {
        RunInThread<Object>(ENamedThreads::GameThread, boundToObject, MoveTemp(func));
    }
    
    /**
     * Simply run a lambda function on the game thread but only use AsyncTask if it's not on the game thread already
     * Check the validity of a target object first before running on the game thread.
     */
    template <CSharedOrWeak Object>
    void EnqueueRenderCommand(const Object& boundToObject, TUniqueFunction<void(FRHICommandListImmediate&)>&& func)
    {
        TWeakPtrFrom<Object> weakObject(boundToObject);
        Detail::EnqueueRenderCommandBoilerplate(MoveTemp(func), [weakObject = MoveTemp(weakObject)]
        {
            return weakObject.Pin();
        });
    }
 
    /**
     * Simply run a lambda function on the selected thread but only use AsyncTask if it's not on the selected thread
     * already This overload doesn't check object lifespans.
     */
    template <
        CFunctorObject Function,
        typename Result = TFunction_Return<Function>
    >
    requires (TFunction_ArgCount<Function> == 0)
    TFuture<Result> PromiseInThread(ENamedThreads::Type threadName, Function&& func)
    {
        return Detail::PromiseInThreadBoilerplate(threadName, MoveTemp(func), []{ return true; });
    }
 
    /**
     * Simply run a lambda function on the selected thread but only use AsyncTask if it's not on the selected thread
     * already Check the validity of a target object first before running on the selected thread.
     */
    template <
        CSharedOrWeak Object,
        CFunctorObject Function,
        typename Result = TFunction_Return<Function>
    >
    requires (TFunction_ArgCount<Function> == 0)
    TFuture<Result> PromiseInThread(ENamedThreads::Type threadName, const Object& boundToObject, Function&& func)
    {
        TWeakPtrFrom<Object> weakObject(boundToObject);
        return Detail::PromiseInThreadBoilerplate(threadName, MoveTemp(func), [weakObject = MoveTemp(weakObject)]
        {
            return weakObject.Pin();
        });
    }
 
    /**
     * Simply run a lambda function on the selected thread but only use AsyncTask if it's not on the selected thread
     * already Check the validity of a target object first before running on the selected thread.
     */
    template <
        CUObject Object,
        CFunctorObject Function,
        typename Result = TFunction_Return<Function>
    >
    requires (TFunction_ArgCount<Function> == 0)
    TFuture<Result> PromiseInThread(ENamedThreads::Type threadName, const Object* boundToObject, Function&& func)
    {
        return Detail::PromiseInThreadBoilerplate(threadName, MoveTemp(func), [boundToObject]
        {
            return IsValid(boundToObject) ? TStrongObjectPtr(boundToObject) : nullptr;
        });
    }
 
    /**
     * Simply run a lambda function on the game thread but only use AsyncTask if it's not on the game thread already
     * This overload doesn't check object lifespans.
     */
    template <
        CFunctorObject Function,
        typename Result = TFunction_Return<Function>
    >
    requires (TFunction_ArgCount<Function> == 0)
    TFuture<Result> PromiseInGameThread(Function&& func)
    {
        return Detail::PromiseInThreadBoilerplate(ENamedThreads::GameThread, MoveTemp(func), []{ return true; });
    }
 
    /**
     * Simply run a lambda function on the game thread but only use AsyncTask if it's not on the game thread already
     * Check the validity of a target object first before running on the game thread.
     */
    template <
        CSharedOrWeak Object,
        CFunctorObject Function,
        typename Result = TFunction_Return<Function>
    >
    requires (TFunction_ArgCount<Function> == 0)
    TFuture<Result> PromiseInGameThread(const Object& boundToObject, Function&& func)
    {
        TWeakPtrFrom<Object> weakObject(boundToObject);
        return Detail::PromiseInThreadBoilerplate(ENamedThreads::GameThread, MoveTemp(func), [weakObject = MoveTemp(weakObject)]
        {
            return weakObject.Pin();
        });
    }
 
    /**
     * Simply run a lambda function on the game thread but only use AsyncTask if it's not on the game thread already
     * Check the validity of a target object first before running on the game thread.
     */
    template <
        CUObject Object,
        CFunctorObject Function,
        typename Result = TFunction_Return<Function>
    >
    requires (TFunction_ArgCount<Function> == 0)
    TFuture<Result> PromiseInGameThread(const Object* boundToObject, Function&& func)
    {
        return Detail::PromiseInThreadBoilerplate(ENamedThreads::GameThread, MoveTemp(func), [boundToObject]
        {
            return IsValid(boundToObject) ? TStrongObjectPtr(boundToObject) : nullptr;
        });
    }
 
    /**
     * Simply run a lambda function on the render thread but only use AsyncTask if it's not on the render thread already
     * This overload doesn't check object lifespans.
     */
    template <
        CFunctorObject Function,
        typename Result = TFunction_Return<Function>
    >
    requires (
        TFunction_ArgCount<Function> == 1
        && CSameAs<FRHICommandListImmediate&, TFunction_Arg<Function, 0>>
    )
    TFuture<Result> EnqueueRenderPromise(Function&& func)
    {
        return Detail::EnqueueRenderPromiseBoilerplate(ENamedThreads::GameThread, MoveTemp(func), []{ return true; });
    }
 
    /**
     * Simply run a lambda function on the render thread but only use AsyncTask if it's not on the render thread already
     * Check the validity of a target object first before running on the render thread.
     */
    template <
        CSharedOrWeak Object,
        CFunctorObject Function,
        typename Result = TFunction_Return<Function>
    >
    requires (
        TFunction_ArgCount<Function> == 1
        && CSameAs<FRHICommandListImmediate&, TFunction_Arg<Function, 0>>
    )
    TFuture<Result> EnqueueRenderPromise(const Object& boundToObject, Function&& func)
    {
        TWeakPtrFrom<Object> weakObject(boundToObject);
        return Detail::EnqueueRenderPromiseBoilerplate(ENamedThreads::GameThread, MoveTemp(func), [weakObject = MoveTemp(weakObject)]
        {
            return weakObject.Pin();
        });
    }
 
    /**
     * Simply run a lambda function on the render thread but only use AsyncTask if it's not on the render thread already
     * Check the validity of a target object first before running on the render thread.
     */
    template <
        CUObject Object,
        CFunctorObject Function,
        typename Result = TFunction_Return<Function>
    >
    requires (
        TFunction_ArgCount<Function> == 1
        && CSameAs<FRHICommandListImmediate&, TFunction_Arg<Function, 0>>
    )
    TFuture<Result> EnqueueRenderPromise(const Object* boundToObject, Function&& func)
    {
        return Detail::EnqueueRenderPromiseBoilerplate(ENamedThreads::GameThread, MoveTemp(func), [boundToObject]
        {
            return IsValid(boundToObject) ? TStrongObjectPtr(boundToObject) : nullptr;
        });
    }
}