o3de/Gems/Atom/RPI/Code/Include/Atom/RPI.Public/Pass/PassSystem.h

/*
 * Copyright (c) Contributors to the Open 3D Engine Project.
 * For complete copyright and license terms please see the LICENSE at the root of this distribution.
 *
 * SPDX-License-Identifier: Apache-2.0 OR MIT
 *
 */
#pragma once

#include <Atom/RHI.Reflect/Base.h>

#include <Atom/RPI.Public/Pass/ParentPass.h>
#include <Atom/RPI.Public/Pass/Pass.h>
#include <Atom/RPI.Public/Pass/PassLibrary.h>
#include <Atom/RPI.Public/Pass/PassFactory.h>
#include <Atom/RPI.Public/Pass/PassSystemInterface.h>

#include <Atom/RPI.Reflect/Asset/AssetHandler.h>

#include <AzFramework/Windowing/WindowBus.h>

namespace AZ
{
    namespace RHI
    {
        class FrameGraphBuilder;
    }

    namespace RPI
    {
        //! The central class of the pass system.
        //! Responsible for preparing the frame and keeping 
        //! track of which passes need rebuilding or deleting.
        //! Holds the root of the pass hierarchy.
        class PassSystem final
            : public PassSystemInterface
        {
            friend class PassTests;
        public:
            AZ_RTTI(PassSystem, "{6AA45529-53CF-4AEF-86DF-A696C760105B}", PassSystemInterface);
            AZ_CLASS_ALLOCATOR(PassSystem, AZ::SystemAllocator, 0);

            static void Reflect(ReflectContext* context);

            static void GetAssetHandlers(AssetHandlerPtrList& assetHandlers);

            PassSystem();

            AZ_DISABLE_COPY_MOVE(PassSystem);
            
            //! Initializes the PassSystem and the Root Pass and creates the Pass InstanceDatabase
            void Init();

            //! Initialize and load pass templates
            //! This function need to be called after Init()
            void InitPassTemplates();

            //! Deletes the Root Pass and shuts down the PassSystem
            void Shutdown();
            
            //! Called every frame, essentially the 'OnTick' of the pass system
            void FrameUpdate(RHI::FrameGraphBuilder& frameGraphBuilder);

            //! Called after the frame has been rendered. Allows passes to execute post frame logic.
            void FrameEnd();

            // PassSystemInterface functions...
            void ProcessQueuedChanges() override;
            bool LoadPassTemplateMappings(const AZStd::string& templateMappingPath) override;
            void WriteTemplateToFile(const PassTemplate& passTemplate, AZStd::string_view assetFilePath) override;
            void DebugPrintPassHierarchy() override;
            bool IsHotReloading() const override;
            void SetHotReloading(bool hotReloading) override;
            void SetTargetedPassDebuggingName(const AZ::Name& targetPassName) override;
            const AZ::Name& GetTargetedPassDebuggingName() const override;
            void ConnectEvent(OnReadyLoadTemplatesEvent::Handler& handler) override;
            PassSystemState GetState() const override;
            SwapChainPass* FindSwapChainPass(AzFramework::NativeWindowHandle windowHandle) const override;

            // PassSystemInterface statistics related functions
            void IncrementFrameDrawItemCount(u32 numDrawItems) override;
            void IncrementFrameRenderPassCount() override;
            PassSystemFrameStatistics GetFrameStatistics() override;

            // PassSystemInterface factory related functions...
            void AddPassCreator(Name className, PassCreator createFunction) override;
            Ptr<Pass> CreatePassFromClass(Name passClassName, Name passName) override;
            Ptr<Pass> CreatePassFromTemplate(const AZStd::shared_ptr<PassTemplate>& passTemplate, Name passName) override;
            Ptr<Pass> CreatePassFromTemplate(Name templateName, Name passName) override;
            Ptr<Pass> CreatePassFromRequest(const PassRequest* passRequest) override;
            bool HasCreatorForClass(Name passClassName) override;

            // PassSystemInterface library related functions...
            bool HasPassesForTemplateName(const Name& templateName) const override;
            bool AddPassTemplate(const Name& name, const AZStd::shared_ptr<PassTemplate>& passTemplate) override;
            const AZStd::shared_ptr<PassTemplate> GetPassTemplate(const Name& name) const override;
            void RemovePassFromLibrary(Pass* pass) override;
            void RegisterPass(Pass* pass) override;
            void UnregisterPass(Pass* pass) override;
            void ForEachPass(const PassFilter& filter, AZStd::function<PassFilterExecutionFlow(Pass*)> passFunction) override;
            Pass* FindFirstPass(const PassFilter& filter) override;

        private:
            // Returns the root of the pass tree hierarchy
            const Ptr<ParentPass>& GetRootPass() override;

            // Calls Build() on passes queued in m_buildPassList
            void BuildPasses();

            // Calls Initialize() on passes queued in m_initializePassList
            void InitializePasses();

            // Validates Pass Hierarchy after building
            void Validate();

            // Removes queued passes in m_deletePassList from the hierarchy
            void RemovePasses();

            // Functions for queuing passes in the lists below
            void QueueForBuild(Pass* pass) override;
            void QueueForRemoval(Pass* pass) override;
            void QueueForInitialization(Pass* pass) override;

            // Resets the frame statistic counters
            void ResetFrameStatistics();

            // Lists for queuing passes for various function calls
            // Name of the list reflects the pass function it will call
            AZStd::vector< Ptr<Pass> > m_buildPassList;
            AZStd::vector< Ptr<Pass> > m_removePassList;
            AZStd::vector< Ptr<Pass> > m_initializePassList;

            // Library of pass descriptors that can be instantiated through data driven pass requests
            PassLibrary m_passLibrary;

            // Class responsible for creating passes
            PassFactory m_passFactory;

            // The root of the pass tree hierarchy
            Ptr<ParentPass> m_rootPass = nullptr;

            // Whether the Pass Hierarchy changed
            bool m_passHierarchyChanged = true;

            // Whether the Pass System is currently hot reloading passes 
            bool m_isHotReloading = false;

            // Name of the pass targeted for debugging
            AZ::Name m_targetedPassDebugName;

            // Counts the number of passes
            u32 m_passCounter = 0;

            // Events
            OnReadyLoadTemplatesEvent m_loadTemplatesEvent;

            // Used to track what phase of execution the pass system is in
            PassSystemState m_state = PassSystemState::Unitialized;

            // Counters used to gather statistics about the frame
            PassSystemFrameStatistics m_frameStatistics;
        };
    }   // namespace RPI
}   // namespace AZ