XCEngine/engine/src/Rendering/Internal/RenderPipelineFactory.cpp

#include "Rendering/Internal/RenderPipelineFactory.h"

#include "Rendering/Pipelines/BuiltinForwardPipeline.h"
#include "Rendering/Pipelines/ManagedScriptableRenderPipelineAsset.h"
#include "Rendering/Pipelines/ScriptableRenderPipelineHost.h"

#include <mutex>
#include <unordered_map>
#include <unordered_set>

namespace XCEngine {
namespace Rendering {
namespace Internal {

namespace {

std::shared_ptr<const RenderPipelineAsset>
CreateBuiltinForwardPipelineRendererAsset() {
    static const std::shared_ptr<const RenderPipelineAsset>
        s_builtinForwardPipelineAsset =
            std::make_shared<Pipelines::BuiltinForwardPipelineAsset>();
    return s_builtinForwardPipelineAsset;
}

using PipelineRendererAssetRegistry =
    std::unordered_map<std::string, PipelineRendererAssetFactory>;

PipelineRendererAssetRegistry& GetPipelineRendererAssetRegistry() {
    static PipelineRendererAssetRegistry registry = {};
    return registry;
}

std::unordered_set<std::string>& GetBuiltinPipelineRendererAssetKeys() {
    static std::unordered_set<std::string> builtinKeys = {};
    return builtinKeys;
}

std::mutex& GetPipelineRendererAssetRegistryMutex() {
    static std::mutex mutex;
    return mutex;
}

void EnsureBuiltinPipelineRendererAssetRegistryInitialized() {
    static const bool initialized = []() {
        PipelineRendererAssetRegistry& registry =
            GetPipelineRendererAssetRegistry();
        registry.emplace(
            "BuiltinForward",
            &CreateBuiltinForwardPipelineRendererAsset);
        GetBuiltinPipelineRendererAssetKeys().insert("BuiltinForward");
        return true;
    }();
    (void)initialized;
}

std::unique_ptr<NativeSceneRenderer> TryCreateNativeSceneRendererFromAsset(
    const std::shared_ptr<const RenderPipelineAsset>& asset) {
    if (asset == nullptr) {
        return nullptr;
    }

    std::unique_ptr<RenderPipeline> pipeline = asset->CreatePipeline();
    if (pipeline == nullptr) {
        return nullptr;
    }

    NativeSceneRenderer* const sceneRenderer =
        dynamic_cast<NativeSceneRenderer*>(pipeline.get());
    if (sceneRenderer == nullptr) {
        return nullptr;
    }

    (void)pipeline.release();
    return std::unique_ptr<NativeSceneRenderer>(sceneRenderer);
}

} // namespace

std::shared_ptr<const RenderPipelineAsset> CreateConfiguredRenderPipelineAsset() {
    return Pipelines::CreateConfiguredManagedRenderPipelineAsset();
}

std::shared_ptr<const RenderPipelineAsset> CreateFallbackRenderPipelineAsset() {
    return std::make_shared<Pipelines::ScriptableRenderPipelineHostAsset>();
}

bool RegisterPipelineRendererAssetFactory(
    const std::string& key,
    PipelineRendererAssetFactory factory) {
    if (key.empty() || !factory) {
        return false;
    }

    EnsureBuiltinPipelineRendererAssetRegistryInitialized();

    std::lock_guard<std::mutex> lock(
        GetPipelineRendererAssetRegistryMutex());
    PipelineRendererAssetRegistry& registry =
        GetPipelineRendererAssetRegistry();
    if (registry.find(key) != registry.end()) {
        return false;
    }

    registry.emplace(key, std::move(factory));
    return true;
}

bool UnregisterPipelineRendererAssetFactory(const std::string& key) {
    if (key.empty()) {
        return false;
    }

    EnsureBuiltinPipelineRendererAssetRegistryInitialized();

    std::lock_guard<std::mutex> lock(
        GetPipelineRendererAssetRegistryMutex());
    if (GetBuiltinPipelineRendererAssetKeys().find(key) !=
        GetBuiltinPipelineRendererAssetKeys().end()) {
        return false;
    }

    PipelineRendererAssetRegistry& registry =
        GetPipelineRendererAssetRegistry();
    return registry.erase(key) != 0u;
}

std::shared_ptr<const RenderPipelineAsset> CreatePipelineRendererAssetByKey(
    const std::string& key) {
    if (key.empty()) {
        return nullptr;
    }

    EnsureBuiltinPipelineRendererAssetRegistryInitialized();

    std::lock_guard<std::mutex> lock(
        GetPipelineRendererAssetRegistryMutex());
    const PipelineRendererAssetRegistry& registry =
        GetPipelineRendererAssetRegistry();
    const auto it = registry.find(key);
    if (it == registry.end() || !it->second) {
        return nullptr;
    }

    return it->second();
}

std::shared_ptr<const RenderPipelineAsset> ResolveRenderPipelineAssetOrDefault(
    std::shared_ptr<const RenderPipelineAsset> preferredAsset) {
    if (preferredAsset != nullptr) {
        return std::move(preferredAsset);
    }

    if (std::shared_ptr<const RenderPipelineAsset> configuredAsset =
            CreateConfiguredRenderPipelineAsset();
        configuredAsset != nullptr) {
        return configuredAsset;
    }

    return CreateFallbackRenderPipelineAsset();
}

std::unique_ptr<RenderPipeline> CreateRenderPipelineOrDefault(
    const std::shared_ptr<const RenderPipelineAsset>& preferredAsset,
    std::shared_ptr<const RenderPipelineAsset>* outResolvedAsset) {
    const std::shared_ptr<const RenderPipelineAsset> resolvedAsset =
        ResolveRenderPipelineAssetOrDefault(preferredAsset);
    if (resolvedAsset != nullptr) {
        if (std::unique_ptr<RenderPipeline> pipeline =
                resolvedAsset->CreatePipeline()) {
            if (outResolvedAsset != nullptr) {
                *outResolvedAsset = resolvedAsset;
            }
            return pipeline;
        }
    }

    const std::shared_ptr<const RenderPipelineAsset> defaultAsset =
        ResolveRenderPipelineAssetOrDefault(nullptr);
    if (defaultAsset != nullptr &&
        defaultAsset != resolvedAsset) {
        if (std::unique_ptr<RenderPipeline> pipeline =
                defaultAsset->CreatePipeline()) {
            if (outResolvedAsset != nullptr) {
                *outResolvedAsset = defaultAsset;
            }
            return pipeline;
        }
    }

    const std::shared_ptr<const RenderPipelineAsset> fallbackAsset =
        CreateFallbackRenderPipelineAsset();
    if (fallbackAsset != nullptr &&
        fallbackAsset != resolvedAsset &&
        fallbackAsset != defaultAsset) {
        if (std::unique_ptr<RenderPipeline> pipeline =
                fallbackAsset->CreatePipeline()) {
            if (outResolvedAsset != nullptr) {
                *outResolvedAsset = fallbackAsset;
            }
            return pipeline;
        }
    }

    if (outResolvedAsset != nullptr) {
        *outResolvedAsset =
            fallbackAsset != nullptr
                ? fallbackAsset
                : (defaultAsset != nullptr
                    ? defaultAsset
                    : resolvedAsset);
    }
    return std::make_unique<Pipelines::ScriptableRenderPipelineHost>();
}

std::unique_ptr<NativeSceneRenderer> CreateNativeSceneRendererFromAsset(
    const std::shared_ptr<const RenderPipelineAsset>& preferredAsset,
    std::shared_ptr<const RenderPipelineAsset>* outResolvedAsset) {
    if (std::unique_ptr<NativeSceneRenderer> sceneRenderer =
            TryCreateNativeSceneRendererFromAsset(preferredAsset)) {
        if (outResolvedAsset != nullptr) {
            *outResolvedAsset = preferredAsset;
        }
        return sceneRenderer;
    }

    if (outResolvedAsset != nullptr) {
        outResolvedAsset->reset();
    }
    return CreateDefaultNativeSceneRenderer();
}

std::unique_ptr<NativeSceneRenderer> CreateDefaultNativeSceneRenderer() {
    return std::make_unique<Pipelines::BuiltinForwardPipeline>();
}

} // namespace Internal
} // namespace Rendering
} // namespace XCEngine