XCEngine/editor/src/Viewport/ViewportHostService.h

#pragma once

#include "Core/IEditorContext.h"
#include "Core/ISceneManager.h"
#include "Core/ISelectionManager.h"
#include "IViewportHostService.h"
#include "SceneViewportCameraController.h"
#include "UI/ImGuiBackendBridge.h"

#include <XCEngine/Components/CameraComponent.h>
#include <XCEngine/Components/GameObject.h>
#include <XCEngine/RHI/D3D12/D3D12Device.h>
#include <XCEngine/RHI/D3D12/D3D12Texture.h>
#include <XCEngine/RHI/RHIEnums.h>
#include <XCEngine/RHI/RHIResourceView.h>
#include <XCEngine/RHI/RHITexture.h>
#include <XCEngine/Rendering/RenderContext.h>
#include <XCEngine/Rendering/RenderSurface.h>
#include <XCEngine/Rendering/SceneRenderer.h>
#include <XCEngine/Scene/Scene.h>

#include <array>
#include <cstdint>
#include <memory>
#include <string>

namespace XCEngine {
namespace Editor {

class ViewportHostService : public IViewportHostService {
public:
    void Initialize(UI::ImGuiBackendBridge& backend, RHI::RHIDevice* device) {
        Shutdown();
        m_backend = &backend;
        m_device = device ? static_cast<RHI::D3D12Device*>(device) : nullptr;
    }

    void Shutdown() {
        for (ViewportEntry& entry : m_entries) {
            DestroyViewportResources(entry);
            entry = {};
        }

        m_sceneViewCamera = {};
        m_device = nullptr;
        m_backend = nullptr;
        m_sceneRenderer.reset();
    }

    void BeginFrame() override {
        for (ViewportEntry& entry : m_entries) {
            entry.requestedThisFrame = false;
            entry.requestedWidth = 0;
            entry.requestedHeight = 0;
        }
    }

    EditorViewportFrame RequestViewport(EditorViewportKind kind, const ImVec2& requestedSize) override {
        ViewportEntry& entry = GetEntry(kind);
        entry.requestedThisFrame = requestedSize.x > 1.0f && requestedSize.y > 1.0f;
        entry.requestedWidth = entry.requestedThisFrame
            ? static_cast<uint32_t>(requestedSize.x)
            : 0u;
        entry.requestedHeight = entry.requestedThisFrame
            ? static_cast<uint32_t>(requestedSize.y)
            : 0u;

        if (entry.requestedThisFrame && m_backend != nullptr && m_device != nullptr) {
            EnsureViewportResources(entry);
        }

        EditorViewportFrame frame = {};
        frame.textureId = entry.textureId;
        frame.requestedSize = requestedSize;
        frame.renderSize = ImVec2(static_cast<float>(entry.width), static_cast<float>(entry.height));
        frame.hasTexture = entry.textureId != ImTextureID{};
        frame.wasRequested = entry.requestedThisFrame;
        frame.statusText = entry.statusText;
        return frame;
    }

    void UpdateSceneViewInput(IEditorContext& context, const SceneViewportInput& input) override {
        if (!EnsureSceneViewCamera()) {
            return;
        }

        if (input.focusSelectionRequested) {
            FocusSceneView(context);
        }

        SceneViewportCameraInputState controllerInput = {};
        controllerInput.viewportHeight = input.viewportSize.y;
        controllerInput.zoomDelta = input.hovered ? input.mouseWheel : 0.0f;
        controllerInput.deltaTime = input.deltaTime;
        controllerInput.moveForward = input.moveForward;
        controllerInput.moveRight = input.moveRight;
        controllerInput.moveUp = input.moveUp;
        controllerInput.fastMove = input.fastMove;

        if (input.looking) {
            controllerInput.lookDeltaX = input.mouseDelta.x;
            controllerInput.lookDeltaY = input.mouseDelta.y;
        }

        if (input.orbiting) {
            controllerInput.orbitDeltaX = input.mouseDelta.x;
            controllerInput.orbitDeltaY = input.mouseDelta.y;
        }

        if (input.panning) {
            controllerInput.panDeltaX = input.mouseDelta.x;
            controllerInput.panDeltaY = input.mouseDelta.y;
        }

        m_sceneViewCamera.controller.ApplyInput(controllerInput);
        ApplySceneViewCameraController();
    }

    SceneViewportOverlayData GetSceneViewOverlayData() const override {
        SceneViewportOverlayData data = {};
        if (m_sceneViewCamera.gameObject == nullptr || m_sceneViewCamera.camera == nullptr) {
            return data;
        }

        const Components::TransformComponent* transform = m_sceneViewCamera.gameObject->GetTransform();
        if (transform == nullptr) {
            return data;
        }

        data.valid = true;
        data.cameraPosition = transform->GetPosition();
        data.cameraForward = transform->GetForward();
        data.cameraRight = transform->GetRight();
        data.cameraUp = transform->GetUp();
        data.verticalFovDegrees = m_sceneViewCamera.camera->GetFieldOfView();
        data.nearClipPlane = m_sceneViewCamera.camera->GetNearClipPlane();
        data.farClipPlane = m_sceneViewCamera.camera->GetFarClipPlane();
        data.orbitDistance = m_sceneViewCamera.controller.GetDistance();
        return data;
    }

    void RenderRequestedViewports(
        IEditorContext& context,
        const Rendering::RenderContext& renderContext) override {
        if (m_backend == nullptr || m_device == nullptr || !renderContext.IsValid()) {
            return;
        }

        EnsureSceneRenderer();
        const auto* scene = context.GetSceneManager().GetScene();

        for (ViewportEntry& entry : m_entries) {
            if (!entry.requestedThisFrame) {
                continue;
            }

            if (!EnsureViewportResources(entry)) {
                entry.statusText = "Failed to create viewport render targets";
                continue;
            }

            RenderViewportEntry(entry, scene, renderContext);
        }
    }

private:
    struct ViewportEntry {
        EditorViewportKind kind = EditorViewportKind::Scene;
        uint32_t width = 0;
        uint32_t height = 0;
        uint32_t requestedWidth = 0;
        uint32_t requestedHeight = 0;
        bool requestedThisFrame = false;
        RHI::RHITexture* colorTexture = nullptr;
        RHI::RHIResourceView* colorView = nullptr;
        RHI::RHITexture* depthTexture = nullptr;
        RHI::RHIResourceView* depthView = nullptr;
        D3D12_CPU_DESCRIPTOR_HANDLE imguiCpuHandle = {};
        D3D12_GPU_DESCRIPTOR_HANDLE imguiGpuHandle = {};
        ImTextureID textureId = {};
        RHI::ResourceStates colorState = RHI::ResourceStates::Common;
        std::string statusText;
    };

    struct SceneViewCameraState {
        std::unique_ptr<Components::GameObject> gameObject;
        Components::CameraComponent* camera = nullptr;
        SceneViewportCameraController controller;
    };

    ViewportEntry& GetEntry(EditorViewportKind kind) {
        const size_t index = kind == EditorViewportKind::Scene ? 0u : 1u;
        m_entries[index].kind = kind;
        return m_entries[index];
    }

    void EnsureSceneRenderer() {
        if (!m_sceneRenderer) {
            m_sceneRenderer = std::make_unique<Rendering::SceneRenderer>();
        }
    }

    bool EnsureSceneViewCamera() {
        if (m_sceneViewCamera.gameObject != nullptr && m_sceneViewCamera.camera != nullptr) {
            return true;
        }

        m_sceneViewCamera.gameObject = std::make_unique<Components::GameObject>("EditorSceneCamera");
        m_sceneViewCamera.camera = m_sceneViewCamera.gameObject->AddComponent<Components::CameraComponent>();
        if (m_sceneViewCamera.camera == nullptr) {
            m_sceneViewCamera.gameObject.reset();
            return false;
        }

        m_sceneViewCamera.camera->SetPrimary(false);
        m_sceneViewCamera.camera->SetProjectionType(Components::CameraProjectionType::Perspective);
        m_sceneViewCamera.camera->SetFieldOfView(60.0f);
        m_sceneViewCamera.camera->SetNearClipPlane(0.03f);
        m_sceneViewCamera.camera->SetFarClipPlane(2000.0f);
        m_sceneViewCamera.controller.Reset();
        ApplySceneViewCameraController();
        return true;
    }

    void ApplySceneViewCameraController() {
        if (m_sceneViewCamera.gameObject == nullptr) {
            return;
        }

        m_sceneViewCamera.controller.ApplyTo(*m_sceneViewCamera.gameObject->GetTransform());
    }

    void FocusSceneView(IEditorContext& context) {
        Components::GameObject* target = nullptr;
        const uint64_t selectedEntity = context.GetSelectionManager().GetSelectedEntity();
        if (selectedEntity != 0) {
            target = context.GetSceneManager().GetEntity(selectedEntity);
        }

        if (target != nullptr) {
            m_sceneViewCamera.controller.Focus(target->GetTransform()->GetPosition());
            return;
        }

        const auto& roots = context.GetSceneManager().GetRootEntities();
        if (roots.empty()) {
            m_sceneViewCamera.controller.Focus(Math::Vector3::Zero());
            return;
        }

        Math::Vector3 center = Math::Vector3::Zero();
        uint32_t count = 0;
        for (const Components::GameObject* root : roots) {
            if (root == nullptr) {
                continue;
            }

            center += root->GetTransform()->GetPosition();
            ++count;
        }

        if (count > 0) {
            center /= static_cast<float>(count);
        }

        m_sceneViewCamera.controller.Focus(center);
    }

    bool EnsureViewportResources(ViewportEntry& entry) {
        if (entry.requestedWidth == 0 || entry.requestedHeight == 0) {
            return false;
        }

        if (entry.width == entry.requestedWidth &&
            entry.height == entry.requestedHeight &&
            entry.colorTexture != nullptr &&
            entry.colorView != nullptr &&
            entry.depthTexture != nullptr &&
            entry.depthView != nullptr &&
            entry.textureId != ImTextureID{}) {
            return true;
        }

        DestroyViewportResources(entry);

        entry.width = entry.requestedWidth;
        entry.height = entry.requestedHeight;

        RHI::TextureDesc colorDesc = {};
        colorDesc.width = entry.width;
        colorDesc.height = entry.height;
        colorDesc.depth = 1;
        colorDesc.mipLevels = 1;
        colorDesc.arraySize = 1;
        colorDesc.format = static_cast<uint32_t>(RHI::Format::R8G8B8A8_UNorm);
        colorDesc.textureType = static_cast<uint32_t>(RHI::TextureType::Texture2D);
        colorDesc.sampleCount = 1;
        colorDesc.sampleQuality = 0;
        colorDesc.flags = 0;
        entry.colorTexture = m_device->CreateTexture(colorDesc);
        if (entry.colorTexture == nullptr) {
            DestroyViewportResources(entry);
            return false;
        }

        RHI::ResourceViewDesc colorViewDesc = {};
        colorViewDesc.format = static_cast<uint32_t>(RHI::Format::R8G8B8A8_UNorm);
        colorViewDesc.dimension = RHI::ResourceViewDimension::Texture2D;
        entry.colorView = m_device->CreateRenderTargetView(entry.colorTexture, colorViewDesc);
        if (entry.colorView == nullptr) {
            DestroyViewportResources(entry);
            return false;
        }

        RHI::TextureDesc depthDesc = {};
        depthDesc.width = entry.width;
        depthDesc.height = entry.height;
        depthDesc.depth = 1;
        depthDesc.mipLevels = 1;
        depthDesc.arraySize = 1;
        depthDesc.format = static_cast<uint32_t>(RHI::Format::D24_UNorm_S8_UInt);
        depthDesc.textureType = static_cast<uint32_t>(RHI::TextureType::Texture2D);
        depthDesc.sampleCount = 1;
        depthDesc.sampleQuality = 0;
        depthDesc.flags = 0;
        entry.depthTexture = m_device->CreateTexture(depthDesc);
        if (entry.depthTexture == nullptr) {
            DestroyViewportResources(entry);
            return false;
        }

        RHI::ResourceViewDesc depthViewDesc = {};
        depthViewDesc.format = static_cast<uint32_t>(RHI::Format::D24_UNorm_S8_UInt);
        depthViewDesc.dimension = RHI::ResourceViewDimension::Texture2D;
        entry.depthView = m_device->CreateDepthStencilView(entry.depthTexture, depthViewDesc);
        if (entry.depthView == nullptr) {
            DestroyViewportResources(entry);
            return false;
        }

        m_backend->AllocateTextureDescriptor(&entry.imguiCpuHandle, &entry.imguiGpuHandle);
        if (entry.imguiCpuHandle.ptr == 0 || entry.imguiGpuHandle.ptr == 0) {
            DestroyViewportResources(entry);
            return false;
        }

        auto* nativeTexture = static_cast<RHI::D3D12Texture*>(entry.colorTexture);
        D3D12_SHADER_RESOURCE_VIEW_DESC srvDesc = {};
        srvDesc.Shader4ComponentMapping = D3D12_DEFAULT_SHADER_4_COMPONENT_MAPPING;
        srvDesc.Format = DXGI_FORMAT_R8G8B8A8_UNORM;
        srvDesc.ViewDimension = D3D12_SRV_DIMENSION_TEXTURE2D;
        srvDesc.Texture2D.MipLevels = 1;
        m_device->GetDevice()->CreateShaderResourceView(
            nativeTexture->GetResource(),
            &srvDesc,
            entry.imguiCpuHandle);

        entry.textureId = static_cast<ImTextureID>(entry.imguiGpuHandle.ptr);
        entry.colorState = RHI::ResourceStates::Common;
        return true;
    }

    Rendering::RenderSurface BuildSurface(const ViewportEntry& entry) const {
        Rendering::RenderSurface surface(entry.width, entry.height);
        surface.SetColorAttachment(entry.colorView);
        surface.SetDepthAttachment(entry.depthView);
        surface.SetColorStateBefore(entry.colorState);
        surface.SetColorStateAfter(RHI::ResourceStates::PixelShaderResource);
        return surface;
    }

    void RenderViewportEntry(
        ViewportEntry& entry,
        const Components::Scene* scene,
        const Rendering::RenderContext& renderContext) {
        if (entry.colorView == nullptr || entry.depthView == nullptr) {
            entry.statusText = "Viewport render target is unavailable";
            return;
        }

        if (scene == nullptr) {
            entry.statusText = "No active scene";
            ClearViewport(entry, renderContext, 0.07f, 0.08f, 0.10f, 1.0f);
            return;
        }

        Rendering::RenderSurface surface = BuildSurface(entry);

        if (entry.kind == EditorViewportKind::Scene) {
            if (!EnsureSceneViewCamera()) {
                entry.statusText = "Scene view camera is unavailable";
                ClearViewport(entry, renderContext, 0.18f, 0.07f, 0.07f, 1.0f);
                return;
            }

            ApplySceneViewCameraController();
            if (!m_sceneRenderer->Render(*scene, m_sceneViewCamera.camera, renderContext, surface)) {
                entry.statusText = "Scene renderer failed";
                ClearViewport(entry, renderContext, 0.18f, 0.07f, 0.07f, 1.0f);
                return;
            }

            entry.colorState = RHI::ResourceStates::PixelShaderResource;
            entry.statusText.clear();
            return;
        }

        const auto cameras = scene->FindObjectsOfType<Components::CameraComponent>();
        if (cameras.empty()) {
            entry.statusText = "No camera in scene";
            ClearViewport(entry, renderContext, 0.10f, 0.09f, 0.08f, 1.0f);
            return;
        }

        if (!m_sceneRenderer->Render(*scene, nullptr, renderContext, surface)) {
            entry.statusText = "Scene renderer failed";
            ClearViewport(entry, renderContext, 0.18f, 0.07f, 0.07f, 1.0f);
            return;
        }

        entry.colorState = RHI::ResourceStates::PixelShaderResource;
        entry.statusText.clear();
    }

    void ClearViewport(
        ViewportEntry& entry,
        const Rendering::RenderContext& renderContext,
        float r,
        float g,
        float b,
        float a) {
        RHI::RHICommandList* commandList = renderContext.commandList;
        if (commandList == nullptr) {
            entry.statusText = "Viewport command list is unavailable";
            return;
        }

        const float clearColor[4] = { r, g, b, a };
        RHI::RHIResourceView* colorView = entry.colorView;
        commandList->TransitionBarrier(
            colorView,
            entry.colorState,
            RHI::ResourceStates::RenderTarget);
        commandList->SetRenderTargets(1, &colorView, entry.depthView);
        commandList->ClearRenderTarget(colorView, clearColor);
        commandList->ClearDepthStencil(entry.depthView, 1.0f, 0);
        commandList->TransitionBarrier(
            colorView,
            RHI::ResourceStates::RenderTarget,
            RHI::ResourceStates::PixelShaderResource);
        entry.colorState = RHI::ResourceStates::PixelShaderResource;
    }

    void DestroyViewportResources(ViewportEntry& entry) {
        if (m_backend != nullptr && entry.imguiCpuHandle.ptr != 0) {
            m_backend->FreeTextureDescriptor(entry.imguiCpuHandle, entry.imguiGpuHandle);
        }

        if (entry.depthView != nullptr) {
            entry.depthView->Shutdown();
            delete entry.depthView;
            entry.depthView = nullptr;
        }

        if (entry.depthTexture != nullptr) {
            entry.depthTexture->Shutdown();
            delete entry.depthTexture;
            entry.depthTexture = nullptr;
        }

        if (entry.colorView != nullptr) {
            entry.colorView->Shutdown();
            delete entry.colorView;
            entry.colorView = nullptr;
        }

        if (entry.colorTexture != nullptr) {
            entry.colorTexture->Shutdown();
            delete entry.colorTexture;
            entry.colorTexture = nullptr;
        }

        entry.width = 0;
        entry.height = 0;
        entry.imguiCpuHandle = {};
        entry.imguiGpuHandle = {};
        entry.textureId = {};
        entry.colorState = RHI::ResourceStates::Common;
    }

    UI::ImGuiBackendBridge* m_backend = nullptr;
    RHI::D3D12Device* m_device = nullptr;
    std::unique_ptr<Rendering::SceneRenderer> m_sceneRenderer;
    std::array<ViewportEntry, 2> m_entries = {};
    SceneViewCameraState m_sceneViewCamera;
};

} // namespace Editor
} // namespace XCEngine