XCEngine/editor/src/Viewport/ViewportHostService.h

#pragma once

#include "Core/IEditorContext.h"
#include "Core/ISceneManager.h"
#include "Core/ISelectionManager.h"
#include "IViewportHostService.h"
#include "SceneViewportPicker.h"
#include "SceneViewportCameraController.h"
#include "ViewportHostRenderFlowUtils.h"
#include "ViewportHostRenderTargets.h"
#include "ViewportObjectIdPicker.h"
#include "UI/ImGuiBackendBridge.h"

#include <XCEngine/Components/CameraComponent.h>
#include <XCEngine/Components/GameObject.h>
#include <XCEngine/Core/Asset/ResourceManager.h>
#include <XCEngine/RHI/RHIDevice.h>
#include <XCEngine/RHI/RHIEnums.h>
#include <XCEngine/RHI/RHIResourceView.h>
#include <XCEngine/RHI/RHITexture.h>
#include <XCEngine/Rendering/Passes/BuiltinInfiniteGridPass.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>
#include <vector>

namespace XCEngine {
namespace Editor {

namespace {

constexpr bool kDebugSceneSelectionMask = false;

Math::Vector3 GetSceneViewportOrientationAxisVector(SceneViewportOrientationAxis axis) {
    switch (axis) {
    case SceneViewportOrientationAxis::PositiveX:
        return Math::Vector3::Right();
    case SceneViewportOrientationAxis::NegativeX:
        return Math::Vector3::Left();
    case SceneViewportOrientationAxis::PositiveY:
        return Math::Vector3::Up();
    case SceneViewportOrientationAxis::NegativeY:
        return Math::Vector3::Down();
    case SceneViewportOrientationAxis::PositiveZ:
        return Math::Vector3::Forward();
    case SceneViewportOrientationAxis::NegativeZ:
        return Math::Vector3::Back();
    default:
        return Math::Vector3::Zero();
    }
}

} // namespace

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

    void Shutdown() {
        for (ViewportEntry& entry : m_entries) {
            DestroyViewportRenderTargets(m_backend, entry.renderTargets);
            entry = {};
        }

        m_sceneViewCamera = {};
        m_sceneViewLastRenderContext = {};
        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.renderTargets.textureId;
        frame.requestedSize = requestedSize;
        frame.renderSize = ImVec2(
            static_cast<float>(entry.renderTargets.width),
            static_cast<float>(entry.renderTargets.height));
        frame.hasTexture = entry.renderTargets.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.flySpeedDelta = input.hovered ? input.flySpeedDelta : 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();
    }

    uint64_t PickSceneViewEntity(
        IEditorContext& context,
        const ImVec2& viewportSize,
        const ImVec2& viewportMousePosition) override {
        if (!EnsureSceneViewCamera()) {
            return 0;
        }

        const Components::Scene* scene = context.GetSceneManager().GetScene();
        if (scene == nullptr) {
            return 0;
        }

        ViewportEntry& entry = GetEntry(EditorViewportKind::Scene);
        uint64_t objectIdEntity = 0;
        if (TryPickSceneViewEntityWithObjectId(
                entry,
                viewportSize,
                viewportMousePosition,
                objectIdEntity)) {
            return objectIdEntity;
        }

        SceneViewportPickRequest request = {};
        request.scene = scene;
        request.overlay = GetSceneViewOverlayData();
        request.viewportSize = Math::Vector2(viewportSize.x, viewportSize.y);
        request.viewportPosition = Math::Vector2(viewportMousePosition.x, viewportMousePosition.y);
        return PickSceneViewportEntity(request).entityId;
    }

    void AlignSceneViewToOrientationAxis(SceneViewportOrientationAxis axis) override {
        if (!EnsureSceneViewCamera()) {
            return;
        }

        const Math::Vector3 axisDirection = GetSceneViewportOrientationAxisVector(axis);
        if (axisDirection.SqrMagnitude() <= Math::EPSILON) {
            return;
        }

        // To make the clicked cone face the screen, the camera must look back along that axis.
        m_sceneViewCamera.controller.AnimateToForward(axisDirection * -1.0f);
        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();
        m_sceneViewLastRenderContext = renderContext;
        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, context, scene, renderContext);
        }
    }

private:
    struct ViewportEntry {
        EditorViewportKind kind = EditorViewportKind::Scene;
        uint32_t requestedWidth = 0;
        uint32_t requestedHeight = 0;
        bool requestedThisFrame = false;
        ViewportRenderTargets renderTargets = {};
        std::string statusText;
    };

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

    struct SceneViewportRenderState {
        SceneViewportOverlayData overlay = {};
        Rendering::BuiltinPostProcessRequest builtinPostProcess = {};
        std::vector<uint64_t> selectedObjectIds;
    };

    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) {
        const ViewportHostResourceReuseQuery reuseQuery =
            BuildViewportRenderTargetsReuseQuery(
                entry.kind,
                entry.renderTargets,
                entry.requestedWidth,
                entry.requestedHeight);
        if (CanReuseViewportResources(reuseQuery)) {
            return true;
        }

        if (entry.requestedWidth == 0 || entry.requestedHeight == 0) {
            return false;
        }

        return CreateViewportRenderTargets(
            entry.kind,
            entry.requestedWidth,
            entry.requestedHeight,
            m_device,
            m_backend,
            entry.renderTargets);
    }

    Rendering::RenderSurface BuildSurface(const ViewportEntry& entry) const {
        return BuildViewportColorSurface(entry.renderTargets);
    }

    void ApplyViewportRenderFailure(
        ViewportEntry& entry,
        const Rendering::RenderContext& renderContext,
        const ViewportRenderFallbackPolicy& policy) {
        ApplyViewportFailureStatus(entry.statusText, policy);
        if (policy.invalidateObjectIdFrame) {
            InvalidateViewportObjectIdFrame(entry.renderTargets);
        }

        if (!policy.shouldClear) {
            return;
        }

        ClearViewport(
            entry,
            renderContext,
            policy.clearColor.r,
            policy.clearColor.g,
            policy.clearColor.b,
            policy.clearColor.a);
    }

    void BuildSceneViewportRenderState(
        ViewportEntry& entry,
        IEditorContext& context,
        const Components::Scene& scene,
        SceneViewportRenderState& outState) {
        (void)scene;
        outState.overlay = GetSceneViewOverlayData();
        if (!outState.overlay.valid) {
            return;
        }

        outState.selectedObjectIds = context.GetSelectionManager().GetSelectedEntities();
        const SceneViewportBuiltinPostProcessBuildResult builtinPostProcess =
            BuildSceneViewportBuiltinPostProcess(
            outState.overlay,
            outState.selectedObjectIds,
            entry.renderTargets.objectIdShaderView != nullptr,
            kDebugSceneSelectionMask);
        outState.builtinPostProcess = builtinPostProcess.request;
        if (builtinPostProcess.warningStatusText != nullptr) {
            SetViewportStatusIfEmpty(entry.statusText, builtinPostProcess.warningStatusText);
        }
    }

    bool RenderSceneViewportEntry(
        ViewportEntry& entry,
        IEditorContext& context,
        const Components::Scene* scene,
        const Rendering::RenderContext& renderContext,
        Rendering::RenderSurface& surface) {
        if (!EnsureSceneViewCamera()) {
            ApplyViewportRenderFailure(
                entry,
                renderContext,
                BuildSceneViewportRenderFailurePolicy(
                    SceneViewportRenderFailure::MissingSceneViewCamera));
            return false;
        }

        ApplySceneViewCameraController();
        entry.statusText.clear();
        if (scene == nullptr) {
            ApplyViewportRenderFailure(
                entry,
                renderContext,
                BuildSceneViewportRenderFailurePolicy(
                    SceneViewportRenderFailure::NoActiveScene));
            return false;
        }

        SceneViewportRenderState sceneState = {};
        BuildSceneViewportRenderState(entry, context, *scene, sceneState);

        std::vector<Rendering::CameraRenderRequest> requests =
            m_sceneRenderer->BuildRenderRequests(*scene, m_sceneViewCamera.camera, renderContext, surface);
        if (requests.empty()) {
            ApplyViewportRenderFailure(
                entry,
                renderContext,
                BuildSceneViewportRenderFailurePolicy(
                    SceneViewportRenderFailure::SceneRendererFailed));
            return false;
        }

        ApplySceneViewportRenderRequestSetup(
            entry.renderTargets,
            &sceneState.builtinPostProcess,
            nullptr,
            requests[0]);
        requests[0].hasClearColorOverride = true;
        requests[0].clearColorOverride = Math::Color(0.27f, 0.27f, 0.27f, 1.0f);

        if (!m_sceneRenderer->Render(requests)) {
            ApplyViewportRenderFailure(
                entry,
                renderContext,
                BuildSceneViewportRenderFailurePolicy(
                    SceneViewportRenderFailure::SceneRendererFailed));
            return false;
        }

        MarkSceneViewportRenderSuccess(entry.renderTargets, requests[0]);
        const Core::uint32 pendingAsyncLoads = Resources::ResourceManager::Get().GetAsyncPendingCount();
        if (pendingAsyncLoads > 0) {
            entry.statusText = "Loading scene assets... (" + std::to_string(pendingAsyncLoads) + ")";
        }
        return true;
    }

    bool RenderGameViewportEntry(
        ViewportEntry& entry,
        const Components::Scene* scene,
        const Rendering::RenderContext& renderContext,
        const Rendering::RenderSurface& surface) {
        if (scene == nullptr) {
            ApplyViewportRenderFailure(
                entry,
                renderContext,
                BuildGameViewportRenderFailurePolicy(
                    GameViewportRenderFailure::NoActiveScene));
            return false;
        }

        const auto cameras = scene->FindObjectsOfType<Components::CameraComponent>();
        if (cameras.empty()) {
            ApplyViewportRenderFailure(
                entry,
                renderContext,
                BuildGameViewportRenderFailurePolicy(
                    GameViewportRenderFailure::NoCameraInScene));
            return false;
        }

        if (!m_sceneRenderer->Render(*scene, nullptr, renderContext, surface)) {
            ApplyViewportRenderFailure(
                entry,
                renderContext,
                BuildGameViewportRenderFailurePolicy(
                    GameViewportRenderFailure::SceneRendererFailed));
            return false;
        }

        MarkGameViewportRenderSuccess(entry.renderTargets);
        entry.statusText.clear();
        return true;
    }

    void RenderViewportEntry(
        ViewportEntry& entry,
        IEditorContext& context,
        const Components::Scene* scene,
        const Rendering::RenderContext& renderContext) {
        if (entry.renderTargets.colorView == nullptr || entry.renderTargets.depthView == nullptr) {
            ApplyViewportFailureStatus(
                entry.statusText,
                BuildViewportRenderTargetUnavailablePolicy());
            InvalidateViewportObjectIdFrame(entry.renderTargets);
            return;
        }

        Rendering::RenderSurface surface = BuildSurface(entry);

        if (entry.kind == EditorViewportKind::Scene) {
            RenderSceneViewportEntry(entry, context, scene, renderContext, surface);
            return;
        }

        RenderGameViewportEntry(entry, scene, renderContext, surface);
    }

    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;
        }

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

    bool TryPickSceneViewEntityWithObjectId(
        ViewportEntry& entry,
        const ImVec2& viewportSize,
        const ImVec2& viewportMousePosition,
        uint64_t& outEntityId) {
        if (m_device == nullptr) {
            outEntityId = 0;
            return false;
        }

        ViewportObjectIdPickContext pickContext = {};
        pickContext.commandQueue = m_sceneViewLastRenderContext.commandQueue;
        pickContext.texture = entry.renderTargets.objectIdTexture;
        pickContext.textureState = entry.renderTargets.objectIdState;
        pickContext.textureWidth = entry.renderTargets.width;
        pickContext.textureHeight = entry.renderTargets.height;
        pickContext.hasValidFrame = entry.renderTargets.hasValidObjectIdFrame;
        pickContext.viewportSize = viewportSize;
        pickContext.viewportMousePosition = viewportMousePosition;

        return TryPickViewportObjectIdEntity(
            pickContext,
            [this](const ViewportObjectIdReadbackRequest& request, std::array<uint8_t, 4>& outRgba) {
                return m_device != nullptr &&
                    m_device->ReadTexturePixelRGBA8(
                        request.commandQueue,
                        request.texture,
                        request.textureState,
                        request.pixelX,
                        request.pixelY,
                        outRgba);
            },
            outEntityId);
    }

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

} // namespace Editor
} // namespace XCEngine