#include "Rendering/SceneRenderer.h"

#include "Components/CameraComponent.h"
#include "Components/GameObject.h"
#include "Scene/Scene.h"

#include <algorithm>
#include <cmath>

namespace XCEngine {
namespace Rendering {

namespace {

bool CompareCameraRenderRequest(const CameraRenderRequest& lhs, const CameraRenderRequest& rhs) {
    if (lhs.cameraStackOrder != rhs.cameraStackOrder) {
        return lhs.cameraStackOrder < rhs.cameraStackOrder;
    }

    if (lhs.cameraDepth != rhs.cameraDepth) {
        return lhs.cameraDepth < rhs.cameraDepth;
    }

    return lhs.camera < rhs.camera;
}

bool IsUsableCamera(const Components::CameraComponent* camera) {
    return camera != nullptr &&
           camera->IsEnabled() &&
           camera->GetGameObject() != nullptr &&
           camera->GetGameObject()->IsActiveInHierarchy();
}

RenderClearFlags ResolveClearFlags(
    const Components::CameraComponent& camera,
    size_t renderedBaseCameraCount,
    size_t renderedRequestCount) {
    switch (camera.GetClearMode()) {
        case Components::CameraClearMode::ColorAndDepth:
            return RenderClearFlags::All;
        case Components::CameraClearMode::DepthOnly:
            return RenderClearFlags::Depth;
        case Components::CameraClearMode::None:
            return RenderClearFlags::None;
        case Components::CameraClearMode::Auto:
        default:
            if (camera.GetStackType() == Components::CameraStackType::Overlay) {
                return renderedRequestCount == 0 ? RenderClearFlags::All : RenderClearFlags::Depth;
            }

            return renderedBaseCameraCount == 0 ? RenderClearFlags::All : RenderClearFlags::Depth;
    }
}

Math::RectInt ResolveCameraRenderArea(
    const Components::CameraComponent& camera,
    const RenderSurface& surface) {
    const Math::Rect viewportRect = camera.GetViewportRect();
    const float surfaceWidth = static_cast<float>(surface.GetWidth());
    const float surfaceHeight = static_cast<float>(surface.GetHeight());

    const int32_t left = static_cast<int32_t>(std::floor(viewportRect.x * surfaceWidth));
    const int32_t top = static_cast<int32_t>(std::floor(viewportRect.y * surfaceHeight));
    const int32_t right = static_cast<int32_t>(std::ceil((viewportRect.x + viewportRect.width) * surfaceWidth));
    const int32_t bottom = static_cast<int32_t>(std::ceil((viewportRect.y + viewportRect.height) * surfaceHeight));
    return Math::RectInt(left, top, right - left, bottom - top);
}

} // namespace

SceneRenderer::SceneRenderer() = default;

SceneRenderer::SceneRenderer(std::unique_ptr<RenderPipeline> pipeline)
    : m_cameraRenderer(std::move(pipeline)) {
}

SceneRenderer::SceneRenderer(std::shared_ptr<const RenderPipelineAsset> pipelineAsset)
    : m_cameraRenderer(std::move(pipelineAsset)) {
}

void SceneRenderer::SetPipeline(std::unique_ptr<RenderPipeline> pipeline) {
    m_cameraRenderer.SetPipeline(std::move(pipeline));
}

void SceneRenderer::SetPipelineAsset(std::shared_ptr<const RenderPipelineAsset> pipelineAsset) {
    m_cameraRenderer.SetPipelineAsset(std::move(pipelineAsset));
}

std::vector<CameraRenderRequest> SceneRenderer::BuildRenderRequests(
    const Components::Scene& scene,
    Components::CameraComponent* overrideCamera,
    const RenderContext& context,
    const RenderSurface& surface) const {
    std::vector<CameraRenderRequest> requests;

    std::vector<Components::CameraComponent*> cameras;
    if (IsUsableCamera(overrideCamera)) {
        cameras.push_back(overrideCamera);
    } else {
        cameras = scene.FindObjectsOfType<Components::CameraComponent>();
        cameras.erase(
            std::remove_if(
                cameras.begin(),
                cameras.end(),
                [](const Components::CameraComponent* camera) {
                    return !IsUsableCamera(camera);
                }),
            cameras.end());
    }

    std::stable_sort(
        cameras.begin(),
        cameras.end(),
        [](const Components::CameraComponent* lhs, const Components::CameraComponent* rhs) {
            if (lhs->GetStackType() != rhs->GetStackType()) {
                return static_cast<int>(lhs->GetStackType()) < static_cast<int>(rhs->GetStackType());
            }

            if (lhs->GetDepth() != rhs->GetDepth()) {
                return lhs->GetDepth() < rhs->GetDepth();
            }

            return lhs < rhs;
        });

    size_t renderedBaseCameraCount = 0;
    for (Components::CameraComponent* camera : cameras) {

        CameraRenderRequest request;
        request.scene = &scene;
        request.camera = camera;
        request.context = context;
        request.surface = surface;
        request.surface.SetRenderArea(ResolveCameraRenderArea(*camera, surface));
        request.cameraDepth = camera->GetDepth();
        request.cameraStackOrder = static_cast<uint8_t>(camera->GetStackType());
        request.clearFlags = ResolveClearFlags(*camera, renderedBaseCameraCount, requests.size());
        if (request.surface.GetRenderAreaWidth() > 0 &&
            request.surface.GetRenderAreaHeight() > 0) {
            requests.push_back(request);
            if (camera->GetStackType() == Components::CameraStackType::Base) {
                ++renderedBaseCameraCount;
            }
        }
    }

    return requests;
}

bool SceneRenderer::Render(const CameraRenderRequest& request) {
    return m_cameraRenderer.Render(request);
}

bool SceneRenderer::Render(const std::vector<CameraRenderRequest>& requests) {
    if (requests.empty()) {
        return false;
    }

    for (const CameraRenderRequest& request : requests) {
        if (!request.IsValid()) {
            return false;
        }
    }

    std::vector<CameraRenderRequest> sortedRequests = requests;
    std::stable_sort(
        sortedRequests.begin(),
        sortedRequests.end(),
        CompareCameraRenderRequest);

    bool rendered = false;
    for (const CameraRenderRequest& request : sortedRequests) {
        if (!m_cameraRenderer.Render(request)) {
            return false;
        }
        rendered = true;
    }

    return rendered;
}

bool SceneRenderer::Render(
    const Components::Scene& scene,
    Components::CameraComponent* overrideCamera,
    const RenderContext& context,
    const RenderSurface& surface) {
    return Render(BuildRenderRequests(scene, overrideCamera, context, surface));
}

} // namespace Rendering
} // namespace XCEngine