#include <gtest/gtest.h>

#include "Viewport/SceneViewportPicker.h"

#include <XCEngine/Components/MeshFilterComponent.h>
#include <XCEngine/Components/MeshRendererComponent.h>
#include <XCEngine/Core/Asset/IResource.h>
#include <XCEngine/Core/Math/Quaternion.h>
#include <XCEngine/Resources/Mesh/Mesh.h>
#include <XCEngine/Scene/Scene.h>

#include <memory>
#include <vector>

namespace {

using XCEngine::Components::GameObject;
using XCEngine::Components::MeshFilterComponent;
using XCEngine::Components::MeshRendererComponent;
using XCEngine::Components::Scene;
using XCEngine::Editor::BuildSceneViewportRay;
using XCEngine::Editor::PickSceneViewportEntity;
using XCEngine::Editor::SceneViewportOverlayData;
using XCEngine::Editor::SceneViewportPickRequest;
using XCEngine::Math::Quaternion;
using XCEngine::Math::Ray;
using XCEngine::Math::Vector2;
using XCEngine::Math::Vector3;
using XCEngine::Resources::Mesh;
using XCEngine::Resources::MeshSection;
using XCEngine::Resources::StaticMeshVertex;

std::unique_ptr<Mesh> CreateTriangleMesh(uint64_t guid) {
    auto mesh = std::make_unique<Mesh>();

    XCEngine::Resources::IResource::ConstructParams params = {};
    params.name = "TestTriangle";
    params.path = "memory://test_triangle";
    params.guid = XCEngine::Resources::ResourceGUID(guid);
    mesh->Initialize(params);

    const StaticMeshVertex vertices[] = {
        { Vector3(-1.0f, -1.0f, 0.0f) },
        { Vector3(1.0f, -1.0f, 0.0f) },
        { Vector3(0.0f, 1.0f, 0.0f) }
    };
    const uint16_t indices[] = { 0, 1, 2 };

    mesh->SetVertexData(
        vertices,
        sizeof(vertices),
        static_cast<uint32_t>(std::size(vertices)),
        sizeof(StaticMeshVertex),
        XCEngine::Resources::VertexAttribute::Position);
    mesh->SetIndexData(indices, sizeof(indices), static_cast<uint32_t>(std::size(indices)), false);
    mesh->SetBounds(XCEngine::Math::Bounds(Vector3(0.0f, 0.0f, 0.0f), Vector3(2.0f, 2.0f, 0.0f)));

    MeshSection section = {};
    section.baseVertex = 0;
    section.vertexCount = static_cast<uint32_t>(std::size(vertices));
    section.startIndex = 0;
    section.indexCount = static_cast<uint32_t>(std::size(indices));
    section.materialID = 0;
    section.bounds = mesh->GetBounds();
    mesh->AddSection(section);
    return mesh;
}

class SceneViewportPickerTest : public ::testing::Test {
protected:
    SceneViewportOverlayData CreateDefaultOverlay() const {
        SceneViewportOverlayData overlay = {};
        overlay.valid = true;
        overlay.cameraPosition = Vector3::Zero();
        overlay.cameraForward = Vector3::Forward();
        overlay.cameraRight = Vector3::Right();
        overlay.cameraUp = Vector3::Up();
        overlay.verticalFovDegrees = 60.0f;
        overlay.nearClipPlane = 0.03f;
        overlay.farClipPlane = 2000.0f;
        return overlay;
    }

    GameObject* CreateTriangleObject(
        Scene& scene,
        const std::string& name,
        const Vector3& position,
        const Quaternion& rotation = Quaternion::Identity(),
        const Vector3& scale = Vector3::One()) {
        std::unique_ptr<Mesh> mesh = CreateTriangleMesh(++m_nextMeshGuid);
        Mesh* meshPtr = mesh.get();
        m_meshes.push_back(std::move(mesh));

        GameObject* object = scene.CreateGameObject(name);
        object->GetTransform()->SetPosition(position);
        object->GetTransform()->SetRotation(rotation);
        object->GetTransform()->SetScale(scale);

        auto* meshFilter = object->AddComponent<MeshFilterComponent>();
        auto* meshRenderer = object->AddComponent<MeshRendererComponent>();
        meshFilter->SetMesh(meshPtr);
        meshRenderer->SetEnabled(true);
        return object;
    }

private:
    uint64_t m_nextMeshGuid = 1;
    std::vector<std::unique_ptr<Mesh>> m_meshes;
};

TEST_F(SceneViewportPickerTest, BuildSceneViewportRayPointsThroughViewportCenter) {
    Ray ray;
    ASSERT_TRUE(BuildSceneViewportRay(
        CreateDefaultOverlay(),
        Vector2(1280.0f, 720.0f),
        Vector2(640.0f, 360.0f),
        ray));

    EXPECT_NEAR(ray.origin.x, 0.0f, 1e-4f);
    EXPECT_NEAR(ray.origin.y, 0.0f, 1e-4f);
    EXPECT_NEAR(ray.origin.z, 0.0f, 1e-4f);
    EXPECT_NEAR(ray.direction.x, 0.0f, 1e-4f);
    EXPECT_NEAR(ray.direction.y, 0.0f, 1e-4f);
    EXPECT_NEAR(ray.direction.z, 1.0f, 1e-4f);
}

TEST_F(SceneViewportPickerTest, PickSceneViewportEntityReturnsNearestHit) {
    Scene scene("PickerScene");
    GameObject* farObject = CreateTriangleObject(scene, "Far", Vector3(0.0f, 0.0f, 6.0f));
    GameObject* nearObject = CreateTriangleObject(scene, "Near", Vector3(0.0f, 0.0f, 3.0f));

    SceneViewportPickRequest request = {};
    request.scene = &scene;
    request.overlay = CreateDefaultOverlay();
    request.viewportSize = Vector2(1280.0f, 720.0f);
    request.viewportPosition = Vector2(640.0f, 360.0f);

    const auto result = PickSceneViewportEntity(request);

    EXPECT_TRUE(result.hit);
    EXPECT_EQ(result.entityId, nearObject->GetID());
    EXPECT_LT(result.distanceSq, (farObject->GetTransform()->GetPosition() - request.overlay.cameraPosition).SqrMagnitude());
}

TEST_F(SceneViewportPickerTest, PickSceneViewportEntityHandlesRotatedAndScaledObjects) {
    Scene scene("PickerScene");
    GameObject* object = CreateTriangleObject(
        scene,
        "Rotated",
        Vector3(0.0f, 0.0f, 4.0f),
        Quaternion::FromEulerAngles(0.0f, 45.0f * XCEngine::Math::DEG_TO_RAD, 0.0f),
        Vector3(2.0f, 2.0f, 2.0f));

    SceneViewportPickRequest request = {};
    request.scene = &scene;
    request.overlay = CreateDefaultOverlay();
    request.viewportSize = Vector2(1280.0f, 720.0f);
    request.viewportPosition = Vector2(640.0f, 360.0f);

    const auto result = PickSceneViewportEntity(request);

    EXPECT_TRUE(result.hit);
    EXPECT_EQ(result.entityId, object->GetID());
}

TEST_F(SceneViewportPickerTest, PickSceneViewportEntityReturnsNoHitForEmptySpace) {
    Scene scene("PickerScene");
    CreateTriangleObject(scene, "Offset", Vector3(3.0f, 0.0f, 4.0f));

    SceneViewportPickRequest request = {};
    request.scene = &scene;
    request.overlay = CreateDefaultOverlay();
    request.viewportSize = Vector2(1280.0f, 720.0f);
    request.viewportPosition = Vector2(640.0f, 360.0f);

    const auto result = PickSceneViewportEntity(request);

    EXPECT_FALSE(result.hit);
    EXPECT_EQ(result.entityId, 0u);
}

} // namespace