#include <filesystem>
#include <memory>
#include <string>

#include <destrum/Event.h>
#include <destrum/ObjectModel/Component.h>
#include <destrum/ObjectModel/GameObject.h>
#include <destrum/Scene/Scene.h>
#include <destrum/Scene/SceneManager.h>
#include <destrum/Serialization/ComponentFactory.h>
#include <destrum/Serialization/ComponentRegistry.h>
#include <destrum/Serialization/GlmJson.h>
#include <destrum/Serialization/SceneSerializer.h>
#include <destrum/Components/Physics/SphereCollider.h>
#include <destrum/Components/Physics/BoxCollider.h>
#include <destrum/Components/Physics/CapsuleCollider.h>
#include <destrum/Components/Physics/Collider.h>
#include <destrum/Components/Animator.h>
#include <destrum/Components/CameraComponent.h>
#include <destrum/Components/UI/Canvas.h>
#include <destrum/Components/UI/RectTransform.h>
#include <destrum/Components/UI/UIImage.h>
#include <destrum/Components/UI/UIText.h>
#include <destrum/Components/LightComponent.h>
#include <destrum/Components/Physics/Rigidbody.h>

#include "TestUtils.h"

using namespace test;

namespace {
    class TestComponent final : public Component {
    public:
        explicit TestComponent(GameObject& owner) : Component(owner, "TestComponent") {}

        void Update(float) override {}
        std::string GetTypeName() const override { return "TestComponent"; }
    };

    class RemovingListener final : public EventListener {
    public:
        explicit RemovingListener(std::unique_ptr<RemovingListener>* victim)
            : victim(victim) {}

        void OnEvent(int) {
            if (victim != nullptr) {
                victim->reset();
                victim = nullptr;
            }
            ++calls;
        }

        int calls{0};

    private:
        std::unique_ptr<RemovingListener>* victim;
    };

    void testTransforms()
    {
        GameObject parent{"parent"};
        GameObject child{"child"};

        parent.GetTransform().SetLocalPosition({10.f, 2.f, -4.f});
        parent.GetTransform().SetLocalRotation({0.f, 0.f, 90.f});
        parent.GetTransform().SetLocalScale({2.f, 2.f, 2.f});
        child.GetTransform().SetLocalPosition({1.f, 0.f, 0.f});

        child.GetTransform().SetParent(&parent.GetTransform(), true);
        const auto worldPosition = child.GetTransform().GetWorldPosition();
        check(close(worldPosition.x, 1.f) && close(worldPosition.y, 0.f),
              "reparenting must preserve world position");

        child.GetTransform().SetWorldPosition({20.f, 10.f, 0.f});
        const auto movedPosition = child.GetTransform().GetWorldPosition();
        check(close(movedPosition.x, 20.f) && close(movedPosition.y, 10.f),
              "world position must account for parent rotation and scale");

        parent.Destroy();
        check(parent.IsBeingDestroyed() && child.IsBeingDestroyed(),
              "destroying a parent must mark descendants");
    }

    void testSceneFindGameObject()
    {
        Scene& scene = SceneManager::GetInstance().CreateScene("find-object");
        GameObject* pending = scene.CreateGameObject("pending");
        check(scene.FindGameObject(pending->GetId()) == pending, "objects must be found while still pending");

        scene.CommitPendingAdditions();
        GameObject* committed = scene.CreateGameObject("committed");
        scene.CommitPendingAdditions();
        check(scene.FindGameObject(committed->GetId()) == committed, "committed objects must be found by id");
        check(scene.FindGameObject(InvalidObjectId) == nullptr, "the invalid id must never match");

        const ObjectId destroyedId = committed->GetId();
        committed->Destroy();
        check(scene.FindGameObject(destroyedId) == nullptr, "objects being destroyed must not be found");

        SceneManager::GetInstance().Destroy();
    }

    void testEventMutation()
    {
        Event<int> event;
        int calls = 0;
        event.AddListener([&](int) { ++calls; });
        event.AddListener([&](int) {
            ++calls;
            event.AddListener([&](int) { ++calls; });
        });

        event.Invoke(1);
        check(calls == 2, "event mutation must not invalidate the current invocation");
        event.Invoke(1);
        check(calls == 5, "new event listeners must run on subsequent invocations");
    }

    void testEventRemoval()
    {
        Event<int> event;
        std::unique_ptr<RemovingListener> victim;
        RemovingListener remover{&victim};
        victim = std::make_unique<RemovingListener>(nullptr);

        event.AddListener(&remover, &RemovingListener::OnEvent);
        event.AddListener(victim.get(), &RemovingListener::OnEvent);
        event.Invoke(1);

        check(remover.calls == 1, "event remover must run once");
        check(victim == nullptr, "event listener must be removable during invocation");
    }

    void testComponentRemoval()
    {
        Scene& scene = SceneManager::GetInstance().CreateScene("component-removal");
        GameObject* object = scene.CreateGameObject("object");
        object->AddComponent<TestComponent>();
        scene.CommitPendingAdditions();

        check(object->GetComponent<TestComponent>() != nullptr,
              "test component must be discoverable before removal");
        check(object->DestroyComponent<TestComponent>() != nullptr,
              "destroying a component must find it");
        scene.CleanupDestroyedGameObjects();
        check(object->GetComponent<TestComponent>() == nullptr,
              "destroyed components must be removed at the scene boundary");

        SceneManager::GetInstance().Destroy();
    }

    void testEngineComponentRegistration()
    {
        RegisterEngineComponents();

        const char* canonicalNames[] = {
            "MeshRendererComponent",
            "LightComponent",
            "Rotator",
            "Spinner",
            "OrbitAndSpin",
            "Animator",
            "Rigidbody",
            "BoxCollider",
            "SphereCollider",
            "CapsuleCollider",
            "Canvas",
            "RectTransform",
            "UIImage",
            "UIText"
        };
        for (const char* name : canonicalNames) {
            check(ComponentFactory::IsRegistered(name),
                  "all canonical engine component names must be registered");
        }

        check(!ComponentFactory::IsRegistered("MeshRenderer"),
              "MeshRenderer legacy alias must not be registered");
        check(!ComponentFactory::IsRegistered("RigidBody"),
              "RigidBody legacy alias must not be registered");
    }

    void testSceneCurrentCamera()
    {
        Scene& scene = SceneManager::GetInstance().CreateScene("cameras");
        check(scene.GetCurrentCamera() == nullptr, "a scene without cameras must have no current camera");

        GameObject* first = scene.CreateGameObject("first camera");
        auto* firstCamera = first->AddComponent<CameraComponent>();
        scene.CommitPendingAdditions();
        check(scene.GetCurrentCamera() == firstCamera, "the only camera in a scene must be the current camera");

        GameObject* second = scene.CreateGameObject("second camera");
        auto* secondCamera = second->AddComponent<CameraComponent>();
        secondCamera->SetFieldOfView(60.0f);
        second->GetTransform().SetWorldPosition({1.0f, 2.0f, 3.0f});
        scene.CommitPendingAdditions();
        secondCamera->MakeCurrent();
        check(scene.GetCurrentCamera() == secondCamera && !firstCamera->IsCurrent(),
              "the selected camera must be the current camera");

        const Camera& camera = secondCamera->GetCamera(16.0f / 9.0f);
        check(camera.GetPosition() == glm::vec3{1.0f, 2.0f, 3.0f} &&
              close(camera.GetForward().z, -1.0f) && camera.GetFOVY() == 60.0f,
              "a camera component must place its camera at its transform, looking down -Z");

        const auto path = std::filesystem::temp_directory_path() / "destrum_camera_scene_test.json";
        check(SceneSerializer::Save(scene, path), "scene with cameras must save");
        check(SceneSerializer::Load(scene, path), "scene with cameras must load");
        std::filesystem::remove(path);

        const CameraComponent* loadedCamera = scene.GetCurrentCamera();
        check(loadedCamera != nullptr && loadedCamera->GetGameObject()->GetName() == "second camera" &&
              loadedCamera->GetFieldOfView() == 60.0f,
              "scene round-trip must preserve the current camera");

        scene.GetCurrentCamera()->GetGameObject()->SetActive(false);
        check(scene.GetCurrentCamera() != nullptr &&
              scene.GetCurrentCamera()->GetGameObject()->GetName() == "first camera",
              "an inactive current camera must fall back to another camera");

        SceneManager::GetInstance().Destroy();
    }

    void testHierarchyMoves()
    {
        Scene& scene = SceneManager::GetInstance().CreateScene("hierarchy");
        GameObject* parent = scene.CreateGameObject("parent");
        GameObject* a = scene.CreateGameObject("a");
        GameObject* b = scene.CreateGameObject("b");
        GameObject* c = scene.CreateGameObject("c");
        GameObject* other = scene.CreateGameObject("other");
        for (GameObject* child : {a, b, c}) {
            child->GetTransform().SetParent(&parent->GetTransform(), false);
        }
        scene.CommitPendingAdditions();

        const auto childNames = [](const GameObject& object) {
            std::string names;
            for (const Transform* child : object.GetTransform().GetChildren()) {
                names += child->GetOwner()->GetName();
            }
            return names;
        };

        check(scene.MoveInHierarchy(*c, parent, a) && childNames(*parent) == "cab",
              "moving before a sibling must reorder the children");
        check(scene.MoveInHierarchy(*c, parent) && childNames(*parent) == "abc",
              "moving without a sibling must put the object last");
        check(scene.MoveInHierarchy(*a, other) && childNames(*parent) == "bc" && childNames(*other) == "a",
              "moving onto another object must reparent it");
        check(!scene.MoveInHierarchy(*other, a) && a->GetTransform().GetParent() == &other->GetTransform(),
              "an object must not be moved under its own child");
        check(scene.MoveInHierarchy(*a, nullptr, parent) && a->GetTransform().GetParent() == nullptr &&
              scene.GetObjects().front().get() == a,
              "moving to the root must unparent and order the roots");
        check(scene.MoveInHierarchy(*c, parent, b) && childNames(*parent) == "cb", "reordering must still work");

        const auto path = std::filesystem::temp_directory_path() / "destrum_hierarchy_scene.json";
        check(SceneSerializer::Save(scene, path), "the hierarchy scene must save");
        Scene& copy = SceneManager::GetInstance().CreateScene("hierarchy copy");
        check(SceneSerializer::Load(copy, path), "the hierarchy scene must load");
        std::filesystem::remove(path);
        copy.CommitPendingAdditions();
        const GameObject* loadedParent = findByName(copy, "parent");
        check(loadedParent != nullptr && childNames(*loadedParent) == "cb", "sibling order must survive a save");
        check(copy.GetObjects().front()->GetName() == "a", "root order must survive a save");

        SceneManager::GetInstance().Destroy();
    }
}

void RunCoreTests()
{
    testTransforms();
    testSceneFindGameObject();
    testEventMutation();
    testEventRemoval();
    testComponentRemoval();
    testEngineComponentRegistration();
    testSceneCurrentCamera();
    testHierarchyMoves();
}