#include <filesystem>
#include <fstream>
#include <string>

#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/GlmJson.h>
#include <destrum/Serialization/PrefabCache.h>
#include <destrum/Serialization/PrefabSerializer.h>
#include <destrum/Serialization/SceneSerializer.h>
#include <destrum/Components/Physics/CapsuleCollider.h>
#include <destrum/Components/Physics/Collider.h>
#include <destrum/Components/Physics/Rigidbody.h>

#include <components/Activatable.h>
#include <components/InteractableButton.h>
#include <components/Checkpoint.h>
#include <components/PlayerRespawn.h>
#include <components/WinGoal.h>

#include "TestUtils.h"

using namespace test;

namespace {
    class TestActivatable final : public Activatable {
    public:
        explicit TestActivatable(GameObject& owner) : Activatable(owner, "TestActivatable") {}

        std::string GetTypeName() const override { return "TestActivatable"; }

        int activations{0};

    protected:
        void OnActivate(GameObject&) override { ++activations; }
    };

    void testButtonTargetsRoundTrip()
    {
        ComponentFactory::Register<InteractableButton>("InteractableButton");
        ComponentFactory::Register<TestActivatable>("TestActivatable");

        Scene& scene = SceneManager::GetInstance().CreateScene("button targets");
        GameObject* door = scene.CreateGameObject("door");
        door->AddComponent<TestActivatable>();
        GameObject* lamp = scene.CreateGameObject("lamp");
        lamp->AddComponent<TestActivatable>();
        GameObject* buttonObject = scene.CreateGameObject("button");
        auto* button = buttonObject->AddComponent<InteractableButton>();
        button->SetCycleColors(false);
        button->AddTarget(*door);
        button->AddTarget(*lamp);
        button->AddTarget(*door);
        scene.CommitPendingAdditions();
        check(button->GetTargets().size() == 2, "a button must not target the same object twice");

        const auto path = std::filesystem::temp_directory_path() / "destrum_button_targets_scene.json";
        check(SceneSerializer::Save(scene, path), "the button scene must save");
        check(SceneSerializer::Load(scene, path), "the button scene must load");

        Scene& copy = SceneManager::GetInstance().CreateScene("button targets copy");
        check(SceneSerializer::Load(copy, path), "the button scene must load into a second scene");
        std::filesystem::remove(path);

        for (Scene* loaded : {&scene, &copy}) {
            loaded->CommitPendingAdditions();
            GameObject* loadedButton = findByName(*loaded, "button");
            auto* loadedComponent = loadedButton != nullptr ? loadedButton->GetComponent<InteractableButton>() : nullptr;
            check(loadedComponent != nullptr, "the button must survive a round-trip");

            const auto& targets = loadedComponent->GetTargets();
            check(targets.size() == 2, "button targets must survive a round-trip");
            GameObject* loadedDoor = targets[0].Get(*loaded);
            GameObject* loadedLamp = targets[1].Get(*loaded);
            check(loadedDoor == findByName(*loaded, "door") && loadedDoor != nullptr &&
                  loadedLamp == findByName(*loaded, "lamp") && loadedLamp != nullptr,
                  "button targets must point at the loaded objects in their own scene");

            loadedComponent->Interact(*loadedButton);
            check(loadedDoor->GetComponent<TestActivatable>()->activations == 1 &&
                  loadedLamp->GetComponent<TestActivatable>()->activations == 1,
                  "pressing a loaded button must activate its targets");
        }

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

    void testButtonDropsMissingTargets()
    {
        ComponentFactory::Register<InteractableButton>("InteractableButton");

        Scene& scene = SceneManager::GetInstance().CreateScene("missing targets");
        const auto path = std::filesystem::temp_directory_path() / "destrum_missing_targets_scene.json";
        std::ofstream{path}
            << R"({"version":2,"objects":[{"id":5,"name":"button","components":)"
               R"([{"type":"InteractableButton","data":{"cycleColors":false,"targets":[5,99]}}]}]})";

        check(SceneSerializer::Load(scene, path), "a button with a dangling target must still load");
        std::filesystem::remove(path);
        scene.CommitPendingAdditions();

        const GameObject* object = scene.GetObjects().front().get();
        const auto* button = object->GetComponent<InteractableButton>();
        check(button != nullptr && button->GetTargets().size() == 1 &&
              button->GetTargets().front().GetId() == object->GetId(),
              "dangling targets must be dropped and valid ones remapped");

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

    GameObject* buildTurret(Scene& scene, const GameObject& door)
    {
        GameObject* turret = scene.CreateGameObject("turret");
        turret->GetTransform().SetLocalPosition(glm::vec3{5.0f, 0.0f, 0.0f});
        GameObject* barrel = scene.CreateGameObject("barrel");
        barrel->GetTransform().SetParent(&turret->GetTransform(), false);
        barrel->GetTransform().SetLocalPosition(glm::vec3{0.0f, 1.0f, 0.0f});
        barrel->AddComponent<TestActivatable>();

        auto* button = turret->AddComponent<InteractableButton>();
        button->SetCycleColors(false);
        button->AddTarget(*barrel);
        button->AddTarget(door);
        return turret;
    }

    GameObject* onlyChild(GameObject& object)
    {
        const auto& children = object.GetTransform().GetChildren();
        return children.size() == 1 ? children.front()->GetOwner() : nullptr;
    }

    void testPrefabRoundTrip()
    {
        ComponentFactory::Register<InteractableButton>("InteractableButton");
        ComponentFactory::Register<TestActivatable>("TestActivatable");

        Scene& source = SceneManager::GetInstance().CreateScene("prefab source");
        GameObject* door = source.CreateGameObject("door");
        door->AddComponent<TestActivatable>();
        GameObject* turret = buildTurret(source, *door);
        source.CommitPendingAdditions();

        const auto path = std::filesystem::temp_directory_path() / "destrum_turret.prefab";
        check(PrefabSerializer::Save(*turret, path), "a hierarchy must save as a prefab");

        Scene& target = SceneManager::GetInstance().CreateScene("prefab target");
        GameObject* holder = target.CreateGameObject("holder");
        GameObject* first = PrefabSerializer::Instantiate(target, path.string());
        GameObject* second = PrefabSerializer::Instantiate(target, path.string(), &holder->GetTransform());
        target.CommitPendingAdditions();
        check(first != nullptr && second != nullptr, "a saved prefab must instantiate");
        check(target.GetObjects().size() == 5, "each instance must create the root and its child");
        check(first != second && first->GetId() != turret->GetId(), "instances must get fresh objects");
        check(first->GetName() == "turret" && first->GetTransform().GetParent() == nullptr,
              "an instance without a parent must be a scene root");
        check(second->GetTransform().GetParent() == &holder->GetTransform(),
              "an instance must be parented to the given transform");
        check(close(first->GetTransform().GetLocalPosition().x, 5.0f),
              "the root transform must come from the prefab");

        for (GameObject* instance : {first, second}) {
            GameObject* barrel = onlyChild(*instance);
            check(barrel != nullptr && barrel->GetName() == "barrel" &&
                  close(barrel->GetTransform().GetLocalPosition().y, 1.0f),
                  "prefab children must keep their local transform");

            const auto* button = instance->GetComponent<InteractableButton>();
            check(button != nullptr && button->GetTargets().size() == 1 &&
                  button->GetTargets().front().Get(target) == barrel,
                  "references inside the prefab must point at the instance's own objects, outside ones are dropped");
        }

        check(PrefabCache::GetInstance().Get(path.string()) == PrefabCache::GetInstance().Get(path.string()),
              "a cached prefab must be parsed once");
        const auto before = PrefabCache::GetInstance().Get(path.string());
        turret->SetName("tower");
        check(PrefabSerializer::Save(*turret, path), "a prefab must save over an existing file");
        const auto after = PrefabCache::GetInstance().Get(path.string());
        check(after != before && after->at("name") == "tower", "saving a prefab must refresh the cache");

        std::filesystem::remove(path);
        check(PrefabSerializer::Instantiate(target, path.string()) == nullptr,
              "instantiating a missing prefab must fail");

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

    void testPrefabDuplicate()
    {
        ComponentFactory::Register<InteractableButton>("InteractableButton");
        ComponentFactory::Register<TestActivatable>("TestActivatable");

        Scene& scene = SceneManager::GetInstance().CreateScene("duplicate");
        GameObject* door = scene.CreateGameObject("door");
        door->AddComponent<TestActivatable>();
        GameObject* holder = scene.CreateGameObject("holder");
        GameObject* turret = buildTurret(scene, *door);
        turret->GetTransform().SetParent(&holder->GetTransform(), false);

        GameObject* copy = PrefabSerializer::Duplicate(*turret);
        scene.CommitPendingAdditions();
        check(copy != nullptr && copy != turret && copy->GetName() == "turret",
              "duplicate must create a new object");
        check(copy->GetTransform().GetParent() == &holder->GetTransform(),
              "a duplicate must keep the original's parent");

        GameObject* barrel = onlyChild(*copy);
        check(barrel != nullptr && barrel != onlyChild(*turret), "a duplicate must copy children");

        const auto* button = copy->GetComponent<InteractableButton>();
        check(button != nullptr && button->GetTargets().size() == 2 &&
              button->GetTargets()[0].Get(scene) == barrel &&
              button->GetTargets()[1].Get(scene) == door,
              "a duplicate must remap inner references and keep outer ones");

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

    void testPrefabValidation()
    {
        using nlohmann::json;
        check(PrefabSerializer::Validate(json::object()).has_value(), "an empty prefab must be rejected");

        const json twoRoots = json::parse(R"({"version":1,"objects":[{"id":1},{"id":2}]})");
        check(PrefabSerializer::Validate(twoRoots).has_value(), "a prefab with two roots must be rejected");

        const json childFirst = json::parse(R"({"version":1,"objects":[{"id":2,"parent":1},{"id":1}]})");
        check(PrefabSerializer::Validate(childFirst).has_value(), "the prefab root must come first");

        const json valid = json::parse(R"({"version":1,"objects":[{"id":1},{"id":2,"parent":1}]})");
        check(!PrefabSerializer::Validate(valid).has_value(), "a single-root prefab must validate");

        const json future = json::parse(R"({"version":99,"objects":[{"id":1}]})");
        check(PrefabSerializer::Validate(future).has_value(), "an unknown prefab version must be rejected");
    }

    void testWinGoalButton()
    {
        ComponentFactory::Register<InteractableButton>("InteractableButton");
        ComponentFactory::Register<WinGoal>("WinGoal");

        Scene& scene = SceneManager::GetInstance().CreateScene("win goal");
        GameObject* goal = scene.CreateGameObject("goal");
        auto* winGoal = goal->AddComponent<WinGoal>();
        GameObject* buttonObject = scene.CreateGameObject("button");
        auto* button = buttonObject->AddComponent<InteractableButton>();
        button->SetCycleColors(false);
        button->AddTarget(*goal);
        scene.CommitPendingAdditions();

        check(!winGoal->IsReached(), "the goal must start unreached");
        button->Interact(*buttonObject);
        check(winGoal->IsReached(), "pressing the win button must reach the goal");

        const auto path = std::filesystem::temp_directory_path() / "destrum_win_goal_scene.json";
        check(SceneSerializer::Save(scene, path), "the win goal scene must save");
        check(SceneSerializer::Load(scene, path), "the win goal scene must load");
        std::filesystem::remove(path);
        scene.CommitPendingAdditions();
        const GameObject* loadedGoal = findByName(scene, "goal");
        check(loadedGoal != nullptr && loadedGoal->GetComponent<WinGoal>()->IsReached(),
              "a reached goal must stay reached after a round-trip");

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

    void testCheckpointRespawn()
    {
        Scene& scene = SceneManager::GetInstance().CreateScene("respawn");
        GameObject* player = scene.CreateGameObject("player");
        player->GetTransform().SetWorldPosition(glm::vec3{1.0f, 2.0f, 3.0f});
        player->AddComponent<CapsuleCollider>(0.4f, 1.8f);
        auto* rigidbody = player->AddComponent<Rigidbody>();
        auto* respawn = player->AddComponent<PlayerRespawn>();
        respawn->SetKillHeight(-10.0f);

        GameObject* checkpointObject = scene.CreateGameObject("checkpoint");
        checkpointObject->GetTransform().SetWorldPosition(glm::vec3{-5.0f, 4.0f, 0.0f});
        auto* checkpoint = checkpointObject->AddComponent<Checkpoint>();
        checkpoint->SetSpawnOffset({0.0f, 0.5f, 0.0f});
        scene.CommitPendingAdditions();
        check(rigidbody->HasPhysicsBody(), "the player must have a physics body");

        respawn->Start();
        check(respawn->GetRespawnPoint() == glm::vec3(1.0f, 2.0f, 3.0f),
              "the respawn point must default to where the player starts");

        checkpoint->OnTriggerEnter(checkpointObject);
        check(respawn->GetRespawnPoint() == glm::vec3(1.0f, 2.0f, 3.0f),
              "a checkpoint must ignore objects without PlayerRespawn");
        checkpoint->OnTriggerEnter(player);
        check(respawn->GetRespawnPoint() == glm::vec3(-5.0f, 4.5f, 0.0f),
              "touching a checkpoint must move the respawn point");

        rigidbody->Teleport(glm::vec3{0.0f, -20.0f, 0.0f});
        rigidbody->SetLinearVelocity(glm::vec3{0.0f, -30.0f, 0.0f});
        respawn->FixedUpdate(1.0f / 60.0f);
        const glm::vec3 position = player->GetTransform().GetWorldPosition();
        check(close(position.x, -5.0f) && close(position.y, 4.5f) && close(position.z, 0.0f),
              "falling below the kill height must respawn at the checkpoint");
        check(glm::length(rigidbody->GetLinearVelocity()) < 0.001f, "respawning must stop the fall");

        scene.GetPhysics().FixedUpdate(1.0f / 60.0f);
        check(player->GetTransform().GetWorldPosition().y > 4.0f,
              "the physics body must have moved with the teleport");

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

void RunGameplayTests()
{
    testButtonTargetsRoundTrip();
    testButtonDropsMissingTargets();
    testPrefabRoundTrip();
    testPrefabDuplicate();
    testPrefabValidation();
    testWinGoalButton();
    testCheckpointRespawn();
}