#include "Scripting/ScriptEngine.h"

#include "Components/GameObject.h"
#include "Scene/Scene.h"
#include "Scripting/ScriptComponent.h"

#include <algorithm>

namespace XCEngine {
namespace Scripting {

ScriptEngine& ScriptEngine::Get() {
    static ScriptEngine instance;
    return instance;
}

void ScriptEngine::SetRuntime(IScriptRuntime* runtime) {
    m_runtime = runtime ? runtime : &m_nullRuntime;
}

void ScriptEngine::OnRuntimeStart(Components::Scene* scene) {
    OnRuntimeStop();

    if (!scene) {
        return;
    }

    m_runtimeScene = scene;
    m_runtimeRunning = true;
    m_runtime->OnRuntimeStart(scene);
    m_runtimeSceneCreatedSubscription = scene->OnGameObjectCreated().Subscribe(
        [this](Components::GameObject* gameObject) {
            HandleGameObjectCreated(gameObject);
        });

    for (Components::GameObject* root : scene->GetRootGameObjects()) {
        CollectScriptComponents(root);
    }

    for (const ScriptInstanceKey& key : m_scriptOrder) {
        auto it = m_scriptStates.find(key);
        if (it == m_scriptStates.end()) {
            continue;
        }

        ScriptInstanceState& state = it->second;
        if (!ShouldScriptRun(state)) {
            continue;
        }

        EnsureScriptReady(state, true);
    }
}

void ScriptEngine::OnRuntimeStop() {
    if (m_runtimeScene && m_runtimeSceneCreatedSubscription != 0) {
        m_runtimeScene->OnGameObjectCreated().Unsubscribe(m_runtimeSceneCreatedSubscription);
        m_runtimeScene->OnGameObjectCreated().ProcessUnsubscribes();
        m_runtimeSceneCreatedSubscription = 0;
    }

    if (!m_runtimeRunning) {
        m_runtimeScene = nullptr;
        m_scriptStates.clear();
        m_scriptOrder.clear();
        return;
    }

    std::vector<ScriptInstanceKey> keys = m_scriptOrder;
    for (const ScriptInstanceKey& key : keys) {
        auto it = m_scriptStates.find(key);
        if (it != m_scriptStates.end()) {
            StopTrackingScript(it->second, true);
        }
    }

    Components::Scene* stoppedScene = m_runtimeScene;
    m_scriptStates.clear();
    m_scriptOrder.clear();
    m_runtimeRunning = false;
    m_runtimeScene = nullptr;
    m_runtime->OnRuntimeStop(stoppedScene);
}

void ScriptEngine::OnFixedUpdate(float fixedDeltaTime) {
    if (!m_runtimeRunning) {
        return;
    }

    for (const ScriptInstanceKey& key : m_scriptOrder) {
        auto it = m_scriptStates.find(key);
        if (it == m_scriptStates.end()) {
            continue;
        }

        ScriptInstanceState& state = it->second;
        if (!ShouldScriptRun(state) || !EnsureScriptReady(state, true) || !state.enabled) {
            continue;
        }

        InvokeLifecycleMethod(state, ScriptLifecycleMethod::FixedUpdate, fixedDeltaTime);
    }
}

void ScriptEngine::OnUpdate(float deltaTime) {
    if (!m_runtimeRunning) {
        return;
    }

    for (const ScriptInstanceKey& key : m_scriptOrder) {
        auto it = m_scriptStates.find(key);
        if (it == m_scriptStates.end()) {
            continue;
        }

        ScriptInstanceState& state = it->second;
        if (!ShouldScriptRun(state) || !EnsureScriptReady(state, true) || !state.enabled) {
            continue;
        }

        if (state.startPending && !state.startCalled) {
            InvokeLifecycleMethod(state, ScriptLifecycleMethod::Start);
            state.startCalled = true;
            state.startPending = false;
        }

        InvokeLifecycleMethod(state, ScriptLifecycleMethod::Update, deltaTime);
    }
}

void ScriptEngine::OnLateUpdate(float deltaTime) {
    if (!m_runtimeRunning) {
        return;
    }

    for (const ScriptInstanceKey& key : m_scriptOrder) {
        auto it = m_scriptStates.find(key);
        if (it == m_scriptStates.end()) {
            continue;
        }

        ScriptInstanceState& state = it->second;
        if (!ShouldScriptRun(state) || !EnsureScriptReady(state, true) || !state.enabled) {
            continue;
        }

        InvokeLifecycleMethod(state, ScriptLifecycleMethod::LateUpdate, deltaTime);
    }
}

void ScriptEngine::OnScriptComponentEnabled(ScriptComponent* component) {
    if (!m_runtimeRunning || !component) {
        return;
    }

    ScriptInstanceState* state = TrackScriptComponent(component);
    if (!state) {
        return;
    }

    if (ShouldScriptRun(*state)) {
        EnsureScriptReady(*state, true);
    }
}

void ScriptEngine::OnScriptComponentDisabled(ScriptComponent* component) {
    if (!m_runtimeRunning || !component) {
        return;
    }

    ScriptInstanceState* state = FindState(component);
    if (!state || !state->enabled) {
        return;
    }

    InvokeLifecycleMethod(*state, ScriptLifecycleMethod::OnDisable);
    state->enabled = false;
}

void ScriptEngine::OnScriptComponentDestroyed(ScriptComponent* component) {
    if (!m_runtimeRunning || !component) {
        return;
    }

    ScriptInstanceState* state = FindState(component);
    if (!state) {
        return;
    }

    StopTrackingScript(*state, false);
}

bool ScriptEngine::HasTrackedScriptComponent(const ScriptComponent* component) const {
    return FindState(component) != nullptr;
}

bool ScriptEngine::HasRuntimeInstance(const ScriptComponent* component) const {
    const ScriptInstanceState* state = FindState(component);
    return state && state->instanceCreated;
}

size_t ScriptEngine::ScriptInstanceKeyHasher::operator()(const ScriptInstanceKey& key) const {
    const size_t h1 = std::hash<uint64_t>{}(key.gameObjectUUID);
    const size_t h2 = std::hash<uint64_t>{}(key.scriptComponentUUID);
    return h1 ^ (h2 + 0x9e3779b97f4a7c15ULL + (h1 << 6) + (h1 >> 2));
}

void ScriptEngine::CollectScriptComponents(Components::GameObject* gameObject) {
    if (!gameObject) {
        return;
    }

    for (ScriptComponent* component : gameObject->GetComponents<ScriptComponent>()) {
        TrackScriptComponent(component);
    }

    for (Components::GameObject* child : gameObject->GetChildren()) {
        CollectScriptComponents(child);
    }
}

void ScriptEngine::EnsureTrackedScriptsReady(Components::GameObject* gameObject) {
    if (!gameObject) {
        return;
    }

    for (ScriptComponent* component : gameObject->GetComponents<ScriptComponent>()) {
        ScriptInstanceState* state = FindState(component);
        if (!state || !ShouldScriptRun(*state)) {
            continue;
        }

        EnsureScriptReady(*state, true);
    }

    for (Components::GameObject* child : gameObject->GetChildren()) {
        EnsureTrackedScriptsReady(child);
    }
}

void ScriptEngine::HandleGameObjectCreated(Components::GameObject* gameObject) {
    if (!m_runtimeRunning || !gameObject || gameObject->GetScene() != m_runtimeScene) {
        return;
    }

    CollectScriptComponents(gameObject);
    EnsureTrackedScriptsReady(gameObject);
}

ScriptEngine::ScriptInstanceState* ScriptEngine::TrackScriptComponent(ScriptComponent* component) {
    if (!component || !component->GetGameObject()) {
        return nullptr;
    }

    const ScriptInstanceKey key{
        component->GetGameObject()->GetUUID(),
        component->GetScriptComponentUUID()
    };

    auto it = m_scriptStates.find(key);
    if (it != m_scriptStates.end()) {
        it->second.context.scene = component->GetScene();
        it->second.context.gameObject = component->GetGameObject();
        it->second.context.component = component;
        it->second.context.gameObjectUUID = component->GetGameObject()->GetUUID();
        it->second.context.scriptComponentUUID = component->GetScriptComponentUUID();
        return &it->second;
    }

    ScriptInstanceState state;
    state.context.scene = component->GetScene();
    state.context.gameObject = component->GetGameObject();
    state.context.component = component;
    state.context.gameObjectUUID = component->GetGameObject()->GetUUID();
    state.context.scriptComponentUUID = component->GetScriptComponentUUID();

    auto [insertedIt, inserted] = m_scriptStates.emplace(key, std::move(state));
    if (inserted) {
        m_scriptOrder.push_back(key);
    }

    return &insertedIt->second;
}

ScriptEngine::ScriptInstanceState* ScriptEngine::FindState(const ScriptComponent* component) {
    if (!component || !component->GetGameObject()) {
        return nullptr;
    }

    const ScriptInstanceKey key{
        component->GetGameObject()->GetUUID(),
        component->GetScriptComponentUUID()
    };

    auto it = m_scriptStates.find(key);
    return it != m_scriptStates.end() ? &it->second : nullptr;
}

const ScriptEngine::ScriptInstanceState* ScriptEngine::FindState(const ScriptComponent* component) const {
    if (!component || !component->GetGameObject()) {
        return nullptr;
    }

    const ScriptInstanceKey key{
        component->GetGameObject()->GetUUID(),
        component->GetScriptComponentUUID()
    };

    auto it = m_scriptStates.find(key);
    return it != m_scriptStates.end() ? &it->second : nullptr;
}

void ScriptEngine::RemoveTrackedScriptComponent(const ScriptComponent* component) {
    if (!component || !component->GetGameObject()) {
        return;
    }

    const ScriptInstanceKey key{
        component->GetGameObject()->GetUUID(),
        component->GetScriptComponentUUID()
    };

    m_scriptStates.erase(key);
    m_scriptOrder.erase(
        std::remove(m_scriptOrder.begin(), m_scriptOrder.end(), key),
        m_scriptOrder.end());
}

bool ScriptEngine::ShouldScriptRun(const ScriptInstanceState& state) const {
    return m_runtimeRunning
        && state.context.scene == m_runtimeScene
        && state.context.scene != nullptr
        && state.context.scene->IsActive()
        && state.context.gameObject != nullptr
        && state.context.gameObject->IsActiveInHierarchy()
        && state.context.component != nullptr
        && state.context.component->IsEnabled()
        && state.context.component->HasScriptClass();
}

bool ScriptEngine::EnsureScriptReady(ScriptInstanceState& state, bool invokeEnableIfNeeded) {
    if (!state.context.component || !state.context.gameObject || !state.context.scene || !state.context.component->HasScriptClass()) {
        return false;
    }

    if (!state.instanceCreated) {
        if (!m_runtime->CreateScriptInstance(state.context)) {
            return false;
        }
        state.instanceCreated = true;
    }

    if (!state.awakeCalled) {
        InvokeLifecycleMethod(state, ScriptLifecycleMethod::Awake);
        state.awakeCalled = true;
    }

    if (invokeEnableIfNeeded && !state.enabled && ShouldScriptRun(state)) {
        InvokeLifecycleMethod(state, ScriptLifecycleMethod::OnEnable);
        state.enabled = true;
        if (!state.startCalled) {
            state.startPending = true;
        }
    }

    return true;
}

void ScriptEngine::InvokeLifecycleMethod(ScriptInstanceState& state, ScriptLifecycleMethod method, float deltaTime) {
    m_runtime->InvokeMethod(state.context, method, deltaTime);
}

void ScriptEngine::StopTrackingScript(ScriptInstanceState& state, bool runtimeStopping) {
    if (state.enabled) {
        InvokeLifecycleMethod(state, ScriptLifecycleMethod::OnDisable);
        state.enabled = false;
    }

    if (state.instanceCreated) {
        InvokeLifecycleMethod(state, ScriptLifecycleMethod::OnDestroy);
        m_runtime->DestroyScriptInstance(state.context);
        state.instanceCreated = false;
    }

    state.startPending = false;

    if (!runtimeStopping) {
        RemoveTrackedScriptComponent(state.context.component);
    }
}

} // namespace Scripting
} // namespace XCEngine