// This is called by the VM when the shared library is first loaded.*
JNIEXPORT jint JNI_OnLoad(JavaVM* vm, void* reserved) {

  *// Initialize the Java VM.*
  fml::jni::InitJavaVM(vm);
  JNIEnv* env = fml::jni::AttachCurrentThread();

  bool result = false;
  *// Register FlutterMain.*
  result = flutter::FlutterMain::Register(env);
  FML_CHECK(result);

  *// Register PlatformView*
  result = flutter::PlatformViewAndroid::Register(env);
  FML_CHECK(result);

  *// Register VSyncWaiter.*
  result = flutter::VsyncWaiterAndroid::Register(env);
  FML_CHECK(result);
  
  return JNI_VERSION_1_4;

}

static JavaVM* g_jvm = nullptr;

void InitJavaVM(JavaVM* vm) {
  FML_DCHECK(g_jvm == nullptr);
  g_jvm = vm;
}

JNIEnv* AttachCurrentThread() {
  FML_DCHECK(g_jvm != nullptr)
      << "Trying to attach to current thread without calling InitJavaVM first.";
  JNIEnv* env = nullptr;
  jint ret = g_jvm->AttachCurrentThread(&env, nullptr);
  FML_DCHECK(JNI_OK == ret);
  return env;
}

bool FlutterMain::Register(JNIEnv* env) {
  static const JNINativeMethod methods[] = {
      {
          .name = "nativeInit",
          .signature = "(Landroid/content/Context;[Ljava/lang/String;Ljava/"
                       "lang/String;Ljava/lang/String;Ljava/lang/String;)V",
          .fnPtr = reinterpret_cast<void*>(&Init),
      },
      {
          .name = "nativeRecordStartTimestamp",
          .signature = "(J)V",
          .fnPtr = reinterpret_cast<void*>(&RecordStartTimestamp),
      },
  };

  jclass clazz = env->FindClass("io/flutter/embedding/engine/FlutterJNI");

  if (clazz == nullptr) {
    return false;
  }

  return env->RegisterNatives(clazz, methods, fml::size(methods)) == 0;
}

void FlutterMain::Init(JNIEnv* env,
                       jclass clazz,
                       jobject context,
                       jobjectArray jargs,
                       jstring kernelPath,
                       jstring appStoragePath,
                       jstring engineCachesPath) {
  std::vector<std::string> args;
  args.push_back("flutter");
  for (auto& arg : fml::jni::StringArrayToVector(env, jargs)) {
    args.push_back(std::move(arg));
  }
  auto command_line = fml::CommandLineFromIterators(args.begin(), args.end());

  auto settings = SettingsFromCommandLine(command_line);

  // Restore the callback cache.
  // TODO(chinmaygarde): Route all cache file access through FML and remove this
  // setter.
  flutter::DartCallbackCache::SetCachePath(
      fml::jni::JavaStringToString(env, appStoragePath));

  fml::paths::InitializeAndroidCachesPath(
      fml::jni::JavaStringToString(env, engineCachesPath));

  flutter::DartCallbackCache::LoadCacheFromDisk();

  if (!flutter::DartVM::IsRunningPrecompiledCode() && kernelPath) {
    // Check to see if the appropriate kernel files are present and configure
    // settings accordingly.
    auto application_kernel_path =
        fml::jni::JavaStringToString(env, kernelPath);

    if (fml::IsFile(application_kernel_path)) {
      settings.application_kernel_asset = application_kernel_path;
    }
  }

  settings.task_observer_add = [](intptr_t key, fml::closure callback) {
    fml::MessageLoop::GetCurrent().AddTaskObserver(key, std::move(callback));
  };

  settings.task_observer_remove = [](intptr_t key) {
    fml::MessageLoop::GetCurrent().RemoveTaskObserver(key);
  };

#if FLUTTER_RUNTIME_MODE == FLUTTER_RUNTIME_MODE_DEBUG
  // There are no ownership concerns here as all mappings are owned by the
  // embedder and not the engine.
  auto make_mapping_callback = [](const uint8_t* mapping, size_t size) {
    return [mapping, size]() {
      return std::make_unique<fml::NonOwnedMapping>(mapping, size);
    };
  };

  settings.dart_library_sources_kernel =
      make_mapping_callback(kPlatformStrongDill, kPlatformStrongDillSize);
#endif  // FLUTTER_RUNTIME_MODE == FLUTTER_RUNTIME_MODE_DEBUG

  // Not thread safe. Will be removed when FlutterMain is refactored to no
  // longer be a singleton.
  g_flutter_main.reset(new FlutterMain(std::move(settings)));

  g_flutter_main->SetupObservatoryUriCallback(env);
}

FlutterMain::FlutterMain(flutter::Settings settings)
    : settings_(std::move(settings)), observatory_uri_callback_() {}