# Represents a jni JavaVM
extern class JavaVM `{JavaVM *`}
	# Create the JVM
	#
	# The corresponding `JniEnv` can be obtained by calling `env`.
	#
	# Unavailable on some platforms, including Android where you cannot instanciate a new JVM.
	private new(args: JavaVMInitArgs) import jni_error `{

	#ifdef ANDROID
		JavaVM_jni_error(NULL, "JVM creation not supported on Android", 0);
		return NULL;
	#endif

		JavaVM *jvm;
		JNIEnv *env;
		jint res;

		res = JNI_CreateJavaVM(&jvm, (void**)&env, args);

		if (res != JNI_OK) {
			JavaVM_jni_error(NULL, "Could not create Java VM", res);
			return NULL;
		}

		return jvm;
	`}

	private fun jni_error(msg: CString, v: Int)
	do
		print "JNI Error: {msg} ({v})"
		abort
	end

	# Unload the Java VM when the calling thread is the only remaining non-daemon attached user thread
	fun destroy `{
		(*self)->DestroyJavaVM(self);
	`}

	# `JniEnv` attached to the calling thread
	#
	# A null pointer is returned if the calling thread is not attached to the JVM.
	fun env: JniEnv import jni_error `{
		JNIEnv *env;
		int res = (*self)->GetEnv(self, (void **)&env, JNI_VERSION_1_6);
		if (res == JNI_EDETACHED) {
			JavaVM_jni_error(NULL, "Requesting JNIEnv from an unattached thread", res);
			return NULL;
		}
		else if (res != JNI_OK) {
			JavaVM_jni_error(NULL, "Could not get JNIEnv from Java VM", res);
			return NULL;
		}
		return env;
	`}

	# Attach the calling thread to the JVM and return its `JniEnv`
	fun attach_current_thread: JniEnv import jni_error `{
		JNIEnv *env;
	#ifdef ANDROID
		// the signature is different (better actually) on Android
		int res = (*self)->AttachCurrentThread(self, &env, NULL);
	#else
		int res = (*self)->AttachCurrentThread(self, (void**)&env, NULL);
	#endif
		if (res != JNI_OK) {
			JavaVM_jni_error(NULL, "Could not attach current thread to Java VM", res);
			return NULL;
		}
		return env;
	`}

	# Detach the calling thread from this JVM
	fun detach_current_thread import jni_error `{
		int res = (*self)->DetachCurrentThread(self);
		if (res != JNI_OK) {
			JavaVM_jni_error(NULL, "Could not detach current thread to Java VM", res);
		}
	`}
end