# Java related services specific to Android and its Dalvik VM
module dalvik

import activities

redef class App
	# Main Java Activity of this application
	#
	# Require: A Nit activity is currently running.
	fun native_activity: NativeActivity is abstract

	# Current reference context, either an activity or a service
	fun native_context: NativeContext do return native_activity
end

redef class Sys

	# We cannot create a JVM on Android
	#
	# This method is not reachable on this platform anyway.
	# `Sys::jvm` is implemented by the main activity modules.
	redef fun create_default_jvm do abort

	redef fun jni_env do return jvm.attach_current_thread

	private var class_loader: nullable JavaObject = null

	private var class_loader_method: nullable JMethodID = null

	redef fun load_jclass(name)
	do
		var class_loader = self.class_loader
		if class_loader == null then
			find_class_loader app.native_context
			class_loader = self.class_loader
			assert class_loader != null
		end

		var class_loader_method = self.class_loader_method
		assert class_loader_method != null

		return load_jclass_intern(class_loader, class_loader_method, name)
	end

	private fun find_class_loader(native_context: NativeContext) import jni_env, class_loader=, JavaObject.as nullable, class_loader_method=, JMethodID.as nullable `{
		JNIEnv *env = Sys_jni_env(self);

		// Retrieve main activity
		jclass class_context = (*env)->GetObjectClass(env, native_context);
		if (class_context == NULL) {
			__android_log_print(ANDROID_LOG_ERROR, "Nit", "Failed to retrieve activity class");
			(*env)->ExceptionDescribe(env);
			exit(1);
		}

		jmethodID class_activity_getClassLoader = (*env)->GetMethodID(env, class_context, "getClassLoader", "()Ljava/lang/ClassLoader;");
		if (class_activity_getClassLoader == NULL) {
			__android_log_print(ANDROID_LOG_ERROR, "Nit", "Failed to retrieve 'getClassLoader' method");
			(*env)->ExceptionDescribe(env);
			exit(1);
		}

		// Call activity.getClassLoader
		jobject instance_class_loader = (*env)->CallObjectMethod(env, native_context, class_activity_getClassLoader);
		if (instance_class_loader == NULL) {
			__android_log_print(ANDROID_LOG_ERROR, "Nit", "Failed to retrieve class loader instance");
			(*env)->ExceptionDescribe(env);
			exit(1);
		}

		jclass class_class_loader = (*env)->GetObjectClass(env, instance_class_loader);
		if (class_class_loader == NULL) {
			__android_log_print(ANDROID_LOG_ERROR, "Nit", "Failed to retrieve class of class loader");
			(*env)->ExceptionDescribe(env);
			exit(1);
		}

		// Get the method ClassLoader.findClass
		jmethodID class_class_loader_findClass = (*env)->GetMethodID(env, class_class_loader, "findClass", "(Ljava/lang/String;)Ljava/lang/Class;");
		if (class_class_loader_findClass == NULL) {
			__android_log_print(ANDROID_LOG_ERROR, "Nit", "Failed to retrieve 'findClass' method");
			(*env)->ExceptionDescribe(env);
			exit(1);
		}

		// Return the values to Nit
		Sys_class_loader__assign(self, JavaObject_as_nullable((*env)->NewGlobalRef(env, instance_class_loader)));
		Sys_class_loader_method__assign(self, JMethodID_as_nullable(class_class_loader_findClass));

		// Clean up
		(*env)->DeleteLocalRef(env, class_context);
		(*env)->DeleteLocalRef(env, instance_class_loader);
		(*env)->DeleteLocalRef(env, class_class_loader);
	`}

	private fun load_jclass_intern(instance_class_loader: JavaObject, class_loader_findClass: JMethodID, name: CString): JClass import jni_env `{
		JNIEnv *env = Sys_jni_env(self);
		jobject class_name = (*env)->NewStringUTF(env, name);

		jclass java_class = (*env)->CallObjectMethod(env, instance_class_loader, class_loader_findClass, class_name);
		if (java_class == NULL) {
			__android_log_print(ANDROID_LOG_ERROR, "Nit", "Failed loading targeted class");
			(*env)->ExceptionDescribe(env);
			exit(1);
		}

		(*env)->DeleteLocalRef(env, class_name);

		return java_class;
	`}
end