#include "build/generated/sources/headers/java/main/ru_dbotthepony_kstarbound_lua_LuaJNI.h"
#include "lua-5.3.6/src/lapi.h"
#include "lua-5.3.6/src/lua.h"
#include "lua-5.3.6/src/lauxlib.h"
#include <stdio.h>

static int lua_jniFunc(lua_State *state) {
	JNIEnv *env = (JNIEnv *) lua_touserdata(state, lua_upvalueindex(1));
	jmethodID callback = (jmethodID) lua_touserdata(state, lua_upvalueindex(2));
	jobject* lua_JCClosure = (jobject*) lua_touserdata(state, lua_upvalueindex(3));

	jint result = (*env)->CallIntMethod(env, *lua_JCClosure, callback, (long long) state);

	if (result <= -1) {
		return lua_error(state);
	}

	return result;
}

static int remove_gc_root(lua_State *state) {
	JNIEnv *env = (JNIEnv *) lua_touserdata(state, lua_upvalueindex(1));
	jobject* obj = (jobject*) lua_touserdata(state, 1);

	if (obj == NULL) {
		printf("Lua Glue: remove_gc_root: obj is NULL! This is VERY LIKELY is going to result into a memory leak!\n");
		return 0;
	}

	(*env)->DeleteGlobalRef(env, *obj);
	return 0;
}

static JNIEXPORT void JNICALL Java_ru_dbotthepony_kstarbound_lua_LuaJNI_lua_1pushcclosure(JNIEnv *env, jclass interface, jlong luaState, jobject lua_JCClosure) {
	lua_State* LluaState = (lua_State*) luaState;

	jclass clazz = (*env)->GetObjectClass(env, lua_JCClosure);

	if (clazz == NULL)
		return;

	jmethodID callback = (*env)->GetMethodID(env, clazz, "invoke", "(J)I");

	if (callback == NULL)
		return;

	lua_pushlightuserdata(LluaState, env);
	lua_pushlightuserdata(LluaState, callback);
	void *umemory = lua_newuserdata(LluaState, sizeof(jobject));
	jobject* rawBlock = (jobject*) umemory;
	*rawBlock = (*env)->NewGlobalRef(env, lua_JCClosure);

	int userdataIndex = lua_gettop(LluaState);

	// local table = {}
	lua_createtable(LluaState, 0, 1);
	int tableIndex = lua_gettop(LluaState);

	// function()
	lua_pushlightuserdata(LluaState, env);
	lua_pushcclosure(LluaState, remove_gc_root, 1);

	// table.__gc = fn
	lua_setfield(LluaState, tableIndex, "__gc");

	// setmetatable(userdata, table)
	lua_setmetatable(LluaState, userdataIndex);

	lua_pushcclosure(LluaState, lua_jniFunc, 3);
}

// pushes Java object to Lua state, creating new GC root
// Created reference is full userdata, hence it can have metatables attached to it
// IT IS EXPECTED that before pushing object, at top of stack there is a table which is to be attached as metatable to newly created object
// After this function returns, freshly created userdata will replace metatable
static JNIEXPORT void JNICALL Java_ru_dbotthepony_kstarbound_lua_LuaJNI_lua_1pushjobject(JNIEnv *env, jclass interface, jlong luaState, jobject obj) {
	lua_State* LluaState = (lua_State*) luaState;

	jobject *umemory = (jobject *) lua_newuserdata(LluaState, sizeof(jobject));
	*umemory = (*env)->NewGlobalRef(env, obj);

	lua_pushlightuserdata(LluaState, env);
	lua_pushcclosure(LluaState, remove_gc_root, 1);
	lua_setfield(LluaState, -3, "__gc");

	lua_pushnil(LluaState);
	lua_copy(LluaState, -3, -1);

	lua_setmetatable(LluaState, -2);
	lua_copy(LluaState, -1, -2);
	lua_settop(LluaState, -2);
}

// returns NULL if index is invalid or doesn't contain userdata
static JNIEXPORT jobject JNICALL Java_ru_dbotthepony_kstarbound_lua_LuaJNI_lua_1tojobject(JNIEnv *env, jclass interface, jlong luaState, jint stackIndex) {
	lua_State* LluaState = (lua_State*) luaState;

	jobject *data = lua_touserdata(LluaState, stackIndex);

	if (data == NULL)
		return NULL;

	return *data;
}