// Handle errors with a Lua function, defined in lua-env.lua
int bll_error_handler(lua_State *L) {
	lua_getfield(L, LUA_GLOBALSINDEX, "_bllua_on_error");
	if (!lua_isfunction(L, -1)) {
		BlPrintf("  Lua error handler: _bllua_on_error not defined.");
		lua_pop(L, 1);
		return 1;
	}
	
	// move function to before arg
	int hpos = lua_gettop(L) - 1;
	lua_insert(L, hpos);
	
	lua_pcall(L, 1, 1, 0);
	return 1;
}
int bll_pcall(lua_State* L, int nargs, int nret) {
	// calculate stack position for message handler
	int hpos = lua_gettop(L) - nargs;
	// push custom error message handler
	lua_pushcfunction(L, bll_error_handler);
	// move it before function and arguments
	lua_insert(L, hpos);
	// call lua_pcall function with custom handler
	int ret = lua_pcall(L, nargs, nret, hpos);
	// remove custom error message handler from stack
	lua_remove(L, hpos);
	return ret;
}

// Display the last Lua error in the BL console
void bll_printError(lua_State* L, const char* operation, const char* item) {
	//error_handler(L);
	BlPrintf("\x03Lua error: %s", lua_tostring(L, -1));
	BlPrintf("\x03  (%s: %s)", operation, item);
	lua_pop(L, 1);
}

// Eval a string of Lua code
bool bll_LuaEval(lua_State* L, const char* str) {
	if(luaL_loadbuffer(L, str, strlen(str), "input") || bll_pcall(L, 0, 1)) {
		bll_printError(L, "eval", str);
		return false;
	}
	return true;
}

// Convert a Lua stack entry into a string for providing to TS
// Use static buffer to avoid excessive malloc
#define BLL_ARG_COUNT 20
#define BLL_ARG_MAX 8192
char bll_arg_buffer[BLL_ARG_COUNT][BLL_ARG_MAX];
bool bll_toarg(lua_State* L, char* buf, int i, bool err) {
	if(lua_isstring(L, i)) {
		const char* str = lua_tostring(L, i);
		if(strlen(str) >= BLL_ARG_MAX) {
			if(err) luaL_error(L, "argument to TS is too long - max length is 8192");
			return true;
		} else {
			strcpy(buf, str);
			return false;
		}
	} else {
		if(err) luaL_error(L, "argument to TS must be a string");
		return true;
	}
}