%%%----------------------------------------------------------------------
%%% File    : ejabberd_node_groups.erl
%%% Author  : Alexey Shchepin <alexey@process-one.net>
%%% Purpose : Distributed named node groups based on pg2 module
%%% Created :  1 Nov 2006 by Alexey Shchepin <alexey@process-one.net>
%%%
%%%
%%% ejabberd, Copyright (C) 2002-2017   ProcessOne
%%%
%%% This program is free software; you can redistribute it and/or
%%% modify it under the terms of the GNU General Public License as
%%% published by the Free Software Foundation; either version 2 of the
%%% License, or (at your option) any later version.
%%%
%%% This program is distributed in the hope that it will be useful,
%%% but WITHOUT ANY WARRANTY; without even the implied warranty of
%%% MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
%%% General Public License for more details.
%%%
%%% You should have received a copy of the GNU General Public License along
%%% with this program; if not, write to the Free Software Foundation, Inc.,
%%% 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
%%%
%%%----------------------------------------------------------------------

-module(ejabberd_node_groups).

-behaviour(ejabberd_config).
-author('alexey@process-one.net').

-behaviour(gen_server).

%% API
-export([start_link/0,
	 join/1,
	 leave/1,
	 get_members/1,
	 get_closest_node/1]).

-export([init/1, handle_call/3, handle_cast/2,
	 handle_info/2, terminate/2, code_change/3, opt_type/1]).

-define(PG2, pg2).

-record(state, {}).

%%====================================================================
%% API
%%====================================================================
%%--------------------------------------------------------------------
%% Function: start_link() -> {ok,Pid} | ignore | {error,Error}
%% Description: Starts the server
%%--------------------------------------------------------------------
start_link() ->
    gen_server:start_link({local, ?MODULE}, ?MODULE, [], []).

join(Name) ->
    PG = {?MODULE, Name},
    pg2:create(PG),
    pg2:join(PG, whereis(?MODULE)).

leave(Name) ->
    PG = {?MODULE, Name},
    pg2:leave(PG, whereis(?MODULE)).

get_members(Name) ->
    PG = {?MODULE, Name},
    [node(P) || P <- pg2:get_members(PG)].

get_closest_node(Name) ->
    PG = {?MODULE, Name},
    node(pg2:get_closest_pid(PG)).

%%====================================================================
%% gen_server callbacks
%%====================================================================

%%--------------------------------------------------------------------
%% Function: init(Args) -> {ok, State} |
%%                         {ok, State, Timeout} |
%%                         ignore               |
%%                         {stop, Reason}
%% Description: Initiates the server
%%--------------------------------------------------------------------
init([]) ->
    {FE, BE} =
	case ejabberd_config:get_option(
               node_type,
               fun(frontend) -> frontend;
                  (backend) -> backend;
                  (generic) -> generic
               end, generic) of
	    frontend ->
		{true, false};
	    backend ->
		{false, true};
	    generic ->
		{true, true};
	    undefined ->
		{true, true}
	end,
    if
	FE ->
	    join(frontend);
	true ->
	    ok
    end,
    if
	BE ->
	    join(backend);
	true ->
	    ok
    end,
    {ok, #state{}}.

%%--------------------------------------------------------------------
%% Function: %% handle_call(Request, From, State) -> {reply, Reply, State} |
%%                                      {reply, Reply, State, Timeout} |
%%                                      {noreply, State} |
%%                                      {noreply, State, Timeout} |
%%                                      {stop, Reason, Reply, State} |
%%                                      {stop, Reason, State}
%% Description: Handling call messages
%%--------------------------------------------------------------------
handle_call(_Request, _From, State) ->
    Reply = ok,
    {reply, Reply, State}.

%%--------------------------------------------------------------------
%% Function: handle_cast(Msg, State) -> {noreply, State} |
%%                                      {noreply, State, Timeout} |
%%                                      {stop, Reason, State}
%% Description: Handling cast messages
%%--------------------------------------------------------------------
handle_cast(_Msg, State) ->
    {noreply, State}.

%%--------------------------------------------------------------------
%% Function: handle_info(Info, State) -> {noreply, State} |
%%                                       {noreply, State, Timeout} |
%%                                       {stop, Reason, State}
%% Description: Handling all non call/cast messages
%%--------------------------------------------------------------------
handle_info(_Info, State) ->
    {noreply, State}.

%%--------------------------------------------------------------------
%% Function: terminate(Reason, State) -> void()
%% Description: This function is called by a gen_server when it is about to
%% terminate. It should be the opposite of Module:init/1 and do any necessary
%% cleaning up. When it returns, the gen_server terminates with Reason.
%% The return value is ignored.
%%--------------------------------------------------------------------
terminate(_Reason, _State) ->
    ok.

%%--------------------------------------------------------------------
%% Func: code_change(OldVsn, State, Extra) -> {ok, NewState}
%% Description: Convert process state when code is changed
%%--------------------------------------------------------------------
code_change(_OldVsn, State, _Extra) ->
    {ok, State}.

%%--------------------------------------------------------------------
%%% Internal functions
%%--------------------------------------------------------------------

opt_type(node_type) ->
    fun (frontend) -> frontend;
	(backend) -> backend;
	(generic) -> generic
    end;
opt_type(_) -> [node_type].
