Ticket #3022: mod_gamelist.erl

%% Copyright (C) 2016 Wildfire Games.
%% This file is part of 0 A.D.
%%
%% 0 A.D. 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.
%%
%% 0 A.D. 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 0 A.D.  If not, see <http://www.gnu.org/licenses/>.

-module(mod_gamelist).

-behaviour(gen_mod).

% Hack to fix build. Ejabberd rewrote the module build system without leaving any
% instructions on how to upgrade. This is from Stack Overflow
% (http://stackoverflow.com/questions/32542102/ejabberd-debugging)
%TODO: Proper version checking
%-ifndef(LAGER).
%-define(LAGER, 1).
%-endif.
%-ifndef(NO_EXT_LIB).
%-define(NO_EXT_LIB, 1).
%-endif.

%% Handy shortcuts to improve readability
-record(xmlelement, {name = ""     :: string(),
                     attrs = []    :: [{string(), string()}],
                     children = [] :: [{xmlcdata, iodata()} | xmlelement()]}).
-type xmlelement() :: #xmlelement{}.
% TODO: Evaluate if we actually need dbentry
-record(dbentry, {key :: jid,
                  value :: xmlelement()}).

-include("ejabberd.hrl").
-include("jlib.hrl").

-export([start/2, stop/1, process_gamelist_iq/3]).

-define(GAMELIST_NS, "jabber:iq:gamelist").

start(Host, _Opts) ->
    ?INFO_MSG("Starting mod_gamelist", []),
    % Create a table named 'games' with the default options
    mnesia:create_table(games,
        [{attributes, record_info(fields, dbentry)}, {record_name, dbentry}]),
    %% Make sure that the table is empty, as create_table won't overwrite an existing
    %% table
    mnesia:clear_table(games),
    %% Handle all stanzas addressed to the server containing the jabberd:iq:gamelist
    %% namespace with process_gamelist_iq/3 and queue pending stanzas. May be
    %% interesting to experiment with using parallel execution instead of queued.
    gen_iq_handler:add_iq_handler(ejabberd_local, Host, ?GAMELIST_NS, ?MODULE,
        process_gamelist_iq, one_queue).

stop(Host) ->
    ?INFO_MSG("Stopping mod_gamelist", []),
    mnesia:delete_table(games),
    gen_iq_handler:remove_iq_handler(ejabberd_local, Host, ?GAMELIST_NS).

% Handle gamelist IQ stanzas
process_gamelist_iq(From, To, IQ) ->
    ?INFO_MSG("Gamelist stanza received from ~p: ~n ~p ~n", [From, IQ]),
    % TODO: Add a checked room field to the message, keep per room databases
    case IQ#iq.type of
        set ->
            % Find and extract the command
            CommandXml = lists:keyfind("command", 2, IQ#iq.sub_el#xmlelement.children),
            [{xmlcdata, Command}] = CommandXml#xmlelement.children,
            ?INFO_MSG("Command: ~p~n", [Command]),
            % TODO: Something about changestate
            case Command of
                <<"register">> ->
                    % Extract game
                    Game = lists:keyfind("game", 2, IQ#iq.sub_el#xmlelement.children),
                    % Get host's (sender's) IP so that client know who to connect to
                    Origin = ejabberd_sm:get_user_ip(From#jid.user, From#jid.server, From#jid.resource),
                    HostIPString = inet_parse:ntoa(element(1, Origin)),
                    % Merge in the IP
                    MergedGameProperties = lists:keyreplace("ip", 1, Game#xmlelement.attrs, {"ip", HostIPString}),
                    MergedGame = Game#xmlelement{attrs = MergedGameProperties},
                    ?INFO_MSG("Attempting to register game: ~p~nFrom: ~p", [MergedGame, From]),
                    % Save the game to the database
                    mnesia:dirty_write(games, {dbentry, From, MergedGame}),
                    % TODO: Multicast new gamelist
                    ?INFO_MSG("'dev' users: ~p", [p1_fsm:sync_send_all_state_event(mnesia:dirty_read(muc_online_room, {"dev", "localhost"}), {get_disco_item, From, "en"}, 100)]),%mod_muc_admin:get_room_occupants("dev", "localhost")]),
                    Room = #jid{user = "dev", server = "localhost", resource = "", luser = "dev", lserver = "localhost", lresource = ""},
                    ejabberd_router:route(To, Room, jlib:iq_to_xml(get_gamelist_result_iq())),
                    % Aknowledge registration
                    IQ#iq{type = result, sub_el = []};
                <<"unregister">> ->
                    ?INFO_MSG("Attempting to unregister game...", []),
                    mnesia:dirty_delete(games, From),
                    IQ#iq{type = result, sub_el = []};
                _Else ->
                    IQ#iq{type = error, sub_el = [IQ#iq.sub_el, ?ERR_NOT_ACCEPTABLE]}
            end;
        get ->
            % Dump database 
            ?INFO_MSG("Attempting to send game listings...", []),
            get_gamelist_result_iq();
        _Else ->
            IQ#iq{type = error, sub_el = [IQ#iq.sub_el, ?ERR_NOT_ACCEPTABLE]}
    end.

get_gamelist_result_iq() ->
    %% Create a Query List Comprehension handle for the database, and
    %% evaluate it to get all the database contents
    {atomic, Games} = mnesia:transaction(fun() -> qlc:eval(mnesia:table(games)) end),
    ?INFO_MSG("Recieved: ~p from DB.~n", [Games]),
    GamesXml = lists:map(fun(Game) -> Game#dbentry.value end, Games),
    SubEl = #xmlelement{name = <<"query">>, attrs = [{<<"xmlns">>, ?GAMELIST_NS}], children = GamesXml},
    #iq{type = result, xmlns = ?GAMELIST_NS, sub_el = [SubEl]}.