-module(m8ball_server).
-behaviour(gen_server).
-export([start_link/0, stop/0, ask/1]).
-export([init/1, handle_call/3, handle_cast/2, handle_info/2,
         code_change/3, terminate/2]).

%%%%%%%%%%%%%%%%%
%%% INTERFACE %%%
%%%%%%%%%%%%%%%%%
start_link() ->
    gen_server:start_link({global, ?MODULE}, ?MODULE, [], []).

stop() ->
    gen_server:call({global, ?MODULE}, stop).

ask(_Question) -> % the question doesn't matter!
    gen_server:call({global, ?MODULE}, question).

%%%%%%%%%%%%%%%%%
%%% CALLBACKS %%%
%%%%%%%%%%%%%%%%%
init([]) ->
    <<A:32, B:32, C:32>> = crypto:rand_bytes(12),
    random:seed(A,B,C),
    {ok, []}.

handle_call(question, _From, State) ->
    {ok, Answers} = application:get_env(m8ball, answers),
    Answer = element(random:uniform(tuple_size(Answers)), Answers),
    {reply, Answer, State};
handle_call(stop, _From, State) ->
    {stop, normal, ok, State};
handle_call(_Call, _From, State) ->
    {noreply, State}.

handle_cast(_Cast, State) ->
    {noreply, State}.

handle_info(_Info, State) ->
    {noreply, State}.

code_change(_OldVsn, State, _Extra) ->
    {ok, State}.

terminate(_Reason, _State) ->
    ok.