%% ---------------------------------------------------------------------
%% File: mathserver.erl
%%
%% This is a simple implementation of a gen_server callback module.

-module(mathserver).

-behaviour(gen_server).

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

-export([
            start_link/0,
            stop/0,
            multiply/2
            ]).

-define(SERVER, ?MODULE).

-record(state, { }).
%%%===================================================================
%%% API
%%%===================================================================


%%--------------------------------------------------------------------
%% @doc Starts the server.
%%
%% @spec start_link() -> {ok, Pid}
%% where
%% Pid = pid()
%% @end
%%--------------------------------------------------------------------
start_link() ->
    gen_server:start_link({local, ?SERVER}, ?MODULE, [], []).

%%--------------------------------------------------------------------
%% @doc Stops the server.
%% @spec stop() -> ok
%% @end
%%--------------------------------------------------------------------
stop() ->
    gen_server:cast(?SERVER, stop).

%%--------------------------------------------------------------------
%% @doc multiplies two integers.
%% @spec multiply(X::integer(), Y::integer()) -> {ok, Product}
%% where
%% Product = integer()
%% @end
%%--------------------------------------------------------------------
multiply(X, Y) ->
    gen_server:call(?SERVER, {multiply, {X, Y}}).


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


init([]) ->
    {ok, #state{}}.

handle_call({multiply, {X, Y}}, _From, State) ->
    Reply = {ok, multiply_impl(X,Y)},
    {reply, Reply, State};
handle_call(_Request, _From, State) ->
    Reply = ok,
    {reply, Reply, State}.

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

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

terminate(_Reason, _State) ->
    ok.

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

%%%===================================================================
%%% API internals
%%%===================================================================

multiply_impl(First, Second) ->
    First * Second.