-module(gmhc_events).
-vsn("0.4.8").

-export([subscribe/1,
         ensure_subscribed/1,
         unsubscribe/1,
         ensure_unsubscribed/1,
         publish/2]).

-export([debug/0]).

-export_type([event/0]).

-type event() :: pool_notification
               | {pool_notification, atom()}
               | error
               | puzzle
               | result
               | connected
               | disconnected.

-spec publish(event(), any()) -> ok.
publish(Event, Info) ->
    Data = #{sender => self(),
             time => os:timestamp(),
             info => Info},
    _ = gproc_ps:publish(l, Event, Data),
    ok.

-spec subscribe(event()) -> true.
subscribe(Event) ->
    gproc_ps:subscribe(l, Event).

-spec ensure_subscribed(event()) -> true.
%% @doc Subscribes to Event. Will not crash if called more than once.
ensure_subscribed(Event) ->
    try subscribe(Event)
    catch
        error:badarg ->
            %% This assertion should not be needed, since there is
            %% no other scenario that would cause subscribe/1 to fail,
            %% other than gproc not running (would also cause a badarg)
            _ = gproc:get_value({p,l,{gproc_ps_event, Event}}, self()),
            true
    end.

-spec unsubscribe(event()) -> true.
unsubscribe(Event) ->
    gproc_ps:unsubscribe(l, Event).

-spec ensure_unsubscribed(event()) -> true.
ensure_unsubscribed(Event) ->
    case lists:member(self(), gproc_ps:list_subs(l,Event)) of
        true ->
            unsubscribe(Event);
        false ->
            true
    end.


debug() ->
    ok = application:ensure_started(gproc),
    spawn(fun() ->
                  subscribe(pool_notification),
                  subscribe({pool_notification, new_generation}),
                  subscribe(connected),
                  subscribe(puzzle),
                  subscribe(result),
                  subscribe(error),
                  subscribe(disconnected),
                  loop()
          end).

loop() ->
    receive
        stop -> ok;
        {gproc_ps_event, E, Data} ->
            io:fwrite("EVENT ~p: ~p~n", [E, Data]),
            loop()
    end.