teleprom

-module(teleprom_registry).

-behaviour(gen_server).

-include("self.hrl").

-include_lib("eunit/include/eunit.hrl").

-export([start_link/0]).
-export([init/1, handle_call/3, handle_cast/2, handle_info/2, terminate/2, code_change/3]).
-export([register_events/3]).

start_link() -> gen_server:start_link({local, ?MODULE}, ?MODULE, [], []).

register_events(App, EventsType, Events) ->
  persistent_term:put(
    iolist_to_binary([atom_to_list(App), <<"_telemetry_events:">>, atom_to_list(EventsType)]),
    Events
  ),
  gen_server:call(?MODULE, {register_events, App, EventsType, Events}).


init(_Args) ->
  erlang:send(self(), register_self_events),
  [Handler:register_metrics() || Handler <- event_handlers()],
  {ok, #{apps => [], events => []}}.


handle_call(
  {register_events, App, EventsType, Events},
  _From,
  #{apps := RegistredApps, events := RegistredEvents} = State
) ->
  NewApplications = lists:usort([App] ++ RegistredApps),
  NewEventsList = lists:usort(Events ++ RegistredEvents),
  [
    Handler:init(#{apps => NewApplications, new_events => {EventsType, Events}})
    || Handler <- event_handlers()
  ],
  {reply, ok, State#{apps => NewApplications, events => NewEventsList}};

handle_call(_Request, _From, State) -> {reply, ok, State}.


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

handle_info(register_self_events, State) ->
  spawn(fun register_telemetry_events/0),
  {noreply, State};

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


terminate(_Reason, _State) -> ok.

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

register_telemetry_events() ->
  ?REGISTER_APP_EVENTS(teleprom, positive, ?TELEPROM_POSITIVE_TELEMETRY_EVENTS),
  ?REGISTER_APP_EVENTS(teleprom, negative, ?TELEPROM_NEGATIVE_TELEMETRY_EVENTS),
  ?REGISTER_APP_EVENTS(teleprom, all, ?TELEPROM_ALL_TELEMETRY_EVENTS),
  ?EXEC_TELEMETRY(?TELEPROM_REGISTER_SELF_EVENTS),
  ok.


event_handlers() -> application:get_env(teleprom, event_handlers, []).