%%%-------------------------------------------------------------------
%%% @doc Пользовательский WebSocket-обработчик.
%%%
%%% Устанавливает WebSocket-соединение после проверки JWT-токена
%%% и подписывает пользователя на обновления календарей.
%%%
%%% Поддерживаемые действия:
%%% - subscribe   – подписаться на обновления календаря
%%% - unsubscribe – отписаться от обновлений
%%% - ping        – проверка соединения
%%% @end
%%%-------------------------------------------------------------------
-module(ws_handler).
-behaviour(cowboy_websocket).

-export([init/2]).
-export([websocket_init/1]).
-export([websocket_handle/2]).
-export([websocket_info/2]).
-export([terminate/3]).

-record(state, {
  user_id       :: binary() | undefined,
  subscriptions = [] :: [binary()]   % ← инициализация пустым списком
}).

%%%===================================================================
%%% cowboy_websocket callback
%%%===================================================================

-spec init(cowboy_req:req(), any()) ->
  {ok, cowboy_req:req(), undefined} |
  {cowboy_websocket, cowboy_req:req(), #state{}}.
init(Req, _Opts) ->
  Qs = cowboy_req:parse_qs(Req),
  case proplists:get_value(<<"token">>, Qs) of
    undefined ->
      Req1 = cowboy_req:reply(401, #{}, <<"Missing token">>, Req),
      {ok, Req1, undefined};
    Token ->
      case logic_auth:verify_jwt(Token) of
        {ok, UserId, _Role} ->
          {cowboy_websocket, Req, #state{user_id = UserId}};
        {error, _} ->
          Req1 = cowboy_req:reply(401, #{}, <<"Invalid token">>, Req),
          {ok, Req1, undefined}
      end
  end.

%%%===================================================================
%%% websocket callbacks
%%%===================================================================

-spec websocket_init(#state{}) -> {ok, #state{}}.
websocket_init(#state{user_id = UserId} = State) ->
  pg:join(eventhub_ws, self()),
  io:format("[WS] User ~s connected~n", [UserId]),
  core_counters:inc(ws_connections),
  {ok, State#state{subscriptions = []}}.

-spec websocket_handle(term(), #state{}) ->
  {ok, #state{}} | {reply, {text, binary()}, #state{}}.
websocket_handle({text, Msg}, State) ->
  io:format("[WS] Received: ~s~n", [Msg]),
  try jsx:decode(Msg, [return_maps]) of
    #{<<"action">> := <<"subscribe">>, <<"calendar_id">> := CalendarId} ->
      handle_subscribe(CalendarId, State);
    #{<<"action">> := <<"unsubscribe">>, <<"calendar_id">> := CalendarId} ->
      handle_unsubscribe(CalendarId, State);
    #{<<"action">> := <<"ping">>} ->
      {reply, {text, <<"{\"status\":\"pong\"}">>}, State};
    Other ->
      io:format("[WS] Unknown action: ~p~n", [Other]),
      {ok, State}
  catch
    _:Error ->
      io:format("[WS] Error parsing message: ~p~n", [Error]),
      {ok, State}
  end;
websocket_handle(_Frame, State) ->
  {ok, State}.

-spec websocket_info(term(), #state{}) ->
  {ok, #state{}} | {reply, {text, binary()}, #state{}}.
websocket_info({notification, Type, Data}, State) ->
  case should_notify(Type, Data, State) of
    true ->
      Msg = jsx:encode(#{
        type      => Type,
        data      => Data,
        timestamp => os:system_time(seconds)
      }),
      {reply, {text, Msg}, State};
    false ->
      {ok, State}
  end;
websocket_info(_Info, State) ->
  {ok, State}.

-spec terminate(term(), cowboy_req:req(), #state{}) -> ok.
terminate(_Reason, _Req, #state{user_id = UserId}) ->
  pg:leave(eventhub_ws, self()),
  core_counters:dec(ws_connections),
  io:format("[WS] User ~s disconnected~n", [UserId]),
  ok.

%%%===================================================================
%%% Внутренние функции
%%%===================================================================

-spec handle_subscribe(binary(), #state{}) -> {reply, {text, binary()}, #state{}}.
handle_subscribe(CalendarId, #state{subscriptions = Subs} = State) ->
  io:format("[WS] Subscribe to calendar: ~s~n", [CalendarId]),
  NewSubs = case lists:member(CalendarId, Subs) of
              true  -> Subs;
              false -> [CalendarId | Subs]
            end,
  Reply = jsx:encode(#{status => <<"subscribed">>, calendar_id => CalendarId}),
  {reply, {text, Reply}, State#state{subscriptions = NewSubs}}.

-spec handle_unsubscribe(binary(), #state{}) -> {reply, {text, binary()}, #state{}}.
handle_unsubscribe(CalendarId, #state{subscriptions = Subs} = State) ->
  io:format("[WS] Unsubscribe from calendar: ~s~n", [CalendarId]),
  NewSubs = lists:delete(CalendarId, Subs),
  Reply = jsx:encode(#{status => <<"unsubscribed">>, calendar_id => CalendarId}),
  {reply, {text, Reply}, State#state{subscriptions = NewSubs}}.

-spec should_notify(atom(), map(), #state{}) -> boolean().
should_notify(calendar_update, #{calendar_id := CalId}, #state{subscriptions = Subs}) ->
  lists:member(CalId, Subs);
should_notify(booking_update, #{user_id := UserId}, #state{user_id = UserId}) ->
  true;
should_notify(booking_update, _, _) ->
  false;
should_notify(event_update, #{calendar_id := CalId}, #state{subscriptions = Subs}) ->
  lists:member(CalId, Subs);
should_notify(_, _, _) ->
  true.