-module(logic_booking).
-include("records.hrl").
-export([create_booking/2, confirm_booking/2, confirm_booking/3,
  cancel_booking/2, cancel_booking/3, get_booking/2,
  list_bookings/2, list_user_bookings/1, delete_booking/2,
  list_bookings_admin/0, get_booking_admin/1,
  list_event_bookings/1, list_event_bookings/2]).

%%%-------------------------------------------------------------------
%%% @doc Создание бронирования со статусом `pending`.
%%% @end
%%%-------------------------------------------------------------------
-spec create_booking(UserId :: binary(), EventId :: binary()) ->
  {ok, #booking{}} | {error, full | already_booked | not_found}.
create_booking(UserId, EventId) ->
  case core_event:get_by_id(EventId) of
    {ok, Event} ->
      case check_capacity(EventId, Event#event.capacity) of
        {ok, _} ->
          case core_booking:get_by_event_and_user(EventId, UserId) of
            {error, not_found} ->
              core_booking:create(EventId, UserId, pending);
            {ok, _} ->
              {error, already_booked}
          end;
        {error, full} ->
          {error, full}
      end;
    {error, not_found} ->
      {error, not_found}
  end.

%%%-------------------------------------------------------------------
%%% @doc Подтверждение бронирования (двухарная версия).
%%% Только владелец календаря события или admin.
%%% @end
%%%-------------------------------------------------------------------
-spec confirm_booking(BookingId :: binary(), UserId :: binary()) ->
  {ok, #booking{}} | {error, not_found | access_denied}.
confirm_booking(BookingId, UserId) ->
  case core_booking:get_by_id(BookingId) of
    {ok, Booking} ->
      case can_manage_event_bookings(UserId, Booking#booking.event_id) of
        true ->
          case Booking#booking.status of
            pending ->
              Now = calendar:universal_time(),
              core_booking:update(BookingId, [{status, confirmed}, {confirmed_at, Now}]);
            _ ->
              {error, access_denied}
          end;
        {error, Reason} ->
          {error, Reason}
      end;
    Error -> Error
  end.

%%%-------------------------------------------------------------------
%%% @doc Подтверждение или отклонение бронирования (для обработчиков).
%%% `decline` переводит pending-заявку в `cancelled`.
%%% @end
%%%-------------------------------------------------------------------
-spec confirm_booking(UserId :: binary(), BookingId :: binary(), confirm | decline) ->
  {ok, #booking{}} | {error, not_found | access_denied}.
confirm_booking(UserId, BookingId, confirm) ->
  confirm_booking(BookingId, UserId);
confirm_booking(UserId, BookingId, decline) ->
  case core_booking:get_by_id(BookingId) of
    {ok, Booking} ->
      case can_manage_event_bookings(UserId, Booking#booking.event_id) of
        true ->
          case Booking#booking.status of
            pending ->
              core_booking:update(BookingId, [{status, cancelled}]);
            _ ->
              {error, access_denied}
          end;
        {error, Reason} ->
          {error, Reason}
      end;
    Error -> Error
  end.

%%%-------------------------------------------------------------------
%%% @doc Отмена бронирования (двухарная версия).
%%% @end
%%%-------------------------------------------------------------------
-spec cancel_booking(BookingId :: binary(), UserId :: binary()) ->
  {ok, #booking{}} | {error, not_found | access_denied}.
cancel_booking(BookingId, UserId) ->
  case core_booking:get_by_id(BookingId) of
    {ok, Booking} ->
      case Booking#booking.status of
        cancelled ->
          {ok, Booking};
        _ ->
          case Booking#booking.user_id =:= UserId of
            true -> core_booking:update(BookingId, [{status, cancelled}]);
            false -> {error, access_denied}
          end
      end;
    Error -> Error
  end.

%%%-------------------------------------------------------------------
%%% @doc Отмена бронирования (трёхарная версия для обработчиков).
%%% @end
%%%-------------------------------------------------------------------
-spec cancel_booking(UserId :: binary(), BookingId :: binary(), cancel) ->
  {ok, #booking{}} | {error, not_found | access_denied}.
cancel_booking(UserId, BookingId, cancel) ->
  cancel_booking(BookingId, UserId).

%%%-------------------------------------------------------------------
%%% @doc Получение бронирования по ID.
%%% @end
%%%-------------------------------------------------------------------
-spec get_booking(BookingId :: binary(), UserId :: binary()) ->
  {ok, #booking{}} | {error, not_found | access_denied}.
get_booking(BookingId, UserId) ->
  case core_booking:get_by_id(BookingId) of
    {ok, Booking} ->
      case Booking#booking.user_id =:= UserId of
        true -> {ok, Booking};
        false -> {error, access_denied}
      end;
    Error -> Error
  end.

%%%-------------------------------------------------------------------
%%% @doc Список бронирований события.
%%% @end
%%%-------------------------------------------------------------------
-spec list_bookings(EventId :: binary(), UserId :: binary()) ->
  {ok, [#booking{}]}.
list_bookings(EventId, UserId) ->
  {ok, Bookings} = core_booking:list_by_event(EventId),
  Filtered = case admin_utils:is_admin(UserId) of
               true -> Bookings;
               false -> [B || B <- Bookings, B#booking.user_id =:= UserId]
             end,
  {ok, Filtered}.

%%%-------------------------------------------------------------------
%%% @doc Список бронирований пользователя.
%%% @end
%%%-------------------------------------------------------------------
-spec list_user_bookings(UserId :: binary()) -> {ok, [#booking{}]}.
list_user_bookings(UserId) ->
  core_booking:list_by_user(UserId).

%%%-------------------------------------------------------------------
%%% @doc Удаление бронирования (только владелец).
%%% @end
%%%-------------------------------------------------------------------
-spec delete_booking(BookingId :: binary(), UserId :: binary()) ->
  ok | {error, not_found | access_denied}.
delete_booking(BookingId, UserId) ->
  case core_booking:get_by_id(BookingId) of
    {ok, Booking} ->
      case Booking#booking.user_id =:= UserId of
        true -> core_booking:delete(BookingId);
        false -> {error, access_denied}
      end;
    Error -> Error
  end.

%%%-------------------------------------------------------------------
%%% @doc Административное получение бронирования.
%%% @end
%%%-------------------------------------------------------------------
-spec get_booking_admin(BookingId :: binary()) ->
  {ok, #booking{}} | {error, not_found}.
get_booking_admin(BookingId) ->
  core_booking:get_by_id(BookingId).

%%%-------------------------------------------------------------------
%%% @doc Список бронирований события (административный / внутренний).
%%% @end
%%%-------------------------------------------------------------------
-spec list_event_bookings(EventId :: binary()) -> {ok, [#booking{}]}.
list_event_bookings(EventId) ->
  core_booking:list_by_event(EventId).

%%%-------------------------------------------------------------------
%%% @doc Список бронирований события для владельца календаря (или admin).
%%% Возвращает полный список заявок без фильтрации по участнику.
%%% @end
%%%-------------------------------------------------------------------
-spec list_event_bookings(UserId :: binary(), EventId :: binary()) ->
  {ok, [#booking{}]} | {error, not_found | access_denied}.
list_event_bookings(UserId, EventId) ->
  case can_manage_event_bookings(UserId, EventId) of
    true ->
      core_booking:list_by_event(EventId);
    {error, Reason} ->
      {error, Reason}
  end.

%%%-------------------------------------------------------------------
%%% @doc Список всех бронирований (административный).
%%% @end
%%%-------------------------------------------------------------------
-spec list_bookings_admin() -> {ok, [#booking{}]}.
list_bookings_admin() ->
  {ok, core_booking:list_all()}.

%%%===================================================================
%%% ВНУТРЕННИЕ ФУНКЦИИ
%%%===================================================================

%%%-------------------------------------------------------------------
%%% @doc Владелец календаря события или admin может управлять заявками.
%%% @end
%%%-------------------------------------------------------------------
-spec can_manage_event_bookings(UserId :: binary(), EventId :: binary()) ->
  true | {error, not_found | access_denied}.
can_manage_event_bookings(UserId, EventId) ->
  case core_event:get_by_id(EventId) of
    {ok, Event} ->
      case core_calendar:get_by_id(Event#event.calendar_id) of
        {ok, Calendar} ->
          case Calendar#calendar.owner_id =:= UserId
                 orelse admin_utils:is_admin(UserId) of
            true  -> true;
            false -> {error, access_denied}
          end;
        {error, not_found} ->
          {error, not_found}
      end;
    {error, not_found} ->
      {error, not_found}
  end.

%%%-------------------------------------------------------------------
%%% @doc Проверка вместимости события.
%%% `undefined` и `0` означают неограниченную вместимость.
%%% @end
%%%-------------------------------------------------------------------
-spec check_capacity(EventId :: binary(), Capacity :: integer() | undefined) ->
  {ok, integer() | unlimited} | {error, full}.
check_capacity(_EventId, undefined) -> {ok, unlimited};
check_capacity(_EventId, 0) -> {ok, unlimited};
check_capacity(EventId, Capacity) ->
  {ok, Bookings} = core_booking:list_by_event(EventId),
  ConfirmedCount = length([B || B <- Bookings, B#booking.status =:= confirmed]),
  case ConfirmedCount < Capacity of
    true -> {ok, Capacity - ConfirmedCount};
    false -> {error, full}
  end.