Re-apply saved bookings

apps/cqrs_booking/src/cqrs_booking.erl

@@ -6,7 +6,9 @@
 
 -behaviour(gen_server).
 
--export([ init/1 , handle_call/3 , handle_cast/2 , handle_info/2, handle_continue/2 ]).
+-export([ init/1 , handle_call/3 , handle_cast/2 , handle_info/2, handle_continue/2, terminate/2 ]).
+
+-include_lib("stdlib/include/ms_transform.hrl").
 
 -type state() :: #{}.
 
@@ -16,18 +18,23 @@ start_link() ->
 
 -spec init(unused) -> {ok, state()}.
 init(unused) ->
+    Version = 0,
     State = #{
               available_rooms => cqrs_booking_hotels:get_available_rooms(),
               bookings => #{},
-              version => 0
+              version => Version
              },
     {ok, _Name} = dets:open_file(bookings, []),
-    {ok, State}.
+    MatchSpec = ets:fun2ms(fun({N,Cmd}) when N >= Version -> {N, Cmd} end),
+    ExistingBookings = lists:sort(fun({A,_}, {B,_}) -> A =< B end, dets:select(bookings, MatchSpec)),
+    io:format("Existing bookings: ~p~n", [ExistingBookings]),
+    NewBookings = lists:foldl(fun({_, Cmd}, B) -> add_new_booking(Cmd, B) end, maps:get(bookings, State), ExistingBookings),
+    {ok, State#{bookings:=NewBookings, version:=Version + length(ExistingBookings)}}.
 
 -spec handle_call(any(), {pid(), any()}, state()) ->
     {reply, any(), state()} | {noreply, state()}.
 handle_call({book_room, Cmd}, _From, #{available_rooms:=AvailableRooms, version:=Version} = State) ->
-    {Client, Hotel, Room, CheckIn, _CheckOut} = Cmd,
+    {_Client, Hotel, Room, CheckIn, _CheckOut} = Cmd,
     AvailableRoomsForHotel = maps:get(Hotel, AvailableRooms),
     AvailableRoomsForDay = maps:get(CheckIn, AvailableRoomsForHotel),
     [_RoomInfo] = lists:filter(fun(R) -> maps:get(id, R) == Room end, AvailableRoomsForDay),
@@ -50,14 +57,21 @@ handle_info(_Request, State) ->
     {noreply, State}.
 
 -spec handle_continue(term(), state()) -> {noreply, state()}.
-handle_continue({new_booking, {Client, _Hotel, _Room, _CheckIn, _CheckOut} = Cmd}, #{bookings:=Bookings} = State) ->
-    NewBookings = case maps:is_key(Client, Bookings) of
+handle_continue({new_booking, Cmd}, #{bookings:=Bookings} = State) ->
+    NewBookings = add_new_booking(Cmd, Bookings),
+    {noreply, State#{bookings:=NewBookings}};
+handle_continue(_Continue, State) ->
+    {noreply, State}.
+
+terminate(_Reason, _State) ->
+    dets:close(bookings),
+    ok.
+
+add_new_booking({Client, _Hotel, _Room, _CheckIn, _CheckOut} = Cmd, Bookings) ->
+    case maps:is_key(Client, Bookings) of
         true ->
             BookingsForClient = maps:get(Client, Bookings),
             maps:update(Client, [Cmd | BookingsForClient], Bookings);
         false ->
             maps:put(Client, [Cmd], Bookings)
-    end,
-    {noreply, State#{bookings:=NewBookings}};
-handle_continue(_Continue, State) ->
-    {noreply, State}.
+    end.

apps/cqrs_booking/test/cqrs_booking_tests.erl

@@ -9,11 +9,15 @@ init_test_() ->
     ].
 
 init_available_rooms() ->
+    clean_dets_files(),
     {ok, #{available_rooms:=AvailableRooms}} = cqrs_booking:init(unused),
+    cqrs_booking:terminate(shutdown, #{}),
     ?_assertEqual(AvailableRooms, cqrs_booking_hotels:get_available_rooms()).
 
 init_bookings_list_is_empty() ->
+    clean_dets_files(),
     {ok, #{bookings:=Bookings}} = cqrs_booking:init(unused),
+    cqrs_booking:terminate(shutdown, #{}),
     ?_assertEqual(0, length(maps:keys(Bookings))).
 
 handle_call_test_() ->
@@ -22,12 +26,21 @@ handle_call_test_() ->
      unavailable_room_cannot_be_booked()
     ].
 
+restore_test_() ->
+    [
+     bookings_should_survive_restart()
+    ].
+
 start() ->
+    clean_dets_files(),
     {ok, Pid} = cqrs_booking:start_link(),
     Pid.
 
+clean_dets_files() ->
+    ok = case file:delete("bookings") of ok -> ok; {error, enoent} -> ok end.
+
 stop(Pid) ->
-    gen_server:stop(Pid).
+    ok = gen_server:stop(Pid).
 
 new_booking_should_be_added(Pid) ->
     Client = 1,
@@ -50,3 +63,15 @@ new_state() ->
       bookings => #{},
       version => 0
      }.
+
+bookings_should_survive_restart() ->
+    Pid1 = start(),
+    Client = 1,
+    Cmd = {Client, 2, <<"101">>, {2023, 12, 1}, {2023, 12, 2}},
+    ok = gen_server:call(Pid1, {book_room, Cmd}),
+    stop(Pid1),
+    {ok, Pid2} = cqrs_booking:start_link(),
+    {ok, BookingsForClient} = gen_server:call(Pid2, {get_bookings, Client}),
+    [
+     ?_assertEqual(1, length(BookingsForClient))
+    ].