feat(waitlist): optional event waitlist with FIFO promote.

Commercial calendars opt in via settings.waitlist_enabled; join when full;
auto-promote on cancel/decline/expire with email and in-app notify.

Refs EventHub/EventHubBack#72

src/handlers/handler_event_waitlist.erl

@@ -0,0 +1,128 @@
+%%%-------------------------------------------------------------------
+%%% @doc Waitlist for events (Back#72).
+%%% POST/DELETE/GET /v1/events/:id/waitlist
+%%% @end
+%%%-------------------------------------------------------------------
+-module(handler_event_waitlist).
+-behaviour(cowboy_handler).
+-export([init/2, trails/0]).
+
+-spec init(cowboy_req:req(), any()) -> {ok, cowboy_req:req(), any()}.
+init(Req, _Opts) ->
+  case cowboy_req:method(Req) of
+    <<"POST">> -> join(Req);
+    <<"DELETE">> -> leave(Req);
+    <<"GET">> -> get_status(Req);
+    _ -> handler_utils:send_error(Req, 405, <<"Method not allowed">>)
+  end.
+
+-spec trails() -> [map()].
+trails() ->
+  [
+    #{
+      path => <<"/v1/events/:id/waitlist">>,
+      method => <<"POST">>,
+      description => <<"Join event waitlist (commercial, waitlist_enabled)">>,
+      tags => [<<"Waitlist">>],
+      responses => #{
+        200 => #{description => <<"Joined">>},
+        400 => #{description => <<"not_full / already_* / waitlist_disabled">>},
+        401 => #{description => <<"Unauthorized">>},
+        403 => #{description => <<"Forbidden">>},
+        404 => #{description => <<"Not found">>}
+      }
+    },
+    #{
+      path => <<"/v1/events/:id/waitlist">>,
+      method => <<"DELETE">>,
+      description => <<"Leave event waitlist">>,
+      tags => [<<"Waitlist">>],
+      responses => #{
+        200 => #{description => <<"Left">>},
+        401 => #{description => <<"Unauthorized">>},
+        404 => #{description => <<"Not on waitlist">>}
+      }
+    },
+    #{
+      path => <<"/v1/events/:id/waitlist">>,
+      method => <<"GET">>,
+      description => <<"Own waitlist status, or full list for owner/specialist">>,
+      tags => [<<"Waitlist">>],
+      responses => #{
+        200 => #{description => <<"Status">>},
+        401 => #{description => <<"Unauthorized">>},
+        404 => #{description => <<"Not found">>}
+      }
+    }
+  ].
+
+join(Req) ->
+  EventId = cowboy_req:binding(id, Req),
+  case handler_utils:auth_user(Req) of
+    {ok, UserId, Req1} ->
+      case logic_waitlist:join(UserId, EventId) of
+        {ok, Body} ->
+          handler_utils:send_json(Req1, 200, Body);
+        {error, not_found} ->
+          handler_utils:send_error(Req1, 404, <<"Event not found">>);
+        {error, personal_calendar} ->
+          handler_utils:send_error(Req1, 403, <<"personal_calendar">>);
+        {error, subscription_inactive} ->
+          handler_utils:send_error(Req1, 403, <<"subscription_inactive">>);
+        {error, own_event} ->
+          handler_utils:send_error(Req1, 403, <<"own_event">>);
+        {error, waitlist_disabled} ->
+          handler_utils:send_error(Req1, 400, <<"waitlist_disabled">>);
+        {error, not_full} ->
+          handler_utils:send_error(Req1, 400, <<"not_full">>);
+        {error, already_booked} ->
+          handler_utils:send_error(Req1, 400, <<"already_booked">>);
+        {error, already_on_waitlist} ->
+          handler_utils:send_error(Req1, 400, <<"already_on_waitlist">>);
+        {error, event_not_active} ->
+          handler_utils:send_error(Req1, 400, <<"event_not_active">>);
+        {error, Reason} when is_atom(Reason) ->
+          handler_utils:send_error(Req1, 400, atom_to_binary(Reason, utf8));
+        {error, _} ->
+          handler_utils:send_error(Req1, 400, <<"Invalid request">>)
+      end;
+    {error, Code, Message, Req1} ->
+      handler_utils:send_error(Req1, Code, Message)
+  end.
+
+leave(Req) ->
+  EventId = cowboy_req:binding(id, Req),
+  case handler_utils:auth_user(Req) of
+    {ok, UserId, Req1} ->
+      case logic_waitlist:leave(UserId, EventId) of
+        ok ->
+          handler_utils:send_json(Req1, 200, #{ok => true});
+        {error, not_found} ->
+          handler_utils:send_error(Req1, 404, <<"Not on waitlist">>)
+      end;
+    {error, Code, Message, Req1} ->
+      handler_utils:send_error(Req1, Code, Message)
+  end.
+
+get_status(Req) ->
+  EventId = cowboy_req:binding(id, Req),
+  case handler_utils:auth_user(Req) of
+    {ok, UserId, Req1} ->
+      case logic_waitlist:list_for_manager(UserId, EventId) of
+        {ok, Body} ->
+          handler_utils:send_json(Req1, 200, Body);
+        {error, access_denied} ->
+          case logic_waitlist:status_for_user(UserId, EventId) of
+            {ok, Body} ->
+              handler_utils:send_json(Req1, 200, Body);
+            {error, not_found} ->
+              handler_utils:send_error(Req1, 404, <<"Event not found">>);
+            {error, _} ->
+              handler_utils:send_error(Req1, 403, <<"Forbidden">>)
+          end;
+        {error, not_found} ->
+          handler_utils:send_error(Req1, 404, <<"Event not found">>)
+      end;
+    {error, Code, Message, Req1} ->
+      handler_utils:send_error(Req1, Code, Message)
+  end.