perf(guild): add a lean channel auth context rpc (#2226)

fluxer_gateway/src/gateway/gateway_rpc_guild.erl

@@ -37,6 +37,7 @@ route(M, P) ->
 -define(HANDLER_MAP, #{
     <<"guild.dispatch">> => fun gateway_rpc_guild_lifecycle:handle/2,
     <<"guild.get_data">> => fun gateway_rpc_guild_lifecycle:handle/2,
+    <<"guild.get_auth_context">> => fun gateway_rpc_guild_lifecycle:handle/2,
     <<"guild.start">> => fun gateway_rpc_guild_lifecycle:handle/2,
     <<"guild.stop">> => fun gateway_rpc_guild_lifecycle:handle/2,
     <<"guild.reload">> => fun gateway_rpc_guild_lifecycle:handle/2,

fluxer_gateway/src/gateway/gateway_rpc_guild_lifecycle.erl

@@ -15,6 +15,7 @@
 -spec handle(binary(), map()) -> term().
 handle(<<"guild.dispatch">>, P) -> handle_dispatch(P);
 handle(<<"guild.get_data">>, P) -> handle_get_data(P);
+handle(<<"guild.get_auth_context">>, P) -> handle_get_auth_context(P);
 handle(<<"guild.start">>, P) -> handle_start(P);
 handle(<<"guild.stop">>, P) -> handle_stop(P);
 handle(<<"guild.reload">>, P) -> handle_reload(P);
@@ -47,6 +48,39 @@ handle_get_data(#{<<"guild_id">> := GuildIdBin, <<"user_id">> := UserIdBin}) ->
         <<"guild_not_found">>
     ).
 
+-spec handle_get_auth_context(map()) -> term().
+handle_get_auth_context(#{<<"guild_id">> := GuildIdBin, <<"user_id">> := UserIdBin} = Params) ->
+    GuildId = validation:snowflake_or_throw(<<"guild_id">>, GuildIdBin),
+    UserId = optional_user_id(UserIdBin),
+    ChannelId = optional_channel_id(maps:get(<<"channel_id">>, Params, null)),
+    gateway_rpc_guild_infra:with_guild(
+        GuildId,
+        fun(Pid) ->
+            get_auth_context_from_guild(Pid, UserId, ChannelId)
+        end,
+        <<"guild_not_found">>
+    ).
+
+-spec optional_channel_id(term()) -> integer() | null.
+optional_channel_id(Value) ->
+    case validation:validate_optional_snowflake(Value) of
+        {ok, null} -> null;
+        {ok, ChannelId} when is_integer(ChannelId) -> ChannelId;
+        _ -> gateway_rpc_error:raise(validation_invalid_params)
+    end.
+
+-spec get_auth_context_from_guild(pid(), integer() | null, integer() | null) -> term().
+get_auth_context_from_guild(Pid, UserId, ChannelId) ->
+    Request = {get_guild_auth_context, #{user_id => UserId, channel_id => ChannelId}},
+    case gen_server:call(Pid, Request, ?GUILD_CALL_TIMEOUT) of
+        #{auth_context := null} ->
+            gateway_rpc_error:raise(<<"forbidden">>);
+        #{auth_context := AuthContext} ->
+            AuthContext;
+        _ ->
+            gateway_rpc_error:raise(<<"guild_data_error">>)
+    end.
+
 -spec optional_user_id(term()) -> integer() | null.
 optional_user_id(Value) ->
     case validation:validate_optional_snowflake(Value) of
@@ -194,4 +228,13 @@ optional_user_id_preserves_null_for_skip_membership_check_test() ->
 
 optional_user_id_accepts_snowflake_test() ->
     ?assertEqual(123, optional_user_id(<<"123">>)).
+
+optional_channel_id_defaults_to_null_test() ->
+    ?assertEqual(null, optional_channel_id(null)).
+
+optional_channel_id_accepts_snowflake_test() ->
+    ?assertEqual(456, optional_channel_id(<<"456">>)).
+
+optional_channel_id_rejects_garbage_test() ->
+    ?assertError({gateway_rpc_error, _}, optional_channel_id(<<"nope">>)).
 -endif.

fluxer_gateway/src/guild/guild.erl

@@ -89,6 +89,7 @@ query_call_handler(get_user_permissions) -> query;
 query_call_handler(can_manage_roles) -> query;
 query_call_handler(can_manage_role) -> query;
 query_call_handler(get_guild_data) -> query;
+query_call_handler(get_guild_auth_context) -> query;
 query_call_handler(get_assignable_roles) -> query;
 query_call_handler(get_user_max_role_position) -> query;
 query_call_handler(check_target_member) -> query;

fluxer_gateway/src/guild/guild_data.erl

@@ -4,6 +4,7 @@
 -typing([eqwalizer]).
 
 -export([get_guild_data/2]).
+-export([get_auth_context/2]).
 -export([get_guild_member/2]).
 -export([get_guild_members_batch/2]).
 -export([has_member/2]).
@@ -33,6 +34,50 @@ get_guild_data(#{user_id := UserId}, State) ->
             get_guild_data_for_user(UserId, Data, State)
     end.
 
+-spec get_auth_context(map(), guild_state()) -> guild_reply(map()).
+get_auth_context(#{user_id := UserId, channel_id := ChannelId}, State) ->
+    Data = guild_data_index:ensure_data_map(State),
+    case UserId of
+        null ->
+            {reply, #{auth_context => build_auth_context(ChannelId, Data, State)}, State};
+        _ ->
+            get_auth_context_for_member(UserId, ChannelId, Data, State)
+    end.
+
+-spec get_auth_context_for_member(user_id(), integer() | null, map(), guild_state()) ->
+    guild_reply(map()).
+get_auth_context_for_member(UserId, ChannelId, Data, State) ->
+    case guild_data_index:get_member(UserId, Data) of
+        undefined ->
+            {reply, #{auth_context => null, error_reason => <<"forbidden">>}, State};
+        _Member ->
+            {reply, #{auth_context => build_auth_context(ChannelId, Data, State)}, State}
+    end.
+
+-spec build_auth_context(integer() | null, map(), guild_state()) -> map().
+build_auth_context(ChannelId, Data, State) ->
+    #{
+        <<"guild">> => build_auth_guild(Data, State),
+        <<"parent_channel">> => find_channel(ChannelId, Data)
+    }.
+
+-spec build_auth_guild(map(), guild_state()) -> map().
+build_auth_guild(Data, State) ->
+    GuildProperties = map_utils:ensure_map(maps:get(<<"guild">>, Data, #{})),
+    GuildProperties#{
+        <<"roles">> => map_utils:ensure_list(maps:get(<<"roles">>, Data, [])),
+        <<"member_count">> => maps:get(
+            member_count, State, guild_data_index:member_count(Data)
+        ),
+        <<"online_count">> => guild_member_list:get_online_count(State)
+    }.
+
+-spec find_channel(integer() | null, map()) -> map() | null.
+find_channel(null, _Data) ->
+    null;
+find_channel(ChannelId, Data) ->
+    maps:get(ChannelId, guild_data_index:channel_index(Data), null).
+
 -spec get_guild_member(map(), guild_state()) -> guild_reply(map()).
 get_guild_member(Request, State) ->
     guild_data_members:get_guild_member(Request, State).

fluxer_gateway/src/guild/guild_query_handler.erl

@@ -241,6 +241,8 @@ handle_max_role_position(#{user_id := UserId}, State) ->
 -spec handle_call_data(term(), guild_state()) -> {reply, term(), guild_state()}.
 handle_call_data({get_guild_data, Req}, State) ->
     guild_data:get_guild_data(request_map(Req), State);
+handle_call_data({get_guild_auth_context, Req}, State) ->
+    guild_data:get_auth_context(request_map(Req), State);
 handle_call_data({get_guild_member, Req}, State) ->
     guild_data:get_guild_member(request_map(Req), State);
 handle_call_data({get_guild_members_batch, Req}, State) ->