Querying Discord members from a guild by username

query.go

// findMembers finds a member with the given username from the state.
func findMembers(s state.Store, guild discord.GuildID, username string) *discord.Member {
	m, err := s.Store.Members(guild)
	if err != nil {
		return nil
	}

	for _, m := range m {
		if strings.HasPrefix(m.User.Username, username) {
			return m
		}
	}

	return nil
}

func queryState(s *state.State, guild discord.GuildID, username string) (*discord.Member, error) {
	if m := findMembers(s.Store, guild, username); m != nil {
		return m, nil
	}

	ev := make(chan *gateway.GuildMembersChunkEvent)
	cc := s.AddHandler(ev)
	defer cc()

	err := s.RequestGuildMembers(gateway.RequestGuildMembersData{
		GuildID: guildID,
		Query:   username,
	})
	if err != nil {
		return nil, errors.Wrap(err, "Failed to request member from gateway")
	}

	ctx, cancel := context.WithTimeout(context.TODO(), 5*time.Second)
	defer cancel()

	for {
		select {
		case <-ctx.Done():
			return nil, ctx.Err()
		case <-ev:
			if ev.GuildID != guildID {
				continue
			}

			if m := findMembers(s.Store, guild, username); m != nil {
				return m, nil
			}
		}
	}
}