1 files changed, 94 insertions, 0 deletions
diff --git a/yggdrasil/muxserver.go b/yggdrasil/muxserver.go
new file mode 100644
index 0000000..7db4021
--- /dev/null
+++ b/yggdrasil/muxserver.go
@@ -0,0 +1,94 @@
+package yggdrasil
+
+import (
+	"fmt"
+	"github.com/avast/retry-go"
+	"github.com/rs/zerolog/log"
+	"github.com/samber/lo"
+	"github.com/samber/mo"
+	"github.com/sourcegraph/conc"
+	"strings"
+	"time"
+)
+
+const (
+	retryInterval = 100 * time.Millisecond
+	maxRetryTimes = 3
+)
+
+type muxServer struct {
+	subServers []Server
+}
+
+func (m muxServer) Name() string {
+	return "muxServer[" + strings.Join(lo.Map(m.subServers, func(item Server, _ int) string {
+		return item.Name()
+	}), ", ") + "]"
+}
+
+func (m muxServer) HasJoined(username string, serverID string) (*HasJoinedResponse, error) {
+	var wg conc.WaitGroup
+	type Ret = *HasJoinedResponse
+	results := make(chan mo.Result[Ret], len(m.subServers))
+	for _, s := range m.subServers {
+		s := s
+		wg.Go(func() {
+			var resp *HasJoinedResponse
+			err := retry.Do(
+				func() error {
+					var err error
+					resp, err = s.HasJoined(username, serverID)
+					return err
+				},
+				retry.Delay(retryInterval),
+				retry.Attempts(maxRetryTimes),
+			)
+			if err != nil {
+				results <- mo.Err[Ret](fmt.Errorf("call hasJoined on server `%v` failed: %w",
+					s.Name(), err))
+			} else {
+				results <- mo.Ok[Ret](resp)
+			}
+		})
+	}
+
+	chPanic := make(chan error, 1)
+	go func() {
+		// wait for all async tasks to finish in another async goroutine
+		// to allow the main request return as early as possible
+		r := wg.WaitAndRecover()
+		close(results)
+		if r != nil {
+			chPanic <- r.AsError()
+		}
+		close(chPanic)
+	}()
+
+	var last *Ret
+	for r := range results {
+		r, err := r.Get()
+		if err != nil {
+			log.Error().Err(err).Msg("hasJoined failed")
+			continue
+		}
+		last = &r
+		// return the first positive result
+		if r.HasJoined() {
+			return r, nil
+		}
+	}
+	if last == nil {
+		// no data generated, all async tasks panicked
+		err := <-chPanic
+		log.Error().Err(err).Msg("all hasJoined async query panicked")
+		return nil, err
+	} else {
+		return *last, nil
+	}
+}
+
+func NewMuxServer(servers ...Server) Server {
+	return muxServer{
+		subServers: servers,
+	}
+}