Add Call.UseSFU to join an SFU without the coordinator

call.go

@@ -735,6 +735,26 @@ func awaitMigrationCompleteOn(client *signal.Client) *event.EventAwaiter[*sfu_ev
 	})
 }
 
+// UseSFU points the call straight at an SFU with credentials the caller already holds, so
+// Join skips the coordinator's join-call request.
+//
+// It is for development and tests against a locally running SFU, where there is no
+// coordinator to hand out an SFU and a token. Production calls get both from the
+// coordinator and should not use it. Call it before Join. Reconnects keep using the same
+// credentials, since there is no coordinator to ask for new ones.
+func (c *Call) UseSFU(cred models.Credentials) {
+	c.GetCred = func(bool, string) (models.Credentials, error) { return cred, nil }
+	// The reconnect and migration paths read the SFU they were on from here.
+	c.coordinatorState.Store(&CallState{
+		Url:          cred.Server.URL,
+		Token:        cred.Token,
+		WebsocketUrl: cred.Server.WsEndpoint,
+		EdgeName:     cred.Server.EdgeName,
+	})
+	c.getPeer().client.Store(signal.NewClient(cred, c, c.signalOptions()...))
+	c.SetCredentials(cred)
+}
+
 func (c *Call) SetCredentials(cred models.Credentials) {
 	c.logger.Debugf("setting credentials: %#+v", cred)
 	state := c.coordinatorState.Load()

use_sfu_test.go

@@ -0,0 +1,40 @@
+package rtc
+
+import (
+	"context"
+	"testing"
+	"time"
+
+	"github.com/stretchr/testify/require"
+
+	"github.com/GetStream/getstream-go-webrtc/internal/testutil"
+)
+
+// TestUseSFUJoinsWithoutTheCoordinator joins a call through the public API with credentials
+// for an SFU the caller already knows, the way a test against a local SFU does.
+func TestUseSFUJoinsWithoutTheCoordinator(t *testing.T) {
+	t.Parallel()
+
+	sfu := testutil.NewFakeSFU()
+	defer sfu.Close()
+
+	const userID = "direct-user"
+	token, err := testutil.GenerateToken("test-api-key", "test-api-secret", userID, time.Hour)
+	require.NoError(t, err)
+	client, err := NewClient(token.APIKey, User{ID: userID}, StaticToken(token.Token),
+		WithoutCoordinatorWS())
+	require.NoError(t, err)
+
+	call := client.Call(testutil.DefaultCallType, "direct-call")
+	call.UseSFU(fakeSFUCredentials(sfu, "local-sfu", "sfu-token"))
+
+	ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
+	defer cancel()
+	_, err = call.Join(ctx)
+	require.NoError(t, err)
+	t.Cleanup(func() { _ = call.Leave("test over") })
+
+	join := nextJoinRequest(t, sfu)
+	require.Equal(t, "sfu-token", join.GetToken(), "the SFU gets the token the caller supplied")
+	require.Equal(t, "local-sfu", call.GetState().EdgeName, "reconnects know which SFU they were on")
+}