feat: handle port forward subdomain conflict

internal/workspace/errors.go

@@ -1,9 +1,19 @@
 package workspace
 
+import "strings"
+
 type errWorkspaceExists struct {
 	message string
 }
 
+type errPortMappingConflicts struct {
+	conflicts []string
+}
+
 func (err *errWorkspaceExists) Error() string {
 	return err.message
 }
+
+func (err *errPortMappingConflicts) Error() string {
+	return "Subdomain(s) already in use: " + strings.Join(err.conflicts, ", ")
+}

internal/workspace/http_handlers.go

@@ -126,6 +126,10 @@ func updateWorkspace(c echo.Context, workspace *workspace) error {
 
 	if len(body.PortMappings) > 0 {
 		if err = mgr.addPortMappings(ctx, workspace, body.PortMappings); err != nil {
+			var errPortMappingConflicts *errPortMappingConflicts
+			if errors.As(err, &errPortMappingConflicts) {
+				return apierror.New(http.StatusConflict, "PORT_MAPPINGS_EXIST", err.Error())
+			}
 			return err
 		}
 	}

internal/workspace/workspace_manager.go

@@ -347,9 +347,23 @@ func (mgr workspaceManager) addPortMappings(ctx context.Context, workspace *work
 		return err
 	}
 
+	var conflictErr errPortMappingConflicts
+
 	for i := range portMappings {
-		portMappings[i].WorkspaceID = workspace.ID
-		mgr.reverseProxy.AddEntry(portMappings[i].Subdomain, urls[i])
+		err = mgr.reverseProxy.AddEntry(portMappings[i].Subdomain, urls[i])
+		if err != nil {
+			if errors.Is(err, reverseproxy.ErrPortMappingConflict) {
+				conflictErr.conflicts = append(conflictErr.conflicts, portMappings[i].Subdomain)
+			} else {
+				return err
+			}
+		} else {
+			portMappings[i].WorkspaceID = workspace.ID
+		}
+	}
+
+	if len(conflictErr.conflicts) > 0 {
+		return &conflictErr
 	}
 
 	_, err = tx.NewInsert().Model(&portMappings).Exec(ctx)