From 0490de4bdcb69a1de47e6d0af3dbc7b19f5a4828 Mon Sep 17 00:00:00 2001
From: Jordan Olshevski <jordanolshevski@gmail.com>
Date: Thu, 14 Dec 2023 23:42:58 -0600
Subject: [PATCH] Try to poll for webhook changes

---
 keycloak/keycloak.go | 20 ++++++++++++++++++++
 main.go              |  6 +++---
 2 files changed, 23 insertions(+), 3 deletions(-)

diff --git a/keycloak/keycloak.go b/keycloak/keycloak.go
index dfc3abb..06bd2b6 100644
--- a/keycloak/keycloak.go
+++ b/keycloak/keycloak.go
@@ -113,6 +113,26 @@ func (k *Keycloak) GetUser(ctx context.Context, userID string) (*User, error) {
 	return k.buildUser(ctx, kcuser)
 }
 
+// GetUserAtETag returns the user object at the given etag, or a possibly different version on timeout.
+//
+// This is useful when avoiding backtracking for cases in which a change has been written to Stripe but
+// the corresponding webhook may not have been handled.
+func (k *Keycloak) GetUserAtETag(ctx context.Context, userID string, etag int64) (user *User, err error) {
+	for i := 0; i < 15; i++ {
+		user, err = k.GetUser(ctx, userID)
+		if err != nil {
+			return nil, err
+		}
+		if etag == 0 || user.StripeETag >= etag {
+			return user, nil
+		}
+
+		time.Sleep(time.Millisecond * 100) // backoff + jitter would be nice here
+	}
+	log.Printf("timeout while waiting for Stripe webhook")
+	return user, nil // timeout
+}
+
 func (k *Keycloak) GetUserByEmail(ctx context.Context, email string) (*User, error) {
 	token, err := k.GetToken(ctx)
 	if err != nil {
diff --git a/main.go b/main.go
index 44f428b..728fbb5 100644
--- a/main.go
+++ b/main.go
@@ -137,14 +137,14 @@ func newRegistrationFormHandler(kc *keycloak.Keycloak) http.HandlerFunc {
 
 func newProfileViewHandler(kc *keycloak.Keycloak, pc *stripeutil.PriceCache) http.HandlerFunc {
 	return func(w http.ResponseWriter, r *http.Request) {
-		user, err := kc.GetUser(r.Context(), getUserID(r))
+		etagString := r.URL.Query().Get("i")
+		etag, _ := strconv.ParseInt(etagString, 10, 0)
+		user, err := kc.GetUserAtETag(r.Context(), getUserID(r), etag)
 		if err != nil {
 			renderSystemError(w, "error while fetching user: %s", err)
 			return
 		}
 
-		etagString := r.URL.Query().Get("i")
-		etag, _ := strconv.ParseInt(etagString, 10, 0)
 		viewData := map[string]any{
 			"page":            "profile",
 			"user":            user,