Handle Strava rate limiting with abort, retry time and daily usage display

Strava sync for 167 rides exceeds the 100/15-min read limit (2 calls per ride).
Previously a 429 was treated as a skipped ride, so every remaining ride also
failed silently. Now GetJSON returns a typed RateLimitError with RetryAfter
computed from Retry-After/Date and X-RateLimit headers (15-min window resets
at :00/:15/:30/:45, daily at midnight UTC) and tracks Read/Overall usage.
syncRides aborts on 429 with partial progress instead of skipping, and
handleSync emits an SSE error with retry time, daily usage vs limit and
structured rateLimit snapshot; progress and complete events also carry the
snapshot for the UI to display. Frontend shows Read daily/15-min usage in
progress details and on completion.

1 files changed, 118 insertions, 4 deletions

diff --git a/web/sync.go b/web/sync.go
index b491ee0..fdb3c4e 100644
--- a/web/sync.go
+++ b/web/sync.go
@@ -79,19 +79,39 @@ func (s *Server) handleSync(w http.ResponseWriter, r *http.Request) {
 	w.Header().Set("Cache-Control", "no-cache")
 	w.Header().Set("Content-Type", "text/event-stream")
 	progress, err := s.syncRides(client, appConfig.Storage.GPXDir, from, to, func(progress SyncProgress) error {
+		enrichProgressRateLimit(&progress, client)
 		return writeSyncEvent(w, flusher, "progress", progress)
 	})
 	if err != nil {
-		_ = writeSyncEvent(w, flusher, "error", syncErrorEvent{Message: err.Error(), Progress: progress})
+		var rateErr *strava.RateLimitError
+		if errors.As(err, &rateErr) {
+			slog.Warn("Strava sync rate limited", "total", progress.Total, "imported", progress.Imported, "retryAfter", rateErr.RetryAfter, "isDaily", rateErr.IsDaily, "readDaily", fmt.Sprintf("%d/%d", rateErr.State.Read.UsageDaily, rateErr.State.Read.LimitDaily), "overallDaily", fmt.Sprintf("%d/%d", rateErr.State.Overall.UsageDaily, rateErr.State.Overall.LimitDaily))
+			enrichProgressWithState(&progress, rateErr.State)
+			_ = writeSyncEvent(w, flusher, "error", syncErrorEvent{
+				Message:       rateLimitMessage(rateErr, progress),
+				Progress:      progress,
+				RetryAfter:    formatRetryAfter(rateErr.RetryAfter),
+				IsRateLimited: true,
+				RateLimit:     progress.RateLimit,
+			})
+			return
+		}
+		enrichProgressRateLimit(&progress, client)
+		_ = writeSyncEvent(w, flusher, "error", syncErrorEvent{Message: err.Error(), Progress: progress, RateLimit: progress.RateLimit})
 		return
 	}
-	slog.Info("Completed Strava sync", "from", from.Format(dateFormat), "to", to.Add(-24*time.Hour).Format(dateFormat), "total", progress.Total, "imported", progress.Imported, "skipped", progress.Skipped)
+	enrichProgressRateLimit(&progress, client)
+	slog.Info("Completed Strava sync", "from", from.Format(dateFormat), "to", to.Add(-24*time.Hour).Format(dateFormat), "total", progress.Total, "imported", progress.Imported, "skipped", progress.Skipped, "readDaily", rateLimitLogValue(progress.RateLimit, true), "overallDaily", rateLimitLogValue(progress.RateLimit, false))
 	_ = writeSyncEvent(w, flusher, "complete", progress)
 }
 
 func (s *Server) syncRides(client syncClient, gpxDir string, from, to time.Time, report func(SyncProgress) error) (SyncProgress, error) {
 	activities, err := client.List(from, to)
 	if err != nil {
+		var rateErr *strava.RateLimitError
+		if errors.As(err, &rateErr) {
+			slog.Warn("Strava sync rate limited while listing activities", "retryAfter", rateErr.RetryAfter, "isDaily", rateErr.IsDaily, "error", err)
+		}
 		return SyncProgress{}, err
 	}
 	progress := SyncProgress{Total: len(activities)}
@@ -118,6 +138,11 @@ func (s *Server) syncRides(client syncClient, gpxDir string, from, to time.Time,
 		}
 		activity, gpxData, err := client.Get(summary.ID)
 		if err != nil {
+			var rateErr *strava.RateLimitError
+			if errors.As(err, &rateErr) {
+				slog.Warn("Strava sync rate limited", "activity", summary.ID, "name", summary.Name, "retryAfter", rateErr.RetryAfter, "isDaily", rateErr.IsDaily, "completed", progress.Completed, "total", progress.Total)
+				return progress, err
+			}
 			if errors.Is(err, strava.ErrNoTrackPoints) {
 				_ = os.Remove(filepath.Join(gpxDir, fmt.Sprintf("activity_%d.gpx", summary.ID)))
 				if saveErr := ride.Save(s.db, rideFromActivity(externalID, "", activity)); saveErr != nil {
@@ -214,8 +239,97 @@ func (s *Server) endSync() {
 }
 
 type syncErrorEvent struct {
-	Message  string       `json:"message"`
-	Progress SyncProgress `json:"progress"`
+	Message       string             `json:"message"`
+	Progress      SyncProgress       `json:"progress"`
+	RetryAfter    string             `json:"retryAfter,omitempty"`
+	IsRateLimited bool               `json:"isRateLimited,omitempty"`
+	RateLimit     *RateLimitSnapshot `json:"rateLimit,omitempty"`
+}
+
+func enrichProgressRateLimit(progress *SyncProgress, client syncClient) {
+	if provider, ok := client.(interface{ RateLimitState() strava.RateLimitState }); ok {
+		state := provider.RateLimitState()
+		if isZeroRateLimit(state) {
+			return
+		}
+		enrichProgressWithState(progress, state)
+	}
+}
+
+func enrichProgressWithState(progress *SyncProgress, state strava.RateLimitState) {
+	progress.RateLimit = &RateLimitSnapshot{Read: state.Read, Overall: state.Overall}
+}
+
+func isZeroRateLimit(state strava.RateLimitState) bool {
+	return state.Read.Limit15 == 0 && state.Read.LimitDaily == 0 && state.Overall.Limit15 == 0 && state.Overall.LimitDaily == 0
+}
+
+func rateLimitLogValue(snapshot *RateLimitSnapshot, read bool) string {
+	if snapshot == nil {
+		return ""
+	}
+	if read {
+		if snapshot.Read.LimitDaily == 0 {
+			return ""
+		}
+		return fmt.Sprintf("%d/%d", snapshot.Read.UsageDaily, snapshot.Read.LimitDaily)
+	}
+	if snapshot.Overall.LimitDaily == 0 {
+		return ""
+	}
+	return fmt.Sprintf("%d/%d", snapshot.Overall.UsageDaily, snapshot.Overall.LimitDaily)
+}
+
+func rateLimitMessage(rateErr *strava.RateLimitError, progress SyncProgress) string {
+	scope := "15-minute"
+	if rateErr.IsDaily {
+		scope = "daily"
+	}
+	retryText := ""
+	if !rateErr.RetryAfter.IsZero() {
+		until := time.Until(rateErr.RetryAfter).Truncate(time.Second)
+		if until < 0 {
+			until = 0
+		}
+		retryText = fmt.Sprintf(" Retry after %s (in %s).", rateErr.RetryAfter.UTC().Format(time.RFC3339), until)
+		if rateErr.IsDaily {
+			retryText = fmt.Sprintf(" Daily limit resets at %s (in %s).", rateErr.RetryAfter.UTC().Format(time.RFC3339), until)
+		}
+	}
+	usageText := formatRateLimitUsage(rateErr.State)
+	if usageText != "" {
+		usageText = " " + usageText
+	}
+	progressText := ""
+	if progress.Total > 0 {
+		remaining := progress.Total - progress.Completed
+		progressText = fmt.Sprintf(" Progress: %d/%d completed, %d imported, %d skipped, %d remaining.", progress.Completed, progress.Total, progress.Imported, progress.Skipped, remaining)
+	}
+	return fmt.Sprintf("Strava %s rate limit reached.%s%s%s Re-run sync after the reset time to import remaining rides.", scope, progressText, usageText, retryText)
+}
+
+func formatRateLimitUsage(state strava.RateLimitState) string {
+	var parts []string
+	if state.Read.LimitDaily > 0 {
+		parts = append(parts, fmt.Sprintf("Read daily %d/%d", state.Read.UsageDaily, state.Read.LimitDaily))
+	}
+	if state.Read.Limit15 > 0 {
+		parts = append(parts, fmt.Sprintf("Read 15-min %d/%d", state.Read.Usage15, state.Read.Limit15))
+	}
+	if state.Overall.LimitDaily > 0 && (state.Overall.LimitDaily != state.Read.LimitDaily || state.Overall.UsageDaily != state.Read.UsageDaily) {
+		parts = append(parts, fmt.Sprintf("Overall daily %d/%d", state.Overall.UsageDaily, state.Overall.LimitDaily))
+	}
+	if len(parts) == 0 {
+		return ""
+	}
+	return "Usage: " + strings.Join(parts, ", ") + "."
+}
+
+func formatRetryAfter(t time.Time) string {
+	if t.IsZero() {
+		return ""
+	}
+	return t.UTC().Format(time.RFC3339)
 }
 
 func writeSyncEvent(w http.ResponseWriter, flusher http.Flusher, event string, data any) error {