chore: add logger for push notifications

internal/service/push_sender.go

@@ -3,8 +3,11 @@ package service
 import (
 	"context"
 	"encoding/json"
+	"io"
 	"net/http"
+	"net/url"
 	"strconv"
+	"strings"
 	"time"
 
 	webpush "github.com/SherClockHolmes/webpush-go"
@@ -81,10 +84,13 @@ func (p *PushSender) SendToUser(ctx context.Context, userID string, payload Push
 			Endpoint: s.Endpoint,
 			Keys:     webpush.Keys{P256dh: s.P256dh, Auth: s.Auth},
 		}
-		status, err := p.sendWithRetry(ctx, body, sub)
+		status, respBody, err := p.sendWithRetry(ctx, body, sub)
 		if err != nil {
 			failed++
-			p.logger.Warn("push: send failed", zap.String("user", userID), zap.Error(err))
+			p.logger.Warn("push: send failed",
+				zap.String("user", userID),
+				zap.String("host", endpointHost(s.Endpoint)),
+				zap.Error(err))
 			continue
 		}
 		switch {
@@ -96,7 +102,13 @@ func (p *PushSender) SendToUser(ctx context.Context, userID string, payload Push
 			}
 		case status >= 400:
 			failed++
-			p.logger.Warn("push: non-2xx", zap.Int("status", status), zap.String("user", userID))
+			// The response body carries the real reason (e.g. a VAPID
+			// credential mismatch, malformed request) — log it.
+			p.logger.Warn("push: non-2xx",
+				zap.Int("status", status),
+				zap.String("user", userID),
+				zap.String("host", endpointHost(s.Endpoint)),
+				zap.String("body", respBody))
 		default:
 			sent++
 		}
@@ -108,8 +120,10 @@ func (p *PushSender) SendToUser(ctx context.Context, userID string, payload Push
 
 // sendWithRetry posts one notification, retrying on transient failures
 // (network error or 429/5xx) with a short backoff that honors Retry-After.
-// Returns the final HTTP status, or an error if every attempt errored.
-func (p *PushSender) sendWithRetry(ctx context.Context, body []byte, sub *webpush.Subscription) (int, error) {
+// Returns the final HTTP status and, on a 4xx/5xx, a snippet of the response
+// body (the push service's error reason). Returns an error if every attempt
+// errored at the transport level.
+func (p *PushSender) sendWithRetry(ctx context.Context, body []byte, sub *webpush.Subscription) (int, string, error) {
 	var lastErr error
 	for attempt := 1; attempt <= pushMaxAttempts; attempt++ {
 		resp, err := webpush.SendNotification(body, sub, &webpush.Options{
@@ -127,18 +141,33 @@ func (p *PushSender) sendWithRetry(ctx context.Context, body []byte, sub *webpus
 				sleepCtx(ctx, backoff(attempt))
 				continue
 			}
-			return 0, err
+			return 0, "", err
 		}
 		status := resp.StatusCode
 		retryAfter := resp.Header.Get("Retry-After")
-		_ = resp.Body.Close()
 		if isTransientStatus(status) && attempt < pushMaxAttempts {
+			_ = resp.Body.Close()
 			sleepCtx(ctx, retryDelay(retryAfter, attempt))
 			continue
 		}
-		return status, nil
+		// Final attempt — capture the body on errors for diagnostics.
+		var snippet string
+		if status >= 400 {
+			b, _ := io.ReadAll(io.LimitReader(resp.Body, 512))
+			snippet = strings.TrimSpace(string(b))
+		}
+		_ = resp.Body.Close()
+		return status, snippet, nil
 	}
-	return 0, lastErr
+	return 0, "", lastErr
+}
+
+// endpointHost extracts the host of a push endpoint for log context.
+func endpointHost(endpoint string) string {
+	if u, err := url.Parse(endpoint); err == nil {
+		return u.Host
+	}
+	return ""
 }
 
 func isTransientStatus(s int) bool {