refactor: centralize avatar URL generation and backfill existing users

cmd/user/main.go

@@ -14,6 +14,7 @@ import (
 	"mal/internal/database"
 	"mal/internal/db"
 	"mal/internal/observability"
+	"mal/internal/users"
 )
 
 func main() {
@@ -91,7 +92,7 @@ func main() {
 	}
 
 	id := uuid.New().String()
-	avatarURL := fmt.Sprintf("https://api.dicebear.com/9.x/dylan/svg?seed=%s", username)
+	avatarURL := users.DefaultAvatarURL(username)
 	_, err = dbConn.Exec("INSERT INTO user (id, username, password_hash, avatar_url) VALUES (?, ?, ?, ?)", id, username, string(hash), avatarURL)
 	if err != nil {
 		observability.Error("cli_user_create_failed", "cmd/user", "", map[string]any{"username": username}, err)
@@ -117,7 +118,7 @@ func updateAvatars(dbConn *sql.DB) {
 			os.Exit(1)
 		}
 
-		avatarURL := fmt.Sprintf("https://api.dicebear.com/9.x/dylan/svg?seed=%s", username)
+		avatarURL := users.DefaultAvatarURL(username)
 		_, err := dbConn.Exec("UPDATE user SET avatar_url = ? WHERE id = ?", avatarURL, id)
 		if err != nil {
 			observability.Error("cli_user_avatar_update_failed", "cmd/user", "", map[string]any{"username": username}, err)

internal/database/fixes/20260528_backfill_avatar_url.go

@@ -0,0 +1,46 @@
+package fixes
+
+import (
+	"context"
+	"database/sql"
+	"fmt"
+	"mal/internal/users"
+)
+
+func init() {
+	Register(Fix{
+		ID: "20260528_backfill_avatar_url",
+		Apply: func(ctx context.Context, sqlDB *sql.DB) error {
+			rows, err := sqlDB.QueryContext(ctx, `SELECT id, username FROM user WHERE avatar_url = ''`)
+			if err != nil {
+				return err
+			}
+			defer func() { _ = rows.Close() }()
+
+			type userRow struct {
+				id       string
+				username string
+			}
+			toUpdate := make([]userRow, 0, 64)
+			for rows.Next() {
+				var r userRow
+				if err := rows.Scan(&r.id, &r.username); err != nil {
+					return err
+				}
+				toUpdate = append(toUpdate, r)
+			}
+			if err := rows.Err(); err != nil {
+				return err
+			}
+
+			for _, u := range toUpdate {
+				avatarURL := users.DefaultAvatarURL(u.username)
+				if _, err := sqlDB.ExecContext(ctx, `UPDATE user SET avatar_url = ? WHERE id = ?`, avatarURL, u.id); err != nil {
+					return fmt.Errorf("update avatar_url for user %s: %w", u.id, err)
+				}
+			}
+
+			return nil
+		},
+	})
+}

internal/users/avatar.go

@@ -0,0 +1,11 @@
+package users
+
+import (
+	"net/url"
+	"strings"
+)
+
+func DefaultAvatarURL(username string) string {
+	seed := url.QueryEscape(strings.TrimSpace(username))
+	return "https://api.dicebear.com/9.x/dylan/svg?seed=" + seed
+}