fix: make addBadgeScan idempotent against a client retry of the same scan

app/Models/Foundation/Summit/Registration/SponsorBadgeScan.php

@@ -92,6 +92,32 @@ class SponsorBadgeScan extends SponsorUserInfoGrant
     #[ORM\Column(name: 'Source', type: 'string', options: ['default' => self::Source_QR])]
     private $source;
 
+    /**
+     * Denormalized "<sponsor>:<badge>:<member>:<scan_date epoch>" identity of the physical
+     * scan this row represents, carrying a UNIQUE index (see the migration that
+     * adds SponsorBadgeScan_ScanDedupKey). That index - not the Redis dedup lock
+     * in SponsorUserInfoGrantService::addBadgeScanLocked - is what actually makes
+     * addBadgeScan idempotent: a lock with a TTL and no renewal cannot guarantee
+     * mutual exclusion (it can expire mid-transaction, and LockManagerService
+     * only logs the mismatch at release time), so the database has to be the
+     * authority on "one row per scan".
+     *
+     * The column has to live here rather than being an index over the tuple
+     * itself: SponsorUserInfoGrant/SponsorBadgeScan is a JOINED inheritance pair
+     * with SponsorID on the parent table and BadgeID/ScanDate on this one, and a
+     * UNIQUE index cannot span both tables.
+     *
+     * Nullable on purpose, and rows created before that migration keep NULL:
+     * MySQL allows any number of NULLs in a UNIQUE index, so pre-existing
+     * duplicates (which this bug already produced in production) neither block
+     * the index creation nor need deleting. Those historical rows stay covered by
+     * the explicit findExistingBadgeScan() check, which matches on the real
+     * columns; every new row gets a key and is covered by the index too.
+     * @var string|null
+     */
+    #[ORM\Column(name: 'ScanDedupKey', type: 'string', nullable: true)]
+    private $scan_dedup_key;
+
     /**
      * @var SponsorBadgeScanExtraQuestionAnswer[]
      */
@@ -169,6 +195,42 @@ public function setScanDate(\DateTime $scan_date): void
         $this->scan_date = $scan_date;
     }
 
+    /**
+     * Builds the value for the ScanDedupKey UNIQUE index from the tuple that
+     * identifies one physical scan. Uses the scan_date's epoch so the key is
+     * insensitive to how the DateTime was constructed (timezone, sub-second
+     * precision the DATETIME column would drop anyway) - the scanning app
+     * sends the timestamp as epoch seconds and resends it unchanged on a retry.
+     * The scanning member is part of the identity: a real retry always comes from
+     * the same member, whereas two reps of one sponsor scanning the same badge in
+     * the same second are two distinct scans, each with its own notes and answers.
+     * @param Sponsor $sponsor
+     * @param SummitAttendeeBadge $badge
+     * @param Member $member
+     * @param \DateTime $scan_date
+     * @return string
+     */
+    public static function buildDedupKey(Sponsor $sponsor, SummitAttendeeBadge $badge, Member $member, \DateTime $scan_date): string
+    {
+        return sprintf('%d:%d:%d:%d', $sponsor->getId(), $badge->getId(), $member->getId(), $scan_date->getTimestamp());
+    }
+
+    /**
+     * @return string|null
+     */
+    public function getScanDedupKey(): ?string
+    {
+        return $this->scan_dedup_key;
+    }
+
+    /**
+     * @param string $scan_dedup_key
+     */
+    public function setScanDedupKey(string $scan_dedup_key): void
+    {
+        $this->scan_dedup_key = $scan_dedup_key;
+    }
+
     public function getAttendeeFirstName():?string{
         $attendee = $this->getBadge()->getTicket()->getOwner();
         return $attendee->hasMember() ? $attendee->getMember()->getFirstName() : $attendee->getFirstName();

app/Models/Foundation/Summit/Repositories/ISponsorUserInfoGrantRepository.php

@@ -11,12 +11,22 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  **/
+use models\main\Member;
 use models\utils\IBaseRepository;
 /**
  * Interface ISponsorUserInfoGrantRepository
  * @package models\summit
  */
 interface ISponsorUserInfoGrantRepository extends IBaseRepository
 {
-
+    /**
+     * Looks up a previously persisted SponsorBadgeScan for the exact same
+     * (sponsor, badge, scan_date) tuple, used to make SponsorUserInfoGrantService::addBadgeScan
+     * idempotent against a client retry of the same scan (SUP-86b9fp53j).
+     * @param Sponsor $sponsor
+     * @param SummitAttendeeBadge $badge
+     * @param \DateTime $scan_date
+     * @return SponsorBadgeScan|null
+     */
+    public function findExistingBadgeScan(Sponsor $sponsor, SummitAttendeeBadge $badge, Member $member, \DateTime $scan_date): ?SponsorBadgeScan;
 }

app/Repositories/Summit/DoctrineSponsorUserInfoGrantRepository.php

@@ -13,10 +13,13 @@
  **/
 use App\Repositories\SilverStripeDoctrineRepository;
 use Doctrine\ORM\QueryBuilder;
+use models\main\Member;
 use models\summit\ISponsorUserInfoGrantRepository;
 use models\summit\Presentation;
+use models\summit\Sponsor;
 use models\summit\SponsorBadgeScan;
 use models\summit\SponsorUserInfoGrant;
+use models\summit\SummitAttendeeBadge;
 use models\summit\SummitEvent;
 use utils\DoctrineFilterMapping;
 use utils\DoctrineInstanceOfFilterMapping;
@@ -124,4 +127,35 @@ protected function getBaseEntity()
     {
         return SponsorUserInfoGrant::class;
     }
-}
+
+    /**
+     * Queries SponsorBadgeScan directly (not the generic filter/order pipeline
+     * above, which matches against the whole SponsorUserInfoGrant hierarchy and
+     * is meant for paged listing) for an exact (sponsor, badge, member, scan_date) match.
+     * Doctrine resolves the SponsorUserInfoGrant/SponsorBadgeScan joined-table
+     * inheritance transparently, so no manual join is needed here.
+     * @param Sponsor $sponsor
+     * @param SummitAttendeeBadge $badge
+     * @param Member $member
+     * @param \DateTime $scan_date
+     * @return SponsorBadgeScan|null
+     */
+    public function findExistingBadgeScan(Sponsor $sponsor, SummitAttendeeBadge $badge, Member $member, \DateTime $scan_date): ?SponsorBadgeScan
+    {
+        $query = $this->getEntityManager()
+            ->createQueryBuilder()
+            ->select("e")
+            ->from(SponsorBadgeScan::class, "e")
+            ->where("e.sponsor = :sponsor")
+            ->andWhere("e.badge = :badge")
+            ->andWhere("e.user = :member")
+            ->andWhere("e.scan_date = :scan_date")
+            ->setParameter("sponsor", $sponsor)
+            ->setParameter("badge", $badge)
+            ->setParameter("member", $member)
+            ->setParameter("scan_date", $scan_date)
+            ->setMaxResults(1);
+
+        return $query->getQuery()->getOneOrNullResult();
+    }
+}