Add isjoined to event info and event list

Signed-off-by: Asai Neko <sugar@sne.moe>

data/attendance.go

@@ -141,6 +141,31 @@ func (self *Attendance) GetAttendanceListByEventId(ctx context.Context, eventId
 	return &result, err
 }
 
+func (self *Attendance) GetJoinedEventIDs(ctx context.Context, userId uuid.UUID, eventIds []uuid.UUID) (map[uuid.UUID]bool, error) {
+	joinedMap := make(map[uuid.UUID]bool)
+
+	if len(eventIds) == 0 {
+		return joinedMap, nil
+	}
+
+	var foundEventIds []uuid.UUID
+
+	err := Database.WithContext(ctx).
+		Model(&Attendance{}).
+		Where("user_id = ? AND event_id IN ?", userId, eventIds).
+		Pluck("event_id", &foundEventIds).Error
+
+	if err != nil {
+		return nil, err
+	}
+
+	for _, id := range foundEventIds {
+		joinedMap[id] = true
+	}
+
+	return joinedMap, nil
+}
+
 func (self *Attendance) CountUsersByEventID(ctx context.Context, eventID uuid.UUID) (int64, error) {
 	var count int64