gruppi

static Future<void> existingGroup(myUID, toUID) async {
    List<String> users = [myUID, toUID];
    final querySnapshot = await FirebaseFirestore.instance
        .collection('users')
        .where('UID', isEqualTo: myUID)
        .get();

    for (var doc in querySnapshot.docs) {
      // Getting data directly
      List<dynamic> groups = doc.get('groups');
      var conteggio = groups.length;
      if (conteggio > 0) {
        groups.forEach(
          (element) async {
            final groupSnapshot = await FirebaseFirestore.instance
                .collection('groups')
                .where('id', isEqualTo: element)
                .where('members', arrayContains: toUID)
                .get();

            for (var gruppos in groupSnapshot.docs) {
              String gruppo = gruppos.get('id');
              print("gruppo $gruppo");
              if (gruppo != '') {
                print('si');
                // GRUPPO ESISTE
              } else {
                print('no');
                // GRUPPO NON ESISTE
                createGroup(myUID, toUID);
              }
            }
          },
        );
      } else {
        createGroup(myUID, toUID);
      }
    }
  }


  static Future<String> createGroup(myUID, toUID) async {
    final Map<String, dynamic> data = {
      "members": [myUID, toUID],
      "createdOn": FieldValue.serverTimestamp(),
      "id": ""
    };
    String chatID = "";
    await FirebaseFirestore.instance
        .collection("groups")
        .add(data)
        .then((docRef) {
      final id = <String, String>{"id": docRef.id};

      FirebaseFirestore.instance.collection("groups").doc(docRef.id).update(id);
      updateUserGroups(docRef.id, myUID);
      updateUserGroups(docRef.id, toUID);
      chatID = docRef.id;
    });
    return chatID;
  }

  static Future<void> updateUserGroups(chatID, userUID) async {
    await FirebaseFirestore.instance.collection('users').doc(userUID).update({
      'groups': FieldValue.arrayUnion([chatID])
    });
  }