deparment sub collection

import 'package:cloud_firestore/cloud_firestore.dart';
import 'package:firebase_core/firebase_core.dart';
import 'package:flutter/material.dart';

void main() async {
  WidgetsFlutterBinding.ensureInitialized();
  await Firebase.initializeApp();
  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Add Subcollections to Existing Departments',
      home: AddSubcollectionsPage(),
    );
  }
}

class AddSubcollectionsPage extends StatelessWidget {
  // List of department names (existing documents in 'departments' collection)
  final List<String> collectionsToDelete = [
    'Biology',
    'Chemistry',
    'Computer Science and Engineering',
    'Electrical and Electronic Engineering',
    'Mathematics',
    'Physics',
  ];

  // List of subcollections for each department
  final List<String> subCollections = [
    '1st year',
    '2nd year',
    '3rd year',
    '4th year',
    'MS',
    'Files',
  ];

  // Method to add subcollections under each existing department
  Future<void> addSubcollections() async {
    try {
      // Reference to the 'departments' collection
      CollectionReference departments = FirebaseFirestore.instance.collection('departments');

      for (var department in collectionsToDelete) {
        // Reference to the department document
        DocumentReference departmentDoc = departments.doc(department);

        // Check if the department document exists
        var docSnapshot = await departmentDoc.get();
        if (docSnapshot.exists) {
          // Create subcollections under the department
          for (var subCollection in subCollections) {
            // Add a document to each subcollection
            await departmentDoc.collection(subCollection).doc('example').set({
              'name': subCollection,
              'createdAt': Timestamp.now(),
            });
            print('Subcollection $subCollection created under department $department.');
          }
        } else {
          print('Department $department does not exist.');
        }
      }
    } catch (e) {
      print('Error adding subcollections: $e');
    }
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('Add Subcollections to Existing Departments'),
      ),
      body: Center(
        child: Text('Press the button to add subcollections under each department'),
      ),
      floatingActionButton: FloatingActionButton(
        onPressed: () async {
          await addSubcollections();
          ScaffoldMessenger.of(context).showSnackBar(
            SnackBar(content: Text('Subcollections added to existing departments!')),
          );
        },
        child: Icon(Icons.add),
        tooltip: 'Add Subcollections',
      ),
    );
  }
}