### Initialize Firestore and Create References in Dart

Source: https://context7.com/firebase/snippets-flutter/llms.txt

Demonstrates how to get the Firestore instance and create references to collections and documents. Useful for setting up data access in your Flutter app.

```dart
import 'package:cloud_firestore/cloud_firestore.dart';

// Get Firestore instance
final db = FirebaseFirestore.instance;

// Create a reference to a specific document
final alovelaceDocumentRef = db.collection("users").doc("alovelace");

// Create a reference to a collection
final usersCollectionRef = db.collection("users");

// Create a reference using a path string
final aLovelaceDocRef = db.doc("users/alovelace");

// Create a reference to a subcollection document
final messageRef = db
    .collection("rooms")
    .doc("roomA")
    .collection("messages")
    .doc("message1");
```

--------------------------------

### Create Cloud Storage References in Flutter

Source: https://context7.com/firebase/snippets-flutter/llms.txt

This snippet demonstrates how to create references to files and directories within Firebase Cloud Storage. It covers getting the default instance, creating child references, navigating through the storage hierarchy, and using non-default buckets or secondary Firebase apps.

```dart
import 'package:firebase_storage/firebase_storage';

// Get default storage instance
final storage = FirebaseStorage.instance;

// Get storage reference
final storageRef = storage.ref();

// Create child references
final imagesRef = storageRef.child('images');
final spaceRef = storageRef.child("images/space.jpg");

// Navigate with references
final parentRef = spaceRef.parent;  // Points to 'images'
final rootRef = spaceRef.root;       // Points to root

// Chain references
final earthRef = spaceRef.parent?.child("earth.jpg");

// Use a non-default bucket
final customStorage = FirebaseStorage.instanceFor(bucket: "gs://my-custom-bucket");

// Use with a secondary Firebase app
final secondApp = Firebase.app('SecondaryApp');
final secondaryStorage = FirebaseStorage.instanceFor(
  app: secondApp,
  bucket: 'gs://my-custom-bucket',
);
```

--------------------------------

### Get Documents with a Query

Source: https://context7.com/firebase/snippets-flutter/llms.txt

Retrieve documents from a collection that match specific filter criteria. Use the `where` clause to define query conditions.

```dart
// Get documents with a query
db.collection("cities").where("capital", isEqualTo: true).get().then(
  (querySnapshot) {
    for (var docSnapshot in querySnapshot.docs) {
      print('${docSnapshot.id} => ${docSnapshot.data()}');
    }
  },
);
```

--------------------------------

### Get All Documents in a Collection

Source: https://context7.com/firebase/snippets-flutter/llms.txt

Retrieve all documents within a specified collection. Iterate through the results to access individual document data.

```dart
// Get all documents in a collection
db.collection("cities").get().then(
  (querySnapshot) {
    for (var docSnapshot in querySnapshot.docs) {
      print('${docSnapshot.id} => ${docSnapshot.data()}');
    }
  },
);
```

--------------------------------

### Get Documents from a Subcollection

Source: https://context7.com/firebase/snippets-flutter/llms.txt

Retrieve documents from a subcollection of a specific document. This allows for hierarchical data organization.

```dart
// Get documents from a subcollection
db.collection("cities").doc("SF").collection("landmarks").get().then(
  (querySnapshot) {
    for (var docSnapshot in querySnapshot.docs) {
      print('${docSnapshot.id} => ${docSnapshot.data()}');
    }
  },
);
```

--------------------------------

### Get a Single Document

Source: https://context7.com/firebase/snippets-flutter/llms.txt

Retrieve a single document from Firestore. Specify the source (cache, server, or default) for the data retrieval.

```dart
// Get a single document
final docRef = db.collection("cities").doc("SF");
docRef.get().then(
  (DocumentSnapshot doc) {
    final data = doc.data() as Map<String, dynamic>;
    print("Document data: $data");
  },
  onError: (e) => print("Error getting document: $e"),
);
```

```dart
// Specify source (cache, server, or default)
docRef.get(const GetOptions(source: Source.cache)).then(
  (res) => print("Successfully completed from cache"),
  onError: (e) => print("Error completing: $e"),
);
```

--------------------------------

### Call Callable Cloud Functions from Flutter

Source: https://context7.com/firebase/snippets-flutter/llms.txt

Invoke Cloud Functions with typed parameters and handle responses or errors. Use `FirebaseFunctions.instance` to get the functions instance.

```dart
import 'package:cloud_functions/cloud_functions.dart';

final functions = FirebaseFunctions.instance;

// Call a function
Future<HttpsCallableResult> addMessage(String text) {
  final data = {
    "text": text,
    "push": true,
  };
  final addMessage = functions.httpsCallable("addMessage");
  return addMessage(data);
}

// Handle responses and errors
final callable = functions.httpsCallable("addMessage");
callable({"text": "message text"}).then(
  (result) => print(result.data['text']),
  onError: (e) => print("Error calling function: $e"),
);
```

--------------------------------

### Initialize Firebase Realtime Database

Source: https://context7.com/firebase/snippets-flutter/llms.txt

Sets up the Realtime Database instance, including using a secondary app and enabling offline persistence.

```dart
import 'package:firebase_database/firebase_database.dart';

// Get default database instance
final FirebaseDatabase database = FirebaseDatabase.instance;

// Use secondary Firebase app
FirebaseApp secondaryApp = Firebase.app('SecondaryApp');
FirebaseDatabase secondaryDatabase = FirebaseDatabase.instanceFor(app: secondaryApp);

// Get root reference
final DatabaseReference ref = FirebaseDatabase.instance.ref();

// Enable offline persistence
FirebaseDatabase.instance.setPersistenceEnabled(true);
```

--------------------------------

### List and Delete Files in Cloud Storage

Source: https://context7.com/firebase/snippets-flutter/llms.txt

Lists files and subdirectories within a Cloud Storage reference, and demonstrates how to delete a file. Includes error handling for operations.

```dart
final storageRef = FirebaseStorage.instance.ref().child("files/uid");

// List all files and prefixes
final listResult = await storageRef.listAll();
for (var prefix in listResult.prefixes) {
  // Subdirectories - can call listAll() recursively
  print("Directory: ${prefix.fullPath}");
}
for (var item in listResult.items) {
  print("File: ${item.fullPath}");
}

// Paginated listing
Stream<ListResult> listAllPaginated(Reference ref) async*
{
  String? pageToken;
  do {
    final listResult = await ref.list(ListOptions(
      maxResults: 100,
      pageToken: pageToken,
    ));
    yield listResult;
    pageToken = listResult.nextPageToken;
  } while (pageToken != null);
}

// Delete a file
final desertRef = storageRef.child("images/desert.jpg");
await desertRef.delete();

// Error handling
try {
  final listResult = await storageRef.listAll();
} on FirebaseException catch (e) {
  print("Failed with error '${e.code}': ${e.message}");
}
```

--------------------------------

### Read and Write Data in Realtime Database

Source: https://context7.com/firebase/snippets-flutter/llms.txt

Demonstrates basic CRUD operations, including writing data, updating specific fields or nested paths, and reading data with listeners or once.

```dart
final DatabaseReference ref = FirebaseDatabase.instance.ref();

// Write data
await ref.set({
  "name": "John",
  "age": 18,
  "address": {"line1": "100 Mountain View"}
});

// Update specific fields
await ref.update({"age": 19});

// Update nested paths
await ref.update({
  "123/age": 19,
  "123/address/line1": "1 Mountain View",
});

// Read data with listener
const postId = '123';
DatabaseReference starCountRef = FirebaseDatabase.instance.ref('posts/$postId/starCount');
starCountRef.onValue.listen((DatabaseEvent event) {
  final data = event.snapshot.value;
  print("Star count: $data");
});

// Read data once
const userId = '123';
final dbRef = FirebaseDatabase.instance.ref();
try {
  final snapshot = await dbRef.child('users/$userId').get();
  if (snapshot.exists) {
    print("User data: ${snapshot.value}");
  }
} on FirebaseException catch (e) {
  print("Error: $e");
}

// Write with completion callback
FirebaseDatabase.instance
    .ref('users/123/email')
    .set('user@example.com')
    .then((_) {
      print("Data saved successfully!");
    }).catchError((error) {
      print("Write failed: $error");
    });
```

--------------------------------

### Manage Lists and Child Events in Realtime Database

Source: https://context7.com/firebase/snippets-flutter/llms.txt

Shows how to push new items to a list, listen for child added, changed, and removed events, and process all values in a list.

```dart
// Push to create new list item with unique key
DatabaseReference postListRef = FirebaseDatabase.instance.ref("posts");
DatabaseReference newPostRef = postListRef.push();
newPostRef.set({
  "title": "New Post",
  "body": "Post content"
});

// Listen for child events
final commentsRef = FirebaseDatabase.instance.ref("post-comments/123");

commentsRef.onChildAdded.listen((event) {
  print("New comment added: ${event.snapshot.value}");
});

commentsRef.onChildChanged.listen((event) {
  print("Comment changed: ${event.snapshot.value}");
});

commentsRef.onChildRemoved.listen((event) {
  print("Comment removed: ${event.snapshot.key}");
});

// Listen for all values
postListRef.onValue.listen((event) {
  for (final child in event.snapshot.children) {
    print("Post: ${child.value}");
  }
}, onError: (error) {
  print("Error: $error");
});
```

--------------------------------

### Implement Pagination with Cursors in Dart

Source: https://context7.com/firebase/snippets-flutter/llms.txt

Use startAt, endAt, and startAfterDocument to implement cursor-based pagination. This allows you to fetch data in manageable chunks, improving performance.

```dart
// Pagination with cursors
db.collection("cities").orderBy("population").startAt([1000000]);
db.collection("cities").orderBy("population").endAt([1000000]);

// Paginate using document snapshots
final first = db.collection("cities").orderBy("population").limit(25);

first.get().then((documentSnapshots) {
  // Get the last visible document
  final lastVisible = documentSnapshots.docs[documentSnapshots.size - 1];

  // Construct next query starting after this document
  final next = db
      .collection("cities")
      .orderBy("population")
      .startAfterDocument(lastVisible)
      .limit(25);
});
```

--------------------------------

### Apple Sign-In for Web in Flutter

Source: https://context7.com/firebase/snippets-flutter/llms.txt

A simplified approach for Apple Sign-In on web platforms using `signInWithPopup` with specified scopes.

```dart
Future<UserCredential> signInWithAppleWeb() async {
  final provider = OAuthProvider("apple.com")
    ..addScope('email')
    ..addScope('name');
  return await FirebaseAuth.instance.signInWithPopup(provider);
}
```

--------------------------------

### Google Sign-In for Web in Flutter

Source: https://context7.com/firebase/snippets-flutter/llms.txt

Handles Google Sign-In on web platforms using `signInWithPopup` or `signInWithRedirect`. Allows adding scopes and custom parameters like `login_hint`.

```dart
Future<UserCredential> signInWithGoogleWeb() async {
  GoogleAuthProvider googleProvider = GoogleAuthProvider();
  googleProvider.addScope('https://www.googleapis.com/auth/contacts.readonly');
  googleProvider.setCustomParameters({'login_hint': 'user@example.com'});

  return await FirebaseAuth.instance.signInWithPopup(googleProvider);
  // Or use: FirebaseAuth.instance.signInWithRedirect(googleProvider);
}
```

--------------------------------

### Listen to Query Results in Real-time

Source: https://context7.com/firebase/snippets-flutter/llms.txt

Listen for real-time updates to documents that match a specific query. Changes to documents satisfying the query are streamed.

```dart
// Listen to query results
db.collection("cities")
    .where("state", isEqualTo: "CA")
    .snapshots()
    .listen((event) {
  final cities = [];
  for (var doc in event.docs) {
    cities.add(doc.data()["name"]);
  }
  print("cities in CA: ${cities.join(", ")}");
});
```

--------------------------------

### Listen to a Single Document in Real-time

Source: https://context7.com/firebase/snippets-flutter/llms.txt

Listen for real-time updates to a single document. Changes are streamed automatically as they occur. Handles errors during the listen process.

```dart
// Listen to a single document
final docRef = db.collection("cities").doc("SF");
docRef.snapshots().listen(
  (event) => print("current data: ${event.data()}"),
  onError: (error) => print("Listen failed: $error"),
);
```

--------------------------------

### Listen to Document Changes (Added, Modified, Removed)

Source: https://context7.com/firebase/snippets-flutter/llms.txt

Listen for real-time updates on documents matching a query and process individual document changes (added, modified, or removed).

```dart
// Listen to document changes (added, modified, removed)
db.collection("cities")
    .where("state", isEqualTo: "CA")
    .snapshots()
    .listen((event) {
  for (var change in event.docChanges) {
    switch (change.type) {
      case DocumentChangeType.added:
        print("New City: ${change.doc.data()}");
        break;
      case DocumentChangeType.modified:
        print("Modified City: ${change.doc.data()}");
        break;
      case DocumentChangeType.removed:
        print("Removed City: ${change.doc.data()}");
        break;
    }
  }
});
```

--------------------------------

### Upload Files to Cloud Storage

Source: https://context7.com/firebase/snippets-flutter/llms.txt

Upload files from various sources like file paths, raw data, or strings. Monitor upload progress and manage the upload task. Requires `dart:io` and `path_provider` imports.

```dart
import 'dart:io';
import 'package:path_provider/path_provider.dart';

final appDocDir = await getApplicationDocumentsDirectory();
final filePath = "${appDocDir.path}/mountains.jpg";
final file = File(filePath);
final storageRef = FirebaseStorage.instance.ref();
final mountainsRef = storageRef.child("mountains.jpg");

// Upload with metadata
final metadata = SettableMetadata(contentType: "image/jpeg");
final uploadTask = storageRef
    .child("images/mountains.jpg")
    .putFile(file, metadata);

// Monitor upload progress
uploadTask.snapshotEvents.listen((TaskSnapshot taskSnapshot) {
  switch (taskSnapshot.state) {
    case TaskState.running:
      final progress = 100.0 * (taskSnapshot.bytesTransferred / taskSnapshot.totalBytes);
      print("Upload is $progress% complete.");
      break;
    case TaskState.paused:
      print("Upload is paused.");
      break;
    case TaskState.canceled:
      print("Upload was canceled");
      break;
    case TaskState.error:
      // Handle error
      break;
    case TaskState.success:
      // Handle success
      break;
  }
});

// Upload from string (base64, data URL, etc.)
String dataUrl = 'data:text/plain;base64,SGVsbG8sIFdvcmxkIQ==';
await mountainsRef.putString(dataUrl, format: PutStringFormat.dataUrl);

// Manage upload task
final task = mountainsRef.putFile(file);
bool paused = await task.pause();
bool resumed = await task.resume();
bool canceled = await task.cancel();

// Get download URL after upload
final downloadUrl = await mountainsRef.getDownloadURL();
```

--------------------------------

### Apple Sign-In with Nonce Generation in Flutter

Source: https://context7.com/firebase/snippets-flutter/llms.txt

Authenticate users with Apple ID, including secure nonce generation and SHA256 hashing for replay attack prevention. Requires `sign_in_with_apple` and `crypto` packages.

```dart
import 'dart:convert';
import 'dart:math';
import 'package:crypto/crypto.dart';
import 'package:sign_in_with_apple/sign_in_with_apple.dart';

String generateNonce([int length = 32]) {
  const charset = '0123456789ABCDEFGHIJKLMNOPQRSTUVXYZabcdefghijklmnopqrstuvwxyz-._';
  final random = Random.secure();
  return List.generate(length, (_) => charset[random.nextInt(charset.length)]).join();
}

String sha256ofString(String input) {
  final bytes = utf8.encode(input);
  final digest = sha256.convert(bytes);
  return digest.toString();
}

Future<UserCredential> signInWithApple() async {
  final rawNonce = generateNonce();
  final nonce = sha256ofString(rawNonce);

  final appleCredential = await SignInWithApple.getAppleIDCredential(
    scopes: [
      AppleIDAuthorizationScopes.email,
      AppleIDAuthorizationScopes.fullName,
    ],
    nonce: nonce,
  );

  final oauthCredential = OAuthProvider("apple.com").credential(
    idToken: appleCredential.identityToken,
    rawNonce: rawNonce,
  );

  return await FirebaseAuth.instance.signInWithCredential(oauthCredential);
}
```

--------------------------------

### Download Files from Cloud Storage

Source: https://context7.com/firebase/snippets-flutter/llms.txt

Download files to memory or local files, or retrieve their download URLs. Handles different reference types (path, gs, https). Requires `dart:io` and `path_provider` imports.

```dart
final storageRef = FirebaseStorage.instance.ref();

// Create references from various sources
final pathReference = storageRef.child("images/stars.jpg");
final gsReference = FirebaseStorage.instance
    .refFromURL("gs://YOUR_BUCKET/images/stars.jpg");
final httpsReference = FirebaseStorage.instance
    .refFromURL("https://firebasestorage.googleapis.com/b/YOUR_BUCKET/o/images%20stars.jpg");

// Download to memory (max 1MB in this example)
final islandRef = storageRef.child("images/island.jpg");
try {
  const oneMegabyte = 1024 * 1024;
  final Uint8List? data = await islandRef.getData(oneMegabyte);
  // Use data...
} on FirebaseException catch (e) {
  print("Error: ${e.message}");
}

// Download to local file
final appDocDir = await getApplicationDocumentsDirectory();
final filePath = "${appDocDir.path}/images/island.jpg";
final file = File(filePath);
final downloadTask = islandRef.writeToFile(file);

downloadTask.snapshotEvents.listen((taskSnapshot) {
  switch (taskSnapshot.state) {
    case TaskState.running:
      break;
    case TaskState.success:
      print("Download complete!");
      break;
    case TaskState.error:
      print("Download failed");
      break;
    default:
      break;
  }
});

// Get download URL (for use with image loading, etc.)
final imageUrl = await storageRef.child("users/me/profile.png").getDownloadURL();
```

--------------------------------

### Google Sign-In for Mobile in Flutter

Source: https://context7.com/firebase/snippets-flutter/llms.txt

Authenticate users with their Google accounts on mobile platforms. Requires the `google_sign_in` package.

```dart
import 'package:google_sign_in/google_sign_in.dart';

Future<UserCredential> signInWithGoogle() async {
  // Trigger the authentication flow
  final GoogleSignInAccount? googleUser = await GoogleSignIn().signIn();

  // Obtain the auth details from the request
  final GoogleSignInAuthentication? googleAuth =
      await googleUser?.authentication;

  // Create a new credential
  final credential = GoogleAuthProvider.credential(
    accessToken: googleAuth?.accessToken,
    idToken: googleAuth?.idToken,
  );

  // Sign in with Firebase
  return await FirebaseAuth.instance.signInWithCredential(credential);
}
```

--------------------------------

### Firebase Email/Password Authentication

Source: https://context7.com/firebase/snippets-flutter/llms.txt

Create accounts and sign in users with email and password credentials. Handles common FirebaseAuthException errors for weak passwords or existing accounts.

```dart
const emailAddress = 'user@example.com';
const password = 'securePassword123!';

// Create a new account
try {
  final credential = await FirebaseAuth.instance.createUserWithEmailAndPassword(
    email: emailAddress,
    password: password,
  );
  print("Account created: ${credential.user?.uid}");
} on FirebaseAuthException catch (e) {
  if (e.code == 'weak-password') {
    print('The password provided is too weak.');
  } else if (e.code == 'email-already-in-use') {
    print('The account already exists for that email.');
  }
}
```

```dart
// Sign in with email and password
try {
  final credential = await FirebaseAuth.instance.signInWithEmailAndPassword(
    email: emailAddress,
    password: password,
  );
} on FirebaseAuthException catch (e) {
  if (e.code == 'user-not-found') {
    print('No user found for that email.');
  } else if (e.code == 'wrong-password') {
    print('Wrong password provided for that user.');
  }
}
```

```dart
// Sign out
await FirebaseAuth.instance.signOut();
```

--------------------------------

### Fetch Remote Config Values in Flutter

Source: https://context7.com/firebase/snippets-flutter/llms.txt

Configure and fetch remote configuration values. Set a minimum fetch interval and default values before fetching. The `fetchAndActivate` method retrieves and applies new values.

```dart
import 'package:firebase_remote_config/firebase_remote_config.dart';

final remoteConfig = FirebaseRemoteConfig.instance;

// Set minimum fetch interval
remoteConfig.settings.minimumFetchInterval = const Duration(hours: 1);

// Set default values
remoteConfig.setDefaults(<String, dynamic שנה>{
  'welcome_message': 'Welcome to the app!',
  'feature_enabled': false,
});

// Get values (uses cached or default values)
final welcomeMessage = remoteConfig.getValue("welcome_message");
final featureEnabled = remoteConfig.getBool("feature_enabled");

// Fetch and activate new values
remoteConfig.fetchAndActivate().then((bool updated) {
  if (updated) {
    final allConfig = remoteConfig.getAll();
    print("Config updated: $allConfig");
  }
});
```

--------------------------------

### Query and Sort Data in Flutter Realtime Database

Source: https://context7.com/firebase/snippets-flutter/llms.txt

Learn how to query and sort data from Firebase Realtime Database using various methods like orderByChild, orderByValue, and limitToLast. This is useful for retrieving specific subsets of data.

```dart
// Order by child value
final myUserId = FirebaseAuth.instance.currentUser?.uid;
final topUserPostsRef = FirebaseDatabase.instance
    .ref("user-posts/$myUserId")
    .orderByChild("starCount");

// Order by nested child
final mostViewedPosts = FirebaseDatabase.instance
    .ref('posts')
    .orderByChild('metrics/views');

// Limit results
final recentPostsRef = FirebaseDatabase.instance
    .ref('posts')
    .limitToLast(100);

// Query offline data
final scoresRef = FirebaseDatabase.instance.ref("scores");
scoresRef.orderByValue().limitToLast(4).onChildAdded.listen((event) {
  print("${event.snapshot.key}: ${event.snapshot.value}");
});
```

--------------------------------

### Add Data to Firestore

Source: https://github.com/firebase/snippets-flutter/blob/main/README.md

Demonstrates how to add a new document with a generated ID to a Firestore collection. Ensure you have initialized Firestore.

```dart
void getStarted_addData() async {
  // [START get_started_add_data_1]
  // Create a new user with a first and last name
  final user = <String, dynamic>{
    "first": "Ada",
    "last": "Lovelace",
    "born": 1815
  };

  // Add a new document with a generated ID
  db.collection("users").add(user).then((DocumentReference doc) =>
      print('DocumentSnapshot added with ID: ${doc.id}'));
  // [END get_started_add_data_1]
}
```

--------------------------------

### Manage File Metadata in Cloud Storage

Source: https://context7.com/firebase/snippets-flutter/llms.txt

Read, update, and set metadata for files in Cloud Storage. This includes content type, cache control, and custom metadata. Requires `FirebaseStorage.instance.ref()`.

```dart
final storageRef = FirebaseStorage.instance.ref();
final forestRef = storageRef.child("images/forest.jpg");

// Get metadata
final metadata = await forestRef.getMetadata();
print("Content type: ${metadata.contentType}");

// Update metadata
final newMetadata = SettableMetadata(
  cacheControl: "public,max-age=300",
  contentType: "image/jpeg",
);
final updatedMetadata = await forestRef.updateMetadata(newMetadata);

// Set custom metadata
final customMetadata = SettableMetadata(
  customMetadata: {
    "location": "Yosemite, CA, USA",
    "activity": "Hiking",
  },
);
await forestRef.updateMetadata(customMetadata);

// Delete metadata (set to null)
final deleteMetadata = SettableMetadata(cacheControl: null);
await forestRef.updateMetadata(deleteMetadata);
```

--------------------------------

### Build Queries with Comparison Operators in Dart

Source: https://context7.com/firebase/snippets-flutter/llms.txt

Use comparison operators like isLessThan, isGreaterThanOrEqualTo, and isLessThanOrEqualTo to filter query results. Ensure the field type is consistent for reliable comparisons.

```dart
final citiesRef = db.collection("cities");

// Simple equality query
final query = citiesRef.where("state", isEqualTo: "CA");
final capitalCities = citiesRef.where("capital", isEqualTo: true);

// Comparison operators
final populationQuery = citiesRef.where("population", isLessThan: 100000);
final stateQuery = citiesRef
    .where("state", isGreaterThanOrEqualTo: "CA")
    .where("state", isLessThanOrEqualTo: "IN");

// Not equal
final notCapitals = citiesRef.where("capital", isNotEqualTo: true);

// Array membership
final westCoastCities = citiesRef.where("regions", arrayContains: "west_coast");
final coastalCities = citiesRef.where("regions",
    arrayContainsAny: ["west_coast", "east_coast"]);

// In queries
final cities = citiesRef.where("country", whereIn: ["USA", "Japan"]);
final otherCities = citiesRef.where("country", whereNotIn: ["USA", "Japan"]);

// Compound queries
citiesRef
    .where("state", isEqualTo: "CO")
    .where("name", isEqualTo: "Denver");
```

--------------------------------

### Detect Local vs Server Changes

Source: https://context7.com/firebase/snippets-flutter/llms.txt

Differentiate between local changes (pending writes) and server-committed changes when listening to document snapshots. Access metadata to determine the source.

```dart
// Detect local vs server changes
docRef.snapshots().listen((event) {
  final source = (event.metadata.hasPendingWrites) ? "Local" : "Server";
  print("$source data: ${event.data()}");
});
```

--------------------------------

### Anonymous and Custom Token Sign-in in Flutter

Source: https://context7.com/firebase/snippets-flutter/llms.txt

Implement anonymous sign-in for temporary accounts or use custom tokens for server-backed authentication. This snippet also shows how to link anonymous accounts to permanent credentials and unlink providers.

```dart
// Anonymous sign-in
try {
  final userCredential = await FirebaseAuth.instance.signInAnonymously();
  print("Signed in with temporary account.");
} on FirebaseAuthException catch (e) {
  if (e.code == "operation-not-allowed") {
    print("Anonymous auth hasn't been enabled for this project.");
  }
}
```

```dart
// Custom token sign-in (token from your server)
const token = 'your-custom-token';
try {
  final userCredential = await FirebaseAuth.instance.signInWithCustomToken(token);
  print("Sign-in successful.");
} on FirebaseAuthException catch (e) {
  switch (e.code) {
    case "invalid-custom-token":
      print("The supplied token is not a Firebase custom auth token.");
      break;
    case "custom-token-mismatch":
      print("The supplied token is for a different Firebase project.");
      break;
  }
}
```

```dart
// Link anonymous account to permanent credentials
final credential = GoogleAuthProvider.credential(idToken: 'idToken');
try {
  final userCredential = await FirebaseAuth.instance.currentUser
      ?.linkWithCredential(credential);
} on FirebaseAuthException catch (e) {
  switch (e.code) {
    case "provider-already-linked":
      print("The provider has already been linked to the user.");
      break;
    case "credential-already-in-use":
      print("The account already exists.");
      break;
  }
}
```

```dart
// Unlink a provider
await FirebaseAuth.instance.currentUser?.unlink('google.com');
```

--------------------------------

### Custom Objects with Type Converters in Dart

Source: https://context7.com/firebase/snippets-flutter/llms.txt

Demonstrates how to use `withConverter()` to automatically serialize and deserialize custom Dart objects to and from Firestore documents. This simplifies data handling for complex types.

```dart
class City {
  final String? name;
  final String? state;
  final String? country;
  final bool? capital;
  final int? population;
  final List<String>? regions;

  City({
    this.name,
    this.state,
    this.country,
    this.capital,
    this.population,
    this.regions,
  });

  factory City.fromFirestore(
    DocumentSnapshot<Map<String, dynamic>> snapshot,
    SnapshotOptions? options,
  ) {
    final data = snapshot.data();
    return City(
      name: data?['name'],
      state: data?['state'],
      country: data?['country'],
      capital: data?['capital'],
      population: data?['population'],
      regions: data?['regions'] is Iterable ? List.from(data?['regions']) : null,
    );
  }

  Map<String, dynamic> toFirestore() {
    return {
      if (name != null) "name": name,
      if (state != null) "state": state,
      if (country != null) "country": country,
      if (capital != null) "capital": capital,
      if (population != null) "population": population,
      if (regions != null) "regions": regions,
    };
  }
}

// Using custom objects with Firestore
final city = City(
  name: "Los Angeles",
  state: "CA",
  country: "USA",
  capital: false,
  population: 5000000,
  regions: ["west_coast", "socal"],
);

final docRef = db
    .collection("cities")
    .withConverter(
      fromFirestore: City.fromFirestore,
      toFirestore: (City city, options) => city.toFirestore(),
    )
    .doc("LA");
await docRef.set(city);

// Reading with custom objects
final ref = db.collection("cities").doc("LA").withConverter(
      fromFirestore: City.fromFirestore,
      toFirestore: (City city, _) => city.toFirestore(),
    );
final docSnap = await ref.get();
final cityObj = docSnap.data(); // Returns City object
```

--------------------------------

### Combine AND/OR Queries in Dart

Source: https://context7.com/firebase/snippets-flutter/llms.txt

Construct complex queries by nesting Filter.and and Filter.or conditions. This allows for sophisticated data retrieval based on multiple criteria.

```dart
var query3 = db.collection("cities").where(
  Filter.and(
    Filter("state", isEqualTo: "CA"),
    Filter.or(
      Filter("capital", isEqualTo: true),
      Filter("population", isGreaterThan: 1000000),
    ),
  ),
);
```

--------------------------------

### Implement OR Queries with Filter in Dart

Source: https://context7.com/firebase/snippets-flutter/llms.txt

Combine multiple conditions using Filter.or for flexible querying. This is useful when a document can satisfy any of the specified conditions.

```dart
var query2 = db.collection("cities").where(
  Filter.or(
    Filter("capital", isEqualTo: true),
    Filter("population", isGreaterThan: 1000000),
  ),
);
```

--------------------------------

### Order and Limit Query Results in Dart

Source: https://context7.com/firebase/snippets-flutter/llms.txt

Sort query results by one or more fields in ascending or descending order and limit the number of documents returned. This is fundamental for displaying data sets.

```dart
final citiesRef = db.collection("cities");

// Order by field
citiesRef.orderBy("name").limit(3);

// Descending order
citiesRef.orderBy("name", descending: true).limit(3);

// Multiple order fields
citiesRef.orderBy("state").orderBy("population", descending: true);

// Combine with filters
citiesRef
    .where("population", isGreaterThan: 100000)
    .orderBy("population")
    .limit(2);
```

--------------------------------

### Listen to Firebase Auth State Changes

Source: https://context7.com/firebase/snippets-flutter/llms.txt

Monitor authentication state changes to react when users sign in or out. This listener provides real-time updates on the user's authentication status.

```dart
import 'package:firebase_auth/firebase_auth.dart';

// Listen to auth state changes
FirebaseAuth.instance.authStateChanges().listen((User? user) {
  if (user != null) {
    final uid = user.uid;
    print("User signed in: $uid");
  } else {
    print("User signed out");
  }
});
```

```dart
// Listen to ID token changes
FirebaseAuth.instance.idTokenChanges().listen((User? user) {
  if (user != null) {
    // User signed in or token refreshed
  }
});
```

```dart
// Listen to user changes (profile updates, etc.)
FirebaseAuth.instance.userChanges().listen((User? user) {
  if (user == null) {
    print('User is currently signed out!');
  } else {
    print('User is signed in!');
  }
});
```

```dart
// Get current user synchronously
final user = FirebaseAuth.instance.currentUser;
if (user != null) {
  final uid = user.uid;
}
```

--------------------------------

### Track E-commerce Events in Firebase Analytics

Source: https://context7.com/firebase/snippets-flutter/llms.txt

Track e-commerce actions such as viewing items, adding to cart, initiating checkout, and purchases. Ensure `AnalyticsEventItem` is properly defined for each product.

```dart
// Define product items
final jeggings = AnalyticsEventItem(
  itemId: "SKU_123",
  itemName: "jeggings",
  itemCategory: "pants",
  itemVariant: "black",
  itemBrand: "Google",
  price: 9.99,
);

// Log view item list
await FirebaseAnalytics.instance.logViewItemList(
  itemListId: "L001",
  itemListName: "Related products",
  items: [jeggings],
);

// Log add to cart
await FirebaseAnalytics.instance.logAddToCart(
  currency: 'USD',
  value: 19.98,
  items: [AnalyticsEventItem(
    itemId: jeggings.itemId,
    itemName: jeggings.itemName,
    price: jeggings.price,
    quantity: 2,
  )],
);

// Log begin checkout
await FirebaseAnalytics.instance.logBeginCheckout(
  currency: 'USD',
  value: 15.98,
  coupon: "SUMMER_FUN",
  items: [jeggings],
);

// Log purchase
await FirebaseAnalytics.instance.logPurchase(
  transactionId: "12345",
  affiliation: "Google Store",
  currency: 'USD',
  value: 15.98,
  shipping: 2.00,
  tax: 1.66,
  coupon: "SUMMER_FUN",
  items: [jeggings],
);

// Log refund
await FirebaseAnalytics.instance.logRefund(
  transactionId: "12345",
  currency: 'USD',
  value: 15.98,
);
```

--------------------------------

### Set User Properties and Track Screens in Firebase Analytics

Source: https://context7.com/firebase/snippets-flutter/llms.txt

Set user identifiers and custom properties for segmentation, and track screen views to monitor user navigation within the app.

```dart
// Set user ID
FirebaseAnalytics.instance.setUserId(id: "123456");

// Set user property
await FirebaseAnalytics.instance.setUserProperty(
  name: 'favorite_food',
  value: 'banana',
);

// Track screen views
await FirebaseAnalytics.instance.setCurrentScreen(
  screenName: 'Products',
);
```

--------------------------------

### Add Data to Firestore in Dart

Source: https://context7.com/firebase/snippets-flutter/llms.txt

Shows how to add documents to Firestore collections using `add()` for auto-generated IDs or `set()` for specific IDs. Supports various data types. Use `set()` with `SetOptions(merge: true)` to update existing fields.

```dart
// Create a new user with a first and last name
final user = <String, dynamic>{
  "first": "Ada",
  "last": "Lovelace",
  "born": 1815
};

// Add a new document with a generated ID
db.collection("users").add(user).then((DocumentReference doc) =>
    print('DocumentSnapshot added with ID: ${doc.id}'));

// Set a document with a specific ID
final city = <String, String>{
  "name": "Los Angeles",
  "state": "CA",
  "country": "USA"
};

db
    .collection("cities")
    .doc("LA")
    .set(city)
    .onError((e, _) => print("Error writing document: $e"));

// Set with merge option (updates existing fields, creates if doesn't exist)
final data = {"capital": true};
db.collection("cities").doc("BJ").set(data, SetOptions(merge: true));

// Add various data types
final docData = {
  "stringExample": "Hello world!",
  "booleanExample": true,
  "numberExample": 3.14159265,
  "dateExample": Timestamp.now(),
  "listExample": [1, 2, 3],
  "nullExample": null,
  "objectExample": {
    "a": 5,
    "b": true,
  }
};

db.collection("data").doc("one").set(docData);
```

--------------------------------

### Manage User Profile in Flutter

Source: https://context7.com/firebase/snippets-flutter/llms.txt

Access and update user profile details like display name, email, and photo URL. Handles potential FirebaseAuthExceptions during updates.

```dart
final user = FirebaseAuth.instance.currentUser;
if (user != null) {
  // Get user profile
  final name = user.displayName;
  final email = user.email;
  final photoUrl = user.photoURL;
  final emailVerified = user.emailVerified;
  final uid = user.uid;

  // Get provider-specific profile data
  for (final providerProfile in user.providerData) {
    final provider = providerProfile.providerId;
    final providerUid = providerProfile.uid;
    final providerName = providerProfile.displayName;
    final providerEmail = providerProfile.email;
    final providerPhotoUrl = providerProfile.photoURL;
  }
}

// Update profile
try {
  await user?.updateDisplayName("Jane Q. User");
  await user?.updatePhotoURL("https://example.com/profile.jpg");
} on FirebaseAuthException catch (e) {
  print("Error updating profile: $e");
}

// Update email
await user?.updateEmail('newemail@example.com');

// Update password
await user?.updatePassword('newSecurePassword');

// Send email verification
await user?.sendEmailVerification();

// Send password reset email
await FirebaseAuth.instance.sendPasswordResetEmail(email: 'user@example.com');

// Set language for emails
await FirebaseAuth.instance.setLanguageCode("fr");

// Delete user account
await user?.delete();
```

--------------------------------

### Log Firebase Analytics Events

Source: https://context7.com/firebase/snippets-flutter/llms.txt

Log predefined and custom analytics events to track user actions. Use `setDefaultEventParameters` to set global parameters for all subsequent events.

```dart
import 'package:firebase_analytics/firebase_analytics.dart';

// Log predefined event
await FirebaseAnalytics.instance.logSelectContent(
  contentType: "image",
  itemId: '1234',
);

// Log event with parameters
await FirebaseAnalytics.instance.logEvent(
  name: "select_content",
  parameters: {
    "content_type": "image",
    "item_id": '1234',
  },
);

// Log custom event
await FirebaseAnalytics.instance.logEvent(
  name: "share_image",
  parameters: {
    "image_name": 'rivers.jpg',
    "full_text": 'This is the full text.',
  },
);

// Set default event parameters
await FirebaseAnalytics.instance.setDefaultEventParameters({
  'version': '1.2.3'
});
```

--------------------------------

### Count Documents in a Collection with Dart

Source: https://context7.com/firebase/snippets-flutter/llms.txt

Efficiently count the number of documents in a collection or a filtered subset using the count() aggregation. This avoids downloading all documents.

```dart
// Count documents in a collection
db.collection("cities").count().get().then(
  (res) => print(res.count),
);

// Count with query filter
db.collection("cities")
    .where("capital", isEqualTo: true)
    .count()
    .get()
    .then((res) => print(res.count));
```

--------------------------------

### Configure Firestore Offline Persistence

Source: https://context7.com/firebase/snippets-flutter/llms.txt

Configure offline persistence and cache settings for Firestore. This allows your app to read and write data even when offline, synchronizing when connectivity is restored. Persistence is enabled by default on mobile platforms.

```dart
// Enable persistence (Apple and Android)
db.settings = const Settings(persistenceEnabled: true);
```

```dart
// Enable persistence on web
await db.enablePersistence(const PersistenceSettings(synchronizeTabs: true));
```

```dart
// Configure cache size
db.settings = const Settings(
  persistenceEnabled: true,
  cacheSizeBytes: Settings.CACHE_SIZE_UNLIMITED,
);
```

```dart
// Listen to offline data
db.collection("cities")
    .where("state", isEqualTo: "CA")
    .snapshots(includeMetadataChanges: true)
    .listen((querySnapshot) {
  for (var change in querySnapshot.docChanges) {
    if (change.type == DocumentChangeType.added) {
      final source =
          (querySnapshot.metadata.isFromCache) ? "local cache" : "server";
      print("Data fetched from $source");
    }
  }
});
```

```dart
// Disable/enable network
db.disableNetwork().then((_) {
  // Do offline things
});
db.enableNetwork().then((_) {
  // Back online
});
```

--------------------------------

### Enable Offline Access and Detect Connection State in Flutter

Source: https://context7.com/firebase/snippets-flutter/llms.txt

Configure Firebase Realtime Database for offline data access and detect the connection state. This ensures your app remains responsive even with intermittent network connectivity.

```dart
// Keep data synced for offline access
final scoresRef = FirebaseDatabase.instance.ref("scores");
scoresRef.keepSynced(true);

// Detect connection state
final connectedRef = FirebaseDatabase.instance.ref(".info/connected");
connectedRef.onValue.listen((event) {
  final connected = event.snapshot.value as bool? ?? false;
  if (connected) {
    print("Connected to Firebase");
  } else {
    print("Disconnected from Firebase");
  }
});

// Set data on disconnect
final presenceRef = FirebaseDatabase.instance.ref('disconnectmessage');
presenceRef.onDisconnect().set('I disconnected!');

// Full presence system
final myConnectionsRef = FirebaseDatabase.instance.ref("users/joe/connections");
final lastOnlineRef = FirebaseDatabase.instance.ref("/users/joe/lastOnline");
final connectedRef2 = FirebaseDatabase.instance.ref(".info/connected");

connectedRef2.onValue.listen((event) {
  final connected = event.snapshot.value as bool? ?? false;
  if (connected) {
    final con = myConnectionsRef.push();
    con.onDisconnect().remove();
    lastOnlineRef.onDisconnect().set(ServerValue.timestamp);
    con.set(true);
  }
});

// Server timestamps
final userLastOnlineRef = FirebaseDatabase.instance.ref("users/joe/lastOnline");
userLastOnlineRef.onDisconnect().set(ServerValue.timestamp);

// Clock skew detection
final offsetRef = FirebaseDatabase.instance.ref(".info/serverTimeOffset");
offsetRef.onValue.listen((event) {
  final offset = event.snapshot.value as num? ?? 0.0;
  final estimatedServerTimeMs = DateTime.now().millisecondsSinceEpoch + offset;
});
```

--------------------------------

### Perform Collection Group Queries in Dart

Source: https://context7.com/firebase/snippets-flutter/llms.txt

Query across all subcollections with the same name, regardless of their parent document. This is useful for querying data like 'reviews' or 'posts' that might exist in many different user profiles.

```dart
db.collectionGroup("landmarks")
    .where("type", isEqualTo: "museum")
    .get();
```

--------------------------------

### Perform Multiple Aggregations in Dart

Source: https://context7.com/firebase/snippets-flutter/llms.txt

Execute multiple aggregations (count, sum, average) in a single query for efficiency. This allows you to retrieve various aggregate statistics simultaneously.

```dart
db.collection("cities")
    .aggregate(
      count(),
      sum("population"),
      average("population"),
    )
    .get()
    .then((res) {
      print(res.count);
      print(res.getSum("population"));
      print(res.getAverage("population"));
    });
```

--------------------------------

### Perform Average Aggregation in Dart

Source: https://context7.com/firebase/snippets-flutter/llms.txt

Calculate the average of a specific field across documents in a collection using the aggregate() method with average(). This is useful for finding average values.

```dart
db.collection("cities").aggregate(average("population")).get().then(
  (res) => print(res.getAverage("population")),
);
```

--------------------------------

### Perform Sum Aggregation in Dart

Source: https://context7.com/firebase/snippets-flutter/llms.txt

Calculate the sum of a specific field across documents in a collection using the aggregate() method with sum(). This is useful for totaling numerical data.

```dart
db.collection("cities").aggregate(sum("population")).get().then(
  (res) => print(res.getSum("population")),
);
```

--------------------------------

### Re-authenticate User in Flutter

Source: https://context7.com/firebase/snippets-flutter/llms.txt

Use this snippet to re-authenticate a user before performing sensitive operations like changing passwords or deleting accounts. It requires the user's current email and password.

```dart
try {
  final userCredential = await FirebaseAuth.instance.signInWithEmailAndPassword(
    email: 'user@example.com',
    password: 'current.password',
  );
  final credential = userCredential.credential!;

  await FirebaseAuth.instance.currentUser!
      .reauthenticateWithCredential(credential);

  // Now safe to perform sensitive operations
} on FirebaseAuthException catch (e) {
  print("Re-authentication failed: $e");
}
```

--------------------------------

### Update Specific Fields in Documents

Source: https://context7.com/firebase/snippets-flutter/llms.txt

Update specific fields in documents without overwriting the entire document. Supports nested field updates, array operations, and atomic increments.

```dart
// Update a single field
final washingtonRef = db.collection("cites").doc("DC");
washingtonRef.update({"capital": true}).then(
    (value) => print("DocumentSnapshot successfully updated!"),
    onError: (e) => print("Error updating document $e"));
```

```dart
// Update nested fields using dot notation
db.collection("users").doc("frank").update({
  "age": 13,
  "favorites.color": "Red"
});
```

```dart
// Server timestamp
final docRef = db.collection("objects").doc("some-id");
docRef.update({"timestamp": FieldValue.serverTimestamp()});
```

```dart
// Atomically add/remove elements from arrays
final washingtonRef2 = db.collection("cities").doc("DC");
washingtonRef2.update({
  "regions": FieldValue.arrayUnion(["greater_virginia"]),
});
washingtonRef2.update({
  "regions": FieldValue.arrayRemove(["east_coast"]),
});
```

```dart
// Atomically increment a numeric value
var washingtonRef3 = db.collection('cities').doc('DC');
washingtonRef3.update({"population": FieldValue.increment(50)});
```

--------------------------------

### Manage FCM Tokens in Flutter

Source: https://context7.com/firebase/snippets-flutter/llms.txt

Obtain the current Firebase Cloud Messaging (FCM) registration token and monitor for token refreshes. Send the token to your server to enable targeted push notifications.

```dart
import 'package:firebase_messaging/firebase_messaging.dart';

// Get current registration token
FirebaseMessaging.instance.getToken().then(
  (token) => print("FCM Token: $token"),
  onError: (e) => print("Error getting token: $e"),
);

// Monitor token refresh
FirebaseMessaging.instance.onTokenRefresh.listen((newToken) {
  print("Refreshed token: $newToken");
  // Send to your server
  _sendRegistrationToServer(newToken);
});

// Subscribe to topics
FirebaseMessaging.instance.subscribeToTopic("weather");
```

--------------------------------

### Firestore Transactions and Batched Writes

Source: https://context7.com/firebase/snippets-flutter/llms.txt

Use transactions for atomic read-modify-write operations, or batched writes for multiple atomic writes. Transactions ensure data consistency by retrying if conflicts occur.

```dart
// Transaction example
final sfDocRef = db.collection("cities").doc("SF");
db.runTransaction((transaction) async {
  final snapshot = await transaction.get(sfDocRef);
  final newPopulation = snapshot.get("population") + 1;
  transaction.update(sfDocRef, {"population": newPopulation});
}).then(
  (value) => print("DocumentSnapshot successfully updated!"),
  onError: (e) => print("Error updating document $e"),
);
```

```dart
// Transaction returning a value
db.runTransaction((transaction) {
  return transaction.get(sfDocRef).then((sfDoc) {
    final newPopulation = sfDoc.get("population") + 1;
    transaction.update(sfDocRef, {"population": newPopulation});
    return newPopulation;
  });
}).then(
  (newPopulation) => print("Population increased to $newPopulation"),
);
```

```dart
// Batched writes
final batch = db.batch();

var nycRef = db.collection("cities").doc("NYC");
batch.set(nycRef, {"name": "New York City"});

var sfRef = db.collection("cities").doc("SF");
batch.update(sfRef, {"population": 1000000});

var laRef = db.collection("cities").doc("LA");
batch.delete(laRef);

// Commit the batch
batch.commit().then((_) {
  print("Batch committed successfully");
});
```