Kotlin: adding Cognito Flutter mobile app

kotlin/usecases/cognito_flutter_mobile_app/.gitignore

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+# Miscellaneous
+*.class
+*.log
+*.pyc
+*.swp
+.DS_Store
+.atom/
+.buildlog/
+.history
+.svn/
+migrate_working_dir/
+
+# IntelliJ related
+*.iml
+*.ipr
+*.iws
+.idea/
+
+# The .vscode folder contains launch configuration and tasks you configure in
+# VS Code which you may wish to be included in version control, so this line
+# is commented out by default.
+#.vscode/
+
+# Flutter/Dart/Pub related
+**/doc/api/
+**/ios/Flutter/.last_build_id
+.dart_tool/
+.flutter-plugins
+.flutter-plugins-dependencies
+.pub-cache/
+.pub/
+/build/
+
+# Symbolication related
+app.*.symbols
+
+# Obfuscation related
+app.*.map.json
+
+# Android Studio will place build artifacts here
+/android/app/debug
+/android/app/profile
+/android/app/release

kotlin/usecases/cognito_flutter_mobile_app/README.md

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+# Sample Flutter App for Integrating with AWS Cognito and implementing Authentication Functionality.
+
+## Prerequisite
+  - Install Android Studio or the Android Command-Line Tools from [https://developer.android.com/](https://developer.android.com/studio/install).
+  - Install Flutter from [https://docs.flutter.dev/get-started](https://docs.flutter.dev/get-started/install/macos/mobile-android?tab=download).
+  - Optionally install IDE with Flutter Plugin for [Visual Studio Code](https://docs.flutter.dev/tools/vs-code), [Android Studio](https://docs.flutter.dev/tools/android-studio) or [IntelliJ IDEA](https://plugins.jetbrains.com/plugin/9212-flutter).
+  - Accept Licences using `flutter doctor --android-licenses`.
+  - Verify Flutter Installation using `flutter doctor -v`.
+  - Add Android emulator using `flutter emulators --create --name android-device`.
+  - Launch Android emulator using `flutter emulators --launch android-device`
+
+## Step-1: Set Up AWS Cognito User Pool and App Client ID
+  - Log in to the AWS Management Console.
+  - Navigate to Amazon Cognito and select "Manage User Pools."
+  - Click "Create a user pool," name it, and follow the prompts to configure settings. 
+  - Set up an App Client if you haven't already.
+  - Make sure to note your Pool ID and App Client ID (without a client secret).
+
+## Step 2: Add Dependencies
+  - Add dependency for AWS cognito by executing `flutter pub add amazon_cognito_identity_dart_2` in your flutter project.
+  - Add dependency for Secure storage by executing `flutter pub add flutter_secure_storage` in your flutter project.
+  - Verify these dependencies to your package's `pubspec.yaml`.
+
+## Step 3: Initialize Cognito
+Update `assets/config.json` and initialize your Cognito user pool with your Pool ID and App Client ID:
+```
+{
+    "UserPoolID": "<<YOUR USER POOL ID>>",
+    "ClientID": "<< YOUR CLIENT ID>>"
+}
+```  
+
+## Step 4: Integrate with AWS Cognito APIs
+See `cognito_manager.dart` for an example of integrating with AWS Cognito, e.g.,,
+
+```
+import 'package:amazon_cognito_identity_dart_2/cognito.dart';
+import 'config.dart';
+
+class CognitoServiceException implements Exception {
+  final String message;
+  CognitoServiceException(this.message);
+}
+
+class User {
+  String username;
+  bool userConfirmed;
+  bool sessionValid;
+  String? userSub;
+  Map<String, dynamic> claims;
+
+  User(this.username, this.userConfirmed, this.sessionValid, this.userSub,
+      this.claims);
+}
+
+class CognitoManager {
+  late final CognitoUserPool userPool;
+
+  CognitoManager();
+
+  Future<void> init() async {
+    final config = await loadConfig();
+    userPool = CognitoUserPool(config.userPoolID, config.clientID);
+  }
+
+  Future<User> signUp(String email, String password) async {
+    final userAttributes = [
+      AttributeArg(name: 'email', value: email),
+      // Add other attributes as needed
+    ];
+
+    try {
+      final result = await userPool.signUp(email, password,
+          userAttributes: userAttributes);
+      return User(
+          email, result.userConfirmed ?? false, false, result.userSub, {});
+    } catch (e) {
+      throw CognitoServiceException(e.toString());
+    }
+  }
+
+  Future<bool> confirmUser(String email, String confirmationCode) async {
+    final cognitoUser = CognitoUser(email, userPool);
+    try {
+      return await cognitoUser.confirmRegistration(confirmationCode);
+    } catch (e) {
+      throw CognitoServiceException(e.toString());
+    }
+  }
+
+  Future<User> signIn(String email, String password) async {
+    final cognitoUser = CognitoUser(email, userPool);
+    final authDetails =
+        AuthenticationDetails(username: email, password: password);
+
+    try {
+      final session = await cognitoUser.authenticateUser(authDetails);
+      if (session == null) {
+        throw CognitoClientException("session not found");
+      }
+      var claims = <String, dynamic>{};
+      claims.addAll(session.idToken.payload);
+      claims.addAll(session.accessToken.payload);
+      return User(email, true, session.isValid(),
+          session.idToken.getSub() ?? "", claims);
+    } catch (e) {
+      throw CognitoServiceException(e.toString());
+    }
+  }
+}
+```  
+
+## Step 4: Implementing UI
+See `main.dart` for a sample UI to implement sign up or sign in functionality, e.g.,
+```
+import 'package:flutter/material.dart';
+import 'cognito_manager.dart';
+
+...
+
+class SignUpView extends StatefulWidget {
+  @override
+  _SignUpViewState createState() => _SignUpViewState();
+}
+
+class _SignUpViewState extends State<SignUpView> {
+  final _emailController = TextEditingController();
+  final _passwordController = TextEditingController();
+  late final CognitoManager _cognitoManager;
+
+  @override
+  void initState() {
+    super.initState();
+    _cognitoManager = CognitoManager();
+    _initCognitoManager();
+  }
+
+  Future<void> _initCognitoManager() async {
+    await _cognitoManager.init();
+  }
+
+  void _signUp() async {
+    final email = _emailController.text;
+    final password = _passwordController.text;
+
+    try {
+      await _cognitoManager.signUp(email, password);
+      DefaultTabController.of(context).animateTo(1);
+    } on CognitoServiceException catch (e) {
+      ScaffoldMessenger.of(context).showSnackBar(
+        SnackBar(content: Text(e.message)),
+      );
+    }
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    return Scaffold(
+      appBar: AppBar(title: const Text('Sign Up')),
+      body: Padding(
+        padding: const EdgeInsets.all(8.0),
+        child: Column(
+          children: [
+            TextField(
+              controller: _emailController,
+              decoration: const InputDecoration(labelText: 'Email'),
+            ),
+            TextField(
+              controller: _passwordController,
+              decoration: const InputDecoration(labelText: 'Password'),
+              obscureText: true,
+            ),
+            ElevatedButton(
+              onPressed: _signUp,
+              child: const Text('Sign Up'),
+            ),
+          ],
+        ),
+      ),
+    );
+  }
+}
+
+...
+```
+## Step 5: Run Application
+Launch the application using `flutter run`.
+
+## Resources
+- [AWS Cognito](https://aws.amazon.com/cognito/)
+- [Flutter Getting Started](https://docs.flutter.dev/get-started/codelab)
+- [Flutter Cookbook](https://docs.flutter.dev/cookbook)
+- [Flutter Documentation](https://docs.flutter.dev/)

kotlin/usecases/cognito_flutter_mobile_app/analysis_options.yaml

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+# This file configures the analyzer, which statically analyzes Dart code to
+# check for errors, warnings, and lints.
+#
+# The issues identified by the analyzer are surfaced in the UI of Dart-enabled
+# IDEs (https://dart.dev/tools#ides-and-editors). The analyzer can also be
+# invoked from the command line by running `flutter analyze`.
+
+# The following line activates a set of recommended lints for Flutter apps,
+# packages, and plugins designed to encourage good coding practices.
+include: package:flutter_lints/flutter.yaml
+
+linter:
+  # The lint rules applied to this project can be customized in the
+  # section below to disable rules from the `package:flutter_lints/flutter.yaml`
+  # included above or to enable additional rules. A list of all available lints
+  # and their documentation is published at https://dart.dev/lints.
+  #
+  # Instead of disabling a lint rule for the entire project in the
+  # section below, it can also be suppressed for a single line of code
+  # or a specific dart file by using the `// ignore: name_of_lint` and
+  # `// ignore_for_file: name_of_lint` syntax on the line or in the file
+  # producing the lint.
+  rules:
+    # avoid_print: false  # Uncomment to disable the `avoid_print` rule
+    # prefer_single_quotes: true  # Uncomment to enable the `prefer_single_quotes` rule
+
+# Additional information about this file can be found at
+# https://dart.dev/guides/language/analysis-options

kotlin/usecases/cognito_flutter_mobile_app/android/.gitignore

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+gradle-wrapper.jar
+/.gradle
+/captures/
+/gradlew
+/gradlew.bat
+/local.properties
+GeneratedPluginRegistrant.java
+
+# Remember to never publicly share your keystore.
+# See https://flutter.dev/docs/deployment/android#reference-the-keystore-from-the-app
+key.properties
+**/*.keystore
+**/*.jks

kotlin/usecases/cognito_flutter_mobile_app/android/app/build.gradle

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+plugins {
+    id "com.android.application"
+    id "kotlin-android"
+    id "dev.flutter.flutter-gradle-plugin"
+}
+
+def localProperties = new Properties()
+def localPropertiesFile = rootProject.file('local.properties')
+if (localPropertiesFile.exists()) {
+    localPropertiesFile.withReader('UTF-8') { reader ->
+        localProperties.load(reader)
+    }
+}
+
+def flutterVersionCode = localProperties.getProperty('flutter.versionCode')
+if (flutterVersionCode == null) {
+    flutterVersionCode = '1'
+}
+
+def flutterVersionName = localProperties.getProperty('flutter.versionName')
+if (flutterVersionName == null) {
+    flutterVersionName = '1.0'
+}
+
+android {
+    namespace "com.example.android_app"
+    compileSdkVersion flutter.compileSdkVersion
+    ndkVersion flutter.ndkVersion
+
+    compileOptions {
+        sourceCompatibility JavaVersion.VERSION_1_8
+        targetCompatibility JavaVersion.VERSION_1_8
+    }
+
+    kotlinOptions {
+        jvmTarget = '1.8'
+    }
+
+    sourceSets {
+        main.java.srcDirs += 'src/main/kotlin'
+    }
+
+    defaultConfig {
+        // TODO: Specify your own unique Application ID (https://developer.android.com/studio/build/application-id.html).
+        applicationId "com.example.android_app"
+        // You can update the following values to match your application needs.
+        // For more information, see: https://docs.flutter.dev/deployment/android#reviewing-the-gradle-build-configuration.
+        minSdkVersion flutter.minSdkVersion
+        targetSdkVersion flutter.targetSdkVersion
+        versionCode flutterVersionCode.toInteger()
+        versionName flutterVersionName
+    }
+
+    buildTypes {
+        release {
+            // TODO: Add your own signing config for the release build.
+            // Signing with the debug keys for now, so `flutter run --release` works.
+            signingConfig signingConfigs.debug
+        }
+    }
+}
+
+flutter {
+    source '../..'
+}
+
+dependencies {}

kotlin/usecases/cognito_flutter_mobile_app/android/app/src/debug/AndroidManifest.xml

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+<manifest xmlns:android="http://schemas.android.com/apk/res/android">
+    <!-- The INTERNET permission is required for development. Specifically,
+         the Flutter tool needs it to communicate with the running application
+         to allow setting breakpoints, to provide hot reload, etc.
+    -->
+    <uses-permission android:name="android.permission.INTERNET"/>
+</manifest>

kotlin/usecases/cognito_flutter_mobile_app/android/app/src/main/AndroidManifest.xml

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+<manifest xmlns:android="http://schemas.android.com/apk/res/android">
+    <application
+        android:label="android-app"
+        android:name="${applicationName}"
+        android:icon="@mipmap/ic_launcher">
+        <activity
+            android:name=".MainActivity"
+            android:exported="true"
+            android:launchMode="singleTop"
+            android:theme="@style/LaunchTheme"
+            android:configChanges="orientation|keyboardHidden|keyboard|screenSize|smallestScreenSize|locale|layoutDirection|fontScale|screenLayout|density|uiMode"
+            android:hardwareAccelerated="true"
+            android:windowSoftInputMode="adjustResize">
+            <!-- Specifies an Android theme to apply to this Activity as soon as
+                 the Android process has started. This theme is visible to the user
+                 while the Flutter UI initializes. After that, this theme continues
+                 to determine the Window background behind the Flutter UI. -->
+            <meta-data
+              android:name="io.flutter.embedding.android.NormalTheme"
+              android:resource="@style/NormalTheme"
+              />
+            <intent-filter>
+                <action android:name="android.intent.action.MAIN"/>
+                <category android:name="android.intent.category.LAUNCHER"/>
+            </intent-filter>
+        </activity>
+        <!-- Don't delete the meta-data below.
+             This is used by the Flutter tool to generate GeneratedPluginRegistrant.java -->
+        <meta-data
+            android:name="flutterEmbedding"
+            android:value="2" />
+    </application>
+</manifest>