Flutter Fullstack #4

readme.md

Flutter Fullstack #4

Created with <3 with dartpad.dev.

main.dart

import 'dart:async';

import 'package:cloud_firestore/cloud_firestore.dart';
import 'package:firebase_auth/firebase_auth.dart';
import 'package:firebase_core/firebase_core.dart';
import 'package:flutter/material.dart';
import 'package:google_fonts/google_fonts.dart';
import 'package:intl/intl.dart';
import 'package:provider/provider.dart';

void main() async {
  WidgetsFlutterBinding.ensureInitialized();

  await Firebase.initializeApp(
    options: const FirebaseOptions(
        apiKey: "AIzaSyB1mTcVNqXCMLviCjb4NZ35l0r2u6jwv0s",
        authDomain: "codelab-flutterbankapp.firebaseapp.com",
        projectId: "codelab-flutterbankapp",
        storageBucket: "codelab-flutterbankapp.appspot.com",
        messagingSenderId: "1005151447135",
        appId: "1:1005151447135:web:663e127a0473fe49a0d3ea",
        measurementId: "G-MH8JWFX1LF"),
  );

  runApp(
    MultiProvider(
      providers: [
        ChangeNotifierProvider(create: (_) {
          return LoginService();
        }),
        ChangeNotifierProvider(create: (_) {
          return FlutterBankService();
        }),
      ],
      child: const FlutterBankApp(),
    ),
  );
}

class FlutterBankApp extends StatelessWidget {
  const FlutterBankApp({super.key});

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      debugShowCheckedModeBanner: false,
      theme: ThemeData(
        textTheme: GoogleFonts.poppinsTextTheme(
          Theme.of(context).textTheme,
        ),
      ),
      home: const FlutterBankSplash(),
    );
  }
}

class FlutterBankSplash extends StatelessWidget {
  const FlutterBankSplash({super.key});

  @override
  Widget build(BuildContext context) {
    // Future.delayed takes two parameters: a Duration object with is seconds
    // property set to 2, and a callback. When the 2 seconds have ellapsed, it will call the callback. The callback has inside a trigger to perform a navigation
    Future.delayed(const Duration(seconds: 2), () {
      Navigator.push(
        context,
        MaterialPageRoute(builder: (context) {
          return const FlutterBankLogin();
        }),
      );
    });

    return const Scaffold(
      backgroundColor: Utils.mainThemeColor,
      body: Stack(
        children: [
          Center(
            child: Icon(
              Icons.savings,
              size: 60.0,
              color: Colors.white,
            ),
          ),
          Center(
              child: SizedBox(
            height: 100.0,
            width: 100.0,
            child: CircularProgressIndicator(
              strokeWidth: 8.0,
              valueColor: AlwaysStoppedAnimation<Color>(Colors.white),
            ),
          )),
        ],
      ),
    );
  }
}

class FlutterBankLogin extends StatefulWidget {
  const FlutterBankLogin({super.key});

  @override
  State<FlutterBankLogin> createState() {
    return _FlutterBankLoginState();
  }
}

class _FlutterBankLoginState extends State<FlutterBankLogin> {
  // At the top of the FlutterBankLoginState class, add two
  // TextEditingController instances, one for each of our fields. The
  // TextEditingController allows us to controller the actions on a TextField
  // widget, get notifications on text field updates, set initial values,
  // get its provided input, etc.
  final TextEditingController emailController = TextEditingController();
  final TextEditingController passwordController = TextEditingController();

  validateEmailAndPassword() {
    return emailController.text.isNotEmpty &&
        passwordController.text.isNotEmpty &&
        Utils.validateEmail(emailController.text);
  }

  @override
  void dispose() {
    // Dispose of the emailController and passwordController instances when the
    // widget is disposed of.
    emailController.dispose();
    passwordController.dispose();
    super.dispose();
  }

  @override
  Widget build(BuildContext context) {
    // Create an instance of the LoginService service, fetching by via the
    // Provider.of factory method, passing the BuildContext and the
    // listen: false flag so it is a one-time fetch and our widget doesn't
    // rebuild all the time.
    LoginService loginService = Provider.of<LoginService>(
      context,
      listen: false,
    );

    return SafeArea(
      child: Scaffold(
        backgroundColor: Colors.white,
        body: Container(
          padding: const EdgeInsets.all(30.0),
          child: Column(
            crossAxisAlignment: CrossAxisAlignment.start,
            children: [
              Container(
                width: 80.0,
                height: 80.0,
                decoration: BoxDecoration(
                  border: Border.all(
                    color: Utils.mainThemeColor,
                    width: 7.0,
                  ),
                  borderRadius: BorderRadius.circular(100.0),
                ),
                child: const Icon(
                  Icons.savings,
                  size: 45.0,
                  color: Utils.mainThemeColor,
                ),
              ),
              const SizedBox(height: 30.0),
              const Text(
                'Welcome to',
                style: TextStyle(
                  color: Colors.grey,
                  fontSize: 15.0,
                ),
              ),
              const Text(
                'Flutter\nSavings Bank',
                style: TextStyle(
                  color: Utils.mainThemeColor,
                  fontSize: 30.0,
                ),
              ),
              Expanded(
                child: Center(
                  child: Column(
                    mainAxisAlignment: MainAxisAlignment.center,
                    crossAxisAlignment: CrossAxisAlignment.stretch,
                    children: [
                      const Text(
                        'Sign Into Your Bank Account',
                        style: TextStyle(
                          color: Colors.grey,
                          fontSize: 12.0,
                        ),
                        textAlign: TextAlign.center,
                      ),
                      const SizedBox(height: 12.0),
                      Container(
                        padding: const EdgeInsets.all(5.0),
                        decoration: BoxDecoration(
                          color: Colors.grey.withOpacity(0.2),
                          borderRadius: BorderRadius.circular(50.0),
                        ),
                        child: TextField(
                          controller: emailController,
                          onChanged: (text) {
                            setState(() {
                              // We use setState to update the state of the widget. In this case,
                              // we are updating the state of the emailController.
                            });
                          },
                          decoration: const InputDecoration(
                            prefixIcon: Icon(
                              Icons.email,
                              color: Utils.mainThemeColor,
                            ),
                            border: InputBorder.none,
                            focusedBorder: InputBorder.none,
                            enabledBorder: InputBorder.none,
                            errorBorder: InputBorder.none,
                            disabledBorder: InputBorder.none,
                            contentPadding:
                                EdgeInsets.fromLTRB(20.0, 11.0, 15.0, 11.0),
                            hintText: 'Email Address',
                          ),
                          style: const TextStyle(
                            fontSize: 16.0,
                          ),
                        ),
                      ),
                      const SizedBox(height: 16.0),
                      Container(
                        padding: const EdgeInsets.all(5.0),
                        decoration: BoxDecoration(
                          color: Colors.grey.withOpacity(0.2),
                          borderRadius: BorderRadius.circular(50.0),
                        ),
                        child: TextField(
                          controller: passwordController,
                          onChanged: (text) {
                            setState(() {
                              // We use setState to update the state of the widget. In this case,
                              // we are updating the state of the passwordController.
                            });
                          },
                          obscureText: true,
                          decoration: const InputDecoration(
                            prefixIcon: Icon(
                              Icons.lock,
                              color: Utils.mainThemeColor,
                            ),
                            border: InputBorder.none,
                            focusedBorder: InputBorder.none,
                            enabledBorder: InputBorder.none,
                            errorBorder: InputBorder.none,
                            disabledBorder: InputBorder.none,
                            contentPadding:
                                EdgeInsets.fromLTRB(20.0, 11.0, 15.0, 11.0),
                            hintText: 'Password',
                          ),
                          style: const TextStyle(
                            fontSize: 16.0,
                          ),
                        ),
                      ),
                      Consumer<LoginService>(
                        builder: (context, loginService, child) {
                          String errorMessage = loginService.getErrorMessage();
                          if (errorMessage.isEmpty) {
                            return const SizedBox(height: 40.0);
                          } else {
                            return Container(
                              padding: const EdgeInsets.all(10.0),
                              child: Row(
                                children: [
                                  const Icon(
                                    Icons.warning,
                                    color: Colors.red,
                                  ),
                                  const SizedBox(width: 10.0),
                                  Expanded(
                                    child: Text(
                                      errorMessage,
                                      style: const TextStyle(
                                        color: Colors.red,
                                      ),
                                    ),
                                  ),
                                ],
                              ),
                            );
                          }
                        },
                      ),
                    ],
                  ),
                ),
              ),
              FlutterBankMainButton(
                label: 'Sign In',
                enabled: validateEmailAndPassword(),
                onTap: () async {
                  String email = emailController.text;
                  String password = passwordController.text;

                  bool isLoggedIn =
                      await loginService.signInWithEmailAndPassword(
                    email,
                    password,
                  );

                  if (isLoggedIn) {
                    emailController.clear();
                    passwordController.clear();
                    if (mounted) {
                      Navigator.push(context,
                          MaterialPageRoute(builder: (context) {
                        return const FlutterBankMain();
                      }));
                    }
                  } else {
                    if (mounted) {
                      ScaffoldMessenger.of(context).showSnackBar(
                        const SnackBar(
                          content: Text('Invalid credentials'),
                          behavior: SnackBarBehavior.floating,
                        ),
                      );
                    }
                  }
                },
              ),
              const SizedBox(height: 16.0),
              FlutterBankMainButton(
                label: 'Register',
                icon: Icons.account_circle,
                enabled: true,
                onTap: () {
                  Navigator.push(context, MaterialPageRoute(builder: (context) {
                    return const FlutterBankRegister();
                  }));
                },
                backgroundColor: Utils.mainThemeColor.withOpacity(0.1),
                iconColor: Utils.mainThemeColor,
                labelColor: Utils.mainThemeColor,
              ),
            ],
          ),
        ),
      ),
    );
  }
}

class FlutterBankRegister extends StatefulWidget {
  const FlutterBankRegister({super.key});

  @override
  State<FlutterBankRegister> createState() {
    return FlutterBankRegisterState();
  }
}

class FlutterBankRegisterState extends State<FlutterBankRegister> {
  TextEditingController emailController = TextEditingController();
  TextEditingController passwordController = TextEditingController();
  TextEditingController confirmPasswordController = TextEditingController();

  @override
  void dispose() {
    // Dispose of the emailController and passwordController instances when the
    // widget is disposed of.
    emailController.dispose();
    passwordController.dispose();
    confirmPasswordController.dispose();
    super.dispose();
  }

  @override
  Widget build(BuildContext context) {
    LoginService loginService = Provider.of<LoginService>(
      context,
      listen: false,
    );

    bool validateFormFields() {
      return Utils.validateEmail(emailController.text) &&
          emailController.text.isNotEmpty &&
          passwordController.text.isNotEmpty &&
          confirmPasswordController.text.isNotEmpty &&
          (passwordController.text == confirmPasswordController.text);
    }

    return SafeArea(
      child: Scaffold(
        backgroundColor: Colors.white,
        appBar: AppBar(
          elevation: 0.0,
          backgroundColor: Colors.transparent,
          iconTheme: const IconThemeData(color: Utils.mainThemeColor),
          title: const Icon(
            Icons.savings,
            color: Utils.mainThemeColor,
            size: 40.0,
          ),
          centerTitle: true,
        ),
        body: Container(
          padding: const EdgeInsets.all(30.0),
          child: Column(
            crossAxisAlignment: CrossAxisAlignment.start,
            children: [
              Expanded(
                child: Column(
                  crossAxisAlignment: CrossAxisAlignment.start,
                  children: [
                    Container(
                      margin: const EdgeInsets.only(bottom: 40.0),
                      child: const Text(
                        'Create New Account',
                        style: TextStyle(
                          color: Utils.mainThemeColor,
                          fontSize: 20.0,
                        ),
                      ),
                    ),
                    Utils.generateInputField(
                        'Email Address', Icons.email, emailController, false,
                        (text) {
                      setState(() {});
                    }),
                    Utils.generateInputField(
                        'Password', Icons.lock, passwordController, true,
                        (text) {
                      setState(() {});
                    }),
                    Utils.generateInputField('Confirm Password', Icons.lock,
                        confirmPasswordController, true, (text) {
                      setState(() {});
                    }),
                  ],
                ),
              ),
              FlutterBankMainButton(
                  label: 'Register',
                  enabled: validateFormFields(),
                  onTap: () async {
                    String email = emailController.text;
                    String password = passwordController.text;

                    bool isAccountCreated = await loginService
                        .createUserWithEmailAndPassword(email, password);

                    if (isAccountCreated) {
                      if (mounted) {
                        Navigator.pop(context);
                      }
                    }
                  }),
            ],
          ),
        ),
      ),
    );
  }
}

class FlutterBankMain extends StatelessWidget {
  const FlutterBankMain({super.key});

  @override
  Widget build(BuildContext context) {
    return SafeArea(
      child: Scaffold(
        backgroundColor: Colors.white,
        drawer: const Drawer(
          child: FlutterBankDrawer(),
        ),
        appBar: AppBar(
          elevation: 0.0,
          backgroundColor: Colors.transparent,
          iconTheme: const IconThemeData(color: Utils.mainThemeColor),
          title: const Icon(Icons.savings,
              color: Utils.mainThemeColor, size: 40.0),
          centerTitle: true,
        ),
        body: Container(
          padding: const EdgeInsets.all(20.0),
          child: Column(
            children: [
              const Row(
                children: [
                  Icon(
                    Icons.account_balance_wallet,
                    color: Utils.mainThemeColor,
                    size: 30.0,
                  ),
                  SizedBox(width: 10.0),
                  Text(
                    'My Accounts',
                    style: TextStyle(
                      color: Utils.mainThemeColor,
                      fontSize: 20.0,
                    ),
                  ),
                ],
              ),
              const SizedBox(height: 20.0),
              Expanded(
                // Consume the service FlutterBankService using a Consumer
                // widget, since we want to be notified of any changes
                // within this service so we can rebuild accordingly.
                child: Consumer<FlutterBankService>(
                    builder: (context, bankService, child) {
                  // FutureBuilder widgets take a future (in our case, the one returned
                  // from FlutterBankService's getAccounts), and a builder (that gets
                  // triggered upon the Future changing its state), which is a callback
                  // method that gets the current BuildContext and a snapshot - a
                  // wrapper object (type AsyncSnapshot that contains the value returned
                  // by the Future object in question (in our case, a List of Account objects)
                  return FutureBuilder(
                      future: bankService.getAccounts(context),
                      builder: (BuildContext context, AsyncSnapshot snapshot) {
                        if (snapshot.connectionState != ConnectionState.done ||
                            !snapshot.hasData) {
                          return const FlutterBankLoading();
                        }
                        List<Account> accounts = snapshot.data as List<Account>;
                        if (accounts.isEmpty) {
                          return const Center(
                            child: Column(
                              crossAxisAlignment: CrossAxisAlignment.center,
                              mainAxisAlignment: MainAxisAlignment.center,
                              children: [
                                Icon(
                                  Icons.account_balance_wallet,
                                  color: Utils.mainThemeColor,
                                  size: 50.0,
                                ),
                                SizedBox(height: 20.0),
                                Text(
                                  'You don\'t have any accounts\nassociated with your profile.',
                                  textAlign: TextAlign.center,
                                  style: TextStyle(
                                    color: Utils.mainThemeColor,
                                  ),
                                ),
                              ],
                            ),
                          );
                        }
                        return ListView.builder(
                            itemCount: accounts.length,
                            itemBuilder: (context, index) {
                              var acct = accounts[index];
                              return AccountCard(account: acct);
                            });
                      });
                }),
              ),
            ],
          ),
        ),
        bottomNavigationBar: const FlutterBankBottomBar(),
      ),
    );
  }
}

// Widgets
class FlutterBankMainButton extends StatelessWidget {
  final Function? onTap;
  final String? label;
  final bool? enabled;
  final IconData? icon;
  final Color? backgroundColor;
  final Color? iconColor;
  final Color? labelColor;

  const FlutterBankMainButton({
    super.key,
    this.onTap,
    this.label,
    this.enabled = true,
    this.icon,
    this.backgroundColor = Utils.mainThemeColor,
    this.iconColor = Colors.white,
    this.labelColor = Colors.white,
  });

  @override
  Widget build(BuildContext context) {
    return Column(
      crossAxisAlignment: CrossAxisAlignment.stretch,
      children: [
        ClipRRect(
          borderRadius: BorderRadius.circular(50.0),
          child: Material(
            color:
                enabled! ? backgroundColor : backgroundColor!.withOpacity(0.5),
            child: InkWell(
              // Assign a callback that wraps the trigger this widget's onTap event only
              // if the enabled property is true, null otherwise.
              onTap: enabled!
                  ? () {
                      onTap!();
                    }
                  : null,
              highlightColor: Colors.white.withOpacity(0.2),
              splashColor: Colors.white.withOpacity(0.1),
              child: Container(
                padding: const EdgeInsets.all(15.0),
                decoration: BoxDecoration(
                  borderRadius: BorderRadius.circular(50.0),
                ),
                child: Row(
                  mainAxisAlignment: MainAxisAlignment.center,
                  crossAxisAlignment: CrossAxisAlignment.center,
                  children: [
                    Visibility(
                        visible: icon != null,
                        child: Container(
                          margin: const EdgeInsets.only(right: 20.0),
                          child: Icon(
                            icon,
                            color: iconColor,
                            size: 20.0,
                          ),
                        )),
                    Text(
                      label!,
                      textAlign: TextAlign.center,
                      style: TextStyle(
                        color: labelColor,
                        fontWeight: FontWeight.bold,
                      ),
                    ),
                  ],
                ),
              ),
            ),
          ),
        ),
      ],
    );
  }
}

class AccountCard extends StatelessWidget {
  final Account? account;
  const AccountCard({Key? key, this.account}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return Container(
      height: 180.0,
      padding: const EdgeInsets.all(20.0),
      margin: const EdgeInsets.only(bottom: 20.0),
      decoration: BoxDecoration(
        borderRadius: BorderRadius.circular(20.0),
        color: Colors.white,
        boxShadow: [
          BoxShadow(
            color: Colors.black.withOpacity(0.1),
            blurRadius: 15.0,
            offset: const Offset(0.0, 5.0),
          ),
        ],
      ),
      child: Column(
        mainAxisAlignment: MainAxisAlignment.spaceBetween,
        crossAxisAlignment: CrossAxisAlignment.start,
        children: [
          Column(
            children: [
              Text(
                '${account!.type?.toUpperCase()} ACCOUNT',
                textAlign: TextAlign.left,
                style: const TextStyle(
                  color: Utils.mainThemeColor,
                  fontSize: 12.0,
                ),
              ),
              Text('*** ${account!.accountNumber}'),
            ],
          ),
          Column(
            crossAxisAlignment: CrossAxisAlignment.start,
            children: [
              const Text(
                'Balance',
                textAlign: TextAlign.left,
                style: TextStyle(
                  color: Utils.mainThemeColor,
                  fontSize: 12.0,
                ),
              ),
              Row(
                children: [
                  const Icon(Icons.monetization_on,
                      color: Utils.mainThemeColor, size: 30.0),
                  Text(
                    '\$${account!.balance?.toStringAsFixed(2)}',
                    style: const TextStyle(
                      color: Colors.black,
                      fontSize: 35.0,
                    ),
                  ),
                ],
              ),
              Text(
                'As of ${DateFormat.yMd().add_jm().format(DateTime.now())}',
                style: const TextStyle(
                  fontSize: 10.0,
                  color: Colors.grey,
                ),
              ),
            ],
          ),
        ],
      ),
    );
  }
}

class FlutterBankLoading extends StatelessWidget {
  const FlutterBankLoading({super.key});

  @override
  Widget build(BuildContext context) {
    return const Center(
      child: SizedBox(
        height: 80.0,
        width: 80.0,
        child: Stack(
          children: [
            Center(
              child: SizedBox(
                width: 80.0,
                height: 80.0,
                child: CircularProgressIndicator(
                  strokeWidth: 8.0,
                  valueColor:
                      AlwaysStoppedAnimation<Color>(Utils.mainThemeColor),
                ),
              ),
            ),
            Center(
              child: Icon(
                Icons.savings,
                color: Utils.mainThemeColor,
                size: 40.0,
              ),
            ),
          ],
        ),
      ),
    );
  }
}

class FlutterBankBottomBarItem {
  String? label;
  IconData? icon;
  Function? onTap;

  FlutterBankBottomBarItem({
    this.label,
    this.icon,
    this.onTap,
  });
}

class FlutterBankBottomBar extends StatelessWidget {
  const FlutterBankBottomBar({super.key});

  @override
  Widget build(BuildContext context) {
    List<FlutterBankBottomBarItem> bottomItems = Utils.getBottomBarItems();

    return Container(
      padding: const EdgeInsets.all(20.0),
      height: 100.0,
      decoration: BoxDecoration(
        color: Colors.white,
        boxShadow: [
          BoxShadow(
            color: Colors.black.withOpacity(0.1),
            blurRadius: 10.0,
            offset: Offset.zero,
          ),
        ],
      ),
      child: Row(
        mainAxisAlignment: MainAxisAlignment.spaceAround,
        children: List.generate(bottomItems.length, (index) {
          FlutterBankBottomBarItem bottomItem = bottomItems[index];
          return Material(
            color: Colors.transparent,
            borderRadius: BorderRadius.circular(10.0),
            clipBehavior: Clip.antiAlias,
            child: InkWell(
              highlightColor: Utils.mainThemeColor.withOpacity(0.2),
              splashColor: Utils.mainThemeColor.withOpacity(0.1),
              onTap: () {
                bottomItem.onTap!();
              },
              child: Container(
                constraints: const BoxConstraints(
                  minWidth: 80.0,
                ),
                padding: const EdgeInsets.all(10.0),
                child: Column(
                  mainAxisAlignment: MainAxisAlignment.end,
                  crossAxisAlignment: CrossAxisAlignment.center,
                  children: [
                    Icon(
                      bottomItem.icon,
                      color: Utils.mainThemeColor,
                      size: 20.0,
                    ),
                    Text(
                      bottomItem.label!,
                      style: const TextStyle(
                        color: Utils.mainThemeColor,
                        fontSize: 10.0,
                      ),
                    ),
                  ],
                ),
              ),
            ),
          );
        }),
      ),
    );
  }
}

class FlutterBankDrawer extends StatelessWidget {
  const FlutterBankDrawer({super.key});

  @override
  Widget build(BuildContext context) {
    return Container(
      padding: const EdgeInsets.all(30.0),
      color: Utils.mainThemeColor,
      child: Column(
        crossAxisAlignment: CrossAxisAlignment.start,
        children: [
          const Icon(Icons.savings, color: Colors.white, size: 60.0),
          const SizedBox(height: 40.0),
          Material(
            color: Colors.transparent,
            child: TextButton(
              style: ButtonStyle(
                backgroundColor: MaterialStateProperty.all<Color>(
                  Colors.white.withOpacity(0.1),
                ),
              ),
              child: const Text(
                'Sign Out',
                textAlign: TextAlign.left,
                style: TextStyle(
                  color: Colors.white,
                ),
              ),
              onPressed: () {},
            ),
          ),
        ],
      ),
    );
  }
}

class Utils {
  static const Color mainThemeColor = Color(0xFF8700C3);

  static List<FlutterBankBottomBarItem> getBottomBarItems() {
    return [
      FlutterBankBottomBarItem(
        label: 'Withdraw',
        icon: Icons.logout,
        onTap: () {},
      ),
      FlutterBankBottomBarItem(
        label: 'Deposit',
        icon: Icons.login,
        onTap: () {},
      ),
      FlutterBankBottomBarItem(
        label: 'Expenses',
        icon: Icons.payments,
        onTap: () {},
      ),
    ];
  }

  static bool validateEmail(String? value) {
    String pattern =
        r"^[a-zA-Z0-9.!#$%&'*+/=?^_`{|}~-]+@[a-zA-Z0-9](?:[a-zA-Z0-9-]"
        r"{0,253}[a-zA-Z0-9])?(?:\.[a-zA-Z0-9](?:[a-zA-Z0-9-]"
        r"{0,253}[a-zA-Z0-9])?)*$";
    RegExp regex = RegExp(pattern);

    return (value != null || value!.isNotEmpty || regex.hasMatch(value));
  }

  static Widget generateInputField(
    String hintText,
    IconData icon,
    TextEditingController controller,
    bool isPasswordField,
    Function onChanged,
  ) {
    return Container(
      padding: const EdgeInsets.all(5.0),
      margin: const EdgeInsets.only(bottom: 20.0),
      decoration: BoxDecoration(
        color: Colors.grey.withOpacity(0.2),
        borderRadius: BorderRadius.circular(50.0),
      ),
      child: TextField(
        controller: controller,
        onChanged: (text) {
          onChanged(text);
        },
        obscureText: isPasswordField,
        decoration: InputDecoration(
          prefixIcon: Icon(
            icon,
            color: Utils.mainThemeColor,
          ),
          border: InputBorder.none,
          focusedBorder: InputBorder.none,
          enabledBorder: InputBorder.none,
          errorBorder: InputBorder.none,
          disabledBorder: InputBorder.none,
          contentPadding: const EdgeInsets.fromLTRB(20.0, 11.0, 15.0, 11.0),
          hintText: hintText,
        ),
        style: const TextStyle(
          fontSize: 16.0,
        ),
      ),
    );
  }

  static void signOutDialog(BuildContext context) {
    showDialog(
      context: context,
      builder: (BuildContext context) {
        return AlertDialog(
          title: const Text(
            'Flutter Savings Bank Sign Out',
            style: TextStyle(
              color: Utils.mainThemeColor,
            ),
          ),
          content: Container(
              padding: const EdgeInsets.all(20.0),
              child: const Text('Are you '
                  'sure you want to sign out?')),
          actions: [
            TextButton(
              onPressed: () {
                Navigator.pop(context);
              },
              child: const Text('Cancel'),
            ),
            TextButton(
              onPressed: () async {
                LoginService loginService =
                    Provider.of<LoginService>(context, listen: false);
                await loginService.signOut();
                if (context.mounted) {
                  Navigator.pushReplacement(context,
                      MaterialPageRoute(builder: (context) {
                    return const FlutterBankLogin();
                  }));
                }
              },
              child: const Text('YES, SIGN OUT'),
            ),
          ],
        );
      },
    );
  }
}

class LoginService extends ChangeNotifier {
  String userId = '';
  String errorMessage = '';

  String getUserId() {
    return userId;
  }

  String getErrorMessage() {
    return errorMessage;
  }

  void setLoginErrorMessage(String message) {
    errorMessage = message;
    notifyListeners();
  }

  void setSignUpErrorMessage(String message) {
    errorMessage = message;
    notifyListeners();
  }

  Future<bool> createUserWithEmailAndPassword(
      String email, String password) async {
    setLoginErrorMessage('');
    try {
      UserCredential userCredential =
          await FirebaseAuth.instance.createUserWithEmailAndPassword(
        email: email,
        password: password,
      );
      userId = userCredential.user!.uid;
      return true;
    } on FirebaseAuthException catch (exc) {
      setSignUpErrorMessage(
          'There was an error during sign-up: ${exc.message}');
      return false;
    }
  }

  Future<bool> signInWithEmailAndPassword(String email, String password) async {
    setLoginErrorMessage('');
    try {
      UserCredential userCredential =
          await FirebaseAuth.instance.signInWithEmailAndPassword(
        email: email,
        password: password,
      );
      userId = userCredential.user!.uid;
      return true;
    } on FirebaseAuthException catch (exc) {
      setLoginErrorMessage('There was an error during sign-in: ${exc.message}');
      return false;
    }
  }

  Future<bool> signOut() {
    Completer<bool> signOutCompleter = Completer();

    FirebaseAuth.instance.signOut().then((value) {
      signOutCompleter.complete(true);
    }, onError: (error) {
      signOutCompleter.completeError({'error': error});
    });
    return signOutCompleter.future;
  }
}

class FlutterBankService extends ChangeNotifier {
  Future<List<Account>> getAccounts(BuildContext context) {
    LoginService loginService =
        Provider.of<LoginService>(context, listen: false);
    String userId = loginService.getUserId();

    List<Account> accounts = [];

    // A Completer allows you to create Futures from scratch and for
    // situations when you have callback-based API calls (like using .then())
    // or when you want to delay the completing of the Future to a later moment.
    Completer<List<Account>> accountsCompleter = Completer();

    // In the one-time read, data is fetched only once, using the .get() call.
    // When querying for a collection of documents, you capture the result in a
    // QuerySnapshot which returns a collection of document references
    // (not the actual documents); when querying for a single document, you
    // capture the result in a DocumentSnapshot, which is a reference to the
    // document (not the actual document); you get the document data when you
    // call .data() on the reference.
    FirebaseFirestore.instance
        .collection('accounts')
        .doc('IJrYcBqjkzcKgqBmSGlPxr2qWmn1')
        .collection('user_accounts')
        .get()
        .then((QuerySnapshot collection) {
      // Inside the callback, loop through the document references returned
      // via the QuerySnapshot by pulling all document references
      // (via the .docs property of the QuerySnapshot). Get the data
      // out of each document reference (via the .data() call) and
      // cast it to a **Map≶String, dynamic>).
      for (var doc in collection.docs) {
        // map this data to a strongly-type model (our Account model
        // created earlier) via its factory method .fromJson.
        // Feed both the data and document it this method which
        // should return an instance of Acount. Push this instance
        // to our accounts collection.
        var acctDoc = doc.data() as Map<String, dynamic>;
        var acct = Account.fromJson(acctDoc, doc.id);
        accounts.add(acct);
      }

      // After mapping and collecting all values, introduce a
      // small delay using Future's utility method delayed and add a
      // 2-second delay, then complete the Future generated by the
      // completer by calling accountsCompleter.complete, passing
      // the already populated collection:
      Future.delayed(const Duration(seconds: 1), () {
        accountsCompleter.complete(accounts);
      });
    });
    return accountsCompleter.future;
    // What this will do is: we'll return a Future from the Completer immediately,
    // to the user. The user will await on this Future while we fetch the data
    // from Firebase; once the data is ready (mapped and collected), we notify
    // them through that same Future via the Completer's .complete call,
    // passing the same type of data this method is returning via the method
    // signature (Future<List<Account>>).
  }
}

// MODELS
class Account {
  String? id;
  String? type;
  String? accountNumber;
  int? balance;

  Account({
    this.id,
    this.type,
    this.accountNumber,
    this.balance,
  });

  // Create a factory method to map the incoming JSON structure from Firebase
  // (as a Map<String, dynamic>), and takes both the Map as well as the
  // unique document's ID.
  factory Account.fromJson(Map<String, dynamic> json, String docId) {
    return Account(
      id: docId,
      type: json['type'],
      accountNumber: json['account_number'],
      balance: json['balance'],
    );
  }
}