added the cubit and fake repo for change phone number process

lib/core/res/strings.dart

@@ -19,4 +19,5 @@ class S {
   static const String networkException =
       "Request couldn't be completed. Make sure the device is online";
   static const String unknownException = "Something went wrong. Please try again later.";
+  static const String wrongOtp = "Wrong OTP entered";
 }

lib/screens/change_number/change_number.dart

@@ -0,0 +1,90 @@
+import 'package:ecellapp/screens/change_number/cubit/change_number_cubit.dart';
+import 'package:ecellapp/screens/change_number/widgets/mobile_number_field.dart';
+import 'package:ecellapp/screens/change_number/widgets/otp_field.dart';
+import 'package:flutter/cupertino.dart';
+import 'package:flutter/material.dart';
+import 'package:flutter_bloc/flutter_bloc.dart';
+
+class ChangeNumberScreen extends StatelessWidget {
+  final TextEditingController mobileController = TextEditingController();
+  final TextEditingController otpController = TextEditingController();
+
+  @override
+  Widget build(BuildContext context) {
+    return Scaffold(
+      body: BlocConsumer<ChangeNumberCubit, ChangeNumberState>(
+        listener: (context, state) {
+          if (state is ChangeNumberError) {
+            Scaffold.of(context).showSnackBar(
+              SnackBar(content: Text(state.error)),
+            );
+          } else if (state is ChangeNumberWrongOtp) {
+            Scaffold.of(context).showSnackBar(
+              SnackBar(content: Text(state.error)),
+            );
+          } else if (state is ChangeNumberOtpSuccessful) {
+            Scaffold.of(context).showSnackBar(
+              SnackBar(content: Text("Successful")),
+            );
+          }
+        },
+        builder: (context, state) {
+          if (state is ChangeNumberInitial) {
+            return _initial(context);
+          } else if (state is ChangeNumberOTP) {
+            return _enterOtp(context);
+          } else if (state is ChangeNumberOtpSuccessful) {
+            ///
+            return _success();
+          } else {
+            return _initial(context);
+          }
+        },
+      ),
+    );
+  }
+
+  Widget _initial(BuildContext context) {
+    return Padding(
+      padding: const EdgeInsets.all(50.0),
+      child: Column(
+        children: [
+          MobileNumberField(mobileController),
+          FlatButton(
+              onPressed: () {
+                final cubit = context.read<ChangeNumberCubit>();
+                cubit.getOtp(mobileController.text);
+              },
+              child: Text("Get otp")),
+        ],
+      ),
+    );
+  }
+
+  Widget _enterOtp(BuildContext context) {
+    return Padding(
+      padding: const EdgeInsets.all(50.0),
+      child: Column(
+        children: [
+          OtpField(otpController),
+          FlatButton(
+            onPressed: () {
+              final cubit = context.read<ChangeNumberCubit>();
+              cubit.verifyOtp(otpController.text);
+            },
+            child: Text("verify"),
+          ),
+        ],
+      ),
+    );
+  }
+
+  Widget _success() {
+    return Padding(
+      padding: const EdgeInsets.all(50.0),
+      child: Column(
+        children: [Text("Success")],
+      ),
+    );
+  }
+}

lib/screens/change_number/change_number_repository.dart

@@ -0,0 +1,33 @@
+import 'dart:math';
+
+import 'package:ecellapp/core/res/errors.dart';
+
+abstract class ChangeNumberRepository {
+  Future<void> getOtp(String number);
+}
+
+class FakeChangeNumberRepository extends ChangeNumberRepository {
+  String generated;
+
+  @override
+  Future<void> getOtp(String number) async {
+    await Future.delayed(Duration(seconds: 1));
+    if (Random().nextBool()) {
+      //print("Fail");
+      // Represents a network failure
+      throw NetworkException();
+    } else {
+      generated = '1234';
+      // returns a dummy otp
+    }
+  }
+
+  Future<int> verifyOtp(String sent) async {
+    await Future.delayed(Duration(seconds: 1));
+    if (sent == generated) {
+      return 200;
+    } else {
+      throw ValidationException("Wrong OTP has been entered");
+    }
+  }
+}

lib/screens/change_number/cubit/change_number_cubit.dart

@@ -0,0 +1,33 @@
+import 'package:bloc/bloc.dart';
+import 'package:ecellapp/core/res/errors.dart';
+import 'package:ecellapp/screens/change_number/change_number_repository.dart';
+import 'package:meta/meta.dart';
+import 'package:ecellapp/core/res/strings.dart';
+
+part 'change_number_state.dart';
+
+class ChangeNumberCubit extends Cubit<ChangeNumberState> {
+  FakeChangeNumberRepository _changeNumberRepository = FakeChangeNumberRepository();
+
+  ChangeNumberCubit() : super(ChangeNumberInitial());
+
+  Future<void> getOtp(String number) async {
+    try {
+      await _changeNumberRepository.getOtp(number);
+      emit(ChangeNumberOTP());
+    } on NetworkException {
+      emit(ChangeNumberError(S.unknownException));
+    }
+  }
+
+  Future<void> verifyOtp(String otp) async {
+    try {
+      int x = await _changeNumberRepository.verifyOtp(otp);
+      if (x == 200) {
+        emit(ChangeNumberOtpSuccessful());
+      }
+    } on ValidationException {
+      emit(ChangeNumberError(S.wrongOtp));
+    }
+  }
+}

lib/screens/change_number/cubit/change_number_state.dart

@@ -0,0 +1,24 @@
+part of 'change_number_cubit.dart';
+
+@immutable
+abstract class ChangeNumberState {
+  const ChangeNumberState();
+}
+
+class ChangeNumberInitial extends ChangeNumberState {}
+
+class ChangeNumberOTP extends ChangeNumberState {}
+
+class ChangeNumberError extends ChangeNumberState {
+  final String error;
+
+  ChangeNumberError(this.error);
+}
+
+class ChangeNumberWrongOtp extends ChangeNumberState {
+  final String error;
+
+  ChangeNumberWrongOtp(this.error);
+}
+
+class ChangeNumberOtpSuccessful extends ChangeNumberState {}

lib/screens/change_number/widgets/mobile_number_field.dart

@@ -0,0 +1,22 @@
+import 'package:flutter/material.dart';
+
+class MobileNumberField extends StatelessWidget {
+  const MobileNumberField(this.controller);
+
+  final TextEditingController controller;
+
+  @override
+  Widget build(BuildContext context) {
+    return TextFormField(
+      controller: controller,
+      keyboardType: TextInputType.number,
+      decoration: InputDecoration(
+        suffixText: '*',
+        suffixStyle: TextStyle(color: Colors.red, fontSize: 20),
+        prefixIcon: Icon(Icons.phone),
+        border: OutlineInputBorder(),
+        labelText: "Mobile Number",
+      ),
+    );
+  }
+}

lib/screens/change_number/widgets/otp_field.dart

@@ -0,0 +1,15 @@
+import 'package:flutter/cupertino.dart';
+import 'package:flutter/material.dart';
+
+class OtpField extends StatelessWidget {
+  final TextEditingController controller;
+
+  OtpField(this.controller);
+
+  @override
+  Widget build(BuildContext context) {
+    return TextField(
+      controller: controller,
+    );
+  }
+}

lib/screens/signup/cubit/signup_state.dart

@@ -3,6 +3,7 @@ part of 'signup_cubit.dart';
 @immutable
 abstract class SignupState extends Equatable {
   const SignupState();
+
   @override
   List<Object> get props => [];
 }
@@ -21,7 +22,9 @@ class SignupSuccess extends SignupState {
 
 class SignupError extends SignupState {
   final String message;
+
   const SignupError(this.message);
+
   @override
   List<Object> get props => [message];
 }