// Copyright 2016 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

import 'dart:async';

import 'package:flutter/material.dart';
import 'package:flutter/services.dart';

class TextFormFieldDemo extends StatefulWidget {
  const TextFormFieldDemo({ Key key }) : super(key: key);

  static const String routeName = '/material/text-form-field';

  @override
  TextFormFieldDemoState createState() => new TextFormFieldDemoState();
}

class PersonData {
  String name = '';
  String phoneNumber = '';
  String password = '';
}

class TextFormFieldDemoState extends State<TextFormFieldDemo> {
  final GlobalKey<ScaffoldState> _scaffoldKey = new GlobalKey<ScaffoldState>();

  PersonData person = new PersonData();

  void showInSnackBar(String value) {
    _scaffoldKey.currentState.showSnackBar(new SnackBar(
      content: new Text(value)
    ));
  }

  bool _autovalidate = false;
  bool _formWasEdited = false;
  final GlobalKey<FormState> _formKey = new GlobalKey<FormState>();
  final GlobalKey<FormFieldState<String>> _passwordFieldKey = new GlobalKey<FormFieldState<String>>();
  final _UsNumberTextInputFormatter _phoneNumberFormatter = new _UsNumberTextInputFormatter();
  void _handleSubmitted() {
    final FormState form = _formKey.currentState;
    if (!form.validate()) {
      _autovalidate = true;  // Start validating on every change.
      showInSnackBar('Please fix the errors in red before submitting.');
    } else {
      form.save();
      showInSnackBar('${person.name}\'s phone number is ${person.phoneNumber}');
    }
  }

  String _validateName(String value) {
    _formWasEdited = true;
    if (value.isEmpty)
      return 'Name is required.';
    final RegExp nameExp = new RegExp(r'^[A-Za-z ]+$');
    if (!nameExp.hasMatch(value))
      return 'Please enter only alphabetical characters.';
    return null;
  }

  String _validatePhoneNumber(String value) {
    _formWasEdited = true;
    final RegExp phoneExp = new RegExp(r'^\(\d\d\d\) \d\d\d\-\d\d\d\d$');
    if (!phoneExp.hasMatch(value))
      return '(###) ###-#### - Please enter a valid US phone number.';
    return null;
  }

  String _validatePassword(String value) {
    _formWasEdited = true;
    final FormFieldState<String> passwordField = _passwordFieldKey.currentState;
    if (passwordField.value == null || passwordField.value.isEmpty)
      return 'Please choose a password.';
    if (passwordField.value != value)
      return 'Passwords don\'t match';
    return null;
  }

  Future<bool> _warnUserAboutInvalidData() async {
    final FormState form = _formKey.currentState;
    if (form == null || !_formWasEdited || form.validate())
      return true;

    return await showDialog<bool>(
      context: context,
      child: new AlertDialog(
        title: const Text('This form has errors'),
        content: const Text('Really leave this form?'),
        actions: <Widget> [
          new FlatButton(
            child: const Text('YES'),
            onPressed: () { Navigator.of(context).pop(true); },
          ),
          new FlatButton(
            child: const Text('NO'),
            onPressed: () { Navigator.of(context).pop(false); },
          ),
        ],
      ),
    ) ?? false;
  }

  @override
  Widget build(BuildContext context) {
    return new Scaffold(
      key: _scaffoldKey,
      appBar: new AppBar(
        title: const Text('Text fields'),
      ),
      body: new Form(
        key: _formKey,
        autovalidate: _autovalidate,
        onWillPop: _warnUserAboutInvalidData,
        child: new ListView(
          padding: const EdgeInsets.symmetric(horizontal: 16.0),
          children: <Widget>[
            new TextFormField(
              decoration: const InputDecoration(
                icon: const Icon(Icons.person),
                hintText: 'What do people call you?',
                labelText: 'Name *',
              ),
              onSaved: (String value) { person.name = value; },
              validator: _validateName,
            ),
            new TextFormField(
              decoration: const InputDecoration(
                icon: const Icon(Icons.phone),
                hintText: 'Where can we reach you?',
                labelText: 'Phone Number *',
                prefixText: '+1'
              ),
              keyboardType: TextInputType.phone,
              onSaved: (String value) { person.phoneNumber = value; },
              validator: _validatePhoneNumber,
              // TextInputFormatters are applied in sequence.
              inputFormatters: <TextInputFormatter> [
                WhitelistingTextInputFormatter.digitsOnly,
                // Fit the validating format.
                _phoneNumberFormatter,
              ],
            ),
            new TextFormField(
              decoration: const InputDecoration(
                hintText: 'Tell us about yourself',
                helperText: 'Keep it short, this is just a demo',
                labelText: 'Life story',
              ),
              maxLines: 3,
            ),
            new TextFormField(
              keyboardType: TextInputType.number,
              decoration: const InputDecoration(
                labelText: 'Salary',
                prefixText: '\$',
                suffixText: 'USD',
                suffixStyle: const TextStyle(color: Colors.green)
              ),
              maxLines: 1,
            ),
            new Row(
              crossAxisAlignment: CrossAxisAlignment.start,
              children: <Widget>[
                new Expanded(
                  child: new TextFormField(
                    key: _passwordFieldKey,
                    decoration: const InputDecoration(
                      hintText: 'How do you log in?',
                      labelText: 'New Password *',
                    ),
                    obscureText: true,
                    onSaved: (String value) { person.password = value; },
                  ),
                ),
                const SizedBox(width: 16.0),
                new Expanded(
                  child: new TextFormField(
                    decoration: const InputDecoration(
                      hintText: 'How do you log in?',
                      labelText: 'Re-type Password *',
                    ),
                    obscureText: true,
                    validator: _validatePassword,
                  ),
                ),
              ],
            ),
            new Container(
              padding: const EdgeInsets.all(20.0),
              alignment: Alignment.center,
              child: new RaisedButton(
                child: const Text('SUBMIT'),
                onPressed: _handleSubmitted,
              ),
            ),
            new Container(
              padding: const EdgeInsets.only(top: 20.0),
              child: new Text('* indicates required field', style: Theme.of(context).textTheme.caption),
            ),
          ],
        )
      ),
    );
  }
}

/// Format incoming numeric text to fit the format of (###) ###-#### ##...
class _UsNumberTextInputFormatter extends TextInputFormatter {
  @override
  TextEditingValue formatEditUpdate(
    TextEditingValue oldValue,
    TextEditingValue newValue
  ) {
    final int newTextLength = newValue.text.length;
    int selectionIndex = newValue.selection.end;
    int usedSubstringIndex = 0;
    final StringBuffer newText = new StringBuffer();
    if (newTextLength >= 1) {
      newText.write('(');
      if (newValue.selection.end >= 1)
        selectionIndex++;
    }
    if (newTextLength >= 4) {
      newText.write(newValue.text.substring(0, usedSubstringIndex = 3) + ') ');
      if (newValue.selection.end >= 3)
        selectionIndex += 2;
    }
    if (newTextLength >= 7) {
      newText.write(newValue.text.substring(3, usedSubstringIndex = 6) + '-');
      if (newValue.selection.end >= 6)
        selectionIndex++;
    }
    if (newTextLength >= 11) {
      newText.write(newValue.text.substring(6, usedSubstringIndex = 10) + ' ');
      if (newValue.selection.end >= 10)
        selectionIndex++;
    }
    // Dump the rest.
    if (newTextLength >= usedSubstringIndex)
      newText.write(newValue.text.substring(usedSubstringIndex));
    return new TextEditingValue(
      text: newText.toString(),
      selection: new TextSelection.collapsed(offset: selectionIndex),
    );
  }
}
