// 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';
import 'package:flutter/gestures.dart' show DragStartBehavior;

import '../../gallery/demo.dart';

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

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

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

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

class PasswordField extends StatefulWidget {
  const PasswordField({
    this.fieldKey,
    this.hintText,
    this.labelText,
    this.helperText,
    this.onSaved,
    this.validator,
    this.onFieldSubmitted,
  });

  final Key fieldKey;
  final String hintText;
  final String labelText;
  final String helperText;
  final FormFieldSetter<String> onSaved;
  final FormFieldValidator<String> validator;
  final ValueChanged<String> onFieldSubmitted;

  @override
  _PasswordFieldState createState() => _PasswordFieldState();
}

class _PasswordFieldState extends State<PasswordField> {
  bool _obscureText = true;

  @override
  Widget build(BuildContext context) {
    return TextFormField(
      key: widget.fieldKey,
      obscureText: _obscureText,
      maxLength: 8,
      onSaved: widget.onSaved,
      validator: widget.validator,
      onFieldSubmitted: widget.onFieldSubmitted,
      decoration: InputDecoration(
        border: const UnderlineInputBorder(),
        filled: true,
        hintText: widget.hintText,
        labelText: widget.labelText,
        helperText: widget.helperText,
        suffixIcon: GestureDetector(
          dragStartBehavior: DragStartBehavior.down,
          onTap: () {
            setState(() {
              _obscureText = !_obscureText;
            });
          },
          child: Icon(
            _obscureText ? Icons.visibility : Icons.visibility_off,
            semanticLabel: _obscureText ? 'show password' : 'hide password',
          ),
        ),
      ),
    );
  }
}

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

  PersonData person = PersonData();

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

  bool _autovalidate = false;
  bool _formWasEdited = false;

  final GlobalKey<FormState> _formKey = GlobalKey<FormState>();
  final GlobalKey<FormFieldState<String>> _passwordFieldKey = GlobalKey<FormFieldState<String>>();
  final _UsNumberTextInputFormatter _phoneNumberFormatter = _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 = 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 = RegExp(r'^\(\d\d\d\) \d\d\d\-\d\d\d\d$');
    if (!phoneExp.hasMatch(value))
      return '(###) ###-#### - Enter a 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 enter a password.';
    if (passwordField.value != value)
      return 'The 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,
      builder: (BuildContext context) {
        return AlertDialog(
          title: const Text('This form has errors'),
          content: const Text('Really leave this form?'),
          actions: <Widget> [
            FlatButton(
              child: const Text('YES'),
              onPressed: () { Navigator.of(context).pop(true); },
            ),
            FlatButton(
              child: const Text('NO'),
              onPressed: () { Navigator.of(context).pop(false); },
            ),
          ],
        );
      },
    ) ?? false;
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      drawerDragStartBehavior: DragStartBehavior.down,
      key: _scaffoldKey,
      appBar: AppBar(
        title: const Text('Text fields'),
        actions: <Widget>[MaterialDemoDocumentationButton(TextFormFieldDemo.routeName)],
      ),
      body: SafeArea(
        top: false,
        bottom: false,
        child: Form(
          key: _formKey,
          autovalidate: _autovalidate,
          onWillPop: _warnUserAboutInvalidData,
          child: SingleChildScrollView(
            dragStartBehavior: DragStartBehavior.down,
            padding: const EdgeInsets.symmetric(horizontal: 16.0),
            child: Column(
              crossAxisAlignment: CrossAxisAlignment.stretch,
              children: <Widget>[
                const SizedBox(height: 24.0),
                TextFormField(
                  textCapitalization: TextCapitalization.words,
                  decoration: const InputDecoration(
                    border: UnderlineInputBorder(),
                    filled: true,
                    icon: Icon(Icons.person),
                    hintText: 'What do people call you?',
                    labelText: 'Name *',
                  ),
                  onSaved: (String value) { person.name = value; },
                  validator: _validateName,
                ),
                const SizedBox(height: 24.0),
                TextFormField(
                  decoration: const InputDecoration(
                    border: UnderlineInputBorder(),
                    filled: true,
                    icon: 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,
                  ],
                ),
                const SizedBox(height: 24.0),
                TextFormField(
                  decoration: const InputDecoration(
                    border: UnderlineInputBorder(),
                    filled: true,
                    icon: Icon(Icons.email),
                    hintText: 'Your email address',
                    labelText: 'E-mail',
                  ),
                  keyboardType: TextInputType.emailAddress,
                  onSaved: (String value) { person.email = value; },
                ),
                const SizedBox(height: 24.0),
                TextFormField(
                  decoration: const InputDecoration(
                    border: OutlineInputBorder(),
                    hintText: 'Tell us about yourself (e.g., write down what you do or what hobbies you have)',
                    helperText: 'Keep it short, this is just a demo.',
                    labelText: 'Life story',
                  ),
                  maxLines: 3,
                ),
                const SizedBox(height: 24.0),
                TextFormField(
                  keyboardType: TextInputType.number,
                  decoration: const InputDecoration(
                    border: OutlineInputBorder(),
                    labelText: 'Salary',
                    prefixText: '\$',
                    suffixText: 'USD',
                    suffixStyle: TextStyle(color: Colors.green)
                  ),
                  maxLines: 1,
                ),
                const SizedBox(height: 24.0),
                PasswordField(
                  fieldKey: _passwordFieldKey,
                  helperText: 'No more than 8 characters.',
                  labelText: 'Password *',
                  onFieldSubmitted: (String value) {
                    setState(() {
                      person.password = value;
                    });
                  },
                ),
                const SizedBox(height: 24.0),
                TextFormField(
                  enabled: person.password != null && person.password.isNotEmpty,
                  decoration: const InputDecoration(
                    border: UnderlineInputBorder(),
                    filled: true,
                    labelText: 'Re-type password',
                  ),
                  maxLength: 8,
                  obscureText: true,
                  validator: _validatePassword,
                ),
                const SizedBox(height: 24.0),
                Center(
                  child: RaisedButton(
                    child: const Text('SUBMIT'),
                    onPressed: _handleSubmitted,
                  ),
                ),
                const SizedBox(height: 24.0),
                Text(
                  '* indicates required field',
                  style: Theme.of(context).textTheme.caption
                ),
                const SizedBox(height: 24.0),
              ],
            ),
          ),
        ),
      ),
    );
  }
}

/// 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 = 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 TextEditingValue(
      text: newText.toString(),
      selection: TextSelection.collapsed(offset: selectionIndex),
    );
  }
}