import 'dart:async';

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

const String _name = "Ivan Murashov";

void main() {
  runApp(new DemoApp());
}

class DemoApp extends StatelessWidget {
  @override Widget build(BuildContext context) {
    return new MaterialApp(title: "DemoApp", home: new ChatScreen());
  }
}

class ChatScreen extends StatefulWidget {
  @override State createState() => new ChatScreenState();
}

class ChatScreenState extends State<ChatScreen> {

  static const platform = const MethodChannel('com.yourcompany.checker/scanner');
  final List<ChatMessage> _messages = <ChatMessage>[];
  final TextEditingController _textController = new TextEditingController();

  @override Widget build(BuildContext context) {
    return new Scaffold(appBar: new AppBar(
        title: new Text("DemoApp")), body: _buildScreen());
  }

  Widget _buildScreen() {
    return new Column(children: <Widget>[
      new Flexible(child: new ListView.builder(
        padding: new EdgeInsets.all(8.0),
        reverse: true,
        itemBuilder: (_, int index) => _messages[index],
        itemCount: _messages.length)),
      new Divider(height: 1.0),
      new Container(decoration: _getDecoratedScreenComposer(),
          child: _buildStyledTextComposer())
    ]);
  }

  BoxDecoration _getDecoratedScreenComposer() {
    return new BoxDecoration(color: Theme.of(context).cardColor);
  }

  Widget _buildStyledTextComposer() {
    return new IconTheme(data: _getIconThemeData(), child: _buildTextComposer());
  }

  IconThemeData _getIconThemeData() {
    return new IconThemeData(color: Theme.of(context).accentColor);
  }

  Widget _buildTextComposer() {
    return new Container(margin: const EdgeInsets.symmetric(horizontal: 8.0),
      child: _buildInputFieldRow());
  }

  Row _buildInputFieldRow() {
    var textField = new InputDecoration.collapsed(hintText: "Send a message");
    return new Row(children: <Widget>[
      new Flexible(child: new TextField(controller: _textController,
                                        onSubmitted: _handleSubmitted,
                                        decoration: textField)),
      new Container(margin: new EdgeInsets.symmetric(horizontal: 4.0),
                    child: new IconButton(icon: new Icon(Icons.send),
                    onPressed: () => startScanner()))
//                    onPressed: () => _handleSubmitted(_textController.text)))
    ]);
  }

  Future<Null> startScanner() async {
    try {
      platform.invokeMethod('startScanner');
    } on PlatformException catch (e) {

    }
  }

  void _handleSubmitted(String text) {
    _textController.clear();
    ChatMessage message = new ChatMessage(text);
    setState(() {_messages.insert(0, message);});
  }
}

class ChatMessage extends StatelessWidget {

  final String text;

  ChatMessage(this.text);

  @override Widget build(BuildContext context) {
    return new Container(margin: const EdgeInsets.symmetric(vertical: 8.0),
                        child: _getMessageRow(context));
  }

  Widget _getMessageRow(BuildContext context) {
    return new Row(crossAxisAlignment: CrossAxisAlignment.start,
        children: <Widget>[
          new Container(margin: const EdgeInsets.only(right: 16.0),
              child: new CircleAvatar(child: new Text(_name[0]))),
          new Column(crossAxisAlignment: CrossAxisAlignment.start,
              children: <Widget>[
                new Text(_name, style: Theme.of(context).textTheme.subhead),
                new Container(margin: const EdgeInsets.only(top: 4.0),
                    child: new Text(text))
              ])
        ]);
  }
}