import 'package:flutter/cupertino.dart';
import 'package:flutter/foundation.dart';
import 'package:flutter/material.dart';

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

final ThemeData iosTheme = new ThemeData(
  primarySwatch: Colors.orange,
  primaryColor: Colors.grey[100],
  primaryColorBrightness: Brightness.light,
);

final ThemeData defaultTheme = new ThemeData(
  primarySwatch: Colors.blue,
  accentColor: Colors.orangeAccent[400],
);

const String _name = "Marvin Borner";

class MessengerApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return new MaterialApp(
      title: "BEAM-Messenger",
      theme:
          defaultTargetPlatform == TargetPlatform.iOS ? iosTheme : defaultTheme,
      home: new ChatScreen(),
    );
  }
}

class ChatMessage extends StatelessWidget {
  ChatMessage({this.text, this.animationController});
  final String text;
  final AnimationController animationController;
  @override
  Widget build(BuildContext context) {
    return new SizeTransition(
        sizeFactor: new CurvedAnimation(
            parent: animationController, curve: Curves.easeOut),
        axisAlignment: 0.0,
        child: new Container(
          margin: const EdgeInsets.symmetric(vertical: 10.0),
          child: 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 Expanded(
                child: new Column(
                  crossAxisAlignment: CrossAxisAlignment.start,
                  children: <Widget>[
                    new Text(_name, style: Theme.of(context).textTheme.subhead),
                    new Container(
                      margin: const EdgeInsets.only(top: 5.0),
                      child: new Text(text),
                    ),
                  ],
                ),
              ),
            ],
          ),
        ));
  }
}

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

class ChatScreenState extends State<ChatScreen> with TickerProviderStateMixin {
  final List<ChatMessage> _messages = <ChatMessage>[];
  final TextEditingController _textController = new TextEditingController();
  bool _isComposing = false;

  void _handleSubmitted(String text) {
    _textController.clear();
    setState(() {
      _isComposing = false;
    });
    ChatMessage message = new ChatMessage(
      text: text,
      animationController: new AnimationController(
        duration: new Duration(milliseconds: 700),
        vsync: this,
      ),
    );
    setState(() {
      _messages.insert(0, message);
    });
    message.animationController.forward();
  }

  void dispose() {
    for (ChatMessage message in _messages)
      message.animationController.dispose();
    super.dispose();
  }

  Widget _buildTextComposer() {
    return new IconTheme(
      data: new IconThemeData(color: Theme.of(context).accentColor),
      child: new Container(
          margin: const EdgeInsets.symmetric(horizontal: 8.0),
          child: new Row(children: <Widget>[
            new Flexible(
              child: new TextField(
                controller: _textController,
                onChanged: (String text) {
                  setState(() {
                    _isComposing = text.length > 0;
                  });
                },
                onSubmitted: _handleSubmitted,
                decoration: new InputDecoration.collapsed(
                    hintText: "Send a message..."),
              ),
            ),
            new Container(
                margin: new EdgeInsets.symmetric(horizontal: 4.0),
                child: Theme.of(context).platform == TargetPlatform.iOS
                    ? new CupertinoButton(
                        child: new Text("Send"),
                        onPressed: _isComposing
                            ? () => _handleSubmitted(_textController.text)
                            : null,
                      )
                    : new IconButton(
                        icon: new Icon(Icons.send),
                        onPressed: _isComposing
                            ? () => _handleSubmitted(_textController.text)
                            : null,
                      )),
          ]),
          decoration: Theme.of(context).platform == TargetPlatform.iOS
              ? new BoxDecoration(
                  border:
                      new Border(top: new BorderSide(color: Colors.grey[200])))
              : null),
    );
  }

  Widget build(BuildContext context) {
    return new Scaffold(
      appBar: new AppBar(
          title: new Text("BEAM-Messenger"),
          elevation:
              Theme.of(context).platform == TargetPlatform.iOS ? 0.0 : 4.0),
      body: new Container(
          child: 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: new BoxDecoration(color: Theme.of(context).cardColor),
              child: _buildTextComposer(),
            ),
          ]),
          decoration: Theme.of(context).platform == TargetPlatform.iOS
              ? new BoxDecoration(
                  border:
                      new Border(top: new BorderSide(color: Colors.grey[200])))
              : null),
    );
  }
}