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

class Toast {
  static const int LENGTH_SHORT = 1;
  static const int LENGTH_LONG = 2;
  static const int BOTTOM = 0;
  static const int CENTER = 1;
  static const int TOP = 2;
  static const int ERROR = -1;
  static const int NORMAL = 0;
  static const int SUCCESS = 1;

  static void show(String msg, BuildContext context,
      {int type = NORMAL,
      int duration = 1,
      int gravity = CENTER,
      Color backgroundColor = const Color(0xAA000000),
      Color textColor = Colors.white,
      double backgroundRadius = 5.0}) {
    ToastView.dismiss();
    ToastView.createView(msg, context, type, duration, gravity, backgroundColor,
        textColor, backgroundRadius);
  }
}

class ToastView {
  static final ToastView _singleton = new ToastView._internal();

  factory ToastView() {
    return _singleton;
  }

  ToastView._internal();

  static OverlayState overlayState;
  static OverlayEntry overlayEntry;
  static bool _isVisible = false;

  static void createView(
      String msg,
      BuildContext context,
      int type,
      int duration,
      int gravity,
      Color background,
      Color textColor,
      double backgroundRadius) async {
    overlayState = Overlay.of(context);
    overlayEntry = new OverlayEntry(
      builder: (BuildContext context) => ToastWidget(
          widget: Container(
            width: MediaQuery.of(context).size.width,
            child: Container(
              alignment: Alignment.center,
              child: Container(
                margin: EdgeInsets.symmetric(horizontal: 83),
                padding: EdgeInsets.all(15.0),
                decoration: BoxDecoration(
                  color: background,
                  borderRadius: BorderRadius.circular(backgroundRadius),
                ),
                constraints: BoxConstraints(minHeight: 52,minWidth: 210),
                child: _buildContent(type, msg, textColor),
              ),
            ),
          ),
          gravity: gravity),
    );
    _isVisible = true;
    overlayState.insert(overlayEntry);
    await new Future.delayed(
        Duration(seconds: duration == null ? Toast.LENGTH_SHORT : duration));
    dismiss();
  }

  static Widget _buildContent(int type, String msg, Color textColor) {
    if (type == 0) {
      return Text(msg,
          maxLines: 20,
          overflow: TextOverflow.ellipsis,
          textAlign: TextAlign.center,
          style: TextStyle(
              fontSize: 16,
              color: textColor,
              decoration: TextDecoration.none,
              fontWeight: FontWeight.normal));
    } else {
      return Column(
        mainAxisAlignment: MainAxisAlignment.center,
        mainAxisSize: MainAxisSize.min,
        children: <Widget>[
          Icon(type ==1 ?Icons.check_circle:Icons.error,color: Colors.white,),
          Padding(padding: EdgeInsets.only(top: 16.0),),
          Text(msg,
              maxLines: 20,
              overflow: TextOverflow.ellipsis,
              style: TextStyle(
                  fontSize: 16,
                  color: textColor,
                  decoration: TextDecoration.none,
                  fontWeight: FontWeight.normal))
        ],
      );
    }
  }

  static dismiss() async {
    if (!_isVisible) {
      return;
    }
    _isVisible = false;
    overlayEntry?.remove();
  }
}

class ToastWidget extends StatelessWidget {
  ToastWidget({
    Key key,
    @required this.widget,
    @required this.gravity,
  }) : super(key: key);

  final Widget widget;
  final int gravity;

  @override
  Widget build(BuildContext context) {
    return new Positioned(
        top: gravity == 2 ? 50 : null,
        bottom: gravity == 0 ? 50 : null,
        child: widget);
  }
}