// Author: fruit.com.cn

import 'dart:async';

import 'package:flutter/material.dart';

const Key _toastKey = Key('centered-toast');
const Duration _fadeDuration = Duration(milliseconds: 200);
const Duration _visibleDuration = Duration(seconds: 2);
const double _toastRadius = 12;
const double _toastMaxWidth = 320;
const double _toastHorizontalInset = 20;
const double _toastVerticalInset = 12;
const double _toastBackgroundOpacity = 0.78;
const TextStyle _toastTextStyle = TextStyle(
  color: Colors.white,
  fontSize: 14,
  height: 1.4,
  fontWeight: FontWeight.w500,
);
const EdgeInsets _toastPadding = EdgeInsets.symmetric(
  horizontal: _toastHorizontalInset,
  vertical: _toastVerticalInset,
);

OverlayEntry? _activeToast;

/// Shows a lightweight centered message and replaces any active toast.
void showCenteredToast(BuildContext context, String message) {
  _removeActiveToast();
  final overlay = Overlay.of(context, rootOverlay: true);
  late final OverlayEntry entry;
  entry = OverlayEntry(
    builder: (_) => _CenteredToast(
      message: message,
      onDismissed: () {
        if (!identical(_activeToast, entry)) return;
        _activeToast = null;
        if (entry.mounted) entry.remove();
      },
    ),
  );
  _activeToast = entry;
  overlay.insert(entry);
}

void _removeActiveToast() {
  final entry = _activeToast;
  _activeToast = null;
  if (entry != null && entry.mounted) entry.remove();
}

class _CenteredToast extends StatefulWidget {
  const _CenteredToast({required this.message, required this.onDismissed});

  final String message;
  final VoidCallback onDismissed;

  @override
  State<_CenteredToast> createState() => _CenteredToastState();
}

class _CenteredToastState extends State<_CenteredToast>
    with SingleTickerProviderStateMixin {
  late final AnimationController _opacity = AnimationController(
    vsync: this,
    duration: _fadeDuration,
  );
  Timer? _dismissTimer;

  @override
  void initState() {
    super.initState();
    _opacity.forward();
    _dismissTimer = Timer(_visibleDuration, _dismiss);
  }

  Future<void> _dismiss() async {
    try {
      await _opacity.reverse();
    } on TickerCanceled {
      return;
    }
    if (mounted) widget.onDismissed();
  }

  @override
  void dispose() {
    _dismissTimer?.cancel();
    _opacity.dispose();
    super.dispose();
  }

  @override
  Widget build(BuildContext context) {
    return Positioned.fill(
      child: IgnorePointer(
        child: Center(
          child: FadeTransition(
            opacity: CurvedAnimation(
              parent: _opacity,
              curve: Curves.easeOutCubic,
            ),
            child: Material(
              type: MaterialType.transparency,
              child: Container(
                key: _toastKey,
                constraints: const BoxConstraints(maxWidth: _toastMaxWidth),
                padding: _toastPadding,
                decoration: BoxDecoration(
                  color: Colors.black.withValues(
                    alpha: _toastBackgroundOpacity,
                  ),
                  borderRadius: BorderRadius.circular(_toastRadius),
                ),
                child: Text(
                  widget.message,
                  textAlign: TextAlign.center,
                  style: _toastTextStyle,
                ),
              ),
            ),
          ),
        ),
      ),
    );
  }
}