school-attendance/lib/ui/app_notice.dart

// 🔔 스낵바 대신 쓰는 알약(pill) 모양 알림. 기능 타일을 누를 때 뜨는
// "OO로 이동합니다" 같은 짧은 안내용. 푸시 알림(FCM)과는 무관 — 그건 그대로 동작한다.
// 웹에서는 왼쪽 위(알림창 자리)에, 폰 앱에서는 기존 스낵바처럼 아래쪽에 뜬다.
import 'package:flutter/foundation.dart' show kIsWeb;
import 'package:flutter/material.dart';
import '../theme/app_palette.dart';

class AppNotice {
  static final List<_QueuedNotice> _queue = [];
  static bool _showing = false;

  static void show(
    BuildContext context,
    String message, {
    IconData? icon,
    Color? color,
  }) {
    _queue.add(_QueuedNotice(context, message, icon, color));
    _tryShowNext();
  }

  static void _tryShowNext() {
    if (_showing || _queue.isEmpty) return;
    final next = _queue.removeAt(0);
    if (!next.context.mounted) {
      _tryShowNext();
      return;
    }
    _showing = true;
    final overlay = Overlay.of(next.context);
    late OverlayEntry entry;
    entry = OverlayEntry(
      builder: (context) => _NoticeBanner(
        message: next.message,
        icon: next.icon,
        color: next.color,
        onDone: () {
          entry.remove();
          _showing = false;
          _tryShowNext();
        },
      ),
    );
    overlay.insert(entry);
  }
}

class _QueuedNotice {
  final BuildContext context;
  final String message;
  final IconData? icon;
  final Color? color;
  _QueuedNotice(this.context, this.message, this.icon, this.color);
}

class _NoticeBanner extends StatefulWidget {
  final String message;
  final IconData? icon;
  final Color? color;
  final VoidCallback onDone;

  const _NoticeBanner({
    required this.message,
    required this.icon,
    required this.color,
    required this.onDone,
  });

  @override
  State<_NoticeBanner> createState() => _NoticeBannerState();
}

class _NoticeBannerState extends State<_NoticeBanner>
    with SingleTickerProviderStateMixin {
  late final AnimationController _controller;

  @override
  void initState() {
    super.initState();
    _controller = AnimationController(
      vsync: this,
      duration: const Duration(milliseconds: 220),
      reverseDuration: const Duration(milliseconds: 180),
    );
    _controller.forward();
    Future.delayed(const Duration(milliseconds: 2600), () async {
      if (!mounted) return;
      await _controller.reverse();
      widget.onDone();
    });
  }

  @override
  void dispose() {
    _controller.dispose();
    super.dispose();
  }

  @override
  Widget build(BuildContext context) {
    final curved = CurvedAnimation(
      parent: _controller,
      curve: Curves.easeOutCubic,
      reverseCurve: Curves.easeInCubic,
    );
    final media = MediaQuery.of(context);

    final pill = Material(
      color: Colors.transparent,
      child: Container(
        constraints: const BoxConstraints(maxWidth: 360),
        padding: const EdgeInsets.symmetric(horizontal: 18, vertical: 14),
        decoration: BoxDecoration(
          color: widget.color ?? AppPalette.ink,
          borderRadius: BorderRadius.circular(999),
          boxShadow: [
            BoxShadow(
              color: Colors.black.withValues(alpha: 0.25),
              blurRadius: 16,
              offset: const Offset(0, 6),
            ),
          ],
        ),
        child: Row(
          mainAxisSize: MainAxisSize.min,
          children: [
            if (widget.icon != null) ...[
              Icon(widget.icon, color: AppPalette.paper, size: 18),
              const SizedBox(width: 8),
            ],
            Flexible(
              child: Text(
                widget.message,
                style: const TextStyle(
                  color: AppPalette.paper,
                  fontSize: 13.5,
                  fontWeight: FontWeight.w600,
                ),
              ),
            ),
          ],
        ),
      ),
    );

    final animatedPill = FadeTransition(
      opacity: curved,
      child: SlideTransition(
        position: Tween<Offset>(
          begin: kIsWeb ? const Offset(0, -0.3) : const Offset(0, 0.3),
          end: Offset.zero,
        ).animate(curved),
        child: pill,
      ),
    );

    if (kIsWeb) {
      return Positioned(
        top: media.padding.top + 16,
        left: 16,
        child: IgnorePointer(child: animatedPill),
      );
    }
    return Positioned(
      left: 16,
      right: 16,
      bottom: media.padding.bottom + 24,
      child: IgnorePointer(child: Center(child: animatedPill)),
    );
  }
}