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

import '../../core/i18n/app_locale.dart';
import '../../core/theme/tokens.dart';

/// 1회성 로컬 Coach Mark — 9/21 회신서 ④-2 A · 10/3 통합회신 1항 · 해석 확인 Q-OB-02 A.
///
/// 온보딩 6단계를 마치면 [armCoachMark] 가 이 기기에 「대기」를 남기고, 그 뒤 처음 ZAP 이 보이는
/// HOME 에서 [maybeShowCoachMark] 가 2단계(① Zap 버튼 ② 하단 탭 MY)를 띄운 뒤 지운다.
/// 서버 데이터는 없다(단말당 1회 · 재설치하면 다시 나올 수 있다).
const _pendingKey = 'coach.pending';

/// 하단 탭 MY 아이콘 위치를 찾는 열쇠 — `AppShell` 이 단다.
final coachMyTabKey = GlobalKey(debugLabel: 'coach-my-tab');

Future<void> armCoachMark() async {
  try {
    await (await SharedPreferences.getInstance()).setBool(_pendingKey, true);
  } catch (_) {}
}

Future<void> maybeShowCoachMark(BuildContext context, GlobalKey zapKey) async {
  SharedPreferences prefs;
  try {
    prefs = await SharedPreferences.getInstance();
  } catch (_) {
    return;
  }
  if (prefs.getBool(_pendingKey) != true || !context.mounted) return;
  final zap = _rectOf(zapKey);
  if (zap == null) return; // ZAP 이 없는 HOME(무소속) — 가입한 뒤 다시 본다.
  await prefs.setBool(_pendingKey, false);
  if (!context.mounted) return;
  // 하단 탭 MY — 셸이 MY 목적지 아이콘에 [coachMyTabKey] 를 단다. 못 찾으면 ①만 보인다.
  final my = _rectOf(coachMyTabKey)?.inflate(12);
  final l10n = context.l10n;
  await showGeneralDialog<void>(
    context: context,
    barrierColor: Colors.transparent,
    pageBuilder: (_, _, _) => _CoachOverlay(
      steps: [
        (zap.inflate(8), l10n.coachZap),
        if (my != null) (my, l10n.coachMy),
      ],
    ),
  );
}

Rect? _rectOf(GlobalKey key) {
  final box = key.currentContext?.findRenderObject() as RenderBox?;
  if (box == null || !box.hasSize) return null;
  return box.localToGlobal(Offset.zero) & box.size;
}

class _CoachOverlay extends StatefulWidget {
  const _CoachOverlay({required this.steps});

  final List<(Rect, String)> steps;

  @override
  State<_CoachOverlay> createState() => _CoachOverlayState();
}

class _CoachOverlayState extends State<_CoachOverlay> {
  int _i = 0;

  void _next() => _i + 1 < widget.steps.length
      ? setState(() => _i++)
      : Navigator.of(context).pop();

  @override
  Widget build(BuildContext context) {
    final (hole, text) = widget.steps[_i];
    final above = hole.center.dy > MediaQuery.sizeOf(context).height / 2;
    return Stack(
      children: [
        Positioned.fill(
          child: GestureDetector(
            onTap: _next,
            child: CustomPaint(painter: _Dim(hole)),
          ),
        ),
        Positioned(
          left: 24,
          right: 24,
          top: above ? null : hole.bottom + 16,
          bottom: above
              ? MediaQuery.sizeOf(context).height - hole.top + 16
              : null,
          child: Material(
            color: AppColors.cosmicSurfaceContainer,
            borderRadius: BorderRadius.circular(AppRadius.md),
            child: Padding(
              padding: const EdgeInsets.all(AppSpace.s4),
              child: Column(
                mainAxisSize: MainAxisSize.min,
                crossAxisAlignment: CrossAxisAlignment.stretch,
                children: [
                  Text(
                    text,
                    style: const TextStyle(
                      fontFamily: AppFonts.body,
                      fontSize: 16,
                      fontWeight: FontWeight.w600,
                      color: AppColors.onCosmic,
                    ),
                  ),
                  const SizedBox(height: AppSpace.s3),
                  Row(
                    mainAxisAlignment: MainAxisAlignment.end,
                    children: [
                      TextButton(
                        onPressed: () => Navigator.of(context).pop(),
                        child: Text(context.l10n.onbSkip),
                      ),
                      FilledButton(
                        onPressed: _next,
                        style: FilledButton.styleFrom(
                          backgroundColor: AppColors.cosmicAccent,
                          foregroundColor: AppColors.onCosmicAccent,
                        ),
                        child: Text(
                          _i + 1 < widget.steps.length
                              ? context.l10n.commonNext
                              : context.l10n.commonConfirm,
                        ),
                      ),
                    ],
                  ),
                ],
              ),
            ),
          ),
        ),
      ],
    );
  }
}

/// 나머지 화면은 어둡게, 가리킨 곳만 둥글게 뚫는다.
class _Dim extends CustomPainter {
  const _Dim(this.hole);

  final Rect hole;

  @override
  void paint(Canvas canvas, Size size) {
    final path = Path()
      ..fillType = PathFillType.evenOdd
      ..addRect(Offset.zero & size)
      ..addRRect(RRect.fromRectAndRadius(hole, const Radius.circular(16)));
    canvas.drawPath(
      path,
      Paint()..color = Colors.black.withValues(alpha: 0.72),
    );
  }

  @override
  bool shouldRepaint(_Dim old) => old.hole != hole;
}