import 'dart:async';

import 'package:flutter/material.dart';

import '../app_navigator.dart';

/// How long a non-gating placeholder stays up before closing itself —
/// short enough not to be a nuisance while testing, long enough to be
/// clearly noticed rather than flickering past.
const _autoDismissAfter = Duration(seconds: 4);

/// Stands in for a real ad while `adsEnabled` is false — see
/// lib/services/ad_config.dart for why that exists.
///
/// [mustConfirm] mirrors the difference between this app's two kinds of ad:
///  - `false` (the report-export and fuel-save interstitials): closes
///    itself after [_autoDismissAfter], the same "you didn't have to do
///    anything" feel as a plain interstitial.
///  - `true` (the cloud-sync gate): waits for the user to tap Continue,
///    standing in for a rewarded ad's watch-it-through requirement, since
///    the upload genuinely shouldn't proceed until they've acted.
///
/// Returns once the placeholder has been dismissed, so callers can treat it
/// exactly like awaiting a real ad's show-and-dismiss cycle. A no-op (and
/// an immediate return) if the navigator isn't mounted yet.
Future<void> showAdPlaceholder({required bool mustConfirm}) async {
  final navigator = navigatorKey.currentState;
  if (navigator == null) return;

  await navigator.push(
    PageRouteBuilder<void>(
      opaque: true,
      transitionDuration: const Duration(milliseconds: 180),
      pageBuilder: (_, _, _) => AdPlaceholderScreen(mustConfirm: mustConfirm),
    ),
  );
}

class AdPlaceholderScreen extends StatefulWidget {
  /// See [showAdPlaceholder] — true for the sync gate, false otherwise.
  final bool mustConfirm;

  const AdPlaceholderScreen({super.key, required this.mustConfirm});

  @override
  State<AdPlaceholderScreen> createState() => _AdPlaceholderScreenState();
}

class _AdPlaceholderScreenState extends State<AdPlaceholderScreen> {
  Timer? _ticker;
  late int _secondsLeft = _autoDismissAfter.inSeconds;

  @override
  void initState() {
    super.initState();
    if (widget.mustConfirm) return;
    _ticker = Timer.periodic(const Duration(seconds: 1), (timer) {
      if (!mounted) {
        timer.cancel();
        return;
      }
      setState(() => _secondsLeft--);
      if (_secondsLeft <= 0) _dismiss();
    });
  }

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

  void _dismiss() {
    _ticker?.cancel();
    if (mounted) Navigator.of(context).pop();
  }

  @override
  Widget build(BuildContext context) {
    final theme = Theme.of(context);
    final colors = theme.colorScheme;

    return PopScope(
      // A real ad can't be dismissed with the system back gesture either;
      // letting it through here would let the sync gate be bypassed.
      canPop: false,
      child: Scaffold(
        backgroundColor: colors.surface,
        body: SafeArea(
          child: Padding(
            padding: const EdgeInsets.all(32),
            child: Column(
              children: [
                Align(
                  alignment: Alignment.topCenter,
                  child: Text(
                    'ADVERTISEMENT',
                    style: theme.textTheme.labelSmall?.copyWith(
                      color: colors.onSurfaceVariant,
                      letterSpacing: 1.6,
                      fontWeight: FontWeight.w600,
                    ),
                  ),
                ),
                Expanded(
                  child: Center(
                    child: Column(
                      mainAxisSize: MainAxisSize.min,
                      children: [
                        Image.asset(
                          'assets/icon/hero_icon.png',
                          height: 96,
                          fit: BoxFit.contain,
                        ),
                        const SizedBox(height: 28),
                        Text(
                          'An advertisement will appear here',
                          textAlign: TextAlign.center,
                          style: theme.textTheme.titleMedium
                              ?.copyWith(fontWeight: FontWeight.w700),
                        ),
                        const SizedBox(height: 10),
                        Text(
                          'Ads are not running yet. This placeholder stands in '
                          'for one so the rest of the app behaves exactly as it '
                          'will once they are.',
                          textAlign: TextAlign.center,
                          style: theme.textTheme.bodyMedium
                              ?.copyWith(color: colors.onSurfaceVariant),
                        ),
                      ],
                    ),
                  ),
                ),
                if (widget.mustConfirm)
                  SizedBox(
                    width: double.infinity,
                    child: FilledButton(
                      onPressed: _dismiss,
                      child: const Text('Continue'),
                    ),
                  )
                else
                  Text(
                    'Closing in $_secondsLeft…',
                    style: theme.textTheme.bodySmall
                        ?.copyWith(color: colors.onSurfaceVariant),
                  ),
              ],
            ),
          ),
        ),
      ),
    );
  }
}