import 'dart:async';

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

import '../core/providers.dart';

class AutoRefresh extends ConsumerStatefulWidget {
  const AutoRefresh({super.key, required this.location, required this.child});
  final String location;
  final Widget child;

  static const pollEvery = Duration(seconds: 60);
  static const gap = Duration(seconds: 30);
  static const resumeGap = Duration(seconds: 30);

  @override
  ConsumerState<AutoRefresh> createState() => _AutoRefreshState();
}

class _AutoRefreshState extends ConsumerState<AutoRefresh>
    with WidgetsBindingObserver {
  Timer? _poll, _cool, _resumeCool;

  static const _lists = ['/results', '/shops', '/orders', '/users'];

  @override
  void initState() {
    super.initState();
    WidgetsBinding.instance.addObserver(this);
    _poll = Timer.periodic(AutoRefresh.pollEvery, (_) => _onPoll());
  }

  @override
  void dispose() {
    WidgetsBinding.instance.removeObserver(this);
    _poll?.cancel();
    _cool?.cancel();
    _resumeCool?.cancel();
    super.dispose();
  }

  bool get _onList => _lists.contains(widget.location);

  bool get _visible {
    final s = WidgetsBinding.instance.lifecycleState;
    return s == null || s == AppLifecycleState.resumed;
  }

  // False while a sheet or dialog sits on top of the screen.
  bool get _uncovered => ModalRoute.of(context)?.isCurrent ?? true;

  bool get _signedIn => ref.read(sessionProvider) != null;

  void _reload() => ref.read(dataVersionProvider.notifier).bump();

  void _onPoll() {
    if (_cool != null ||
        !_visible ||
        !_signedIn ||
        !_uncovered ||
        widget.location != '/orders') {
      return;
    }
    _reload();
  }

  @override
  void didChangeAppLifecycleState(AppLifecycleState state) {
    if (state != AppLifecycleState.resumed) return;
    if (_resumeCool != null || !_signedIn || !_onList || !_uncovered) return;
    _reload();
    _resumeCool = Timer(AutoRefresh.resumeGap, () => _resumeCool = null);
  }

  @override
  Widget build(BuildContext context) {
    // Every reload, whoever started it, restarts the quiet period.
    ref.listen(dataVersionProvider, (_, _) {
      _cool?.cancel();
      _cool = Timer(AutoRefresh.gap, () => _cool = null);
    });
    return widget.child;
  }
}