import 'dart:developer';

import 'package:barcode_scan2/barcode_scan2.dart';
import 'package:calorimeter/food_entry/food_entry_bloc.dart';
import 'package:calorimeter/perdate/perdate_pageview.dart';
import 'package:calorimeter/utils/app_drawer.dart';
import 'package:calorimeter/utils/calendar_floating_button.dart';
import 'package:calorimeter/utils/date_time_helper.dart';
import 'package:calorimeter/utils/rectangular_notch_shape.dart';
import 'package:calorimeter/utils/scan_food_floating_button.dart';
import 'package:calorimeter/utils/sum_widget.dart';
import 'package:calorimeter/utils/theme_switcher_button.dart';
import 'package:flutter/material.dart';
import 'package:intl/intl.dart';
import 'package:provider/provider.dart';

class PerDatePageViewController extends StatelessWidget {
  // this is the date for which the PerDate widget will be shown on screen
  // left of it will be yesterday's PerDate widget
  // right of it will be tomorrow's PerDate widget
  final DateTime initialDate;
  final PageController pageController;
  static final int initialOffset = 36500000;

  const PerDatePageViewController._(
      {required this.initialDate, required this.pageController});

  factory PerDatePageViewController({required initialDate}) {
    return PerDatePageViewController._(
        initialDate: initialDate,
        pageController: PageController(initialPage: initialOffset));
  }

  @override
  Widget build(BuildContext context) {
    return ChangeNotifierProvider(
      create: (context) => PageViewStateProvider(
        initialDate: initialDate,
        initialOffset: initialOffset,
      ),
      child: Builder(builder: (context) {
        return BackButtonListener(
          onBackButtonPressed: () async {
            context.read<PageViewStateProvider>().backButtonWasPressed = true;
            var visitedIndexes =
                context.read<PageViewStateProvider>().visitedIndexes;
            if (visitedIndexes.length == 1) {
              return false;
            }

            visitedIndexes.removeLast();
            pageController.jumpToPage(visitedIndexes.last);

            return true;
          },
          child: Scaffold(
            appBar: AppBar(
              title: Builder(builder: (context) {
                return Text(DateFormat.yMMMMd('de').format(
                    context.watch<PageViewStateProvider>().displayedDate));
              }),
              actions: const [ThemeSwitcherButton()],
            ),
            bottomNavigationBar: BottomAppBar(
              shape: const RectangularNotchShape(),
              color: Theme.of(context).colorScheme.secondary,
              child: Builder(builder: (context) {
                return SumWidget(
                    date: context.watch<PageViewStateProvider>().displayedDate);
              }),
            ),
            drawer: const AppDrawer(),
            floatingActionButton: OverflowBar(children: [
              ScanFoodFAB(
                onPressed: () {
                  var result = BarcodeScanner.scan();
                  context.read<FoodEntryBloc>().add(
                        BarcodeScanned(
                          scanResultFuture: result,
                          forDate: context
                              .read<PageViewStateProvider>()
                              .displayedDate,
                        ),
                      );
                },
              ),
              const SizedBox(width: 8),
              CalendarFAB(
                startFromDate: DateTimeHelper.now(),
                onDateSelected: (dateSelected) {
                  if (dateSelected == null) return;

                  var dateDiff = dateSelected.difference(initialDate).inDays;

                  log("dateDiff = $dateDiff");
                  pageController.jumpToPage(initialOffset - dateDiff);
                },
              ),
            ]),
            floatingActionButtonLocation:
                FloatingActionButtonLocation.endDocked,
            body: PerDatePageView(
              pageController: pageController,
              initialDate: initialDate,
            ),
          ),
        );
      }),
    );
  }
}

class PageViewStateProvider with ChangeNotifier {
  DateTime _displayedDate;
  final List<int> _visitedIndexes;
  bool _backButtonWasPressed = false;

  PageViewStateProvider({required DateTime initialDate, int initialOffset = 0})
      : _displayedDate = initialDate,
        _visitedIndexes = [] {
    _visitedIndexes.add(initialOffset);
  }

  set backButtonWasPressed(val) => _backButtonWasPressed = val;
  get backButtonWasPressed => _backButtonWasPressed;

  get displayedDate => _displayedDate;
  void setDisplayedDate(date) {
    _displayedDate = date;
    notifyListeners();
  }

  get visitedIndexes => _visitedIndexes;

  void addVisitedIndex(int index) {
    _visitedIndexes.add(index);
  }

  void addVisitedindexIfNotVisitedByBackButton(int index) {
    if (_backButtonWasPressed) {
      _backButtonWasPressed = false;
      return;
    }

    addVisitedIndex(index);
  }
}