using System;
using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.Diagnostics;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using WheresMyMoney.Maui.Core;

namespace WheresMyMoney.Maui;

public partial class BalanceHistoryPage : ContentPage
{
    private DateTime _nearestPayday = DateTime.MinValue;
    private decimal _balanceAmount = 0;
    public ObservableCollection<GroupedBalanceChangeViewModel> GroupedBalanceChangeViewModels { get; } = [];
    private static readonly GroupedBalanceChangeViewModel Empty = new("Pusto", []);

    public BalanceHistoryPage()
    {
        InitializeComponent();
        BindingContext = this;
        UpdateUi();
        Repository.Instance.DataChanged += OnDataChanged;
    }

    private void OnDataChanged(object? sender, EventArgs e)
    {
        UpdateUi();
    }

    private void UpdateUi()
    {
        GroupedBalanceChangeViewModels.Clear();
        var balances = Repository.Instance.GetAllBalances().GroupBy(x => x.Date.Date).OrderBy(x => x.Key);

        var now = DateTime.Now;
        _nearestPayday = Repository.Instance.GetNearestPayday(now);
        var allPlannedPayments = Repository.Instance.GetAllPlannedPayments().OrderBy(x => x.DateStart).ToList();
        var plannedPayments = allPlannedPayments.Where(x =>
                (!x.IsSubscription && x.DateStart <= _nearestPayday) ||
                (x.IsSubscription && (x.DateEnd == null || x.DateEnd >= now)))
            .SelectMany(x =>
                x.ExpandSubscription(balances.FirstOrDefault()?.Key.Date ?? DateTime.MinValue, _nearestPayday))
            .OrderBy(x => x.DateStart).ToList();
        _balanceAmount = 0;
        foreach (var balanceGroup in balances)
        {
            var balanceDate = balanceGroup.Key.Date;
            var payments = plannedPayments.Where(x => x.DateStart.Date < balanceDate).ToList();
            foreach (var paymentGroup in payments.GroupBy(x => x.DateStart.Date).OrderBy(x => x.Key))
            {
                var paymentDate = paymentGroup.Key.Date;
                var paymentVm = new GroupedBalanceChangeViewModel(paymentDate.ToString("yyyy MMMM dd"), []);
                foreach (var payment in paymentGroup)
                {
                    _balanceAmount -= payment.Amount;
                    paymentVm.BalanceChanges.Add(new BalanceChangeViewModel(payment.Name,
                        $"{(payment.Amount < 0 ? "+" : "")}{payment.Amount * -1m:C}",
                        _balanceAmount.ToString("C"), payment.Amount >= 0, _balanceAmount < 0));
                }

                GroupedBalanceChangeViewModels.Add(paymentVm);
            }

            plannedPayments = plannedPayments.Except(payments).ToList();
            var vm = new GroupedBalanceChangeViewModel(balanceDate.ToString("yyyy MMMM dd"), []);
            foreach (var thisBalanceAmount in balanceGroup.Select(x => x.Amount))
            {
                var change = thisBalanceAmount - _balanceAmount;
                _balanceAmount = thisBalanceAmount;
                vm.BalanceChanges.Add(new BalanceChangeViewModel("Zmiana salda",
                    $"{(change < 0 ? "" : "+")}{change:C}",
                    thisBalanceAmount.ToString("C"), change < 0, _balanceAmount < 0));
            }

            payments = plannedPayments.Where(x => x.DateStart.Date == balanceDate).ToList();
            foreach (var payment in payments)
            {
                _balanceAmount -= payment.Amount;
                vm.BalanceChanges.Add(new BalanceChangeViewModel(payment.Name,
                    $"{(payment.Amount < 0 ? "+" : "")}{payment.Amount * -1m:C}",
                    _balanceAmount.ToString("C"), payment.Amount >= 0, _balanceAmount < 0));
            }

            GroupedBalanceChangeViewModels.Add(vm);
            plannedPayments = plannedPayments.Except(payments).ToList();
        }

        foreach (var paymentGroup in plannedPayments.GroupBy(x => x.DateStart.Date).OrderBy(x => x.Key))
        {
            var paymentDate = paymentGroup.Key.Date;
            var paymentVm = new GroupedBalanceChangeViewModel(paymentDate.ToString("yyyy MMMM dd"), []);
            foreach (var payment in paymentGroup)
            {
                _balanceAmount -= payment.Amount;
                paymentVm.BalanceChanges.Add(new BalanceChangeViewModel(payment.Name,
                    $"{(payment.Amount < 0 ? "+" : "")}{payment.Amount * -1m:C}",
                    _balanceAmount.ToString("C"), payment.Amount >= 0, _balanceAmount < 0));
            }

            GroupedBalanceChangeViewModels.Add(paymentVm);
        }

        if (!GroupedBalanceChangeViewModels.Any())
        {
            GroupedBalanceChangeViewModels.Add(Empty);
        }
    }

    private void ItemsView_OnRemainingItemsThresholdReached(object? sender, EventArgs e)
    {
        Debug.WriteLine($"ItemsView_OnRemainingItemsThresholdReached");
        var start = _nearestPayday.AddDays(1);
        _nearestPayday = _nearestPayday.AddMonths(1);
        Debug.WriteLine($"Start: {start}");
        Debug.WriteLine($"End: {_nearestPayday}");
        var plannedPayments = Repository.Instance.GetAllPlannedPayments().Where(x =>
                (!x.IsSubscription && x.DateStart >= start && x.DateStart <= _nearestPayday) ||
                (x.IsSubscription && (x.DateEnd == null || x.DateEnd >= start)))
            .SelectMany(x => x.ExpandSubscription(start, _nearestPayday))
            .OrderBy(x => x.DateStart).ToList();

        if (GroupedBalanceChangeViewModels.FirstOrDefault() == Empty)
        {
            GroupedBalanceChangeViewModels.Clear();
        }
        foreach (var paymentGroup in plannedPayments.GroupBy(x => x.DateStart.Date).OrderBy(x => x.Key))
        {
            var paymentDate = paymentGroup.Key.Date;
            var paymentVm = new GroupedBalanceChangeViewModel(paymentDate.ToString("yyyy MMMM dd"), []);
            foreach (var payment in paymentGroup)
            {
                _balanceAmount -= payment.Amount;
                paymentVm.BalanceChanges.Add(new BalanceChangeViewModel(payment.Name,
                    $"{(payment.Amount < 0 ? "+" : "")}{payment.Amount * -1m:C}",
                    _balanceAmount.ToString("C"), payment.Amount >= 0, _balanceAmount < 0));
            }

            GroupedBalanceChangeViewModels.Add(paymentVm);
        }
        if (!GroupedBalanceChangeViewModels.Any())
        {
            GroupedBalanceChangeViewModels.Add(Empty);
        }
    }
}

public record GroupedBalanceChangeViewModel(string DateText, List<BalanceChangeViewModel> BalanceChanges);

public record BalanceChangeViewModel(
    string Name,
    string AmountText,
    string BalanceText,
    bool IsPayment,
    bool IsBalanceNegative);