using System.Collections.ObjectModel;
using CommunityToolkit.Mvvm.ComponentModel;
using CommunityToolkit.Mvvm.Input;
using LehrerApp.Core.Interfaces;
using LehrerApp.Core.Models;
using LehrerApp.Desktop.Services;

namespace LehrerApp.Desktop.ViewModels.Planning;

public sealed record WebUntisGroupOption(Guid Id, string DisplayName);

public partial class WebUntisTimetableRow : ObservableObject
{
    public required DayOfWeek Weekday { get; init; }
    public required int PeriodNumber { get; init; }
    public required string TimeLabel { get; init; }
    public required string UntisLabel { get; init; }
    public required string SuggestedGroupName { get; init; }
    public string? SubjectName { get; init; }
    public string? Room { get; init; }
    public ObservableCollection<WebUntisGroupOption> GroupOptions { get; } = [];
    [ObservableProperty] private WebUntisGroupOption? _selectedGroup;
    public string WeekdayLabel => Weekday switch
    {
        DayOfWeek.Monday => "Mo", DayOfWeek.Tuesday => "Di", DayOfWeek.Wednesday => "Mi",
        DayOfWeek.Thursday => "Do", DayOfWeek.Friday => "Fr", _ => Weekday.ToString()[..2],
    };
}

public partial class WebUntisTimetableImportViewModel : ObservableObject
{
    private readonly WebUntisIntegrationService _untis;
    private readonly WebUntisSettingsService _settings;
    private readonly ITimetableSlotRepository _slots;
    private readonly IGroupRepository _groups;

    public ObservableCollection<UntisTeacherDto> Teachers { get; } = [];
    public ObservableCollection<WebUntisTimetableRow> Rows { get; } = [];
    [ObservableProperty] private UntisTeacherDto? _selectedTeacher;
    [ObservableProperty] private DateTimeOffset? _weekDate = DateTimeOffset.Now;
    [ObservableProperty] private string _status = "Lehrkraft auswählen und Untis-Woche laden.";
    [ObservableProperty] private bool _busy;
    public bool Saved { get; private set; }
    public Func<WebUntisTimetableRow, Task<LearningGroup?>>? OnCreateGroup { get; set; }

    public WebUntisTimetableImportViewModel(WebUntisIntegrationService untis, WebUntisSettingsService settings,
        ITimetableSlotRepository slots, IGroupRepository groups)
    {
        _untis = untis; _settings = settings; _slots = slots; _groups = groups;
    }

    public async Task InitializeAsync()
    {
        Busy = true;
        try
        {
            foreach (var teacher in (await _untis.GetTeachersAsync()).Where(x => x.Active).OrderBy(x => x.DisplayName))
                Teachers.Add(teacher);
            SelectedTeacher = Teachers.FirstOrDefault(x => x.UntisId == _settings.TeacherUntisId)
                              ?? Teachers.FirstOrDefault();
            Status = Teachers.Count == 0 ? "WebUntis hat keine Lehrkräfte geliefert." : "Bereit zum Laden.";
        }
        catch (WebUntisIntegrationException ex) { Status = ex.Message; }
        finally { Busy = false; }
    }

    [RelayCommand]
    private async Task Load()
    {
        if (SelectedTeacher is null) { Status = "Bitte eine Lehrkraft auswählen."; return; }
        Busy = true; Rows.Clear();
        try
        {
            var selected = DateOnly.FromDateTime((WeekDate ?? DateTimeOffset.Now).LocalDateTime);
            var monday = selected.AddDays(-(((int)selected.DayOfWeek + 6) % 7));
            var periods = await _untis.GetTimetableAsync(SelectedTeacher.UntisId, monday, monday.AddDays(6));
            var grid = await _untis.GetTimeGridAsync();
            var groupOptions = BuildGroupOptions();
            var localSlots = _slots.GetAll().ToDictionary(x => (x.Weekday, x.PeriodNumber));

            foreach (var period in periods.Where(x => string.IsNullOrWhiteSpace(x.Code) || x.Code != "cancelled")
                         .GroupBy(x => (x.Date, x.StartTime, x.EndTime, x.StudentGroup,
                             Class: string.Join("/", x.Classes.Select(c => c.Name)),
                             Subject: string.Join("/", x.Subjects.Select(s => s.Name)),
                             Room: string.Join("/", x.Rooms.Select(r => r.Name))))
                         .Select(x => x.First()).OrderBy(x => x.Date).ThenBy(x => x.StartTime))
            {
                if (!TryDate(period.Date, out var date) || date.DayOfWeek is DayOfWeek.Saturday or DayOfWeek.Sunday)
                    continue;
                var dayGrid = grid.FirstOrDefault(x => x.Day == UntisDay(date.DayOfWeek));
                var number = dayGrid?.TimeUnits.ToList().FindIndex(x => x.StartTime == period.StartTime) + 1 ?? 0;
                if (number <= 0) continue;
                var className = period.Classes.FirstOrDefault()?.Name ?? "";
                var subject = period.Subjects.FirstOrDefault()?.Name;
                var suggested = !string.IsNullOrWhiteSpace(period.StudentGroup) ? period.StudentGroup! : className;
                var row = new WebUntisTimetableRow
                {
                    Weekday = date.DayOfWeek, PeriodNumber = number,
                    TimeLabel = $"{Time(period.StartTime)}–{Time(period.EndTime)}",
                    UntisLabel = string.Join(" · ", new[] { subject, suggested, period.Rooms.FirstOrDefault()?.Name }
                        .Where(x => !string.IsNullOrWhiteSpace(x))),
                    SuggestedGroupName = suggested, SubjectName = subject,
                    Room = period.Rooms.FirstOrDefault()?.Name,
                };
                foreach (var option in groupOptions) row.GroupOptions.Add(option);
                if (localSlots.TryGetValue((row.Weekday, row.PeriodNumber), out var existing))
                    row.SelectedGroup = groupOptions.FirstOrDefault(x => x.Id == existing.GroupId);
                row.SelectedGroup ??= BestMatch(groupOptions, suggested, className, subject);
                Rows.Add(row);
            }
            _settings.SetTeacherUntisId(SelectedTeacher.UntisId);
            Status = Rows.Count == 0 ? "In dieser Woche wurde kein Unterricht gefunden."
                : $"{Rows.Count} regelmäßige Termine gefunden. Zuordnung prüfen und übernehmen.";
        }
        catch (WebUntisIntegrationException ex) { Status = ex.Message; }
        finally { Busy = false; }
    }

    [RelayCommand]
    private async Task CreateGroup(WebUntisTimetableRow row)
    {
        if (OnCreateGroup is null) return;
        var group = await OnCreateGroup(row);
        if (group is null) return;
        var option = new WebUntisGroupOption(group.Id, group.Name);
        foreach (var item in Rows.Where(x => x.SuggestedGroupName == row.SuggestedGroupName))
        {
            item.GroupOptions.Add(option);
            item.SelectedGroup = option;
        }
    }

    [RelayCommand]
    private void Save()
    {
        var selected = Rows.Where(x => x.SelectedGroup is not null).ToList();
        foreach (var row in selected)
        {
            var existing = _slots.GetAll().FirstOrDefault(x => x.Weekday == row.Weekday && x.PeriodNumber == row.PeriodNumber);
            var slot = existing ?? new TimetableSlot { Weekday = row.Weekday, PeriodNumber = row.PeriodNumber };
            slot.GroupId = row.SelectedGroup!.Id;
            slot.Room = string.IsNullOrWhiteSpace(row.Room) ? null : row.Room;
            _slots.Save(slot);
        }
        Saved = true;
        Status = $"{selected.Count} Stundenplan-Einträge übernommen.";
    }

    private List<WebUntisGroupOption> BuildGroupOptions() => _groups.GetAll().OrderBy(x => x.Name)
        .Select(x => new WebUntisGroupOption(x.Id, x.Name)).ToList();

    private static WebUntisGroupOption? BestMatch(IEnumerable<WebUntisGroupOption> options, params string?[] terms) =>
        options.FirstOrDefault(x => terms.Any(term => !string.IsNullOrWhiteSpace(term) &&
            (x.DisplayName.Equals(term, StringComparison.OrdinalIgnoreCase) ||
             x.DisplayName.Contains(term, StringComparison.OrdinalIgnoreCase))));
    private static int UntisDay(DayOfWeek day) => day == DayOfWeek.Sunday ? 7 : (int)day;
    private static bool TryDate(int value, out DateOnly date) => DateOnly.TryParseExact(value.ToString(), "yyyyMMdd", out date);
    private static string Time(int value) => $"{value / 100:00}:{value % 100:00}";
}