presence/Presence.Desktop/ViewModels/MainWindowViewModel.cs

using domain.UseCase;
using Presence.Desktop.Models;
using System;
using System.Linq;
using ReactiveUI;
using System.Collections.Generic;
using System.Collections.ObjectModel;

namespace Presence.Desktop.ViewModels
{
    public class MainWindowViewModel : ViewModelBase
    {
        private readonly IGroupUseCase _groupService;
        private List<GroupPresenter> groupPresenters = new List<GroupPresenter>();
        private ObservableCollection<GroupPresenter> _groups;
        public ObservableCollection<GroupPresenter> Groups
        {
            get => _groups;
            set => this.RaiseAndSetIfChanged(ref _groups, value);
        }

        private GroupPresenter? _selectedGroupItem;
        public GroupPresenter? SelectedGroupItem
        {
            get => _selectedGroupItem;
            set => this.RaiseAndSetIfChanged(ref _selectedGroupItem, value);
        }

        private ObservableCollection<StudentPresenter> _students;
        public ObservableCollection<StudentPresenter> Students
        {
            get => _students;
            set => this.RaiseAndSetIfChanged(ref _students, value);
        }

        public MainWindowViewModel()
        {
            _groupService = null;
            _groups = new();
            _students = new();
        }

        public MainWindowViewModel(IGroupUseCase gService, IGroupUseCase groupService, ObservableCollection<GroupPresenter> groups, ObservableCollection<StudentPresenter> students)
        {
            _groupService = gService;

            foreach (var item in _groupService.GetGroupsWithStudents())
            {
                GroupPresenter groupPresenter = new GroupPresenter
                {
                    Id = item.Id,
                    Name = item.Name,
                    students = item.Users?.Select(u => new StudentPresenter
                    {
                        Id = u.Id,
                        FirstName = u.FirstName,
                        LastName = u.LastName,
                        Patronymic = u.Patronymic,
                        Group = new GroupPresenter
                        {
                            Id = item.Id,
                            Name = item.Name
                        }
                    })
                };
                groupPresenters.Add(groupPresenter);
            }

            _groups = new(groupPresenters);

            _students = new();

            this.WhenAnyValue(vm => vm.SelectedGroupItem)
                .Subscribe(_ => SetStudents());
        }

        private void SetStudents()
        {
            if (SelectedGroupItem == null) return;
            if (SelectedGroupItem.students == null) return;

            Students.Clear();

            foreach (var student in SelectedGroupItem.students)
                Students.Add(student);
        }

    }
}