presence/Presence.Desktop/ViewModels/GroupViewModel.cs

using Demo.Domain.UseCase;
using Presence.Desktop.Models;
using ReactiveUI;
using System;
using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.Linq;
using System.Reactive;
using System.Reactive.Linq;
using Avalonia.Controls;
using System.IO;
using Demo.Domain.Models;

namespace Presence.Desktop.ViewModels
{
    public class GroupViewModel : ViewModelBase, IRoutableViewModel
    {
        private readonly List<GroupPresenter> _groupPresentersDataSource = new List<GroupPresenter>();
        private ObservableCollection<GroupPresenter> _groups;
        public ObservableCollection<GroupPresenter> Groups => _groups;

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

        private GroupPresenter? _selectedGroupItem;

        public ReactiveCommand<Unit, Unit> DeleteUsersByGroupCommand { get; }

        public ReactiveCommand<Unit, Unit> ImportStudentsCommand { get; }

        public ObservableCollection<UserPresenter> Users { get => _users;}
        public ObservableCollection<UserPresenter> _users;

        public GroupViewModel(IGroupUseCase groupUseCase, IUserUseCase userUseCase)
        {
            foreach (var item in groupUseCase.GetAllGroupsWithUsers())
            {
                GroupPresenter groupPresenter = new GroupPresenter
                {
                    Id = item.ID,
                    Name = item.Name,
                    users = item.Users?.Select(user => new UserPresenter
                    {
                        Name = user.FIO,
                        Guid = user.Guid,
                        Group = new GroupPresenter { Id = item.ID, Name = item.Name }
                    }
                    ).ToList()
                };
                _groupPresentersDataSource.Add(groupPresenter);
            }
            _groups = new ObservableCollection<GroupPresenter>(_groupPresentersDataSource);
            
            _users = new ObservableCollection<UserPresenter>();

            DeleteUsersByGroupCommand = ReactiveCommand.Create(() => DeleteUsersByGroupID(userUseCase));

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

            ImportStudentsCommand = ReactiveCommand.CreateFromTask(async () =>
            {
                var openFileDialog = new OpenFileDialog
                {
                    Filters = new List<FileDialogFilter>
                    {
                        new FileDialogFilter { Name = "CSV Files", Extensions = { "csv" } }
                    },
                    AllowMultiple = false
                };

                var result = await openFileDialog.ShowAsync(new Window());
                if (result?.Length > 0) {
                    var filePath = result[0];
                    ImportStudents(filePath, userUseCase);
                }
            });
        }

        private void ImportStudents(string filePath, IUserUseCase userUseCase)
        {
            if (SelectedGroupItem == null || SelectedGroupItem.Id == null)
            {
                return;
            }
            var lines = File.ReadAllLines(filePath);

            foreach (var line in lines.Skip(1))
            {
                var columns = line.Split(',');
                if (columns.Length < 1) continue;

                var fio = columns[0];

                var newUser = new User
                {
                    FIO = fio,
                    Group = new Group
                    {
                        Name = SelectedGroupItem.Name,
                        ID = SelectedGroupItem.Id
                    }
                };

                var result = userUseCase.CreateUser(newUser);

                if (result)
                {
                    var userPresenter = new UserPresenter
                    {
                        Name = fio,
                        Guid = Guid.NewGuid(),
                        Group = SelectedGroupItem
                    };
                    _users.Add(userPresenter);
                }
            }
        }

        private void DeleteUsersByGroupID(IUserUseCase userUseCase) {

            if (SelectedGroupItem == null)
                return;

            var groupID = SelectedGroupItem.Id;
            bool res = userUseCase.RemoveUsersByGroupID(groupID);

            if (res) {
                Users.Clear();
            }
        }

        private void SetUsers()
        {
            if(SelectedGroupItem == null) return;
            if (SelectedGroupItem.users == null) return;
            Users.Clear();
            foreach (var item in SelectedGroupItem.users)
            {
                Users.Add(item);
            }
        }

        public string? UrlPathSegment { get; }
        public IScreen HostScreen { get; }
    }
}