presence_sample_v2/Presence.Desktop/ViewModels/GroupViewModel.cs

using domain.UseCase;
using DynamicData;
using DynamicData.Binding;
using Presence.Desktop.Models;
using ReactiveUI;
using System;
using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.Linq;
using System.Reactive.Linq;
using Tmds.DBus.Protocol;

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;


        private IGroupUseCase _groupUseCase;
        public ObservableCollection<UserPresenter> Users { get => _users;}
        public ObservableCollection<UserPresenter> _users;
        public GroupViewModel(IGroupUseCase groupUseCase)
        {
            _groupUseCase = groupUseCase;
            _users = new ObservableCollection<UserPresenter>();
            RefreshGroups();
            this.WhenAnyValue(vm => vm.SelectedGroupItem)
                .Subscribe(_ =>
                {   RefreshGroups();
                    SetUsers();
                });

        }

        private void SetUsers()
        {
            if(SelectedGroupItem == null) return;
            Users.Clear();
            var group = _groups.First(it => it.Id == SelectedGroupItem.Id);
            if(group.users == null) return;
            foreach (var item in group.users)
            {
                Users.Add(item);
            }
        }

        private void RefreshGroups()
        {
            _groupPresentersDataSource.Clear();
            foreach (var item in _groupUseCase.GetGroupsWithStudents())
            {
                GroupPresenter groupPresenter = new GroupPresenter
                {
                    Id = item.Id,
                    Name = item.Name,
                    users = item.Users?.Select(user => new UserPresenter
                        {
                            Name = user.Name,
                            Guid = user.Guid,
                            Group = new GroupPresenter { Id = item.Id, Name = item.Name }
                        }
                    ).ToList()
                };
                _groupPresentersDataSource.Add(groupPresenter);
            }
            _groups = new ObservableCollection<GroupPresenter>(_groupPresentersDataSource);
        }
        public string? UrlPathSegment { get; }
        public IScreen HostScreen { get; }
    }
}