Initial commit

Decho/ViewModels/ChannelViewModel.cs

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+using System.Collections.ObjectModel;
+using System.Linq;
+
+using Decho.Models;
+
+namespace Decho.ViewModels;
+
+public sealed class ChannelViewModel : ViewModelBase
+{
+    public ChannelViewModel(ChannelModel model)
+    {
+        Model = model;
+        Messages = new ObservableCollection<MessageViewModel>(
+            model.Messages.Select(message => new MessageViewModel(message)));
+    }
+
+    public ChannelModel Model { get; }
+
+    public string Name => Model.Name;
+
+    public ObservableCollection<MessageViewModel> Messages { get; }
+
+    public void AddMessage(MessageModel message)
+    {
+        Model.Messages.Add(message);
+        Messages.Add(new MessageViewModel(message));
+    }
+}

Decho/ViewModels/ChatViewModel.cs

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+using System.Collections.ObjectModel;
+
+namespace Decho.ViewModels;
+
+public sealed class ChatViewModel : ViewModelBase
+{
+    private ObservableCollection<MessageViewModel> _messages = new();
+    private string _channelTitle = "Select a channel";
+
+    public ChatViewModel()
+    {
+        Composer = new MessageComposerViewModel();
+    }
+
+    public ObservableCollection<MessageViewModel> Messages
+    {
+        get => _messages;
+        private set => this.RaiseAndSetIfChanged(ref _messages, value);
+    }
+
+    public string ChannelTitle
+    {
+        get => _channelTitle;
+        private set => this.RaiseAndSetIfChanged(ref _channelTitle, value);
+    }
+
+    public MessageComposerViewModel Composer { get; }
+
+    public void SetChannel(ChannelViewModel? channel)
+    {
+        if (channel is null)
+        {
+            Messages = new ObservableCollection<MessageViewModel>();
+            ChannelTitle = "Select a channel";
+            return;
+        }
+
+        Messages = channel.Messages;
+        ChannelTitle = "#" + channel.Name;
+    }
+}

Decho/ViewModels/MainWindowViewModel.cs

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+using System;
+using System.Collections.Generic;
+using System.Collections.ObjectModel;
+using System.Reactive.Linq;
+
+using Decho.Models;
+using ReactiveUI;
+
+namespace Decho.ViewModels;
+
+public sealed class MainWindowViewModel : ViewModelBase
+{
+    private readonly UserModel _currentUser;
+
+    public string Title { get; } = "Decho";
+
+    public SidebarViewModel Sidebar { get; }
+
+    public ChatViewModel Chat { get; }
+
+    public MainWindowViewModel()
+    {
+        _currentUser = new UserModel("user-1", "You");
+
+        var servers = SeedServers();
+        Sidebar = new SidebarViewModel(servers);
+        Chat = new ChatViewModel();
+
+        Sidebar.WhenAnyValue(x => x.SelectedChannel)
+            .Subscribe(channel => Chat.SetChannel(channel));
+
+        Chat.Composer.SendRequested += HandleSendRequested;
+
+        if (Sidebar.SelectedChannel is not null)
+            Chat.SetChannel(Sidebar.SelectedChannel);
+    }
+
+    private void HandleSendRequested(string text)
+    {
+        if (Sidebar.SelectedChannel is null)
+            return;
+
+        var message = new MessageModel(
+            Guid.NewGuid().ToString("N"),
+            _currentUser,
+            DateTimeOffset.Now,
+            text);
+
+        Sidebar.SelectedChannel.AddMessage(message);
+    }
+
+    private static IReadOnlyList<ServerModel> SeedServers()
+    {
+        var alex = new UserModel("user-2", "Alex");
+        var sam = new UserModel("user-3", "Sam");
+
+        var general = new ChannelModel(
+            "channel-1",
+            "general",
+            new ObservableCollection<MessageModel>
+            {
+                new("message-1", alex, DateTimeOffset.Now.AddMinutes(-30), "This is a message."),
+                new("message-2", sam, DateTimeOffset.Now.AddMinutes(-25), "Another message for the channel."),
+                new("message-3", alex, DateTimeOffset.Now.AddMinutes(-10), "We should test the new layout."),
+            });
+
+        var random = new ChannelModel(
+            "channel-2",
+            "random",
+            new ObservableCollection<MessageModel>
+            {
+                new("message-4", sam, DateTimeOffset.Now.AddMinutes(-5), "Random chat keeps the vibe light."),
+            });
+
+        var music = new ChannelModel(
+            "channel-3",
+            "music",
+            new ObservableCollection<MessageModel>());
+
+        var server = new ServerModel(
+            "server-1",
+            "Server",
+            new ObservableCollection<ChannelModel> { general, random });
+
+        var anotherServer = new ServerModel(
+            "server-2",
+            "Another Server",
+            new ObservableCollection<ChannelModel>() { general, music});
+
+        return new[] { server, anotherServer };
+    }
+}

Decho/ViewModels/MessageComposerViewModel.cs

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+using System;
+using System.Reactive;
+using System.Reactive.Linq;
+
+using ReactiveUI;
+
+namespace Decho.ViewModels;
+
+public sealed class MessageComposerViewModel : ViewModelBase
+{
+    private string _draft = string.Empty;
+
+    public MessageComposerViewModel()
+    {
+        var canSend = this.WhenAnyValue(x => x.Draft, draft => !string.IsNullOrWhiteSpace(draft));
+        SendCommand = ReactiveCommand.Create(Send, canSend);
+    }
+
+    public string Draft
+    {
+        get => _draft;
+        set => this.RaiseAndSetIfChanged(ref _draft, value);
+    }
+
+    public ReactiveCommand<Unit, Unit> SendCommand { get; }
+
+    public event Action<string>? SendRequested;
+
+    private void Send()
+    {
+        var text = Draft.Trim();
+        if (string.IsNullOrWhiteSpace(text))
+            return;
+
+        Draft = string.Empty;
+        SendRequested?.Invoke(text);
+    }
+}

Decho/ViewModels/MessageViewModel.cs

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+using Decho.Models;
+
+namespace Decho.ViewModels;
+
+public sealed class MessageViewModel : ViewModelBase
+{
+    public MessageViewModel(MessageModel model)
+    {
+        Model = model;
+    }
+
+    public MessageModel Model { get; }
+
+    public string AuthorName => Model.Author.DisplayName;
+
+    public string Content => Model.Content;
+
+    public string TimeText => Model.SentAt.ToLocalTime().ToString("h:mm tt");
+}

Decho/ViewModels/ServerViewModel.cs

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+using System.Collections.ObjectModel;
+using System.Linq;
+
+using Decho.Models;
+
+namespace Decho.ViewModels;
+
+public sealed class ServerViewModel : ViewModelBase
+{
+    private bool _isExpanded = true;
+    private ChannelViewModel? _selectedChannel;
+
+    public ServerViewModel(ServerModel model)
+    {
+        Model = model;
+        Channels = new ObservableCollection<ChannelViewModel>(
+            model.Channels.Select(channel => new ChannelViewModel(channel)));
+    }
+
+    public ServerModel Model { get; }
+
+    public string Name => Model.Name;
+
+    public ObservableCollection<ChannelViewModel> Channels { get; }
+
+    public ChannelViewModel? SelectedChannel
+    {
+        get => _selectedChannel;
+        set => this.RaiseAndSetIfChanged(ref _selectedChannel, value);
+    }
+
+    public bool IsExpanded
+    {
+        get => _isExpanded;
+        set => this.RaiseAndSetIfChanged(ref _isExpanded, value);
+    }
+}

Decho/ViewModels/SidebarViewModel.cs

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+using System;
+using System.Collections.Generic;
+using System.Collections.ObjectModel;
+using System.Linq;
+using System.Reactive.Linq;
+
+using Decho.Models;
+using ReactiveUI;
+
+namespace Decho.ViewModels;
+
+public sealed class SidebarViewModel : ViewModelBase
+{
+    private ChannelViewModel? _selectedChannel;
+
+    public SidebarViewModel(IEnumerable<ServerModel> servers)
+    {
+        Servers = new ObservableCollection<ServerViewModel>(
+            servers.Select(server => new ServerViewModel(server)));
+        SelectedChannel = Servers.FirstOrDefault()?.Channels.FirstOrDefault();
+
+        foreach (var server in Servers)
+        {
+            server.WhenAnyValue(s => s.SelectedChannel)
+                .Where(channel => channel is not null)
+                .Subscribe(new Action<ChannelViewModel?>(channel => SelectedChannel = channel!));
+        }
+    }
+
+    public ObservableCollection<ServerViewModel> Servers { get; }
+
+    public ChannelViewModel? SelectedChannel
+    {
+        get => _selectedChannel;
+        set
+        {
+            if (ReferenceEquals(_selectedChannel, value))
+                return;
+
+            this.RaiseAndSetIfChanged(ref _selectedChannel, value);
+
+            if (value is null)
+                return;
+
+            foreach (var server in Servers)
+            {
+                if (server.Channels.Contains(value))
+                {
+                    if (!ReferenceEquals(server.SelectedChannel, value))
+                        server.SelectedChannel = value;
+                }
+                else if (server.SelectedChannel is not null)
+                {
+                    server.SelectedChannel = null;
+                }
+            }
+        }
+    }
+}

Decho/ViewModels/ViewModelBase.cs

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+using ReactiveUI;
+
+namespace Decho.ViewModels;
+
+public abstract class ViewModelBase : ReactiveObject
+{
+}