Refactor code to remove unused variables and add new features

- Remove unused private variable in Profile class
- Add a new public method to ObservableCollectionExtensions class that removes the last N elements from an observable collection
- Add a new string resource for "No recent posts" in en.json file
- Modify the Profile class to use a placeholder image if no picture is available, or generate one with the user's name if it is available.
- Modify MainViewModel class to limit the number of posts displayed on screen by removing old ones when there are more than 100 posts.
- Modify LoginView.xaml file to make password entry field hidden while typing
- Add event handler for UnreadBtn_Clicked event in MainView.xaml.cs file.

src/NuSocial/Core/UsefulExtensions.cs

@@ -1,13 +1,25 @@
-using System;
-using System.Collections.Generic;
-using System.Linq;
-using System.Text;
-using System.Threading.Tasks;
-
-namespace NuSocial.Core
+namespace NuSocial.Core
 {
-    internal static class UsefulExtensions
+    public static class ObservableCollectionExtensions
     {
+        public static void RemoveLastN<T>(this ObservableCollection<T> collection, int n)
+        {
+            if (collection == null)
+            {
+                throw new ArgumentNullException(nameof(collection));
+            }
+
+            if (n < 0)
+            {
+                throw new ArgumentOutOfRangeException(nameof(n), "n must be non-negative");
+            }
+
+            int removeCount = Math.Min(n, collection.Count);
 
+            for (int i = 0; i < removeCount; i++)
+            {
+                collection.RemoveAt(collection.Count - 1);
+            }
+        }
     }
 }

src/NuSocial/Localization/NuSocial/en.json

@@ -17,6 +17,7 @@
     "AccountKeyPlaceholder": "nsec1...",
     "NuSocial": "NuSocial",
     "TapToRegenerate": "Tap to regenerate",
-    "WelcomeText": "#nostr NuSocial: Your Universe, Nu Connections"
+    "WelcomeText": "#nostr NuSocial: Your Universe, Nu Connections",
+    "NoRecentPosts": "No recent posts"
   }
 }

src/NuSocial/Models/User.cs

@@ -32,15 +32,15 @@ public string PrivateKeyString
 
 public class Profile
 {
-    private string? _picture;
+    private string? _picture = "https://placehold.co/60x60";
 
     public string Name { get; internal set; } = string.Empty;
     public string? DisplayName { get; internal set; }
     public string? Picture
     {
         get
         {
-            if (string.IsNullOrEmpty(_picture))
+            if (string.IsNullOrEmpty(_picture) || (_picture.Equals("https://placehold.co/60x60", StringComparison.OrdinalIgnoreCase) && !string.IsNullOrEmpty(Name)))
             {
                 _picture = $"https://placehold.co/60x60?text={Name}";
             }
@@ -70,11 +70,8 @@ public class UserConfiguration
 }
 
 /// <summary>
-/// A simple model for a contact.
+/// A contact on the #nostr network
 /// </summary>
-/// <param name="Name">Gets the name of the contact.</param>
-/// <param name="Email">Gets the email of the contact.</param>
-/// <param name="Picture">Gets the picture of the contact.</param>
 public sealed record Contact
 {
     [JsonPropertyName("name")]

src/NuSocial/ViewModels/MainViewModel.cs

@@ -1,5 +1,6 @@
 using CommunityToolkit.Mvvm.Messaging;
 using Nostr.Client.Messages;
+using NuSocial.Core;
 using NuSocial.Core.ViewModel;
 using NuSocial.Messages;
 using System.Collections.Immutable;
@@ -12,6 +13,7 @@ public partial class MainViewModel : BaseViewModel, ITransientDependency, IDispo
 {
     private readonly IAuthorService _authorService;
     private CancellationTokenSource? _cts = new();
+    private const int _postThreshold = 100;
 
     [ObservableProperty]
     private ObservableCollection<Post> _posts = new();
@@ -143,8 +145,14 @@ private Task UpdatePostsAsync()
         return SetBusyAsync(() =>
         {
             var posts = _postsWaiting.ToImmutableList();
+
             _postsWaiting.Clear();
             OnPropertyChanged(nameof(UnreadLabel));
+
+            if (Posts.Count > _postThreshold)
+            {
+                Posts.RemoveLastN(posts.Count);
+            }
             foreach (var post in posts)
             {
                 Posts.AddFirst(post);

src/NuSocial/Views/LoginView.xaml

@@ -19,6 +19,7 @@
         <Label Text="Enter your account key to login:" VerticalOptions="Center" />
         <Entry
             Grid.Row="1"
+            IsPassword="True"
             Placeholder="{loc:Translate AccountKeyPlaceholder}"
             Text="{Binding AccountKey}" />
         <Button

src/NuSocial/Views/MainView.xaml

@@ -160,7 +160,7 @@
                 CornerRadius="5"
                 IsEnabled="{Binding IsNotBusy}"
                 Style="{StaticResource PrimaryActionButtonStyle}"
-                Text="{Binding UnreadLabel}" />
+                Text="{Binding UnreadLabel}" x:Name="UnreadBtn" Clicked="UnreadBtn_Clicked" />
         </Grid>
         <RefreshView Grid.Row="1" Command="{Binding RefreshCommand}">
             <CollectionView

src/NuSocial/Views/MainView.xaml.cs

@@ -1,4 +1,5 @@
 using CommunityToolkit.Mvvm.DependencyInjection;
+using Microsoft.Maui.Controls;
 using NuSocial.Core.View;
 
 namespace NuSocial.Views;
@@ -12,4 +13,10 @@ public MainView(MainViewModel vm) : base(vm)
     public MainView() : this(Ioc.Default.GetRequiredService<MainViewModel>())
     {
     }
+
+    private void UnreadBtn_Clicked(object sender, EventArgs e)
+    {
+        // We should always scroll to the top when loading new posts because we're inserting at the top
+        //collectionView.ScrollTo(0);
+    }
 }