fix(app): validate contact addresses when saving

Adding a contact now checks the address against the wallet's network and
rejects duplicates; whitespace in a pasted address is removed. Before, any
string was stored and the error only surfaced at send time.

CHANGELOG.md

@@ -17,6 +17,10 @@ release and covers the full history from the initial commit.
 
 ### Fixed
 
+- Adding a contact now validates the address for the wallet's network and rejects duplicates
+  (case-insensitive); whitespace and line breaks in a pasted address are removed. Before, any
+  string was saved and the error only appeared at send time. Contacts already stored with an
+  invalid address still load and display.
 - The wallet now verifies the chain identity of a server right after connecting: the
   `genesis_hash` from `server.features` must match the profile and, on mainnet (which shares
   Bitcoin's genesis), the header at the highest checkpoint not above the server's tip must match

USERGUIDE.md

@@ -508,9 +508,11 @@ them is normal.
 
 A simple per-wallet address book, on its own tab:
 
-- **Add**: name + address, both required (whitespace is trimmed). Note: the address format
-  is **not validated when saving** — it is only validated when you actually send to it. Copy
-  addresses carefully.
+- **Add**: name + address, both required. The address is **validated when saving** against
+  the wallet's network: an invalid or wrong-network address, or one already in the list, is
+  refused with a message. Spaces and line breaks in a pasted address are removed. Contacts
+  saved by an older version without validation are still shown; the send form validates the
+  destination again when you use them.
 - **Remove selected**: deletes the highlighted contact. There is no edit function — remove
   and re-add.
 - Contacts are used by the **From contacts** dropdown on the Send tab.

src/App/Localization/Loc.cs

@@ -477,6 +477,22 @@ public sealed class Loc
             "服务器 {0} 不在 Palladium 链上（创世块或检查点不同）。请选择其他服务器。"],
 
         // Contacts
+        ["msg.contact.address.invalid"] = [
+            "Indirizzo non valido per questa rete: il contatto non è stato salvato.",
+            "Invalid address for this network: the contact was not saved.",
+            "Dirección no válida para esta red: el contacto no se guardó.",
+            "Adresse invalide pour ce réseau : le contact n'a pas été enregistré.",
+            "Endereço inválido para esta rede: o contato não foi salvo.",
+            "Ungültige Adresse für dieses Netzwerk: Der Kontakt wurde nicht gespeichert.",
+            "该网络的地址无效：联系人未保存。"],
+        ["msg.contact.duplicate"] = [
+            "Esiste già un contatto con questo indirizzo.",
+            "A contact with this address already exists.",
+            "Ya existe un contacto con esta dirección.",
+            "Un contact avec cette adresse existe déjà.",
+            "Já existe um contato com este endereço.",
+            "Ein Kontakt mit dieser Adresse existiert bereits.",
+            "已存在相同地址的联系人。"],
         ["contacts.name"]         = ["Nome",                                                              "Name",                         "Nombre",                               "Nom",                                      "Nome",                                     "Name",                                          "姓名"],
         ["contacts.address"]      = ["Indirizzo",                                                         "Address",                      "Dirección",                            "Adresse",                                  "Endereço",                                 "Adresse",                                       "地址"],
         ["contacts.name.ph"]      = ["Nome contatto",                                                     "Contact name",                 "Nombre del contacto",                  "Nom du contact",                           "Nome do contato",                          "Kontaktname",                                   "联系人姓名"],

src/App/ViewModels/MainWindowViewModel.Contacts.cs

@@ -2,6 +2,9 @@ using System.Collections.ObjectModel;
 using System.Linq;
 using CommunityToolkit.Mvvm.ComponentModel;
 using CommunityToolkit.Mvvm.Input;
+using NBitcoin;
+using PalladiumWallet.App.Localization;
+using PalladiumWallet.Core.Chain;
 using PalladiumWallet.Core.Storage;
 
 namespace PalladiumWallet.App.ViewModels;
@@ -33,8 +36,23 @@ public partial class MainWindowViewModel
     private void AddContact()
     {
         var name = NewContactName.Trim();
-        var addr = NewContactAddress.Trim();
+        // Pasted addresses often carry spaces or line breaks anywhere: drop all whitespace.
+        var addr = string.Concat(NewContactAddress.Where(c => !char.IsWhiteSpace(c)));
         if (string.IsNullOrEmpty(name) || string.IsNullOrEmpty(addr)) return;
+        try
+        {
+            BitcoinAddress.Create(addr, PalladiumNetworks.For(Net));
+        }
+        catch (System.FormatException)
+        {
+            StatusMessage = Loc.Tr("msg.contact.address.invalid");
+            return;
+        }
+        if (Contacts.Any(c => string.Equals(c.Address, addr, System.StringComparison.OrdinalIgnoreCase)))
+        {
+            StatusMessage = Loc.Tr("msg.contact.duplicate");
+            return;
+        }
         Contacts.Add(new ContactEntry(name, addr));
         NewContactName = NewContactAddress = "";
         PersistContacts();

tests/PalladiumWallet.Tests/App/MainWindowViewModelTests.cs

@@ -291,7 +291,8 @@ public sealed class MainWindowViewModelTests : VmTestBase
         var vm = new MainWindowViewModel();
         RestoreFlow(vm, Mnemonic, null, "c");
 
-        vm.NewContactName = "Alice"; vm.NewContactAddress = "plm1qexample";
+        var alice = Address(1);
+        vm.NewContactName = "Alice"; vm.NewContactAddress = alice;
         vm.AddContactCommand.Execute(null);
         vm.NewContactName = ""; vm.NewContactAddress = "ignored";
         vm.AddContactCommand.Execute(null); // blank name → ignored
@@ -306,6 +307,77 @@ public sealed class MainWindowViewModelTests : VmTestBase
         Assert.Empty(WalletStore.Load(Assert.Single(AppPaths.WalletFiles(NetKind.Mainnet))).Contacts);
     });
 
+    private static string Address(int index) =>
+        HdAccount.FromMnemonic(ParseMnemonic(), null, ScriptKind.NativeSegwit, ChainProfiles.Mainnet)
+            .GetReceiveAddress(index).ToString();
+
+    [Theory]
+    [InlineData("plm1qexample")]                                   // garbage
+    [InlineData("not an address")]
+    [InlineData("tplm1qw508d6qejxtdg4y5r3zarvary0c5xw7kxpjzsx")]  // wrong network / bad checksum
+    public Task Contacts_RejectInvalidAddresses(string bad) => UiSession.Run(() =>
+    {
+        var vm = new MainWindowViewModel();
+        RestoreFlow(vm, Mnemonic, null, "c1");
+
+        vm.NewContactName = "Bob"; vm.NewContactAddress = bad;
+        vm.AddContactCommand.Execute(null);
+
+        Assert.Empty(vm.Contacts);
+        Assert.Equal(Loc.Tr("msg.contact.address.invalid"), vm.StatusMessage);
+        Assert.Empty(WalletStore.Load(Assert.Single(AppPaths.WalletFiles(NetKind.Mainnet))).Contacts);
+    });
+
+    [Fact]
+    public Task Contacts_RejectAnAddressFromAnotherNetwork() => UiSession.Run(() =>
+    {
+        var vm = new MainWindowViewModel();
+        RestoreFlow(vm, Mnemonic, null, "c2");
+        var regtest = HdAccount.FromMnemonic(ParseMnemonic(), null, ScriptKind.NativeSegwit, ChainProfiles.Regtest)
+            .GetReceiveAddress(0).ToString();
+
+        vm.NewContactName = "Eve"; vm.NewContactAddress = regtest;
+        vm.AddContactCommand.Execute(null);
+
+        Assert.Empty(vm.Contacts);
+        Assert.Equal(Loc.Tr("msg.contact.address.invalid"), vm.StatusMessage);
+    });
+
+    [Fact]
+    public Task Contacts_RejectDuplicatesAndCleanPastedWhitespace() => UiSession.Run(() =>
+    {
+        var vm = new MainWindowViewModel();
+        RestoreFlow(vm, Mnemonic, null, "c3");
+        var a = Address(2);
+
+        vm.NewContactName = "  Carol "; vm.NewContactAddress = $" {a[..10]}\n{a[10..]}\r\n";
+        vm.AddContactCommand.Execute(null);
+        Assert.Equal(new ContactEntry("Carol", a), Assert.Single(vm.Contacts));
+
+        vm.NewContactName = "Carol again"; vm.NewContactAddress = a.ToUpperInvariant();
+        vm.AddContactCommand.Execute(null);
+        Assert.Single(vm.Contacts);
+        Assert.Equal(Loc.Tr("msg.contact.duplicate"), vm.StatusMessage);
+    });
+
+    [Fact]
+    public Task Contacts_AlreadyStoredWithAnInvalidAddress_StillLoadAndDisplay() => UiSession.Run(() =>
+    {
+        var vm = new MainWindowViewModel();
+        RestoreFlow(vm, Mnemonic, null, "c4");
+        var path = Assert.Single(AppPaths.WalletFiles(NetKind.Mainnet));
+        var doc = WalletStore.Load(path);
+        doc.Contacts = [new StoredContact { Name = "Legacy", Address = "whatever" }];
+        WalletStore.Save(doc, path, null);
+        vm.CloseWalletCommand.Execute(null);
+
+        vm.WizardStartOpenCommand.Execute(null);
+        vm.OpenExistingCommand.Execute(null);
+
+        Assert.True(vm.IsWalletOpen);
+        Assert.Equal(new ContactEntry("Legacy", "whatever"), Assert.Single(vm.Contacts));
+    });
+
     // ---- sync + send against the fake server ----
 
     [Fact]