ios: offer creating a profile when accepting an invitation

Adds "Add profile" to the profile picker shown above the compose box for a
prepared chat, so connecting as someone new does not mean leaving the invitation
to create a profile in settings.

NewUser and createActiveUser gain keepActiveUser, with apiCreateProfileKeepingActive
as the named entry point; the flag never appears at a call site. The profile is
created without becoming active so the profile that owns the prepared chat stays
active for the reassignment.

The row is emitted first: unlike the Android/desktop list this one is not
reverse-laid-out, so first renders at the top. After switching, the chat is
reopened explicitly - keepingChatId only preserves its place in the reloaded
list.

Reuses the existing "Add profile" and "Error changing chat profile" strings, so
no new translation entries.

apps/ios/Shared/Model/AppAPITypes.swift

@@ -14,7 +14,7 @@ import SwiftUI
 // Spec: spec/api.md#ChatCommand
 enum ChatCommand: ChatCmdProtocol {
     case showActiveUser
-    case createActiveUser(profile: Profile?, pastTimestamp: Bool)
+    case createActiveUser(profile: Profile?, pastTimestamp: Bool, keepActiveUser: Bool)
     case listUsers
     case apiSetActiveUser(userId: Int64, viewPwd: String?)
     case setAllContactReceipts(enable: Bool)
@@ -201,8 +201,8 @@ enum ChatCommand: ChatCmdProtocol {
         get {
             switch self {
             case .showActiveUser: return "/u"
-            case let .createActiveUser(profile, pastTimestamp):
-                let user = NewUser(profile: profile, pastTimestamp: pastTimestamp)
+            case let .createActiveUser(profile, pastTimestamp, keepActiveUser):
+                let user = NewUser(profile: profile, pastTimestamp: pastTimestamp, keepActiveUser: keepActiveUser)
                 return "/_create user \(encodeJSON(user))"
             case .listUsers: return "/users"
             case let .apiSetActiveUser(userId, viewPwd): return "/_user \(userId)\(maybePwd(viewPwd))"
@@ -1363,6 +1363,10 @@ struct NewUser: Encodable {
     var profile: Profile?
     var pastTimestamp: Bool
     var userChatRelay: Bool = false
+    // when set, the user is created without becoming active, preserving the current one;
+    // absent/false activates it as before. The response is activeUser either way - it
+    // carries the created user, which is then not the active one.
+    var keepActiveUser: Bool = false
 }
 
 enum ChatPagination {

apps/ios/Shared/Model/SimpleXAPI.swift

@@ -254,7 +254,18 @@ func apiGetActiveUser(ctrl: chat_ctrl? = nil) throws -> User? {
 }
 
 func apiCreateActiveUser(_ p: Profile?, pastTimestamp: Bool = false, ctrl: chat_ctrl? = nil) throws -> User {
-    let r: ChatResponse0 = try chatSendCmdSync(.createActiveUser(profile: p, pastTimestamp: pastTimestamp), ctrl: ctrl)
+    try createUser(p, pastTimestamp: pastTimestamp, keepActiveUser: false, ctrl: ctrl)
+}
+
+// Creates a profile *without* activating it: apiChangePreparedContactUser resolves the
+// prepared chat under the active user, so the profile that owns it must stay active until
+// the chat has moved. The returned user is therefore not the active one.
+func apiCreateProfileKeepingActive(_ p: Profile) throws -> User {
+    try createUser(p, pastTimestamp: false, keepActiveUser: true, ctrl: nil)
+}
+
+private func createUser(_ p: Profile?, pastTimestamp: Bool, keepActiveUser: Bool, ctrl: chat_ctrl?) throws -> User {
+    let r: ChatResponse0 = try chatSendCmdSync(.createActiveUser(profile: p, pastTimestamp: pastTimestamp, keepActiveUser: keepActiveUser), ctrl: ctrl)
     if case let .activeUser(user) = r { return user }
     throw r.unexpected
 }

apps/ios/Shared/Views/Chat/ComposeMessage/ContextProfilePickerView.swift

@@ -21,6 +21,8 @@ struct ContextProfilePickerView: View {
     @State private var listExpanded = false
     @State private var expandedListReady = false
     @State private var showIncognitoSheet = false
+    @State private var showAddProfile = false
+    @State private var creatingProfile = false
 
     @AppStorage(GROUP_DEFAULT_INCOGNITO, store: groupDefaults) private var incognitoDefault = false
 
@@ -79,6 +81,12 @@ struct ContextProfilePickerView: View {
                 if expandedListReady {
                     let scroll = ScrollView {
                         LazyVStack(spacing: 0) {
+                            addProfileOption()
+                                .contentShape(Rectangle())
+                            Divider()
+                                .padding(.leading)
+                                .padding(.leading, 48)
+
                             let otherUsers = users
                                 .filter { u in u.userId != selectedUser.userId }
                                 .sorted(using: KeyPathComparator<User>(\.activeOrder))
@@ -113,7 +121,7 @@ struct ContextProfilePickerView: View {
                             }
                         }
                     }
-                        .frame(maxHeight: USER_ROW_SIZE * min(MAX_VISIBLE_USER_ROWS, CGFloat(users.count + 1))) // + 1 for incognito
+                        .frame(maxHeight: USER_ROW_SIZE * min(MAX_VISIBLE_USER_ROWS, CGFloat(users.count + 2))) // + 1 for incognito, + 1 for "Add profile"
                         .onAppear {
                             DispatchQueue.main.async {
                                 withAnimation(nil) {
@@ -142,6 +150,17 @@ struct ContextProfilePickerView: View {
                 }
             }
         }
+        // Attached to the picker, not to the row: the row lives in a lazy container that
+        // may dispose it, taking the presented sheet with it. Not the root either - two
+        // .sheet modifiers on the same view conflict, and body already presents
+        // IncognitoHelp.
+        .sheet(isPresented: $showAddProfile) {
+            NavigationView {
+                CreateProfile(onSubmit: { displayName, shortDescr, image in
+                    try await createProfileForChat(displayName, shortDescr, image)
+                })
+            }
+        }
     }
     
     private func profilerPickerUserOption(_ user: User) -> some View {
@@ -193,6 +212,65 @@ struct ContextProfilePickerView: View {
         }
     }
 
+    private func addProfileOption() -> some View {
+        Button {
+            showAddProfile = true
+        } label: {
+            HStack {
+                Image(systemName: "person.crop.circle.badge.plus")
+                    .resizable()
+                    .scaledToFit()
+                    .frame(width: 38, height: 38)
+                    .foregroundColor(theme.colors.primary)
+                Text("Add profile")
+                    .foregroundColor(theme.colors.primary)
+                    .lineLimit(1)
+
+                Spacer()
+            }
+            .padding(.leading, 12)
+            .padding(.trailing)
+            .frame(height: USER_ROW_SIZE)
+        }
+        .disabled(creatingProfile)
+    }
+
+    // Creates a profile to use for this invitation. It is created without becoming
+    // active, because changeProfile below reassigns the prepared chat and the API
+    // resolves that chat under the currently active user - so the profile that owns the
+    // invitation has to stay active until the chat has been moved.
+    private func createProfileForChat(_ displayName: String, _ shortDescr: String?, _ image: String?) async throws {
+        // Atomic check-and-set on the main actor: a plain check-then-set leaves a window
+        // where two submits both pass, and @State must not be read off the main actor.
+        let alreadyCreating = await MainActor.run { () -> Bool in
+            if creatingProfile { return true }
+            creatingProfile = true
+            return false
+        }
+        if alreadyCreating { return }
+        defer { Task { @MainActor in creatingProfile = false } }
+        let profile = Profile(displayName: displayName, fullName: "", shortDescr: shortDescr, image: image)
+        let newUser = try apiCreateProfileKeepingActive(profile)
+        let users = try? listUsers()
+        await MainActor.run {
+            if let users = users { chatModel.users = users }
+        }
+        if newUser.activeUser {
+            // The core did not honour keepActiveUser and activated the profile - an older
+            // remote host ignoring the unknown field. Reassigning would now fail, so
+            // resync to what the host actually did and report it.
+            try await changeActiveUserAsync_(newUser.userId, viewPwd: nil)
+            // The form stays open, as it does for any other failure, so the alert is not
+            // presented while a sheet is dismissing - it would be swallowed.
+            await MainActor.run {
+                showAlert(NSLocalizedString("Error changing chat profile", comment: "alert title"))
+            }
+            return
+        }
+        await MainActor.run { showAddProfile = false }
+        changeProfile(newUser)
+    }
+
     private func changeProfile(_ newUser: User) {
         Task {
             do {
@@ -215,6 +293,10 @@ struct ContextProfilePickerView: View {
                 }
                 do {
                     try await changeActiveUserAsync_(newUser.userId, viewPwd: nil, keepingChatId: chat.id)
+                    // Reopen the chat under the new profile: keepingChatId only preserves
+                    // its place in the reloaded list, so without this the switch lands on
+                    // the chat list rather than the invitation it was chosen for.
+                    await MainActor.run { chatModel.chatId = chat.id }
                 } catch {
                     await MainActor.run {
                         showAlert(