Add an AccountProvider type and use it within the authentication flow. (#6103)

* Add an AccountProvider type and use it within AppSettings.

* Use the AccountProvider type within the Authentication flow too.

* Fix unit test compilation with Swift 6.4

* Make sure defaultAccountProvider takes allowOtherAccountProviders into account.

* Document a caveat on using AuthenticationService.homeserver.value.accountProvider.

ElementX/Sources/Application/Settings/AccountProvider.swift

@@ -0,0 +1,65 @@
+//
+// Copyright 2026 Element Creations Ltd.
+//
+// SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial.
+// Please see LICENSE files in the repository root for full details.
+//
+
+import Foundation
+
+nonisolated enum AccountProvider: Equatable {
+    /// An account provider that was input/chosen by the user.
+    case generic(String)
+    /// An account provider as provided by the app.
+    case managed(serverName: String, baseURL: URL, canUseServerName: Bool = true)
+    
+    /// The account provider's string value, shown in the UI and used to build a `Client` with.
+    var serverNameOrBaseURL: String {
+        let serverNameOrBaseURL = switch self {
+        case .generic(let serverNameOrBaseURL):
+            serverNameOrBaseURL
+        case .managed(let serverName, let baseURL, let canUseServerName):
+            canUseServerName ? serverName : baseURL.absoluteString
+        }
+        
+        return sanitize(serverNameOrBaseURL)
+    }
+    
+    var isGeneric: Bool {
+        switch self {
+        case .generic: true
+        case .managed: false
+        }
+    }
+    
+    /// Sanitizes an address with the following rules:
+    /// - Trim any whitespace.
+    /// - Lowercase the address.
+    /// - Removes an https scheme (treating it as implicit).
+    /// - Remove any trailing slashes.
+    private func sanitize(_ serverNameOrBaseURL: String) -> String {
+        serverNameOrBaseURL
+            .trimmingCharacters(in: .whitespacesAndNewlines)
+            .lowercased()
+            .trimmingPrefix("https://") // Intentionally continue to show http:// as an indicator (and for history).
+            .trimmingCharacters(in: CharacterSet(charactersIn: "/"))
+    }
+}
+
+// MARK: - Array
+
+extension [AccountProvider] {
+    /// Whether the collection includes a provider matching the given server name or base URL.
+    func contains(serverName: String?, orBaseURL baseURL: URL?) -> Bool {
+        contains { accountProvider in
+            switch accountProvider {
+            case .generic(let serverNameOrBaseURL):
+                // Lower case potential user input to be safe. Full sanitisation is wrong given the scheme would be ignored.
+                serverNameOrBaseURL.lowercased() == serverName || serverNameOrBaseURL.lowercased() == baseURL?.absoluteString
+            case .managed(let providerServerName, let providerBaseURL, _):
+                // We can ignore canUseServerName here, it's about constructing a client rather than matching.
+                providerServerName == serverName || providerBaseURL == baseURL
+            }
+        }
+    }
+}

ElementX/Sources/Application/Settings/AppSettings.swift

@@ -78,7 +78,7 @@ final nonisolated class AppSettings: @unchecked Sendable {
     // MARK: - Hooks
     
     // swiftlint:disable:next function_parameter_count
-    func override(accountProviders: [String],
+    func override(accountProviders: [AccountProvider],
                   allowOtherAccountProviders: Bool,
                   hideBrandChrome: Bool,
                   pushGatewayBaseURL: URL,
@@ -143,7 +143,7 @@ final nonisolated class AppSettings: @unchecked Sendable {
     ///
     /// Account provider is the friendly term for the server name. It should not contain an `https` prefix and should
     /// match the last part of the user ID. For example `example.com` and not `https://matrix.example.com`.
-    private(set) var accountProviders = ["matrix.org"]
+    private(set) var accountProviders: [AccountProvider] = [.managed(serverName: "matrix.org", baseURL: "https://matrix-client.matrix.org")]
     /// Whether or not the user is allowed to manually enter their own account provider or must select from one of `defaultAccountProviders`.
     private(set) var allowOtherAccountProviders = true
     /// Whether the components surrounding the app brand/logo should be hidden or not
@@ -188,8 +188,12 @@ final nonisolated class AppSettings: @unchecked Sendable {
     @UserPreference(key: "previousServers", defaultValue: [])
     var previousServers: [String]
     
-    var defaultServer: String {
-        previousServers.first ?? accountProviders[0]
+    var defaultAccountProvider: AccountProvider {
+        if allowOtherAccountProviders {
+            previousServers.first.map { .generic($0) } ?? accountProviders[0]
+        } else {
+            accountProviders[0]
+        }
     }
     
     // MARK: - Security