添加登录流程、会话路由和对齐参考 UI 的主 Tab 框架

suixinkan/UI/Login/LoginViewModel.swift

@@ -0,0 +1,61 @@
+//
+//  LoginViewModel.swift
+//  suixinkan
+//
+
+import Foundation
+
+/// 登录页 ViewModel，UI 状态与 Android `LoginViewModel` 对齐。
+final class LoginViewModel {
+
+    private(set) var account = ""
+    private(set) var password = ""
+    private(set) var isPrivacyChecked = false
+    private(set) var enableRegister = false
+
+    var isLoginEnabled: Bool {
+        !account.isEmpty && !password.isEmpty
+    }
+
+    var onStateChange: (() -> Void)?
+
+    func updateAccount(_ value: String) {
+        account = value
+        notifyStateChange()
+    }
+
+    func updatePassword(_ value: String) {
+        password = value
+        notifyStateChange()
+    }
+
+    func togglePrivacyChecked() {
+        isPrivacyChecked.toggle()
+        notifyStateChange()
+    }
+
+    func updateEnableRegister(_ enabled: Bool) {
+        enableRegister = enabled
+        notifyStateChange()
+    }
+
+    func login() {
+        guard isPrivacyChecked else {
+            onShowMessage?("请先阅读并同意用户协议与隐私政策")
+            return
+        }
+        guard isLoginEnabled else { return }
+        onLogin?()
+    }
+
+    var onShowMessage: ((String) -> Void)?
+    var onLogin: (() -> Void)?
+    var onLoginByCode: (() -> Void)?
+    var onRegister: (() -> Void)?
+    var onUserAgreement: (() -> Void)?
+    var onPrivacyPolicy: (() -> Void)?
+
+    private func notifyStateChange() {
+        onStateChange?()
+    }
+}