Initial commit: suixinkan_ios UIKit rewrite project.

Co-authored-by: Cursor <cursoragent@cursor.com>

suixinkan_ios/Features/Profile/ViewModels/AccountSwitchViewModel.swift

@@ -0,0 +1,77 @@
+//
+//  AccountSwitchViewModel.swift
+//  suixinkan
+//
+//  Created by Codex on 2026/6/22.
+//
+
+import Foundation
+
+@MainActor
+/// 账号切换 ViewModel，管理可切换账号列表、选择状态和提交状态。
+final class AccountSwitchViewModel {
+    var onChange: (() -> Void)?
+    private(set) var accounts: [AccountSwitchAccount] = [] { didSet { onChange?() } }
+    var selectedAccountId: String? { didSet { onChange?() } }
+    private(set) var loading = false { didSet { onChange?() } }
+    private(set) var switching = false { didSet { onChange?() } }
+    private var didLoad = false
+
+    /// 当前选中的账号。
+    var selectedAccount: AccountSwitchAccount? {
+        accounts.first { $0.id == selectedAccountId }
+    }
+
+    /// 拉取可切换账号列表，默认只加载一次。
+    func load(api: ProfileAPI, force: Bool = false, currentAccountId: String? = nil) async throws {
+        guard force || !didLoad else { return }
+        didLoad = true
+        loading = true
+        defer { loading = false }
+
+        let response = try await api.switchableAccounts()
+        accounts = response.accounts.filter { $0.businessUserId > 0 }
+        selectedAccountId = accounts.first(where: { $0.isCurrent || isCurrent($0, currentAccountId: currentAccountId) })?.id
+            ?? accounts.first?.id
+    }
+
+    /// 选择指定账号。
+    func select(_ account: AccountSwitchAccount) {
+        selectedAccountId = account.id
+    }
+
+    /// 提交账号切换，调用 set-user 换取正式 token。
+    func switchAccount(_ account: AccountSwitchAccount, api: AuthAPI) async throws -> V9AuthResponse {
+        guard !switching else {
+            throw AccountSwitchError.submitting
+        }
+        guard account.businessUserId > 0 else {
+            throw AccountSwitchError.invalidAccount
+        }
+
+        switching = true
+        defer { switching = false }
+        return try await api.setUser(account.toSetUserRequest())
+    }
+
+    /// 判断账号是否与当前账号标识一致。
+    func isCurrent(_ account: AccountSwitchAccount, currentAccountId: String?) -> Bool {
+        guard let currentAccountId else { return false }
+        return account.id == currentAccountId || String(account.businessUserId) == currentAccountId
+    }
+}
+
+/// 账号切换错误实体，表示重复提交或账号数据异常。
+enum AccountSwitchError: LocalizedError, Equatable {
+    case submitting
+    case invalidAccount
+
+    var errorDescription: String? {
+        switch self {
+        case .submitting:
+            "账号正在切换，请稍候"
+        case .invalidAccount:
+            "账号信息异常，请重新选择账号"
+        }
+    }
+}