//
//  AccountSwitchViewModel.swift
//  suixinkan
//

import Foundation

/// 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 {
    private(set) var accounts: [AccountSwitchAccount] = []
    private(set) var selectedAccountId: String?
    private(set) var loading = false
    private(set) var switching = false
    private var didLoad = false

    var onStateChange: (() -> Void)?

    var selectedAccount: AccountSwitchAccount? {
        accounts.first { $0.id == selectedAccountId }
    }

    func load(api: ProfileAPI, force: Bool = false, currentAccountId: String? = nil) async throws {
        guard force || !didLoad else { return }
        didLoad = true
        loading = true
        notifyStateChange()
        defer {
            loading = false
            notifyStateChange()
        }

        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
        notifyStateChange()
    }

    func select(_ account: AccountSwitchAccount) {
        selectedAccountId = account.id
        notifyStateChange()
    }

    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
        notifyStateChange()
        defer {
            switching = false
            notifyStateChange()
        }
        return try await api.setUser(account.toSetUserRequest())
    }

    func isCurrent(_ account: AccountSwitchAccount, currentAccountId: String?) -> Bool {
        guard let currentAccountId else { return false }
        return account.id == currentAccountId || String(account.businessUserId) == currentAccountId
    }

    private func notifyStateChange() {
        onStateChange?()
    }
}

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"
        }
    }
}