import SwiftUI

/// 短信登录状态机(对齐安卓 SmsLoginViewModel)。一键登录首版不做。
@MainActor
@Observable
final class LoginViewModel {
    var phone: String = ""
    var code: String = ""
    var countdown: Int = 0
    var isSending = false
    var isLoggingIn = false
    var isMock = false
    var errorMessage: String?

    private let auth = AuthService()
    private var timerTask: Task<Void, Never>?

    var isValidPhone: Bool { phone.count == 11 && phone.hasPrefix("1") }
    var canSendCode: Bool { countdown == 0 && !isSending && isValidPhone }
    var canLogin: Bool { isValidPhone && code.count >= 4 && !isLoggingIn }

    func sendCode() async {
        guard canSendCode else { return }
        errorMessage = nil
        isSending = true
        defer { isSending = false }
        do {
            let resp = try await auth.smsSend(phone: phone)
            isMock = resp.mock
            startCountdown(resp.cooldownSec > 0 ? resp.cooldownSec : 60)
        } catch {
            errorMessage = (error as? LocalizedError)?.errorDescription ?? "验证码发送失败,请重试"
        }
    }

    /// 登录成功则已写入 session,返回 true(供 View 关闭页面)。
    func login(into session: SessionStore) async -> Bool {
        guard canLogin else { return false }
        errorMessage = nil
        isLoggingIn = true
        defer { isLoggingIn = false }
        do {
            let resp = try await auth.smsLogin(phone: phone, code: code)
            await session.loginSucceeded(resp)
            return true
        } catch APIError.http(let status, _) where status == 400 {
            errorMessage = "验证码错误或已失效,请重新获取"
            return false
        } catch {
            errorMessage = (error as? LocalizedError)?.errorDescription ?? "登录失败,请重试"
            return false
        }
    }

    private func startCountdown(_ seconds: Int) {
        countdown = seconds
        timerTask?.cancel()
        timerTask = Task { @MainActor [weak self] in
            while true {
                do { try await Task.sleep(for: .seconds(1)) }
                catch { return }   // 被 cancel(重发时)→ 立即退出,不再误减新一轮计时
                guard let self, self.countdown > 0 else { return }
                self.countdown -= 1
            }
        }
    }
}