// Author: fruit.com.cn

import CoreTelephony
import Flutter
import Foundation

/// 监听系统无线数据选择，并用 URLSession 唤起系统选择框。
final class WirelessDataPrompt {
  static let channelName = "com.stormg.lumadrama/wireless-data"
  static let awaitDecisionMethod = "awaitDecision"

  /// 系统选择框由 URLSession 触发，Dart 的 Socket 请求不会弹出。
  private static let promptURL = URL(string: "https://captive.apple.com/hotspot-detect.html")

  private let cellularData = CTCellularData()
  private let lock = NSLock()
  private var pending: [FlutterResult] = []
  private var decided = false
  private var didRequestPrompt = false

  init() {
    cellularData.cellularDataRestrictionDidUpdateNotifier = { [weak self] state in
      DispatchQueue.main.async {
        self?.completeIfDecided(state)
      }
    }
  }

  /// 应用进入前台后请求一次，促使系统弹出无线数据选择。
  func requestSystemPrompt() {
    guard !didRequestPrompt, let promptURL = Self.promptURL else {
      return
    }
    didRequestPrompt = true
    _ = cellularData.restrictedState
    URLSession.shared.dataTask(with: promptURL) { _, _, _ in }.resume()
  }

  /// 未允许前先挂起；用户允许无线数据后再放行。
  func awaitDecision(_ result: @escaping FlutterResult) {
    lock.lock()
    if decided {
      lock.unlock()
      DispatchQueue.main.async {
        result(nil)
      }
      return
    }
    pending.append(result)
    lock.unlock()
  }

  private func completeIfDecided(_ state: CTCellularDataRestrictedState) {
    if state != .notRestricted {
      return
    }
    lock.lock()
    if decided {
      lock.unlock()
      return
    }
    decided = true
    let waiters = pending
    pending.removeAll()
    lock.unlock()
    waiters.forEach { $0(nil) }
  }
}