import Foundation
import UIKit

/// Brownfield 运行时启动失败时抛出的错误。
public enum DuooomiBleRuntimeError: Error, LocalizedError {
  case hostManagerUnavailable
  case reactNativeViewUnavailable

  public var errorDescription: String? {
    switch self {
    case .hostManagerUnavailable:
      return "Unable to locate ReactNativeHostManager. Make sure the brownfield framework is linked correctly."
    case .reactNativeViewUnavailable:
      return "Unable to create ReactNativeView automatically. Pass createReactNativeView when starting the runtime."
    }
  }
}

/// 负责在宿主视图层中挂载隐藏的 RN 容器并启动 JS 运行时。
public final class DuooomiBleRuntime {
  /// 供宿主全局复用的单例实例。
  public static let shared = DuooomiBleRuntime()

  private weak var mountedView: UIView?
  private weak var containerView: UIView?

  private init() {}

  /// 在指定容器中启动 Brownfield 运行时。
  ///
  /// - Parameters:
  ///   - containerView: 用于挂载隐藏 React Native 视图的宿主容器。
  ///   - initializeHost: 可选的宿主初始化逻辑；若不传则尝试自动初始化。
  ///   - createReactNativeView: 可选的 RN View 构造逻辑；若不传则尝试自动创建。
  /// - Throws: `DuooomiBleRuntimeError`。
  public func start(
    in containerView: UIView,
    initializeHost: (() -> Void)? = nil,
    createReactNativeView: (() -> UIView)? = nil
  ) throws {
    if mountedView != nil {
      return
    }

    if let initializeHost {
      initializeHost()
    } else {
      try autoInitializeHostManager()
    }

    let reactNativeView = createReactNativeView?() ?? try autoCreateReactNativeView()
    reactNativeView.isHidden = true
    reactNativeView.isUserInteractionEnabled = false
    reactNativeView.frame = CGRect(x: 0, y: 0, width: 1, height: 1)
    reactNativeView.accessibilityElementsHidden = true

    containerView.addSubview(reactNativeView)

    self.containerView = containerView
    self.mountedView = reactNativeView

    DuooomiBleManager.shared.start()
  }

  /// 停止运行时并移除已挂载的隐藏 RN 视图。
  public func stop() {
    DuooomiBleManager.shared.stop()
    mountedView?.removeFromSuperview()
    mountedView = nil
    containerView = nil
  }

  private func autoInitializeHostManager() throws {
    let possibleClassNames = [
      "ReactNativeHostManager",
      "DuooomiBleSDK.ReactNativeHostManager",
    ]

    for className in possibleClassNames {
      guard let managerClass = NSClassFromString(className) as? NSObject.Type else {
        continue
      }

      let sharedSelector = NSSelectorFromString("shared")
      let initializeSelector = NSSelectorFromString("initialize")
      let managerObject = (managerClass as AnyObject).perform(sharedSelector)?.takeUnretainedValue() as? NSObject

      if let managerObject, managerObject.responds(to: initializeSelector) {
        managerObject.perform(initializeSelector)
        return
      }
    }

    throw DuooomiBleRuntimeError.hostManagerUnavailable
  }

  private func autoCreateReactNativeView() throws -> UIView {
    let possibleClassNames = [
      "ReactNativeView",
      "DuooomiBleSDK.ReactNativeView",
    ]

    for className in possibleClassNames {
      guard let viewClass = NSClassFromString(className) as? NSObject.Type else {
        continue
      }

      if let view = viewClass.init() as? UIView {
        return view
      }
    }

    throw DuooomiBleRuntimeError.reactNativeViewUnavailable
  }
}