import Flutter
import UIKit
import CommonCrypto
import Security

@main
@objc class AppDelegate: FlutterAppDelegate {
  private let CHANNEL = "iq.urukprize.uruk_prize/device_fingerprint"
  private let KEYCHAIN_KEY = "iq.urukprize.device_persistent_id"

  override func application(
    _ application: UIApplication,
    didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?
  ) -> Bool {
    let controller : FlutterViewController = window?.rootViewController as! FlutterViewController
    let channel = FlutterMethodChannel(name: CHANNEL, binaryMessenger: controller.binaryMessenger)

    channel.setMethodCallHandler({ [weak self] (call: FlutterMethodCall, result: @escaping FlutterResult) -> Void in
      guard let self = self else { return }

      switch call.method {
      case "getHardwareFingerprint":
        let rawData = self.getHardwareDetails()
        let hashed = self.sha256(data: rawData)
        result(hashed)
      case "getDeviceModel":
        result(self.getDeviceModel())
      case "getHardwareRawData":
        result(self.getHardwareDetails())
      default:
        result(FlutterMethodNotImplemented)
      }
    })

    GeneratedPluginRegistrant.register(with: self)
    return super.application(application, didFinishLaunchingWithOptions: launchOptions)
  }

  private func getHardwareDetails() -> String {
    let vendorId = UIDevice.current.identifierForVendor?.uuidString ?? "UNKNOWN_IDFV"
    let model = getDeviceModel()
    let systemName = UIDevice.current.systemName
    let systemVersion = UIDevice.current.systemVersion
    let persistentKey = getOrCreatePersistentKeychainId()

    return "idfv=\(vendorId);keychain_id=\(persistentKey);model=\(model);sys=\(systemName)_\(systemVersion)"
  }

  private func getDeviceModel() -> String {
    var systemInfo = utsname()
    uname(&systemInfo)
    let machineMirror = Mirror(reflecting: systemInfo.machine)
    let identifier = machineMirror.children.reduce("") { identifier, element in
      guard let value = element.value as? Int8, value != 0 else { return identifier }
      return identifier + String(UnicodeScalar(UInt8(value)))
    }
    return identifier
  }

  private func getOrCreatePersistentKeychainId() -> String {
    let tag = KEYCHAIN_KEY.data(using: .utf8)!
    
    // Query Keychain
    let query: [String: Any] = [
      kSecClass as String: kSecClassKey,
      kSecAttrApplicationTag as String: tag,
      kSecAttrKeyType as String: kSecAttrKeyTypeRSA,
      kSecReturnData as String: true
    ]

    var item: CFTypeRef?
    let status = SecItemCopyMatching(query as CFDictionary, &item)
    if status == errSecSuccess, let existingData = item as? Data, let string = String(data: existingData, encoding: .utf8) {
      return string
    }

    // Generate new persistent UUID and save to Keychain
    let newId = UUID().uuidString
    let newIdData = newId.data(using: .utf8)!

    let addQuery: [String: Any] = [
      kSecClass as String: kSecClassKey,
      kSecAttrApplicationTag as String: tag,
      kSecValueData as String: newIdData,
      kSecAttrAccessible as String: kSecAttrAccessibleAfterFirstUnlockThisDeviceOnly
    ]
    SecItemAdd(addQuery as CFDictionary, nil)
    return newId
  }

  private func sha256(data: String) -> String {
    guard let inputData = data.data(using: .utf8) else { return "" }
    var digest = [UInt8](repeating: 0, count: Int(CC_SHA256_DIGEST_LENGTH))
    inputData.withUnsafeBytes {
      _ = CC_SHA256($0.baseAddress, CC_LONG(inputData.count), &digest)
    }
    return digest.map { String(format: "%02hhx", $0) }.joined()
  }
}