//
//  DAKeychain.swift
//  DAKeychain
//
//  Created by Dejan on 28/02/2017.
//  Copyright © 2017 Dejan. All rights reserved.
//

import Foundation

open class DAKeychain {
  
  open var loggingEnabled = false
  
  private init() {}
  public static let shared = DAKeychain()
  
  open subscript(key: String) -> String? {
    get {
      return load(withKey: key)
    } set {
      DispatchQueue.global().sync(flags: .barrier) {
        self.save(newValue, forKey: key)
      }
    }
  }
  
  private func save(_ string: String?, forKey key: String) {
    let query = keychainQuery(withKey: key)
    let objectData: Data? = string?.data(using: .utf8, allowLossyConversion: false)
    
    if SecItemCopyMatching(query, nil) == noErr {
      if let dictData = objectData {
        let status = SecItemUpdate(query, NSDictionary(dictionary: [kSecValueData: dictData]))
        logPrint("Update status: ", status)
      } else {
        let status = SecItemDelete(query)
        logPrint("Delete status: ", status)
      }
    } else {
      if let dictData = objectData {
        query.setValue(dictData, forKey: kSecValueData as String)
        let status = SecItemAdd(query, nil)
        logPrint("Update status: ", status)
      }
    }
  }
  
  private func load(withKey key: String) -> String? {
    let query = keychainQuery(withKey: key)
    query.setValue(kCFBooleanTrue, forKey: kSecReturnData as String)
    query.setValue(kCFBooleanTrue, forKey: kSecReturnAttributes as String)
    
    var result: CFTypeRef?
    let status = SecItemCopyMatching(query, &result)
    
    guard
      let resultsDict = result as? NSDictionary,
      let resultsData = resultsDict.value(forKey: kSecValueData as String) as? Data,
      status == noErr
    else {
      logPrint("Load status: ", status)
      return nil
    }
    return String(data: resultsData, encoding: .utf8)
  }
  
  private func keychainQuery(withKey key: String) -> NSMutableDictionary {
    let result = NSMutableDictionary()
    result.setValue(kSecClassGenericPassword, forKey: kSecClass as String)
    result.setValue(key, forKey: kSecAttrService as String)
    result.setValue(kSecAttrAccessibleWhenUnlocked, forKey: kSecAttrAccessible as String)
    return result
  }
  
  private func logPrint(_ items: Any...) {
    if loggingEnabled {
      print(items)
    }
  }
}