MigrateTwitterkitSession.swift

## MigrateTwitterkitSession.swift
//
//  MigrateTwitterkitSession.swift
//
//
//  Created by jonnyijapan on 2018/06/28.
//  Copyright © 2018 jonnyijapan. All rights reserved.
//

import Foundation

import KeychainAccess // https://github.com/kishikawakatsumi/KeychainAccess


class MigratedTwitterkitSession: NSObject, NSCoding {
	let authToken: String
	let authTokenSecret: String
	let userName: String

	enum Result {
		case migrated(session: MigratedTwitterkitSession)
		case nosession(errors: [Error])
	}

	/// Searches for any existing TwitterKit OAuth session. If found, returns it after deleting all of the TwitterKit service data.
	///
	/// - Returns: A Result object. If result is migrated, the session parameter containts a TWTRSession object consisting of OAuth key and secret, and Twitter screenname.
	static func tryToMigrateSession() -> Result {

		NSKeyedUnarchiver.setClass(MigratedTwitterkitSession.self, forClassName: "TWTRSession")

		let keychain = Keychain.init(service: "com.twitter.api-service.user-session-store-service-name")
		//print("keychain.allKeys(): \(keychain.allKeys())")

		var errors = [Error]()
		for key in keychain.allKeys() {
			if let value: Data = keychain[data: key] {
				//print("key: \(key), data value: \(value)")

				let unarchiver = NSKeyedUnarchiver.init(forReadingWith: value)

				do {
					let obj = try unarchiver.decodeTopLevelObject(forKey: "root")
					if let object = obj {
						//print("Unarchived root object: \(object)")
						if let session = object as? MigratedTwitterkitSession {
							//print("Got session session.authToken: \(session.authToken), session.userName: \(session.userName), session.authTokenSecret: \(session.authTokenSecret)")

							try keychain.removeAll()

							return .migrated(session: session)
						}
					}
					else {
						print("Failed unarchiving root object")
					}
				}
				catch {
					errors.append(error)
				}
			}
		}

		return .nosession(errors: errors)
	}

	func encode(with aCoder: NSCoder) {
	}

	required init?(coder aDecoder: NSCoder) {
		if let token = aDecoder.decodeObject(forKey: "oauth_token") as? String, let secret = aDecoder.decodeObject(forKey: "oauth_token_secret") as? String, let screenname = aDecoder.decodeObject(forKey: "screen_name") as? String {
			self.authToken = token
			self.authTokenSecret = secret
			self.userName = screenname
		}
		else {
			return nil
		}
	}
}