Keychain.swift

/**
 * Keychain.swift
 * Created by frzi (github.com/frzi)
 */

import Foundation
import Security

class Keychain {
	fileprivate class func getKeychainQuery(_ key: String) -> NSMutableDictionary {
		return [
			kSecClass: kSecClassGenericPassword,
			kSecAttrService: "myapp_identifier",
			kSecAttrAccount: key,
		]
	}
	
	@discardableResult
	class func set(_ value: Data, forKey key: String) -> Bool {
		let query = getKeychainQuery(key)
		query[kSecValueData] = value
		return SecItemAdd(query, nil) == noErr
	}
	
	@discardableResult
	class func delete(_ key: String) -> Bool {
		let query = getKeychainQuery(key)
		return SecItemDelete(query) == noErr
	}
	
	class func get(_ key: String) -> Data? {
		let query = getKeychainQuery(key)
		var result: AnyObject?
		
		query[kSecReturnData] = true
		query[kSecMatchLimit] = kSecMatchLimitOne
		
		if SecItemCopyMatching(query, &result) == noErr {
			return result as? Data
		}
				
		return nil
	}
}

// MARK: - JSON helpers.
extension Keychain {
	private static let encoder: JSONEncoder = {
		let encoder = JSONEncoder()
		encoder.keyEncodingStrategy = .convertToSnakeCase
		return encoder
	}()

	private static let decoder: JSONDecoder = {
		let decoder = JSONDecoder()
		decoder.keyDecodingStrategy = .convertFromSnakeCase
		return decoder
	}()
	
	@discardableResult
	class func set<T: Encodable>(_ value: T, forKey key: String) -> Bool {
		if let encoded = try? encoder.encode(value) {
			return set(encoded, forKey: key)
		}
		return false
	}
	
	class func get<T: Decodable>(_ key: String, as type: T.Type) -> T? {
		if let data = get(key),
		   let decoded = try? decoder.decode(type, from: data)
		{
			return decoded
		}
		return nil
	}
}