/**
 * Copyright 2014 Oracle | BlueKai
 */
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.util.EnumMap;
import java.util.Map;

/**
 * Demonstration on email and phone hashing
 *
 */
class Hashing {

       public enum Algorithm {

              SHA256("SHA-256");

              private final String messageDigestAlgorithmName;

              private Algorithm(String messageDigestAlgorithmName) {
                     this.messageDigestAlgorithmName = messageDigestAlgorithmName;
              }

              public String getMessageDigestAlgorithmName() {
                     return messageDigestAlgorithmName;
              }
       }

       Map<Algorithm, MessageDigest> mdMap = new EnumMap<Algorithm, MessageDigest>(Algorithm.class);

       public MessageDigest digestInstance(Algorithm algorithm) throws NoSuchAlgorithmException {
              if (algorithm == null) {
                     throw new NoSuchAlgorithmException();
              }
              MessageDigest md;
              if (!mdMap.containsKey(algorithm)) {
                     md = MessageDigest.getInstance(algorithm.getMessageDigestAlgorithmName());
                     mdMap.put(algorithm, md);
              } else {
                     md = mdMap.get(algorithm);
              }
              return md;
       }

       public String normalizeEmail(String email) {
              return email.trim().toLowerCase().replaceFirst("\\+[^@]*@", "@");
       }

       public String normalizePhoneNumber(String phoneNumber) {
              return phoneNumber.trim().replaceFirst("^0+", "").replaceAll("[^0-9]", "");
       }

       private String createHash(String stringToHash, Algorithm algorithm) throws NoSuchAlgorithmException {
              MessageDigest md = digestInstance(algorithm);

              md.update(stringToHash.getBytes());

              byte byteData[] = md.digest();

              StringBuilder sb = new StringBuilder();
              for (int i = 0; i < byteData.length; i++) {
                     sb.append(Integer.toString((byteData[i] & 0xff) + 0x100, 16).substring(1));
              }

              return sb.toString();

       }

       public String createEmailHash(String email, Algorithm algorithm) throws NoSuchAlgorithmException {
              return createHash(normalizeEmail(email), algorithm);
       }

       public String createPhoneHash(String phoneNumber, Algorithm algorithm) throws NoSuchAlgorithmException {
              return createHash(normalizePhoneNumber(phoneNumber), algorithm);
       }

       /**
        * Notice: This is the end of hashing class functionality The rest of this class is an actual use cases and demo
        */
       public static void assertEqual(Object actual, Object expected) throws AssertionError {
              if ((actual == null && expected != null) || (actual != null && !actual.equals(expected))) {
                     throw new AssertionError(String.format("'%s' is expected to be equal to '%s'", actual, expected));
              }
       }

       public static void main(String[] args) throws NoSuchAlgorithmException {
              Hashing hashCreator = new Hashing();
              assertEqual(hashCreator.normalizeEmail("  Test@somewhere.com  "), "test@somewhere.com");
              assertEqual(hashCreator.normalizeEmail("Test+alias@gMail.Com  "), "test@gmail.com");
              assertEqual(hashCreator.normalizePhoneNumber("   00123-456-7890      "), "1234567890");

              assertEqual(hashCreator.createEmailHash("  Test@somewhere.com ", Algorithm.SHA256), "c6835820412cddddd5197dab400fec65c3d9a2617ae4ceb1442ec753abeec0ba");

              assertEqual(hashCreator.createPhoneHash("   00123-456-7890    ", Algorithm.SHA256), "c775e7b757ede630cd0aa1113bd102661ab38829ca52a6422ab782862f268646");

              System.out.println("All tests pass!");
       }
}