package com.easypaymentsgateway.utils;

import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;

import javax.crypto.Cipher;
import javax.crypto.spec.SecretKeySpec;

import org.apache.commons.codec.binary.Base64;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import com.easypaymentsgateway.exceptions.EncryptionException;
import com.easypaymentsgateway.exceptions.EncryptionException.ErrorCode;

public class EncryptionUtils {

	/**
	 * Logger
	 */
	private static Logger logger = LoggerFactory.getLogger(EncryptionUtils.class);

	private static final String AES = "AES";
	public static String SHA256 = "SHA-256";

	/**
	 * Encrypts using AES algorithm
	 * 
	 * @param input
	 * @param key
	 * @return
	 */
	public static String encrypt(String input, String key) {
		byte[] crypted = null;
		try {
			SecretKeySpec skey = new SecretKeySpec(key.getBytes(), AES);
			Cipher cipher = Cipher.getInstance("AES/ECB/PKCS5Padding");
			cipher.init(Cipher.ENCRYPT_MODE, skey);
			crypted = cipher.doFinal(input.getBytes());
		} catch (Exception e) {
			logger.error("Unable to encrypt: ", e);
		}
		return new String(Base64.encodeBase64(crypted));
	}

	/**
	 * Method that encrypts the message using an algorithm
	 * 
	 * @param message
	 *            to encrypt
	 * @param algorithm
	 *            used to encrypt
	 * @return Message encrypted
	 * @throws NoSuchAlgorithmException
	 */
	public static String hashMessage(String message, String algorithm) {

		byte[] digest = null;
		byte[] buffer = message.getBytes();
		MessageDigest messageDigest;
		try {
			messageDigest = MessageDigest.getInstance(algorithm);
			messageDigest.reset();
			messageDigest.update(buffer);
			digest = messageDigest.digest();
		} catch (NoSuchAlgorithmException e) {
			throw new EncryptionException(ErrorCode.UNABLE_TO_FIND_HASH_ALGORITHM, "Internal error found");
		}
		return toHexadecimal(digest);
	}

	/**
	 * Convert digest Hexadecimal
	 * 
	 * @param digest
	 * @return
	 */
	private static String toHexadecimal(byte[] digest) {
		StringBuilder hash = new StringBuilder();
		for (byte aux : digest) {
			int b = aux & 0xff;
			if (Integer.toHexString(b).length() == 1)
				hash.append("0");
			hash.append(Integer.toHexString(b));
		}
		return hash.toString();
	}
}