package org.duniter.core.util.crypto;
   
   /*
    * #%L
    * Duniter4j :: Core API
    * %%
    * Copyright (C) 2014 - 2015 EIS
    * %%
    * This program is free software: you can redistribute it and/or modify
   * it under the terms of the GNU General Public License as
   * published by the Free Software Foundation, either version 3 of the 
   * License, or (at your option) any later version.
   * 
   * This program is distributed in the hope that it will be useful,
   * but WITHOUT ANY WARRANTY; without even the implied warranty of
   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   * GNU General Public License for more details.
   * 
   * You should have received a copy of the GNU General Public 
   * License along with this program.  If not, see
   * <http://www.gnu.org/licenses/gpl-3.0.html>.
   * #L%
   */
  
  
  import com.lambdaworks.crypto.SCrypt;
  import org.duniter.core.exception.TechnicalException;
  import jnr.ffi.byref.LongLongByReference;
  import org.abstractj.kalium.crypto.Util;
  
  import java.security.GeneralSecurityException;
  
  import static org.duniter.core.util.crypto.CryptoUtils.zeros;
  import static org.abstractj.kalium.NaCl.Sodium.*;
  import static org.abstractj.kalium.NaCl.sodium;
  import static org.abstractj.kalium.crypto.Util.checkLength;
  import static org.abstractj.kalium.crypto.Util.isValid;
  import static org.abstractj.kalium.crypto.Util.removeZeros;
  
  
  public class SecretBox {
  
  	// Length of the key
  	private static int SEED_LENGTH = 32;
  	private static int SIGNATURE_BYTES = 64;
  	private static int SCRYPT_PARAMS_N = 4096;
  	private static int SCRYPT_PARAMS_r = 16;
  	private static int SCRYPT_PARAMS_p = 1;
  
  	private final String pubKey;
      private final byte[] secretKey;
      private final byte[] seed;
  
  	public SecretBox(String salt, String password) {
  		this(computeSeedFromSaltAndPassword(salt, password));
  	}
  	
  	public SecretBox(byte[] seed) {
  		checkLength(seed, SEED_LENGTH);
  		this.seed = seed;
          this.secretKey = CryptoUtils.zeros(SECRETKEY_BYTES * 2);
          byte[] publicKey = CryptoUtils.zeros(PUBLICKEY_BYTES);
          isValid(sodium().crypto_sign_ed25519_seed_keypair(publicKey, secretKey, seed),
                  "Failed to generate a key pair");
          this.pubKey = Base58.encode(publicKey);
  	}
  	
  	/**
  	 * Retrun the public key, encode in Base58
  	 * @return
  	 */
  	public String getPublicKey() {
  		return pubKey;
  	}
  	
  	/**
  	 * Return the secret key, encode in Base58
  	 * @return
  	 */
  	public String getSecretKey() {
  		return Base58.encode(secretKey);
  	}
  	
  	public String sign(String message) {
  		byte[] messageBinary = CryptoUtils.decodeUTF8(message);
  		return CryptoUtils.encodeBase64(
  				sign(messageBinary)
  				);
  	}
  	
  	public byte[] sign(byte[] message) {
          byte[] signature = Util.prependZeros(SIGNATURE_BYTES, message);
          LongLongByReference bufferLen = new LongLongByReference(0);
          sodium().crypto_sign_ed25519(signature, bufferLen, message, message.length, secretKey);
          signature = Util.slice(signature, 0, SIGNATURE_BYTES);
          
          checkLength(signature, SIGNATURE_BYTES);
          return signature;
      }
 
 
     public byte[] encrypt(byte[] nonce, byte[] message) {
         checkLength(nonce, XSALSA20_POLY1305_SECRETBOX_NONCEBYTES);
         byte[] msg = Util.prependZeros(ZERO_BYTES, message);
         byte[] ct = Util.zeros(msg.length);
         isValid(sodium().crypto_secretbox_xsalsa20poly1305(ct, msg, msg.length,
                 nonce, seed), "Encryption failed");
         return removeZeros(BOXZERO_BYTES, ct);
     }
 
     public byte[] decrypt(byte[] nonce, byte[] ciphertext) {
         checkLength(nonce, XSALSA20_POLY1305_SECRETBOX_NONCEBYTES);
         byte[] ct = Util.prependZeros(BOXZERO_BYTES, ciphertext);
         byte[] message = Util.zeros(ct.length);
         isValid(sodium().crypto_secretbox_xsalsa20poly1305_open(message, ct,
                 ct.length, nonce, seed), "Decryption failed. Ciphertext failed verification");
         return removeZeros(ZERO_BYTES, message);
     }
     
 	/* -- Internal methods -- */
 	
 	public static byte[] computeSeedFromSaltAndPassword(String salt, String password) {
 		try {
 			byte[] seed = SCrypt.scrypt(
 					CryptoUtils.decodeAscii(password),
 					CryptoUtils.decodeAscii(salt),
 					SCRYPT_PARAMS_N, SCRYPT_PARAMS_r,
 					SCRYPT_PARAMS_p, SEED_LENGTH);
 			return seed;
 		} catch (GeneralSecurityException e) {
 			throw new TechnicalException(
 					"Unable to salt password, using Scrypt library", e);
 		}
 	}
 	
 	
 }