package cn.home1.oss.lib.common.crypto;
   
   import static com.google.common.base.Charsets.UTF_8;
   import static com.google.common.base.Preconditions.checkArgument;
   
   import lombok.Getter;
   import lombok.SneakyThrows;
   
   import java.security.Key;
  import java.security.Provider;
  
  import javax.crypto.Cipher;
  
  import cn.home1.oss.lib.common.CodecUtils;
  
  /**
   * Created by zhanghaolun on 16/10/25.
   */
  public class RsaDecryptor implements EncodeDecryptor {
  
    private final Provider provider;
    @Getter
    private final RsaKey key;
  
    public RsaDecryptor(final Provider provider, final KeyExpression keyExpression) {
      this.provider = provider;
      this.key = new RsaKey(keyExpression);
    }
  
    @Override
    public String decrypt(final String ciphertext) {
      return decodeAndDecrypt(this.provider, this.key.getRsaPrivateKey(), ciphertext);
    }
  
    @SneakyThrows
    public static byte[] decryptBytes(final Provider provider, final Key key, final byte[] binary) {
      final Cipher cipher = Cipher.getInstance(CryptoConstants.RSA_ECB_PKCS1_PADDING, provider);
      cipher.init(Cipher.DECRYPT_MODE, key);
      return cipher.doFinal(binary);
    }
  
    @SneakyThrows
    public static String decodeAndDecrypt(final Provider provider, final Key key, final String ciphertext) {
      checkArgument(key != null, "key must not null");
  
      final String result;
      if (ciphertext == null) {
        result = null;
      } else if (ciphertext.length() == 0) {
        result = "";
      } else {
        final byte[] binary = CodecUtils.decodeBase64(ciphertext);
        final byte[] decrypted = decryptBytes(provider, key, binary);
        result = new String(decrypted, UTF_8);
      }
      return result;
    }
  }