import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import sun.security.tools.keytool.CertAndKeyGen;
import sun.security.x509.X500Name;

import java.io.IOException;
import java.security.InvalidKeyException;
import java.security.KeyStore;
import java.security.KeyStoreException;
import java.security.NoSuchAlgorithmException;
import java.security.NoSuchProviderException;
import java.security.SignatureException;
import java.security.cert.Certificate;
import java.security.cert.CertificateException;
import java.security.cert.X509Certificate;

public class CertificateUtils {

    public static final String KEY_TYPE_RSA = "RSA";
    public static final String SIG_ALG_SHA_RSA = "SHA1WithRSA";
    public static final int KEY_SIZE = 1024;
    public static final long CERT_VALIDITY = 365 * 24 * 3600L;
    public static final String ALIAS_PRIVATE = "private";
    public static final String ALIAS_CERT = "cert";
    public static final String IN_MEMORY_PWD = "notReallyImportant"; // this would only ever be relevant if/when persisted.
    private static final Logger LOGGER = LoggerFactory.getLogger(CertificateUtils.class);

    /**
     * @param certValues e.g. CN=Dave, OU=JavaSoft, O=Sun Microsystems, C=US
     * @return
     */
    public static KeyStore createSelfSigned(String certValues) {
        try {
            CertAndKeyGen keyGen = new CertAndKeyGen(KEY_TYPE_RSA, SIG_ALG_SHA_RSA);
            keyGen.generate(KEY_SIZE);

            KeyStore ks = emptyStore();
            if (ks == null) {
                return null;
            }
            X509Certificate certificate = keyGen.getSelfCertificate(new X500Name(certValues), CERT_VALIDITY);
            ks.setCertificateEntry(ALIAS_CERT, certificate);
            ks.setKeyEntry(ALIAS_PRIVATE, keyGen.getPrivateKey(), IN_MEMORY_PWD.toCharArray(), new Certificate[]{certificate});
            return ks;

        } catch (KeyStoreException | NoSuchAlgorithmException | NoSuchProviderException | CertificateException | SignatureException | InvalidKeyException | IOException e) {
            LOGGER.error("Cannot create self signed certificate.", e);
        }
        return null;
    }

    public static KeyStore createSelfSignedForHost(String host) {
        return createSelfSigned("CN=" + host);
    }

    public static KeyStore emptyStore() {
        try {
            KeyStore ks = KeyStore.getInstance("JKS");

            // Loading creates the store, can't do anything with it until it's loaded
            ks.load(null, IN_MEMORY_PWD.toCharArray());
            return ks;
        } catch (KeyStoreException | CertificateException | NoSuchAlgorithmException | IOException e) {
            LOGGER.error("Cannot create empty keystore.", e);
        }
        return null;
    }

}