/*************************************************************************
 *                                                                       *
 *  EJBCA Community: The OpenSource Certificate Authority                *
 *                                                                       *
 *  This software is free software; you can redistribute it and/or       *
 *  modify it under the terms of the GNU Lesser General Public           *
 *  License as published by the Free Software Foundation; either         *
 *  version 2.1 of the License, or any later version.                    *
 *                                                                       *
 *  See terms of license at gnu.org.                                     *
 *                                                                       *
 *************************************************************************/
package org.cesecore.certificates.certificate;

import java.io.IOException;
import java.math.BigInteger;
import java.security.cert.CertificateException;
import java.security.cert.X509Certificate;

import javax.security.auth.x500.X500Principal;

import org.apache.log4j.Logger;
import org.bouncycastle.asn1.x500.X500Name;
import org.bouncycastle.cert.X509CertificateHolder;
import org.bouncycastle.cert.jcajce.JcaX509CertificateConverter;
import org.bouncycastle.util.encoders.Base64;
import org.cesecore.keys.util.KeyTools;
import org.cesecore.util.CertTools;

/**
 * An object of this class is identifying one or several certificates or a CRL.
 *
 * @version $Id: HashID.java 26020 2017-06-14 12:41:08Z mikekushner $
 */
public class HashID {
	/** Log4j instance for Base */
	private static final Logger log = Logger.getLogger(HashID.class);
	/**
	 * True if the ID confirms to a RFC4387 ID.
	 */
	private final boolean isOK;
	/*
	 * The RFC4387 identification string. This is a base64 encoding of the hash.
	 */
	private final String b64;

    /**
	 * The b64 with \ substituted with %2B to be used for URLs
	 */
	private final String b64url;
	/**
	 * Key to be used for hash tables.
	 */
	private final Integer key;
	
	private HashID(byte hash[]) {
		final String b64padded = new String(Base64.encode(hash));
		if ( b64padded.length()!=28 || b64padded.charAt(27)!='=' ) {
			this.isOK = false;
			this.b64 = b64padded;
		} else {
			this.isOK = true;
			this.b64 = b64padded.substring(0, 27);
		}
		this.b64url = this.b64.replaceAll("\\+", "%2B");
		this.key = Integer.valueOf(new BigInteger(hash).hashCode());
	}
	private static byte[] hashFromPrincipalDN( X500Principal principal ) {
		return CertTools.generateSHA1Fingerprint(principal.getEncoded());
	}
	private static HashID getFromDN(X500Principal principal) {
		final HashID id = new HashID(hashFromPrincipalDN(principal));
		if ( id.isOK ) {
			if ( log.isDebugEnabled() ) {
				log.debug("The DN '"+principal.getName()+"' is identified by the Hash string '"+id.b64+"' when accessing the VA.");
			}
		} else {
			log.error("The DN '"+principal.getName()+"' has a non valid Hash identification string: "+id.b64);
		}
		return id;
	}
	/**
	 * @param cert The subject DN of the certificate should be the identifier.
	 * @return the ID
	 */
	public static HashID getFromSubjectDN(X509Certificate cert) {
		return getFromDN( cert.getSubjectX500Principal() );
	}
	/**
	 * @param cert The issuer DN of the certificate should be the identifier.
	 * @return the ID
	 */
	public static HashID getFromIssuerDN(X509Certificate cert) {
		return getFromDN( cert.getIssuerX500Principal() );
	}
	
	/**
     * @param cert The issuer DN of the certificate should be the identifier.
     * @return the ID
	 * @throws CertificateException 
     */
	public static HashID getFromIssuerDN(X509CertificateHolder certificateHolder) throws CertificateException {
        return getFromIssuerDN(new JcaX509CertificateConverter().getCertificate(certificateHolder));
    }
    /**
     * @param sDN A string representation of a DN to be as ID. The DN will not be transformed in any way.
     * @return the ID.
     */
    public static HashID getFromDNString(String sDN) {
		// Note that the DN string has to be encoded to an ASN1 with the BC lib. BC endcoding is EJBCA standard.
        try {
            return getFromDN( new X500Principal(new X500Name(CertTools.isDNReversed(sDN) ? CertTools.reverseDN(sDN) : sDN).getEncoded()));
        } catch (IOException e) {
           throw new IllegalStateException(e);
        }
	}
	/**
	 * @param s The hash base64 encoded. See RFC4387
	 * @return the ID.
	 */
	public static HashID getFromB64( String s ) {
		return new HashID( Base64.decode(s.length()==27 ? s+'=' : s) );
	}
	/**
	 * @param cert The public key of the certificate will be used as ID.
	 * @return the ID.
	 */
	public static HashID getFromKeyID(X509Certificate cert) {
		final HashID id  = new HashID( KeyTools.createSubjectKeyId(cert.getPublicKey()).getKeyIdentifier() );
		if ( id.isOK ) {
			if ( log.isDebugEnabled() ) {
				log.debug("The certificate with subject DN '"+cert.getSubjectX500Principal().getName()+"' can be fetched with 'search.cgi?sKIDHash="+id.b64+"' from the VA.");
			}
		} else {
			log.error("The certificate with subject DN '"+cert.getSubjectX500Principal().getName()+"' gives a sKIDHash with a not valid format: "+id.b64);
		}
		return id;
	}
	public static HashID getFromAuthorityKeyId(X509Certificate cert) throws IOException {
		final byte hash[]  = CertTools.getAuthorityKeyId(cert);
		if ( hash==null ) {
			return null;
		}
		final HashID id  = new HashID( CertTools.getAuthorityKeyId(cert) );
		if ( !id.isOK ) {
			log.error("The certificate with subject DN '"+cert.getSubjectX500Principal().getName()+"' don't have a valid AuthorityKeyId: "+id.b64);
		}
		return id;
	}
    public String getB64url() {
        return b64url;
    }
    public Integer getKey() {
        return key;
    }
    
    public String getB64() {
        return b64;
    }
}