/*
 *  Licensed to the Apache Software Foundation (ASF) under one or more
 *  contributor license agreements.  See the NOTICE file distributed with
 *  this work for additional information regarding copyright ownership.
 *  The ASF licenses this file to You under the Apache License, Version 2.0
 *  (the "License"); you may not use this file except in compliance with
 *  the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 */

/**
* @author Alexander Y. Kleymenov
* @version $Revision$
*/

package org.apache.harmony.security.provider.cert;

import java.io.IOException;
import java.io.InputStream;
import java.security.cert.CertPath;
import java.security.cert.CertificateEncodingException;
import java.security.cert.CertificateException;
import java.security.cert.X509Certificate;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collection;
import java.util.Collections;
import java.util.Iterator;
import java.util.List;
import org.apache.harmony.security.asn1.ASN1Any;
import org.apache.harmony.security.asn1.ASN1Explicit;
import org.apache.harmony.security.asn1.ASN1Implicit;
import org.apache.harmony.security.asn1.ASN1Oid;
import org.apache.harmony.security.asn1.ASN1Sequence;
import org.apache.harmony.security.asn1.ASN1SequenceOf;
import org.apache.harmony.security.asn1.ASN1Type;
import org.apache.harmony.security.asn1.BerInputStream;
import org.apache.harmony.security.pkcs7.ContentInfo;
import org.apache.harmony.security.pkcs7.SignedData;
import org.apache.harmony.security.x509.Certificate;

/**
 * This class is an implementation of X.509 CertPath. This implementation
 * provides ability to create the instance of X.509 Certification Path
 * by several means:<br>
 *
 * &nbsp;  1. It can be created over the list of X.509 certificates
 * (implementations of X509Certificate class) provided in constructor.<br>
 *
 * &nbsp;  2. It can be created by means of <code>getInstance</code> methods
 * on the base of the following ASN.1 DER encoded forms:<br>
 *
 * &nbsp;&nbsp;  - PkiPath as defined in
 * ITU-T Recommendation X.509(2000) Corrigendum 1(2001)
 * (can be seen at
 * ftp://ftp.bull.com/pub/OSIdirectory/DefectResolution/TechnicalCorrigenda/ApprovedTechnicalCorrigendaToX.509/8%7CX.509-TC1(4th).pdf)
 * <br>
 * &nbsp;&nbsp;  - PKCS #7 SignedData object provided in the form of
 * ContentInfo structure. CertPath object is generated on the base of
 * certificates presented in <code>certificates</code> field of the SignedData
 * object which in its turn is retrieved from ContentInfo structure.
 * (see http://www.ietf.org/rfc/rfc2315.txt
 * for more info on PKCS #7)
 * <br>
 * &nbsp;
 */
public class X509CertPathImpl extends CertPath {

    /**
     * @serial
     */
    private static final long serialVersionUID = 7989755106209515436L;

    // supported encoding types:
    public static final int PKI_PATH = 0;
    public static final int PKCS7 = 1;

    // supported encoding names
    private static final String[] encodingsArr = new String[] {"PkiPath", "PKCS7"};
    static final List encodings = Collections.unmodifiableList(Arrays.asList(encodingsArr));
    // the list of certificates representing this certification path
    private final List certificates;
    // PkiPath encoding of the certification path
    private byte[] pkiPathEncoding;
    // PKCS7 encoding of the certification path
    private byte[] pkcs7Encoding;

    /**
     * Creates an instance of X.509 Certification Path over the specified
     * list of certificates.
     * @throws CertificateException if some of the object in the list
     * is not an instance of subclass of X509Certificate.
     */
    public X509CertPathImpl(List certs) throws CertificateException {
        super("X.509");
        int size = certs.size();
        certificates = new ArrayList(size);
        for (int i=0; i<size; i++) {
            Object cert = certs.get(i);
            if (!(cert instanceof X509Certificate) ) {
                throw new CertificateException(
                        "One of the provided certificates is not an X509 certificate");
            }
            certificates.add(cert);
        }
    }

    /*
     * Internally used constructor.
     * Creates an X.509 Certification Path over the specified
     * list of certificates and their encoded form of specified type.
     * @param certs - the list of certificates
     * @param type - the type of the encoded form on the base of which
     * this list of certificates had been built.
     * @param encoding - encoded form of certification path.
     */
    private X509CertPathImpl(List certs, int type, byte[] encoding) {
        super("X.509");
        if (type == PKI_PATH) {
            this.pkiPathEncoding = encoding;
        } else { // PKCS7
            this.pkcs7Encoding = encoding;
        }
        // We do not need the type check and list cloning here,
        // because it has been done during decoding.
        certificates = certs;
    }

    /**
     * Generates certification path object on the base of PkiPath
     * encoded form provided via input stream.
     * @throws CertificateException if some problems occurred during
     * the decoding.
     */
    public static X509CertPathImpl getInstance(InputStream in) throws CertificateException {
        try {
            return (X509CertPathImpl) ASN1.decode(in);
        } catch (IOException e) {
            throw new CertificateException("Incorrect encoded form: " + e.getMessage());
        }
    }

    /**
     * Generates certification path object on the base of encoding provided via
     * input stream. The format of provided encoded form is specified by
     * parameter <code>encoding</code>.
     * @throws CertificateException if specified encoding form is not supported,
     * or some problems occurred during the decoding.
     */
    public static X509CertPathImpl getInstance(InputStream in, String encoding)
            throws CertificateException {
        if (!encodings.contains(encoding)) {
            throw new CertificateException("Unsupported encoding");
        }
        try {
            if (encodingsArr[0].equals(encoding)) {
                // generate the object from PkiPath encoded form
                return (X509CertPathImpl) ASN1.decode(in);
            } else {
                // generate the object from PKCS #7 encoded form
                ContentInfo ci = (ContentInfo) ContentInfo.ASN1.decode(in);
                SignedData sd = ci.getSignedData();
                if (sd == null) {
                    throw new CertificateException(
                            "Incorrect PKCS7 encoded form: missing signed data");
                }
                List<Certificate> certs = sd.getCertificates();
                if (certs == null) {
                    // empty chain of certificates
                    certs = new ArrayList<Certificate>();
                }
                List<X509CertImpl> result = new ArrayList<X509CertImpl>();
                for (Certificate cert : certs) {
                    result.add(new X509CertImpl(cert));
                }
                return new X509CertPathImpl(result, PKCS7, ci.getEncoded());
            }
        } catch (IOException e) {
            throw new CertificateException("Incorrect encoded form: " + e.getMessage());
        }
    }

    /**
     * Generates certification path object on the base of PkiPath
     * encoded form provided via array of bytes.
     * @throws CertificateException if some problems occurred during
     * the decoding.
     */
    public static X509CertPathImpl getInstance(byte[] in) throws CertificateException {
        try {
            return (X509CertPathImpl) ASN1.decode(in);
        } catch (IOException e) {
            throw new CertificateException("Incorrect encoded form: " + e.getMessage());
        }
    }

    /**
     * Generates certification path object on the base of encoding provided via
     * array of bytes. The format of provided encoded form is specified by
     * parameter <code>encoding</code>.
     * @throws CertificateException if specified encoding form is not supported,
     * or some problems occurred during the decoding.
     */
    public static X509CertPathImpl getInstance(byte[] in, String encoding)
            throws CertificateException {
        if (!encodings.contains(encoding)) {
            throw new CertificateException("Unsupported encoding");
        }
        try {
            if (encodingsArr[0].equals(encoding)) {
                // generate the object from PkiPath encoded form
                return (X509CertPathImpl) ASN1.decode(in);
            } else {
                // generate the object from PKCS #7 encoded form
                ContentInfo ci = (ContentInfo) ContentInfo.ASN1.decode(in);
                SignedData sd = ci.getSignedData();
                if (sd == null) {
                    throw new CertificateException("Incorrect PKCS7 encoded form: missing signed data");
                }
                List<Certificate> certs = sd.getCertificates();
                if (certs == null) {
                    certs = new ArrayList<Certificate>();
                }
                List<X509CertImpl> result = new ArrayList<X509CertImpl>();
                for (Certificate cert : certs) {
                    result.add(new X509CertImpl(cert));
                }
                return new X509CertPathImpl(result, PKCS7, ci.getEncoded());
            }
        } catch (IOException e) {
            throw new CertificateException("Incorrect encoded form: " + e.getMessage());
        }
    }

    // ---------------------------------------------------------------------
    // ---- java.security.cert.CertPath abstract method implementations ----
    // ---------------------------------------------------------------------

    /**
     * @see java.security.cert.CertPath#getCertificates()
     * method documentation for more info
     */
    public List getCertificates() {
        return Collections.unmodifiableList(certificates);
    }

    /**
     * @see java.security.cert.CertPath#getEncoded()
     * method documentation for more info
     */
    public byte[] getEncoded() throws CertificateEncodingException {
        if (pkiPathEncoding == null) {
            pkiPathEncoding = ASN1.encode(this);
        }
        byte[] result = new byte[pkiPathEncoding.length];
        System.arraycopy(pkiPathEncoding, 0, result, 0, pkiPathEncoding.length);
        return result;
    }

    /**
     * @see java.security.cert.CertPath#getEncoded(String)
     * method documentation for more info
     */
    public byte[] getEncoded(String encoding) throws CertificateEncodingException {
        if (!encodings.contains(encoding)) {
            throw new CertificateEncodingException("Unsupported encoding");
        }
        if (encodingsArr[0].equals(encoding)) {
            // PkiPath encoded form
            return getEncoded();
        } else {
            // PKCS7 encoded form
            if (pkcs7Encoding == null) {
                pkcs7Encoding = PKCS7_SIGNED_DATA_OBJECT.encode(this);
            }
            byte[] result = new byte[pkcs7Encoding.length];
            System.arraycopy(pkcs7Encoding, 0, result, 0,
                                        pkcs7Encoding.length);
            return result;
        }
    }

    /**
     * @see java.security.cert.CertPath#getEncodings()
     * method documentation for more info
     */
    public Iterator getEncodings() {
        return encodings.iterator();
    }

    /**
     * ASN.1 DER Encoder/Decoder for PkiPath structure.
     */
    public static final ASN1SequenceOf ASN1 =
                                    new ASN1SequenceOf(ASN1Any.getInstance()) {

        /**
         * Builds the instance of X509CertPathImpl on the base of the list
         * of ASN.1 encodings of X.509 certificates provided via
         * PkiPath structure.
         * This method participates in decoding process.
         */
        public Object getDecodedObject(BerInputStream in) throws IOException {
            // retrieve the decoded content
            List encodings = (List) in.content;
            int size = encodings.size();
            List certificates = new ArrayList(size);
            for (int i=0; i<size; i++) {
                // create the X.509 certificate on the base of its encoded form
                // and add it to the list.
                certificates.add(
                    new X509CertImpl((Certificate)
                        Certificate.ASN1.decode((byte[]) encodings.get(i))));
            }
            // create and return the resulting object
            return new X509CertPathImpl(
                    certificates, PKI_PATH, in.getEncoded());
        }

        /**
         * Returns the Collection of the encoded form of certificates contained
         * in the X509CertPathImpl object to be encoded.
         * This method participates in encoding process.
         */
        public Collection getValues(Object object) {
            // object to be encoded
            X509CertPathImpl cp = (X509CertPathImpl) object;
            // if it has no certificates in it - create the sequence of size 0
            if (cp.certificates == null) {
                return new ArrayList();
            }
            int size = cp.certificates.size();
            List encodings = new ArrayList(size);
            try {
                for (int i=0; i<size; i++) {
                    // get the encoded form of certificate and place it into the
                    // list to be encoded in PkiPath format
                    encodings.add(((X509Certificate) cp.certificates.get(i)).getEncoded());
                }
            } catch (CertificateEncodingException e) {
                throw new IllegalArgumentException("Encoding Error occurred");
            }
            return encodings;
        }
    };


    //
    // encoder for PKCS#7 SignedData
    // it is assumed that only certificate field is important
    // all other fields contain precalculated encodings:
    //
    // encodes X509CertPathImpl objects
    //
    private static final ASN1Sequence ASN1_SIGNED_DATA = new ASN1Sequence(
            new ASN1Type[] {
                    // version ,digestAlgorithms, content info
                    ASN1Any.getInstance(),
                    // certificates
                    new ASN1Implicit(0, ASN1),
                    // set of crls is optional and is missed here
                    ASN1Any.getInstance(),// signers info
            }) {

        // precalculated ASN.1 encodings for
        // version ,digestAlgorithms, content info field of SignedData
        private final byte[] PRECALCULATED_HEAD = new byte[] { 0x02, 0x01,
                0x01,// version (v1)
                0x31, 0x00,// empty set of DigestAlgorithms
                0x30, 0x03, 0x06, 0x01, 0x00 // empty ContentInfo with oid=0
        };

        // precalculated empty set of SignerInfos
        private final byte[] SIGNERS_INFO = new byte[] { 0x31, 0x00 };

        protected void getValues(Object object, Object[] values) {
            values[0] = PRECALCULATED_HEAD;
            values[1] = object; // pass X509CertPathImpl object
            values[2] = SIGNERS_INFO;
        }

        // stub to prevent using the instance as decoder
        public Object decode(BerInputStream in) throws IOException {
            throw new RuntimeException(
                    "Invalid use of encoder for PKCS#7 SignedData object");
        }
    };

    private static final ASN1Sequence PKCS7_SIGNED_DATA_OBJECT = new ASN1Sequence(
            new ASN1Type[] { ASN1Any.getInstance(), // contentType
                    new ASN1Explicit(0, ASN1_SIGNED_DATA) // SignedData
            }) {

        // precalculated ASN.1 encoding for SignedData object oid
        private final byte[] SIGNED_DATA_OID = ASN1Oid.getInstance().encode(
                ContentInfo.SIGNED_DATA);

        protected void getValues(Object object, Object[] values) {
            values[0] = SIGNED_DATA_OID;
            values[1] = object; // pass X509CertPathImpl object
        }

        // stub to prevent using the instance as decoder
        public Object decode(BerInputStream in) throws IOException {
            throw new RuntimeException(
                    "Invalid use of encoder for PKCS#7 SignedData object");
        }
    };
}