/**
 * 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.
 */
package org.apache.xml.security.utils;

import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.nio.file.Files;
import java.nio.file.Paths;
import java.security.SecurityPermission;

/**
 * A collection of different, general-purpose methods for JAVA-specific things
 */
public final class JavaUtils {

    private static final org.slf4j.Logger LOG =
        org.slf4j.LoggerFactory.getLogger(JavaUtils.class);

    private static final SecurityPermission REGISTER_PERMISSION =
        new SecurityPermission("org.apache.xml.security.register");

    private JavaUtils() {
        // we don't allow instantiation
    }

    /**
     * Method getBytesFromFile
     *
     * @param fileName
     * @return the bytes read from the file
     *
     * @throws FileNotFoundException
     * @throws IOException
     */
    public static byte[] getBytesFromFile(String fileName)
        throws FileNotFoundException, IOException {

        byte[] refBytes = null;

        try (InputStream inputStream = Files.newInputStream(Paths.get(fileName));
            UnsyncByteArrayOutputStream baos = new UnsyncByteArrayOutputStream()) {
            byte[] buf = new byte[1024];
            int len;

            while ((len = inputStream.read(buf)) > 0) {
                baos.write(buf, 0, len);
            }

            refBytes = baos.toByteArray();
        }

        return refBytes;
    }

    /**
     * Method writeBytesToFilename
     *
     * @param filename
     * @param bytes
     */
    public static void writeBytesToFilename(String filename, byte[] bytes) {
        if (filename != null && bytes != null) {
            try (OutputStream outputStream = Files.newOutputStream(Paths.get(filename))) {
                outputStream.write(bytes);
            } catch (IOException ex) {
                LOG.debug(ex.getMessage(), ex);
            }
        } else {
            LOG.debug("writeBytesToFilename got null byte[] pointed");
        }
    }

    /**
     * This method reads all bytes from the given InputStream till EOF and
     * returns them as a byte array.
     *
     * @param inputStream
     * @return the bytes read from the stream
     *
     * @throws FileNotFoundException
     * @throws IOException
     */
    public static byte[] getBytesFromStream(InputStream inputStream) throws IOException {
        try (UnsyncByteArrayOutputStream baos = new UnsyncByteArrayOutputStream()) {
            byte[] buf = new byte[4 * 1024];
            int len;
            while ((len = inputStream.read(buf)) > 0) {
                baos.write(buf, 0, len);
            }
            return baos.toByteArray();
        }
    }

    /**
     * Converts an ASN.1 DSA value to a XML Signature DSA Value.
     *
     * The JCE DSA Signature algorithm creates ASN.1 encoded (r, s) value
     * pairs (see section 2.2.2 of RFC 3279); the XML Signature requires the
     * core BigInteger values.
     *
     * @param asn1Bytes the ASN.1 encoded bytes
     * @param size size of r and s in bytes
     * @return the XML Signature encoded bytes
     * @throws IOException if the bytes are not encoded correctly
     * @see <A HREF="http://www.w3.org/TR/xmldsig-core1/#sec-DSA">6.4.1 DSA</A>
     */
    public static byte[] convertDsaASN1toXMLDSIG(byte[] asn1Bytes, int size)
        throws IOException
    {
        if (asn1Bytes[0] != 48 || asn1Bytes[1] != asn1Bytes.length - 2
            || asn1Bytes[2] != 2) {
            throw new IOException("Invalid ASN.1 format of DSA signature");
        }

        byte rLength = asn1Bytes[3];
        int i;
        for (i = rLength; i > 0 && asn1Bytes[4 + rLength - i] == 0; i--); //NOPMD

        byte sLength = asn1Bytes[5 + rLength];
        int j;
        for (j = sLength; j > 0 && asn1Bytes[6 + rLength + sLength - j] == 0; j--); //NOPMD

        if (i > size || asn1Bytes[4 + rLength] != 2 || j > size) {
            throw new IOException("Invalid ASN.1 format of DSA signature");
        } else {
            byte[] xmldsigBytes = new byte[size * 2];
            System.arraycopy(asn1Bytes, 4 + rLength - i, xmldsigBytes,
                             size - i, i);
            System.arraycopy(asn1Bytes, 6 + rLength + sLength - j,
                             xmldsigBytes, size * 2 - j, j);
            return xmldsigBytes;
        }
    }

    /**
     * Converts an XML Signature DSA Value to a ASN.1 DSA value.
     *
     * The JCE DSA Signature algorithm creates ASN.1 encoded (r, s) value
     * pairs (see section 2.2.2 of RFC 3279); the XML Signature requires the
     * core BigInteger values.
     *
     * @param xmldsigBytes the XML Signature encoded bytes
     * @param size size of r and s in bytes
     * @return the ASN.1 encoded bytes
     * @throws IOException if the bytes are not encoded correctly
     * @see <A HREF="http://www.w3.org/TR/xmldsig-core1/#sec-DSA">6.4.1 DSA</A>
     */
    public static byte[] convertDsaXMLDSIGtoASN1(byte[] xmldsigBytes, int size)
        throws IOException
    {
        int totalSize = size * 2;
        if (xmldsigBytes.length != totalSize) {
            throw new IOException("Invalid XMLDSIG format of DSA signature");
        }

        int i;
        for (i = size; i > 0 && xmldsigBytes[size - i] == 0; i--); //NOPMD

        int j = i;
        if (xmldsigBytes[size - i] < 0) {
            j++;
        }

        int k;
        for (k = size; k > 0 && xmldsigBytes[totalSize - k] == 0; k--); //NOPMD

        int l = k;
        if (xmldsigBytes[totalSize - k] < 0) {
            l++;
        }

        byte[] asn1Bytes = new byte[6 + j + l];
        asn1Bytes[0] = 48;
        asn1Bytes[1] = (byte)(4 + j + l);
        asn1Bytes[2] = 2;
        asn1Bytes[3] = (byte)j;
        System.arraycopy(xmldsigBytes, size - i, asn1Bytes, 4 + j - i, i);

        asn1Bytes[4 + j] = 2;
        asn1Bytes[5 + j] = (byte) l;
        System.arraycopy(xmldsigBytes, totalSize - k, asn1Bytes,
                         6 + j + l - k, k);

        return asn1Bytes;
    }

    /**
     * Throws a {@code SecurityException} if a security manager is installed
     * and the caller is not allowed to register an implementation of an
     * algorithm, transform, or other security sensitive XML Signature function.
     *
     * @throws SecurityException if a security manager is installed and the
     *    caller has not been granted the
     *    {@literal "org.apache.xml.security.register"}
     *    {@code SecurityPermission}
     */
    public static void checkRegisterPermission() {
        SecurityManager sm = System.getSecurityManager();
        if (sm != null) {
            sm.checkPermission(REGISTER_PERMISSION);
        }
    }
}
