/*
 * 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 com.sun.jini.discovery.internal;

import java.nio.ByteBuffer;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.util.Iterator;
import net.jini.core.constraint.Integrity;
import net.jini.core.constraint.InvocationConstraint;
import net.jini.core.constraint.InvocationConstraints;
import net.jini.io.UnsupportedConstraintException;

/**
 * Superclass for endpoint-based unicast discovery providers.
 */
class EndpointBasedProvider extends BaseProvider {

    /** Object providing access to non-public endpoint operations */
    protected final EndpointInternals endpointInternals;

    /**
     * Constructs instance with the given format name and object providing
     * access to non-public endpoint operations.
     */
    EndpointBasedProvider(String formatName,
			  EndpointInternals endpointInternals)
    {
	super(formatName);
	if (endpointInternals == null) {
	    throw new NullPointerException();
	}
	this.endpointInternals = endpointInternals;
    }

    /**
     * Returns true if the given constraints include Integrity.YES as a
     * requirement or preference; returns false otherwise.  If the required
     * constraints include any constraint other than an Integrity constraint,
     * an UnsupportedConstraintException is thrown.
     */
    static boolean checkIntegrity(InvocationConstraints constraints)
	throws UnsupportedConstraintException
    {
	boolean integrity = false;
	for (Iterator i = constraints.requirements().iterator(); i.hasNext(); )
	{
	    InvocationConstraint c = (InvocationConstraint) i.next();
	    if (c == Integrity.YES) {
		integrity = true;
	    } else if (!(c instanceof Integrity)) {
		throw new UnsupportedConstraintException(
		    "cannot satisfy constraint: " + c);
	    }
	    // NYI: support ConstraintAlternatives containing Integrity
	}
	if (!integrity) {
	    for (Iterator i = constraints.preferences().iterator();
		 i.hasNext(); )
	    {
		if (i.next() == Integrity.YES) {
		    integrity = true;
		    break;
		}
		// NYI: support ConstraintAlternatives containing Integrity
	    }
	}
	return integrity;
    }

    /**
     * Returns the SHA-1 hash of the concatenation of the given unicast
     * discovery request and response handshake bytes.
     */
    static byte[] calcHandshakeHash(ByteBuffer request, ByteBuffer response) {
	try {
	    MessageDigest md = MessageDigest.getInstance("SHA-1");
	    update(md, request);
	    update(md, response);
	    return md.digest();
	} catch (NoSuchAlgorithmException e) {
	    throw new AssertionError(e);
	}
    }

    private static void update(MessageDigest md, ByteBuffer buf) {
	if (buf.hasArray()) {
	    md.update(buf.array(),
		      buf.arrayOffset() + buf.position(),
		      buf.remaining());
	    buf.position(buf.limit());
	} else {
	    byte[] b = new byte[buf.remaining()];
	    buf.get(b);
	    md.update(b, 0, b.length);
	}
    }
}