/*
 * 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;

import java.io.IOException;
import java.net.DatagramPacket;
import java.net.Socket;
import java.util.Collection;
import net.jini.core.constraint.InvocationConstraints;
import net.jini.io.UnsupportedConstraintException;

/**
 * Class providing methods for participating in versions 1 and 2 of the
 * discovery protocol. <p>
 *
 * <b><font size="+1">Logging</font></b> <p>
 *
 * This implementation uses the {@link java.util.logging.Logger}s named
 * <code>com.sun.jini.discovery.DiscoveryV1</code> and
 * <code>com.sun.jini.discovery.DiscoveryV2</code> to log information at the
 * following logging levels: <p>
 *
 * <table border="1" cellpadding="5"
 *	  summary="Describes logging performed by the
 *		   Discovery class to the DiscoveryV1 logger at various
 *		   logging levels">
 *
 * <caption halign="center" valign="top"><b><code>
 *	    com.sun.jini.discovery.DiscoveryV1</code></b></caption>
 *
 * <tr> <th scope="col"> Level <th scope="col"> Description
 *
 * <tr> <td> {@link java.util.logging.Level#FINEST FINEST}
 *	<td> Encoding and decoding of discovery protocol version 1 multicast
 *	     requests, multicast announcements, and unicast responses
 *
 * </table> <p>
 *
 * <table border="1" cellpadding="5"
 *	  summary="Describes logging performed by the
 *		   Discovery class to the DiscoveryV2 logger at various logging
 *		   levels">
 *
 * <caption halign="center" valign="top"><b><code>
 *	    com.sun.jini.discovery.DiscoveryV2</code></b></caption>
 *
 * <tr> <th scope="col"> Level <th scope="col"> Description
 *
 * <tr> <td> {@link java.util.logging.Level#WARNING WARNING}
 *	<td> Truncation of unicast request format ID list due to length;
 *	     discovery format providers that are unusable or have conflicting
 *	     discovery format IDs
 *
 * <tr> <td> {@link com.sun.jini.logging.Levels#HANDLED HANDLED}
 *	<td> Constraint check failures encountered during the unicast discovery
 *	     handshake when determining a suitable discovery format to use
 *
 * <tr> <td> {@link java.util.logging.Level#FINEST FINEST}
 *	<td> Encoding and decoding of discovery protocol version 2 multicast
 *	     requests, multicast announcements, and unicast responses; also,
 *	     access of <code>Discovery</code> instances implementing protocol
 *	     version 2
 *
 * </table>
 *
 * @since 2.0
 */
public abstract class Discovery {

    /** The version number for discovery protocol version 1. */
    public static final int PROTOCOL_VERSION_1 = 1;

    /** The version number for discovery protocol version 2. */
    public static final int PROTOCOL_VERSION_2 = 2;

    static final int MIN_MAX_PACKET_SIZE = 512;

    /**
     * Returns an instance implementing protocol version 1.
     *
     * @return an instance implementing protocol version 1
     */
    public static Discovery getProtocol1() {
	return DiscoveryV1.getInstance();
    }

    /**
     * Returns an instance implementing protocol version 2 which uses providers
     * loaded from the given class loader, or the current context class loader
     * if the given loader is <code>null</code>.  Available providers are
     * determined by interpreting any resources of the indicated class loader
     * named
     * <code>"META-INF/services/com.sun.jini.discovery.DiscoveryFormatProvider"</code>
     * as files containing names of provider classes, with one name per line.
     *
     * @param loader class loader from which to load providers, or
     * <code>null</code> to indicate the current context class loader
     * @return an instance implementing protocol version 2
     */
    public static Discovery getProtocol2(ClassLoader loader) {
	return DiscoveryV2.getInstance(loader);
    }

    /**
     * Returns an instance implementing protocol version 2 which uses the given
     * providers.  Contents of arrays are copied; <code>null</code> array
     * values are equivalent to empty arrays.
     *
     * @param mre providers for encoding multicast requests
     * @param mrd providers for decoding multicast requests
     * @param mae providers for encoding multicast announcements
     * @param mad providers for decoding multicast announcements
     * @param udc providers for performing the client side of unicast discovery
     * @param uds providers for performing the server side of unicast discovery
     * @return an instance implementing protocol version 2
     */
    public static Discovery getProtocol2(MulticastRequestEncoder[] mre,
					 MulticastRequestDecoder[] mrd,
					 MulticastAnnouncementEncoder[] mae,
					 MulticastAnnouncementDecoder[] mad,
					 UnicastDiscoveryClient[] udc,
					 UnicastDiscoveryServer[] uds)
    {
	return DiscoveryV2.getInstance(mre, mrd, mae, mad, udc, uds);
    }

    /**
     * Returns an iterator which can be used to encode the given multicast
     * request data into sets of {@link DatagramPacket}s, each bounded in
     * length by the specified maximum packet size, in a manner that satisfies
     * the given constraints.  <code>null</code> constraints are considered
     * equivalent to empty constraints.  The destination of each
     * <code>DatagramPacket</code> produced by the returned iterator is set to
     * the address returned by
     * {@link net.jini.discovery.Constants#getRequestAddress}, with the value
     * of {@link net.jini.discovery.Constants#discoveryPort} used as the
     * destination port.
     *
     * @param request the request data to encode
     * @param maxPacketSize the maximum size of packets to produce
     * @param constraints the constraints to apply when encoding the data, or
     * <code>null</code>
     * @return an iterator to use for encoding the data
     * @throws NullPointerException if <code>request</code> is
     * <code>null</code>
     */
    public abstract EncodeIterator encodeMulticastRequest(
					MulticastRequest request,
					int maxPacketSize,
					InvocationConstraints constraints);

    /**
     * Decodes the multicast request data contained in the given datagram in a
     * manner that satisfies the specified constraints and client subject
     * checker (if any), returning a {@link MulticastRequest} instance that
     * contains the decoded data.  <code>null</code> constraints are considered
     * equivalent to empty constraints.  All the specified constraints are
     * checked before this method returns.
     *
     * @param packet the packet to decode
     * @param constraints the constraints to apply when decoding the packet, or
     * <code>null</code>
     * @param checker the object to use to check the client subject, or
     * <code>null</code>
     * @return the decoded multicast request data
     * @throws IOException if an error occurs in interpreting the data
     * @throws UnsupportedConstraintException if unable to satisfy the
     * specified constraints
     * @throws SecurityException if the given constraints cannot be satisfied
     * due to insufficient caller permissions, or if the client subject check
     * fails
     * @throws NullPointerException if <code>packet</code> is <code>null</code>
     */
    public abstract MulticastRequest decodeMulticastRequest(
					DatagramPacket packet,
					InvocationConstraints constraints,
					ClientSubjectChecker checker)
	throws IOException;

    /**
     * Decodes the multicast request data contained in the given datagram in a
     * manner that satisfies the specified constraints and client subject
     * checker (if any), returning a {@link MulticastRequest} instance that
     * contains the decoded data, with constraint checking optionally
     * delayed.  <code>null</code> constraints are considered
     * equivalent to empty constraints.
     * <p>The <code>delayConstraintCheck</code> flag is used to control delayed
     * constraint checking. Delayed constraint checking is useful for
     * potentially delaying the expense of complete constraint checking, until
     * other checks have been made on the returned
     * <code>MulticastRequest</code> for preliminary validation.
     * Implementations may ignore the flag, in which case, the behavior is
     * equivalent to that of {@link
     * Discovery#decodeMulticastRequest(DatagramPacket, InvocationConstraints,
     * ClientSubjectChecker) decodeMulticastRequest}.
     * <p>If <code>delayConstraintCheck</code> is <code>true</code>, the method
     * behaves as follows:<ul>
     * <li> Some of the specified constraints may not be checked before this
     * method returns; the returned <code>MulticastRequest</code>'s
     * {@link MulticastRequest#checkConstraints checkConstraints}
     * method must be invoked to complete checking of all the constraints.
     * <li> Constraints which must be checked before accessor methods of the
     * returned <code>MulticastRequest</code> can be invoked are always
     * checked before this method returns.</ul>
     * <p>If <code>delayConstraintCheck</code> is <code>false</code>, all the
     * specified constraints are checked before this method returns.
     * <p><code>Discovery</code> implements this method to simply invoke {@link
     * Discovery#decodeMulticastRequest(DatagramPacket, InvocationConstraints,
     * ClientSubjectChecker) decodeMulticastRequest}, and thus checks all the
     * specified constraints before returning.
     *
     * @param packet the packet to decode
     * @param constraints the constraints to apply when decoding the packet, or
     * <code>null</code>
     * @param checker the object to use to check the client subject, or
     * <code>null</code>
     * @param delayConstraintCheck flag to control delayed constraint checking
     * @return the decoded multicast request data.
     * @throws IOException if an error occurs in interpreting the data
     * @throws SecurityException if the given constraints cannot be satisfied
     * due to insufficient caller permissions, or if the client subject check
     * fails
     * @throws NullPointerException if <code>packet</code> is <code>null</code>
     * @since 2.1
     */
    public MulticastRequest decodeMulticastRequest(
					DatagramPacket packet,
					InvocationConstraints constraints,
					ClientSubjectChecker checker,
                                        boolean delayConstraintCheck)
	throws IOException 
    {
	return decodeMulticastRequest(packet, constraints, checker);
    }
    
    /**
     * Returns an iterator which can be used to encode the given multicast
     * announcement data into sets of {@link DatagramPacket}s, each bounded in
     * length by the specified maximum packet size, in a manner that satisfies
     * the given constraints.  <code>null</code> constraints are considered
     * equivalent to empty constraints.  The destination of each
     * <code>DatagramPacket</code> produced by the returned iterator is set to
     * the address returned by
     * {@link net.jini.discovery.Constants#getAnnouncementAddress}, with the
     * value of {@link net.jini.discovery.Constants#discoveryPort} used as the
     * destination port.
     *
     * @param announcement the announcement data to encode
     * @param maxPacketSize the maximum size of packets to produce
     * @param constraints the constraints to apply when encoding the data, or
     * <code>null</code>
     * @return an iterator to use for encoding the data
     * @throws NullPointerException if <code>announcement</code> is
     * <code>null</code>
     */
    public abstract EncodeIterator encodeMulticastAnnouncement(
					MulticastAnnouncement announcement,
					int maxPacketSize,
					InvocationConstraints constraints);

    /**
     * Decodes the multicast announcement data contained in the given datagram
     * in a manner that satisfies the specified constraints, returning a {@link
     * MulticastAnnouncement} instance that contains the decoded data.
     * <code>null</code> constraints are considered equivalent to empty
     * constraints.  All the specified constraints are checked before this
     * method returns.
     *
     * @param packet the packet to decode
     * @param constraints the constraints to apply when decoding the packet, or
     * <code>null</code>
     * @return the decoded multicast announcement data
     * @throws IOException if an error occurs in interpreting the data
     * @throws UnsupportedConstraintException if unable to satisfy the
     * specified constraints
     * @throws SecurityException if the given constraints cannot be satisfied
     * due to insufficient caller permissions
     * @throws NullPointerException if <code>packet</code> is <code>null</code>
     */
    public abstract MulticastAnnouncement decodeMulticastAnnouncement(
					DatagramPacket packet,
					InvocationConstraints constraints)
	throws IOException;
    
    /**
     * Decodes the multicast announcement data contained in the given datagram
     * in a manner that satisfies the specified constraints, returning a {@link
     * MulticastAnnouncement} instance that contains the decoded data, with
     * constraint checking optionally delayed.  <code>null</code> constraints
     * are considered equivalent to empty constraints.
     * <p>The <code>delayConstraintCheck</code> flag is used to control delayed
     * constraint checking.  Delayed constraint checking is useful for
     * potentially delaying the expense of complete constraint checking, until
     * other checks have been made on the returned
     * <code>MulticastAnnouncement</code> for preliminary validation.
     * Implementations may ignore the flag, in which case, the behavior is
     * equivalent to that of {@link 
     * Discovery#decodeMulticastAnnouncement(DatagramPacket,
     * InvocationConstraints) decodeMulticastAnnouncement}.
     * <p>If <code>delayConstraintCheck</code> is <code>true</code>, the method
     * behaves as follows:<ul>
     * <li> Some of the specified constraints may not be checked before this
     * method returns; the returned <code>MulticastAnnouncement</code>'s
     * {@link MulticastAnnouncement#checkConstraints checkConstraints}
     * method must be invoked to complete checking of all the constraints.
     * <li> Constraints which must be checked before accessor methods of the
     * returned <code>MulticastAnnouncement</code> can be invoked are always
     * checked before this method returns.</ul>
     * <p> If <code>delayConstraintCheck</code> is <code>false</code>,
     * all the specified constraints are checked before this method returns.
     * <p><code>Discovery</code> implements this method to simply invoke {@link
     * Discovery#decodeMulticastAnnouncement(DatagramPacket,
     * InvocationConstraints) decodeMulticastAnnouncement}, and thus checks
     * all the specified constraints before returning.
     *
     * @param packet the packet to decode
     * @param constraints the constraints to apply when decoding the packet, or
     * <code>null</code>
     * @param delayConstraintCheck flag to control delayed constraint checking
     * @return the decoded multicast announcement data.
     * @throws IOException if an error occurs in interpreting the data
     * @throws UnsupportedConstraintException if unable to satisfy the
     * specified constraints
     * @throws SecurityException if the given constraints cannot be satisfied
     * due to insufficient caller permissions.
     * @throws NullPointerException if <code>packet</code> is <code>null</code>
     * @since 2.1
     */
    public MulticastAnnouncement decodeMulticastAnnouncement(
					DatagramPacket packet,
					InvocationConstraints constraints,
                                        boolean delayConstraintCheck)
	throws IOException
    {
	return decodeMulticastAnnouncement(packet, constraints);
    }
    
    /**
     * Performs the client side of unicast discovery, obtaining the returned
     * response data over the provided socket using the given default and
     * codebase verifier class loaders and collection of object stream context
     * objects in a manner that satisfies the specified constraints.
     * <code>null</code> constraints are considered equivalent to empty
     * constraints.  
     *
     * @param socket the socket on which to perform unicast discovery
     * @param constraints the constraints to apply to unicast discovery, or
     * <code>null</code>
     * @param defaultLoader the class loader value (possibly <code>null</code>)
     * to be passed as the <code>defaultLoader</code> argument to
     * <code>RiverClassLoader</code> methods when unmarshalling the registrar
     * proxy
     * @param verifierLoader the class loader value (possibly
     * <code>null</code>) to pass to {@link
     * net.jini.security.Security#verifyCodebaseIntegrity
     * Security.verifyCodebaseIntegrity}, if codebase integrity verification is
     * used when unmarshalling the registrar proxy
     * @param context the collection of context information objects (possibly
     * <code>null</code>) to use when unmarshalling the registrar proxy
     * @return the received unicast response data
     * @throws IOException if an error occurs in interpreting received data or
     * in formatting data to send
     * @throws UnsupportedConstraintException if unable to satisfy the
     * specified constraints
     * @throws SecurityException if the given constraints cannot be satisfied
     * due to insufficient caller permissions
     * @throws ClassNotFoundException if the class of the discovered registrar
     * cannot be resolved
     * @throws NullPointerException if <code>socket</code> is <code>null</code>
     */
    public abstract UnicastResponse doUnicastDiscovery(
					Socket socket,
					InvocationConstraints constraints,
					ClassLoader defaultLoader,
					ClassLoader verifierLoader,
					Collection context)
	throws IOException, ClassNotFoundException;

    /**
     * Handles the server side of unicast discovery, transmitting the given
     * response data over the provided socket using the given collection of
     * object stream context objects in a manner that satisfies the specified
     * constraints and client subject checker (if any).  This method assumes
     * that the protocol version number has already been consumed from the
     * socket, but that no further processing of the connection has occurred.
     * <code>null</code> constraints are considered equivalent to empty
     * constraints.
     *
     * @param response the unicast response data to transmit
     * @param socket the socket on which to handle unicast discovery
     * @param constraints the constraints to apply to unicast discovery, or
     * <code>null</code>
     * @param checker the object to use to check the client subject, or
     * <code>null</code>
     * @param context the collection of context information objects to use when
     * marshalling the registrar proxy
     * @throws IOException if the protocol handshake fails, or if an error
     * occurs in interpreting received data or in formatting data to send
     * @throws UnsupportedConstraintException if unable to satisfy the
     * specified constraints
     * @throws SecurityException if the given constraints cannot be satisfied
     * due to insufficient caller permissions, or if the client subject check
     * fails
     * @throws NullPointerException if <code>response</code>,
     * <code>socket</code>, or <code>context</code> is <code>null</code>
     */
    public abstract void handleUnicastDiscovery(
					UnicastResponse response,
					Socket socket,
					InvocationConstraints constraints,
					ClientSubjectChecker checker,
					Collection context)
	throws IOException;
}