/*_############################################################################
  _## 
  _##  SNMP4J-AgentX - AgentXMasterAgent.java  
  _## 
  _##  Copyright (C) 2005-2026  Frank Fock (SNMP4J.org)
  _##  
  _##  This program is free software; you can redistribute it and/or modify
  _##  it under the terms of the GNU General Public License version 2 as 
  _##  published by the Free Software Foundation.
  _##
  _##  This program is distributed in the hope that it will be useful,
  _##  but WITHOUT ANY WARRANTY; without even the implied warranty of
  _##  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  _##  GNU General Public License for more details.
  _##
  _##  You should have received a copy of the GNU General Public License
  _##  along with this program; if not, write to the Free Software
  _##  Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, 
  _##  MA  02110-1301  USA
  _##  
  _##########################################################################*/

package org.snmp4j.agent.agentx.master;

import java.io.File;

import org.snmp4j.TransportMapping;
import org.snmp4j.agent.*;
import org.snmp4j.agent.agentx.AgentX;
import org.snmp4j.agent.agentx.AgentXMessageDispatcherImpl;
import org.snmp4j.agent.agentx.AgentXProtocol;
import org.snmp4j.agent.audit.AgentAuditPolicy;
import org.snmp4j.agent.mo.MOFactory;
import org.snmp4j.agent.mo.snmp.dh.DHKickstartParameters;
import org.snmp4j.log.LogAdapter;
import org.snmp4j.log.LogFactory;
import org.snmp4j.mp.MPv3;
import org.snmp4j.smi.IpAddress;
import org.snmp4j.smi.OctetString;
import org.snmp4j.transport.ConnectionOrientedTransportMapping;
import org.snmp4j.transport.TransportStateEvent;
import org.snmp4j.transport.TransportStateListener;

import org.snmp4j.cfg.EngineBootsProvider;
import org.snmp4j.MessageDispatcher;
import org.snmp4j.agent.io.MOPersistenceProvider;
import org.snmp4j.util.WorkerPool;
import org.snmp4j.agent.io.MOInputFactory;
import org.snmp4j.agent.security.VACM;
import org.snmp4j.MessageDispatcherImpl;
import org.snmp4j.util.ThreadPool;
import org.snmp4j.agent.io.DefaultMOPersistenceProvider;
import org.snmp4j.cfg.EngineBootsCounterFile;
import org.snmp4j.agent.agentx.version.VersionInfo;

import java.io.IOException;
import java.util.Collection;

/**
 * The {@code AgentXMasterAgent} is the base agent class for
 * AgentX master agents. It extends the {@link AgentConfigManager} class
 * provided by SNMP4J-Agent.
 * <p>
 * To implement a master agent, simply extend this class instead of
 * {@link AgentConfigManager} as you would do for a non-AgentX agent.
 *
 * @author Frank Fock
 * @version 4.2.0
 */
public class AgentXMasterAgent extends AgentConfigManager implements TransportStateListener {

    private static final LogAdapter LOGGER = LogFactory.getLogger(AgentXMasterAgent.class);

    private static short maxGetBulkRepetitions = Short.MAX_VALUE;
    private final AgentX agentX;
    private AgentXCommandProcessor commandProcessor;
    private final AgentXQueue queue = new AgentXQueue();
    private AgentXMib agentXMIB;
    private boolean localhostSubagentsOnly;
    private AgentAuditPolicy agentAuditPolicy;

    /**
     * Creates an SNMP agent configuration which can be run by calling
     * {@link #run()} later.
     *
     * @param agentsOwnEngineID
     *         the authoritative engine ID of the agent.
     * @param messageDispatcher
     *         the MessageDispatcher to use. The message dispatcher must be configured
     *         outside, i.e. transport mappings have to be added before this
     *         constructor is being called.
     * @param vacm
     *         a view access control model. Typically, this parameter is set to
     *         {@code null} to use the default VACM associated with the
     *         {@code VacmMIB}.
     * @param moServers
     *         the managed object server(s) that server the managed objects available
     *         to this agent.
     * @param workerPool
     *         the {@code WorkerPool} to be used to process incoming request.
     * @param configurationFactory
     *         a {@code MOInputFactory} that creates a {@code MOInput} stream
     *         with containing serialized ManagedObject information with the agent's
     *         configuration or {@code null} otherwise.
     * @param persistenceProvider
     *         the primary {@code MOPersistenceProvider} to be used to load
     *         and store persistent MOs.
     * @param engineBootsProvider
     *         the provider of engine boots counter.
     * @param moFactory
     *         the {@code MOFactory} to be used to create managed objects or {@code null}
     *         if the {@link org.snmp4j.agent.mo.DefaultMOFactory} is to be used.
     * @param dhParameters
     *         the collection of Diffie-Hellman parameters to be used for
     *         authentication or {@code null} if no Diffie-Hellman parameters
     *         are to be used.
     * @param agentAuditPolicy
     *         the agent audit policy to be used to audit agent activity.
     * @since 4.2.0
     */
    public AgentXMasterAgent(OctetString agentsOwnEngineID,
                             MessageDispatcher messageDispatcher,
                             VACM vacm,
                             MOServer[] moServers,
                             WorkerPool workerPool,
                             MOInputFactory configurationFactory,
                             MOPersistenceProvider persistenceProvider,
                             EngineBootsProvider engineBootsProvider,
                             MOFactory moFactory,
                             Collection<DHKickstartParameters> dhParameters,
                             AgentAuditPolicy agentAuditPolicy) {
        super(agentsOwnEngineID, messageDispatcher, vacm, moServers,
                workerPool, configurationFactory, persistenceProvider, engineBootsProvider,
                moFactory, dhParameters, agentAuditPolicy);
        sysDescr.setValue("SNMP4J-AgentX " +
                VersionInfo.getVersion() + " [" +
                org.snmp4j.agent.version.VersionInfo.getVersion() +
                "," + org.snmp4j.version.VersionInfo.getVersion() +
                "]" +
                " - " + System.getProperty("os.name", "") +
                " - " + System.getProperty("os.arch") +
                " - " + System.getProperty("os.version"));
        agentX = new AgentX(new AgentXMessageDispatcherImpl());
    }

    /**
     * Creates the command processor.
     *
     * @param engineID
     *         the engine ID of the agent.
     *
     * @return a new CommandProcessor instance.
     */
    @Override
    protected CommandProcessor createCommandProcessor(OctetString engineID) {
        AgentXCommandProcessor cp = new AgentXCommandProcessor(engineID, queue, agentX, servers);
        agentX.addCommandResponder(cp);
        this.agentXMIB = new AgentXMib(cp);
        cp.setNotificationOriginator(getNotificationOriginator());
        cp.addAgentXMasterListener(this.agentXMIB);
        this.commandProcessor = cp;
        return cp;
    }

    /**
     * Adds a transport mapping for AgentX communication.
     * @param transport
     *    a {@link TransportMapping}.
     */
    public void addAgentXTransportMapping(TransportMapping<?> transport) {
        agentX.getMessageDispatcher().addTransportMapping(transport);
        if (transport instanceof ConnectionOrientedTransportMapping<?> cotm) {
            cotm.addTransportStateListener(this);
            cotm.setConnectionTimeout(0);
            cotm.setMessageLengthDecoder(new AgentXProtocol());
        }
    }

    /**
     * Removes a transport mapping for AgentX communication.
     * @param transport
     *    a {@link TransportMapping}.
     */
    public void removeAgentXTransportMapping(TransportMapping<?> transport) {
        agentX.getMessageDispatcher().removeTransportMapping(transport);
        if (transport instanceof ConnectionOrientedTransportMapping<?> cotm) {
            cotm.removeTransportStateListener(this);
        }
    }

    /**
     * Gets the upper limit for AgentX Get Bulk repetitions field send on behalf
     * of all master agents of this JVM.
     *
     * @return the upper limit for the maximum repetitions field for AgentX Get Bulk
     * requests.
     * @see #setMaxGetBulkRepetitions
     */
    public static short getMaxGetBulkRepetitions() {
        return maxGetBulkRepetitions;
    }

    /**
     * Gets a reference to the AGENTX-MIB implementation of this master agent.
     * @return
     *    a {@link AgentXMib} reference.
     */
    public AgentXMib getAgentXMIB() {
        return agentXMIB;
    }

    /**
     * Gets the command processor.
     * @return
     *    the internal {@link AgentXCommandProcessor}.
     */
    public AgentXCommandProcessor getCommandProcessor() {
        return commandProcessor;
    }

    /**
     * Gets the local engine ID.
     *
     * @return the engine ID of the master agent.
     */
    public OctetString getLocalEngineID() {
        return super.engineID;
    }

    /**
     * Indicates whether only subagents from the local host or from any host
     * are allowed to connect to this master agent (default is any host).
     *
     * @return {@code true} if only connections from the local host are allowed
     * and {@code false} if connections from any host are allowed.
     */
    public boolean isLocalhostSubagentsOnly() {
        return localhostSubagentsOnly;
    }

    /**
     * Sets the maximum repetitions value used by this master agent for its
     * AgentX Get Bulk requests to subagents. The default is the maximum short
     * value. The SNMP GETBULK request already defines a maximum repetitions
     * value that is always the upper limit also for AgentX Get Bulk requests on
     * its behalf.
     * <p>
     * The NET-SNMP AgentX sub-agent has a bug in its AgentX Get Bulk processing
     * that causes endless loops in the sub-agent when the max-repetitions value
     * is greater than one. Since this bug is in NET-SNMP since v4.2 and still
     * present in version 5.4, it is likely, that you will need to set this
     * value to one, if your master agent should ever communicate with a NET-SNMP
     * sub-agent.
     *
     * @param maxRepetitions
     *         the upper limit of the maximum repetitions for AgentX Get Bulk
     *         sub-requests.
     */
    public static void setMaxGetBulkRepetitions(short maxRepetitions) {
        if (maxRepetitions < 1) {
            throw new IllegalArgumentException("Max repetitions needs an unsigned value");
        }
        maxGetBulkRepetitions = maxRepetitions;
    }

    /**
     * Sets the local engine ID. This method must not be called after
     * {@link #initialize()} has been called for the first time.
     *
     * @param localEngineID
     *         the (authoritative) engine ID of the master agent.
     */
    public void setLocalEngineID(OctetString localEngineID) {
        if (runState.getState() < org.snmp4j.agent.AgentState.STATE_INITIALIZED) {
            super.engineID = localEngineID;
        }
        else {
            throw new IllegalStateException("Agent is already initialized -> engine ID cannot be changed anymore");
        }
    }

    /**
     * Sets the local host only connection filter flag.
     *
     * @param localhostSubagentsOnly
     *         {@code true} if only connections from the local host are allowed
     *         and {@code false} if connections from any host are allowed.
     */
    public void setLocalhostSubagentsOnly(boolean localhostSubagentsOnly) {
        this.localhostSubagentsOnly = localhostSubagentsOnly;
    }

    @Override
    public void connectionStateChanged(TransportStateEvent change) {
        if (localhostSubagentsOnly &&
                (change.getNewState() == TransportStateEvent.STATE_CONNECTED) &&
                (change.getPeerAddress() instanceof IpAddress peerAddress)) {
            if (!peerAddress.getInetAddress().isLoopbackAddress()) {
                LOGGER.warn("Connection attempt made from non loopback (i.e. local) address '" +
                        peerAddress + "' which will be ignored");
                change.setCancelled(true);
                return;
            }
        }
        ((AgentXCommandProcessor) agent).connectionStateChanged(change);
    }

    @Override
    protected void registerMIBs(OctetString context) throws
            DuplicateRegistrationException {
        super.registerMIBs(context);
        try {
            agentXMIB.registerMOs(agent.getServer(context), context);
        } catch (DuplicateRegistrationException ex) {
            String txt = "Unable to register AgentX MIB";
            LOGGER.error(txt, ex);
            throw new DuplicateRegistrationException(txt);
        }
    }

    @Override
    protected void unregisterMIBs(OctetString context) {
        agentXMIB.unregisterMOs(agent.getServer(context), null);
    }

    /**
     * Launch (or relaunch) AgentX transport mappings.
     *
     * @throws IOException
     *         if the necessary ports could not be opened or bound.
     */
    @Override
    protected void launchTransportMappings() throws IOException {
        super.launchTransportMappings();
        launchTransportMappings(agentX.getMessageDispatcher().getTransportMappings());
    }

    /**
     * Shutdown communication be stopping all AgentX transport mappings.
     */
    @Override
    public void shutdown() {
        try {
            stopTransportMappings(agentX.getMessageDispatcher().getTransportMappings());
        } catch (IOException ex) {
            LOGGER.error("Failed to shutdown AgentX: " + ex.getMessage(), ex);
        }
        super.shutdown();
    }

}
