/*
 * Copyright (c) 2001, 2006, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * This code 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
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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 */
package com.sun.jmx.snmp.internal;

import java.net.InetAddress;
import java.net.UnknownHostException;
import java.util.Hashtable;
import java.util.logging.Level;
import java.io.Serializable;

import com.sun.jmx.snmp.SnmpDefinitions;
import com.sun.jmx.snmp.SnmpEngineId;
import com.sun.jmx.snmp.SnmpEngine;
import com.sun.jmx.snmp.SnmpUsmKeyHandler;
import com.sun.jmx.snmp.SnmpEngineFactory;
import com.sun.jmx.snmp.SnmpUnknownModelException;

import com.sun.jmx.snmp.internal.SnmpTools;
import com.sun.jmx.snmp.SnmpBadSecurityLevelException;
import static com.sun.jmx.defaults.JmxProperties.SNMP_LOGGER;

/**
 * This engine is conformant with the RFC 2571. It is the main object within
 * an SNMP entity (agent, manager...).
 * To an engine is associated an {@link com.sun.jmx.snmp.SnmpEngineId}.
 * The way the engineId is retrieved is linked to the way the engine is
 * instantiated. See each <CODE>SnmpEngine</CODE> constructor for more details.
 * An engine is composed of a set of sub systems
 * {@link com.sun.jmx.snmp.internal.SnmpSubSystem}. An <CODE>SNMP</CODE>
 * engine can contain a:
 *<ul>
 *<li> Message Processing Sub System :
 * {@link com.sun.jmx.snmp.internal.SnmpMsgProcessingSubSystem}</li>
 *<li> Security Sub System :
 * {@link com.sun.jmx.snmp.internal.SnmpSecuritySubSystem} </li>
 *<li> Access Control Sub System :
 * {@link com.sun.jmx.snmp.internal.SnmpAccessControlSubSystem}</li>
 *</ul>
 *<P> Each sub system contains a set of models. A model is an implementation
 * of a particular treatement (eg: the User based Security Model defined in
 * RFC 2574 is a functional element dealing with authentication and privacy).
 *</P>
 * Engine instantiation is based on a factory. This factory, implementing
 * mandatorily {@link com.sun.jmx.snmp.SnmpEngineFactory  SnmpEngineFactory}
 * is set in the method <CODE>setFactory</CODE>.
 * <p><b>This API is a Sun Microsystems internal API  and is subject
 * to change without notice.</b></p>
 * @since 1.5
 */
public class SnmpEngineImpl implements SnmpEngine, Serializable {
    private static final long serialVersionUID = -2564301391365614725L;

    /**
     * Security level. No authentication, no privacy. Value is 0,
     * as defined in RFC 2572
     */
    public static final int noAuthNoPriv = 0;
    /**
     * Security level. Authentication, no privacy. Value is 1, as
     * defined in RFC 2572
     */
    public static final int authNoPriv = 1;
    /**
     * Security level. Authentication, privacy. Value is 3,
     * as defined in RFC 2572
     */
    public static final int authPriv = 3;
    /**
     * Flag that indicates that a report is to be sent. Value is 4, as defined in RFC 2572
     */
    public static final int reportableFlag = 4;

    /**
     * Mask used to isolate authentication information within a message flag.
     */
    public static final int authMask = 1;
    /**
     * Mask used to isolate privacy information within a message flag.
     */
    public static final int privMask = 2;
    /**
     * Mask used to isolate authentication and privacy information within a message flag.
     */
    public static final int authPrivMask = 3;

    private SnmpEngineId engineid = null;
    private SnmpEngineFactory factory = null;
    private long startTime = 0;

    private int boot = 0;
    private boolean checkOid = false;

    transient private SnmpUsmKeyHandler usmKeyHandler = null;
    transient private SnmpLcd lcd = null;

    transient private SnmpSecuritySubSystem securitySub = null;

    transient private SnmpMsgProcessingSubSystem messageSub = null;

    transient private SnmpAccessControlSubSystem accessSub = null;

    /**
     * Gets the engine time in seconds. This is the time from the last reboot.
     * @return The time from the last reboot.
     */
    public synchronized int getEngineTime() {
        //We do the counter wrap in a lazt way. Each time Engine is asked for his time it checks. So if nobody use the Engine, the time can wrap and wrap again without incrementing nb boot. We can imagine that it is irrelevant due to the amount of time needed to wrap.
        long delta = (System.currentTimeMillis() / 1000) - startTime;
        if(delta >  0x7FFFFFFF) {
            //67 years of running. That is a great thing!
            //Reinitialize startTime.
            startTime = System.currentTimeMillis() / 1000;

            //Can't do anything with this counter.
            if(boot != 0x7FFFFFFF)
                boot += 1;
            //Store for future use.
            storeNBBoots(boot);
        }

        return (int) ((System.currentTimeMillis() / 1000) - startTime);
    }

    /**
     * Gets the engine Id. This is unique for each engine.
     * @return The engine Id object.
     */
    public SnmpEngineId getEngineId() {
        return engineid;
    }

    /**
     * Gets the Usm key handler.
     * @return The key handler.
     */
    public SnmpUsmKeyHandler getUsmKeyHandler() {
        return usmKeyHandler;
    }

    /**
     * Gets the engine Lcd.
     * @return The engine Lcd.
     */
    public SnmpLcd getLcd() {
        return lcd;
    }
    /**
     * Gets the engine boot number. This is the number of time this engine has rebooted. Each time an <CODE>SnmpEngine</CODE> is instantiated, it will read this value in its Lcd, and store back the value incremented by one.
     * @return The engine's number of reboot.
     */
    public int getEngineBoots() {
        return boot;
    }

     /**
     * Constructor. A Local Configuration Datastore is passed to the engine. It will be used to store and retrieve data (engine Id, engine boots).
     * <P> WARNING : The SnmpEngineId is computed as follow:
     * <ul>
     * <li> If an lcd file is provided containing the property "localEngineID", this property value is used.</li>.
     * <li> If not, if the passed engineID is not null, this engine ID is used.</li>
     * <li> If not, a time based engineID is computed.</li>
     * </ul>
     * This constructor should be called by an <CODE>SnmpEngineFactory</CODE>. Don't call it directly.
     * @param fact The factory used to instantiate this engine.
     * @param lcd The local configuration datastore.
     * @param engineid The engine ID to use. If null is provided, an SnmpEngineId is computed using the current time.
     * @throws UnknownHostException Exception thrown, if the host name located in the property "localEngineID" is invalid.
     */
    public SnmpEngineImpl(SnmpEngineFactory fact,
                          SnmpLcd lcd,
                          SnmpEngineId engineid) throws UnknownHostException {

        init(lcd, fact);
        initEngineID();
        if(this.engineid == null) {
            if(engineid != null)
                this.engineid = engineid;
            else
                this.engineid = SnmpEngineId.createEngineId();
        }
        lcd.storeEngineId(this.engineid);
        if (SNMP_LOGGER.isLoggable(Level.FINER)) {
            SNMP_LOGGER.logp(Level.FINER, SnmpEngineImpl.class.getName(),
                    "SnmpEngineImpl(SnmpEngineFactory,SnmpLcd,SnmpEngineId)",
                    "LOCAL ENGINE ID: " + this.engineid);
        }
    }
    /**
     * Constructor. A Local Configuration Datastore is passed to the engine. It will be used to store and retrieve data (engine ID, engine boots).
     * <P> WARNING : The SnmpEngineId is computed as follow:
     * <ul>
     * <li> If an lcd file is provided containing the property "localEngineID", this property value is used.</li>.
     * <li> If not, the passed address and port are used to compute one.</li>
     * </ul>
     * This constructor should be called by an <CODE>SnmpEngineFactory</CODE>. Don't call it directly.
     * @param fact The factory used to instantiate this engine.
     * @param lcd The local configuration datastore.
     * @param port UDP port to use in order to calculate the engine ID.
     * @param address An IP address used to calculate the engine ID.
     * @throws UnknownHostException Exception thrown, if the host name located in the property "localEngineID" is invalid.
     */
    public SnmpEngineImpl(SnmpEngineFactory fact,
                          SnmpLcd lcd,
                          InetAddress address,
                          int port) throws UnknownHostException {
        init(lcd, fact);
        initEngineID();
        if(engineid == null)
            engineid = SnmpEngineId.createEngineId(address, port);

        lcd.storeEngineId(engineid);

        if (SNMP_LOGGER.isLoggable(Level.FINER)) {
            SNMP_LOGGER.logp(Level.FINER, SnmpEngineImpl.class.getName(),
                    "SnmpEngineImpl(SnmpEngineFactory,SnmpLcd,InetAddress,int)",
                    "LOCAL ENGINE ID: " + engineid + " / " +
                    "LOCAL ENGINE NB BOOTS: " + boot + " / " +
                    "LOCAL ENGINE START TIME: " + getEngineTime());
        }
    }

    /**
     * Constructor. A Local Configuration Datastore is passed to the engine. It will be used to store and retrieve data (engine ID, engine boots).
     * <P> WARNING : The SnmpEngineId is computed as follow:
     * <ul>
     * <li> If an lcd file is provided containing the property "localEngineID", this property value is used.</li>.
     * <li> If not, The passed port is used to compute one.</li>
     * </ul>
     * This constructor should be called by an <CODE>SnmpEngineFactory</CODE>. Don't call it directly.
     * @param fact The factory used to instantiate this engine.
     * @param lcd The local configuration datastore
     * @param port UDP port to use in order to calculate the engine ID.
     * @throws UnknownHostException Exception thrown, if the host name located in the property "localEngineID" is invalid.
     */
    public SnmpEngineImpl(SnmpEngineFactory fact,
                          SnmpLcd lcd,
                          int port) throws UnknownHostException {
        init(lcd, fact);
        initEngineID();
        if(engineid == null)
           engineid = SnmpEngineId.createEngineId(port);

        lcd.storeEngineId(engineid);

        if (SNMP_LOGGER.isLoggable(Level.FINER)) {
            SNMP_LOGGER.logp(Level.FINER, SnmpEngineImpl.class.getName(),
                    "SnmpEngineImpl(SnmpEngineFactory,SnmpLcd,int)",
                    "LOCAL ENGINE ID: " + engineid + " / " +
                    "LOCAL ENGINE NB BOOTS: " + boot + " / " +
                    "LOCAL ENGINE START TIME: " + getEngineTime());
        }
    }

    /**
     * Constructor. A Local Configuration Datastore is passed to the engine. It will be used to store and retrieve data (engine ID, engine boots).
     * <P> WARNING : The SnmpEngineId is computed as follow:
     * <ul>
     * <li> If an lcd file is provided containing the property "localEngineID", this property value is used.</li>.
     * <li> If not, a time based engineID is computed.</li>
     * </ul>
     * When no configuration nor java property is set for the engine ID value, a unique time based engine ID will be generated.
     * This constructor should be called by an <CODE>SnmpEngineFactory</CODE>. Don't call it directly.
     * @param fact The factory used to instantiate this engine.
     * @param lcd The local configuration datastore.
     */
    public SnmpEngineImpl(SnmpEngineFactory fact,
                          SnmpLcd lcd) throws UnknownHostException {
        init(lcd, fact);
        initEngineID();
        if(engineid == null)
            engineid = SnmpEngineId.createEngineId();

        lcd.storeEngineId(engineid);

        if (SNMP_LOGGER.isLoggable(Level.FINER)) {
            SNMP_LOGGER.logp(Level.FINER, SnmpEngineImpl.class.getName(),
                    "SnmpEngineImpl(SnmpEngineFactory,SnmpLcd)",
                    "LOCAL ENGINE ID: " + engineid + " / " +
                    "LOCAL ENGINE NB BOOTS: " + boot + " / " +
                    "LOCAL ENGINE START TIME: " + getEngineTime());
        }
    }

    /**
     * Access Control will check the oids. By default is false.
     */
    public synchronized void activateCheckOid() {
        checkOid = true;
    }

    /**
     * Access Control will not check the oids. By default is false.
     */
    public synchronized void deactivateCheckOid() {
        checkOid = false;
    }

    /**
     * Access Control check or not the oids. By default is false.
     */
    public synchronized boolean isCheckOidActivated() {
        return checkOid;
    }

    //Do some check and store the nb boots value.
    private void storeNBBoots(int boot) {
        if(boot < 0 || boot == 0x7FFFFFFF) {
            boot = 0x7FFFFFFF;
            lcd.storeEngineBoots(boot);
        }
        else
            lcd.storeEngineBoots(boot + 1);
    }

    // Initialize internal status.
    private void init(SnmpLcd lcd, SnmpEngineFactory fact) {
        this.factory = fact;
        this.lcd = lcd;
        boot = lcd.getEngineBoots();

        if(boot == -1 || boot == 0)
            boot = 1;

        storeNBBoots(boot);

        startTime = System.currentTimeMillis() / 1000;

    }

    void setUsmKeyHandler(SnmpUsmKeyHandler usmKeyHandler) {
        this.usmKeyHandler = usmKeyHandler;
    }

    //Initialize the engineID.
    private void initEngineID() throws UnknownHostException {
        String id = lcd.getEngineId();
        if(id != null) {
            engineid = SnmpEngineId.createEngineId(id);
        }
    }


    /**
     * Returns the Message Processing Sub System.
     * @return The Message Processing Sub System.
     */
    public SnmpMsgProcessingSubSystem getMsgProcessingSubSystem() {
        return messageSub;
    }

    /**
     * Sets the Message Processing Sub System.
     * @param sys The Message Processing Sub System.
     */
    public void setMsgProcessingSubSystem(SnmpMsgProcessingSubSystem sys) {
        messageSub = sys;
    }

     /**
     * Returns the Security Sub System.
     * @return The Security Sub System.
     */
    public SnmpSecuritySubSystem getSecuritySubSystem() {
        return securitySub;
    }
    /**
     * Sets the Security Sub System.
     * @param sys The Security Sub System.
     */
    public void setSecuritySubSystem(SnmpSecuritySubSystem sys) {
        securitySub = sys;
    }
     /**
     * Sets the Access Control Sub System.
     * @param sys The Access Control Sub System.
     */
    public void setAccessControlSubSystem(SnmpAccessControlSubSystem sys) {
        accessSub = sys;
    }

    /**
     * Returns the Access Control Sub System.
     * @return The Access Control Sub System.
     */
    public SnmpAccessControlSubSystem getAccessControlSubSystem() {
        return accessSub;
    }
    /**
     * Checks the passed msg flags according to the rules specified in RFC 2572.
     * @param msgFlags The msg flags.
     */
    public static void checkSecurityLevel(byte msgFlags)
        throws SnmpBadSecurityLevelException {
        int secLevel = msgFlags & SnmpDefinitions.authPriv;
        if((secLevel & SnmpDefinitions.privMask) != 0)
            if((secLevel & SnmpDefinitions.authMask) == 0) {
                throw new SnmpBadSecurityLevelException("Security level:"+
                                                        " noAuthPriv!!!");
            }
    }

}