/*
 * @(#)AOMEntry.java	1.28 03/12/19
 * 
 * Copyright 2004 Sun Microsystems, Inc. All rights reserved.
 * SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 */

package com.sun.corba.se.impl.oa.poa ;

import org.omg.CORBA.INTERNAL ;

import com.sun.corba.se.spi.orb.ORB ;

import com.sun.corba.se.spi.orbutil.fsm.Action ;
import com.sun.corba.se.spi.orbutil.fsm.ActionBase ;
import com.sun.corba.se.spi.orbutil.fsm.Guard ;
import com.sun.corba.se.spi.orbutil.fsm.GuardBase ;
import com.sun.corba.se.spi.orbutil.fsm.State ;
import com.sun.corba.se.spi.orbutil.fsm.StateImpl ;
import com.sun.corba.se.spi.orbutil.fsm.Input ;
import com.sun.corba.se.spi.orbutil.fsm.InputImpl ;
import com.sun.corba.se.spi.orbutil.fsm.FSM ;
import com.sun.corba.se.spi.orbutil.fsm.FSMImpl ;
import com.sun.corba.se.spi.orbutil.fsm.StateEngine ;
import com.sun.corba.se.spi.orbutil.fsm.StateEngineFactory ;

import com.sun.corba.se.impl.orbutil.concurrent.Mutex ;
import com.sun.corba.se.impl.orbutil.concurrent.CondVar ;

/** AOMEntry represents a Servant or potential Servant in the ActiveObjectMap.
* It may be in several states to allow for long incarnate or etherealize operations.
* The methods on this class mostly represent input symbols to the state machine
* that controls the lifecycle of the entry.  A library is used to build the state
* machine rather than the more usual state pattern so that the state machine
* transitions are explicitly visible.
*/
public class AOMEntry extends FSMImpl {
    private final Thread[] etherealizer ;   // The actual etherealize operation 
					    // for this entry.  It is 
					    // represented as a Thread because
					    // the POA.deactivate_object never 
					    // waits for the completion.
    private final int[] counter ;	    // single element holder for counter 
					    // accessed in actions
    private final CondVar wait ;	    // accessed in actions

    final POAImpl poa ;

    public static final State INVALID = new StateImpl( "Invalid" ) ;
    public static final State INCARN  = new StateImpl( "Incarnating" ) {
	public void postAction( FSM fsm ) {
	    AOMEntry entry = (AOMEntry)fsm ;
	    entry.wait.broadcast() ;
	}
    };
    public static final State VALID   = new StateImpl( "Valid" ) ;
    public static final State ETHP    = new StateImpl( "EtherealizePending" ) ;
    public static final State ETH     = new StateImpl( "Etherealizing" ) {
	public void preAction( FSM fsm ) {
	    AOMEntry entry = (AOMEntry)fsm ;
	    Thread etherealizer = entry.etherealizer[0] ;
	    if (etherealizer != null) 
		etherealizer.start() ;
	}

	public void postAction( FSM fsm ) {
	    AOMEntry entry = (AOMEntry)fsm ;
	    entry.wait.broadcast() ;
	}
    };
    public static final State DESTROYED = new StateImpl( "Destroyed" ) ;

    static final Input START_ETH    = new InputImpl( "startEtherealize" ) ;
    static final Input ETH_DONE	    = new InputImpl( "etherealizeDone" ) ;
    static final Input INC_DONE	    = new InputImpl( "incarnateDone" ) ;
    static final Input INC_FAIL	    = new InputImpl( "incarnateFailure" ) ;
    static final Input ACTIVATE	    = new InputImpl( "activateObject" ) ;
    static final Input ENTER	    = new InputImpl( "enter" ) ;
    static final Input EXIT	    = new InputImpl( "exit" ) ;

    private static Action incrementAction = new ActionBase( "increment" ) {
	public void doIt( FSM fsm, Input in ) {
	    AOMEntry entry = (AOMEntry)fsm ;
	    entry.counter[0]++ ;
	}
    } ;

    private static Action decrementAction = new ActionBase( "decrement" ) {
	public void doIt( FSM fsm, Input in ) {
	    AOMEntry entry = (AOMEntry)fsm ;
	    if (entry.counter[0] > 0)
		entry.counter[0]-- ;
	    else
		throw entry.poa.lifecycleWrapper().aomEntryDecZero() ;
	}
    } ;

    private static Action throwIllegalStateExceptionAction = new ActionBase( 
	"throwIllegalStateException" ) {
	public void doIt( FSM fsm, Input in ) {
	    throw new IllegalStateException( 
		"No transitions allowed from the DESTROYED state" ) ;
	} 
    } ;

    private static Guard waitGuard = new GuardBase( "wait" ) {
	public Guard.Result evaluate( FSM fsm, Input in ) {
	    AOMEntry entry = (AOMEntry)fsm ;
	    try {
		entry.wait.await() ;
	    } catch (InterruptedException exc) {
		// XXX Log this
		// NO-OP
	    }

	    return Guard.Result.DEFERED ;
	}
    } ;


    private static class CounterGuard extends GuardBase {
	private int value ;

	public CounterGuard( int value ) 
	{
	    super( "counter>" + value ) ;
	    this.value = value ;
	}

	public Guard.Result evaluate( FSM fsm, Input in ) 
	{
	    AOMEntry entry = (AOMEntry)fsm ;
	    return Guard.Result.convert( entry.counter[0] > value ) ;
	}
    } ;

    private static GuardBase greaterZeroGuard = new CounterGuard( 0 ) ;
    private static Guard zeroGuard = new Guard.Complement( greaterZeroGuard ) ;
    private static GuardBase greaterOneGuard = new CounterGuard( 1 ) ;
    private static Guard oneGuard = new Guard.Complement( greaterOneGuard ) ;

    private static StateEngine engine ;

    static {
	engine = StateEngineFactory.create() ;

	//	    State,   Input,     Guard,			Action,		    new State

	engine.add( INVALID, ENTER,				incrementAction,    INCARN	) ;
	engine.add( INVALID, ACTIVATE,				null,		    VALID	) ;
	engine.setDefault( INVALID ) ;

	engine.add( INCARN,  ENTER,	waitGuard,		null,		    INCARN	) ;
	engine.add( INCARN,  EXIT,				null,		    INCARN	) ;
	engine.add( INCARN,  START_ETH,	waitGuard,		null,		    INCARN	) ;
	engine.add( INCARN,  INC_DONE,				null,		    VALID	) ;
	engine.add( INCARN,  INC_FAIL,				decrementAction,    INVALID	) ;  

	engine.add( VALID,   ENTER,				incrementAction,    VALID	) ;
	engine.add( VALID,   EXIT,				decrementAction,    VALID	) ;
	engine.add( VALID,   START_ETH, greaterZeroGuard,	null,		    ETHP	) ;
	engine.add( VALID,   START_ETH, zeroGuard,		null,		    ETH		) ;

	engine.add( ETHP,    ENTER,	waitGuard,		null,		    ETHP	) ;
	engine.add( ETHP,    START_ETH,				null,		    ETHP	) ;
	engine.add( ETHP,    EXIT,	greaterOneGuard,	decrementAction,    ETHP	) ;
	engine.add( ETHP,    EXIT,	oneGuard,		decrementAction,    ETH		) ;

	engine.add( ETH,     START_ETH,				null,		    ETH		) ;
	engine.add( ETH,     ETH_DONE,				null,		    DESTROYED	) ;
	engine.add( ETH,     ENTER,	waitGuard,		null,		    ETH		) ;
	
	engine.setDefault( DESTROYED, throwIllegalStateExceptionAction, DESTROYED ) ;

	engine.done() ;
    }

    public AOMEntry( POAImpl poa )
    {
	super( engine, INVALID, ((ORB)poa.getORB()).poaFSMDebugFlag ) ;
	this.poa = poa ;
	etherealizer = new Thread[1] ;
	etherealizer[0] = null ;
	counter = new int[1] ;
	counter[0] = 0 ;
	wait = new CondVar( poa.poaMutex, 
	    ((ORB)poa.getORB()).poaConcurrencyDebugFlag ) ;
    }

    // Methods that drive the FSM: the real interface to this class
    // Most just call the doIt method, but startEtherealize needs
    // the etherealizer.
    public void startEtherealize( Thread etherealizer ) 
    { 
	this.etherealizer[0] = etherealizer ;
	doIt( START_ETH ) ; 
    }

    public void etherealizeComplete() { doIt( ETH_DONE ) ; }
    public void incarnateComplete() { doIt( INC_DONE ) ; }
    public void incarnateFailure() { doIt( INC_FAIL ) ; }
    public void activateObject() { doIt( ACTIVATE ) ; }
    public void enter() { doIt( ENTER ) ; }
    public void exit() { doIt( EXIT ) ; }
}