source: fedd/abac-src/ttg/process/Strategy.java @ 181cf9c

package com.nailabs.abac.process;

import com.nailabs.abac.trust.*;
import com.nailabs.abac.test.*;
import java.util.*;
/**
 * The strategy handles processing a working list of nodes in the trust target
 * graph to be processed.
 */
public class Strategy extends Observable {
    /** The context for which this strategy is negotiating */
    protected NegotiationContext context;

    /** The worklist for nodes to be processed */
    private LinkedList workList = new LinkedList();

    private SatisfactionState state = 
        new SatisfactionState(SatisfactionState.UNKNOWN);

    /** The last message sent out */
    protected Message lastMessage = null;

    /** The current message just received */
    protected Message currentMessage = null;

    /** creates a new strategy to process a trust negotiation */
    public Strategy(NegotiationContext context) {
        this.context = context;
        //context.setStrategy(this);
    }

    /** Adds a node to the work list of nodes to be processed */
    public void addToWorklist(TTGNode node) {
        if(node != null && workList.add(node)) {
            debug("worklist", node.getGoal() + " added to worklist");
            debug("strategy", "worklist = " + workList);
        }
    }

    /** Adds a set of node to the work list */
    public void addToWorklist(TTGNodeSet list) {
        if(list == null)return;
        Iterator i = list.values().iterator();
        while(i.hasNext()) {
            try {
                TTGNode node = (TTGNode)i.next();
                addToWorklist(node);
            }
            catch(Exception ex) {
                ex.printStackTrace(System.err);
            }
        }
    }

    /** determine the current state of negotiation */
    public int getSatisfactionState() {
        int state = SatisfactionState.UNKNOWN;
        try {
            state = context.getGraph().getRoot().getSatisfactionValue();
        }
        catch(Exception ex) {
            debug("strategy", "graph = " + context.getGraph());
            debug("strategy", "root = " + context.getGraph().getRoot());
            ex.printStackTrace(System.err);
        }
        if(isStuck() && (state != SatisfactionState.SATISFIED)) {
            debug("strategy", "Strategy: is stuck!");
            return SatisfactionState.FAILED;
        }
        return state;
    }
    /** process nodes on the work list until the list is empty */
    public SatisfactionState process(Message msg) {
        TTG graph = context.getGraph();
        int state = getSatisfactionState();

        addMessage(msg);

        if(state == SatisfactionState.SATISFIED || 
           state == SatisfactionState.FAILED) {
        debug("strategy", "negotiation is complete status: " + state);
            return new SatisfactionState(state);
        }
        if(isStuck()) {
        debug("strategy", "negotiation is stuck!");
            return new SatisfactionState(SatisfactionState.FAILED);
        }
        iterate();
    addMessage(graph.getChanges());
        if(isStuck()) {
        debug("strategy", "negotiation is stuck!");
            return new SatisfactionState(SatisfactionState.FAILED);
        }
        return new SatisfactionState(state); 
    }

    /** iterate through the work list until it is empty */
    public void iterate() {
        debug("worklist", "worklist = " + workList);
        setChanged();
        notifyObservers("location = local");
        //while worklist is not empty 
        while(!workList.isEmpty()) {
            //check for success or failure
            if(getSatisfactionState() != SatisfactionState.UNKNOWN) {
                return;
            }
            //process node at head of list
            //add list of nodes returned from process to the worklist
            TTGNode current = ((TTGNode)workList.removeFirst());
            setCurrentParent(current);
            current.process(context);
            scheduleOperationsForNode(current);
            debug("strategy", "processing node " + current.getGoal());
            debug("worklist", "worklist = " + workList);
        }
    }

    /** 
     * Notify the strategy that a new edge needs to be added to the graph.
     * The strategy is responsible for performing the operation on the graph,
     * whether the strategy chooses to  defer the operation or not.
     */
    public void scheduleOperation(Operation op) {
        if(op instanceof EdgeOperation) {
            context.getGraph().performEdge((EdgeOperation)op);
        } else {
            context.getGraph().performNode((NodeOperation)op);
        }
        
    }

    /** Place-holder for stingy strategy. */
    public void addSatisfiedControlChild(TTGNode node) {

    }


    /** Place-holder for stingy strategy */
    public void addNewNode(TTGNode node) {
        
    }

    /** 
     * convenience method for determining whether this negotiator has
     * a deadlock in processing the negotiation. This method can be
     * overridden is subsequent versions.
     */
    protected boolean isStuck() {
        // if there's no history, we cannot be stuck yet
        if(currentMessage == null)
            return false;
        // if both messages contain no changes, then a deadlock has occurred
        return (currentMessage.getOperationsCount() == 0 );
   }

    /** 
     * add the current message to the queue. Note: the initial message will 
     * also be null.
     */
    protected void addMessage(Message msg) {
        lastMessage = currentMessage;
        currentMessage = msg;
    }


    /** Note the beginning of a new parent node being processed */
    protected void setCurrentParent(TTGNode parent) {
        
    }

    /** Note the conclusion of a new parent node being processed */
    protected void scheduleOperationsForNode(TTGNode parent) {

    }

    /** */
    protected void debug(String key, String message) {
        StringBuffer buff = new StringBuffer("Strategy[");
        buff.append(context.getSelf()).append("]: ").append(message);
        Debug.debug(key, buff.toString());
    }

    /** */
    public void addObserver(Observer o) {
        super.addObserver(o);
        setChanged();
        notifyObservers("location = init");
    }

}