source: fedd/abac-src/rbtm/engine/AbstractProofNode.java @ c9318dc

package edu.stanford.peer.rbtm.engine;

import java.util.*;

import edu.stanford.peer.rbtm.credential.*;
import edu.stanford.peer.rbtm.util.*;

/**
 * The parent class of all proof nodes. This is the base class which contains
 * default implementations of all common methods.
 */
public abstract class AbstractProofNode implements ProofNode
{
    // The following two fields can't be changed by other classes.  
    // If subclasses need to access them, use get methods

    /** The EntityExpression this node is about. */
    EntityExpression   _roleExp;  
    
    /** 
     * The proof _graph this node is in, this reference is used while 
     * processing this node 
     */
    ProofGraph       _graph;

    /** Processing mode for subclassed node types */
    public final boolean addRole = true;
    
    /** Nodes that can reach this node directly, evidences are credentials. */
    protected ResultEvidenceMap  parents;

    /** Nodes that this node can reach directly, evidecens are credentials. */
    protected ResultEvidenceMap  children; 

        /** Backward solutions on this node  */
    protected ResultEvidenceMap  backwardSolutions;

        /** Forward solutions on this node */
    protected ResultEvidenceMap  forwardSolutions;

    protected ArrayList  backwardListeners;
    protected ArrayList  forwardListeners;

    boolean backwardProcessed;
    boolean forwardProcessed;

    AbstractProofNode (ProofGraph graph, EntityExpression re, int trackType)
    {
        _graph = graph;
        _roleExp = re;
        Debug.debugInfo("A new node is created for " + re);

        parents = new ResultEvidenceMap(trackType);  
        children = new ResultEvidenceMap(trackType); 
        backwardSolutions = new ResultEvidenceMap(trackType);
        forwardSolutions = new ResultEvidenceMap(trackType);
        
        backwardListeners = new ArrayList(10);
        forwardListeners = new ArrayList(10);
    }

    public ProofGraph getGraph() {
        return _graph;
    }
    
    public EntityExpression getRoleExp() {
        return _roleExp;
    }
    
    public ResultEvidenceMap getForwardSolutions() {
        return forwardSolutions;
    }
    
    public ResultEvidenceMap getBackwardSolutions() {
        return backwardSolutions;
    }
    
    public ResultEvidenceMap getChildren() {
        return children;
    }
    
    public ResultEvidenceMap getParents() {
        return parents;
    }
    
    /** 
     * A single iteration of evidence gathering. This recursive method is 
     * polymorphic and may be extended in child proof node implementations. 
     * @param size the size of the evidence set (of credentials)
     * @param target the parent expression to be found in the cred graph
     */
    public HashSet getChain(int size, EntityExpression target) {
        return new HashSet(size);
    }


    public void invalidateForward() {
        Debug.debugInfo("Invalidate forward result on " + this);
        if(forwardProcessed) {
            forwardProcessed = false;
            //reuse the credential and update the forward search
            getGraph().addForwardNode(getRoleExp());
        }
    }

    public void invalidateBackward() {
        Debug.debugInfo("Invalidate backward result on " + this);
        if(backwardProcessed) {
            backwardProcessed = false;
            //reuse the credential and update the backward search
            getGraph().addBackwardNode(getRoleExp());
        }
    }

    public void backwardProcess() {
        if (backwardProcessed) { return; }
        Predicate p = getGraph().getPredicate();
        EntityExpression expr = getRoleExp();
        Debug.debugInfo("Backward processing " + this);
        if(p == null) { // cred mgr has null predicate
            // backwards compatibility for credential manager
            backwardSolutionAdded(this, expr);
            additionalBackwardProcess();
        }
        else {
            if(p.test(expr)) { 
                // add this expression to the soln and stop
                backwardSolutionAdded(this, expr);
            } else {    
                // skip this soln and continue processing 
                additionalBackwardProcess();
            }
        }
        backwardProcessed = true;
    }
    
    // The method that does the work when we visit a node
    public void forwardProcess() 
    {
        if (forwardProcessed) {
            return;
        }
        
        // first step: go over all credentials that have this as subject
        Debug.debugInfo("Forward processing " + this);
        Iterator  credIt = _graph.findCredentialsBySubject(_roleExp);
        while (credIt.hasNext()) { 
            StaticCredential credential = (StaticCredential) credIt.next();
            Debug.debugInfo("Find one credential: " + credential);
            ProofNode node = _graph.addForwardNode(credential.getDefinedRole());
            node.addParent(this, credential);
            //_graph.addProofEdge(this, node, credential);
        }
        
                  additionalForwardProcess();
                  forwardProcessed = true;
                  
                  // second step: find partial solutions which match this node's
                  //              role expression, unless its an intersection
                  if (_roleExp instanceof Intersection) { return;       }
                  credIt = _graph.findCredentialsByPartialSubject(_roleExp);
                  while (credIt.hasNext()) { 
                                StaticCredential credential = (StaticCredential) credIt.next();
                                ProofNode node = _graph.addForwardNode(credential.getSubject());
                                node.backwardProcess();
                                // Forward discovery of roles
                                //
                                // This is not reuired according to the algorithm from 
                                // "Distributed Credential Chain Discovery in Trust Management" 
                                // in JCS but is needed for credential discovery in ATN where 
                                // forward search takes place from sensitive roles.
                                node.forwardProcess();
                                //int j = 
                                //((Intersection) credential.getSubject()).getIndexOf(_roleExp);
                                //forward.solutionAdded(new PartialSolution(_roleExp, j));
                  }
    }
    
    abstract protected void additionalForwardProcess();
    abstract protected void additionalBackwardProcess();
    
    
    public void addBackwardListener(BackwardSolutionListener sl) {
        Debug.debugInfo(sl + " is now listening on " + this + 
                        " for backward solutions");
        backwardListeners.add(sl);
        propagateBackwardSolutionsTo(sl);
    }
    
    public void addForwardListener(ForwardSolutionListener sl) {
        Debug.debugInfo(sl + " is now listening on " + this + 
                        " for forward solutions");
        forwardListeners.add(sl);
        propagateForwardSolutionsTo(sl);
    }
    
    /**
     * Add a node as a parent to this node
     * @param  node: the parent node
     */
    public void addParent(ProofNode node, Object evidence) {
        if (parents.putResultEvidence(node.getRoleExp(), evidence)) {  
            addForwardListener(node);
        }
    }
    
    public void addChild(ProofNode node, Object evidence) {
        if (children.putResultEvidence(node.getRoleExp(), evidence)) {  
            addBackwardListener(node);
        }
    }
    
    public void backwardSolutionAdded(ProofNode s, BackwardSolution r)
    {
        if (backwardSolutions.putResultEvidence(r, s)) {   
            // when solution r is new
            Debug.debugInfo("Backward solution added to: " + this + 
                            " from: " + s + " value: " + r);
            propagateBackwardSolution(r);
        }
    }
    
    public void forwardSolutionAdded(ProofNode s, ForwardSolution r) {
        /*
       if (r instanceof PartialSolution) {
            Intersection re = r.getIntersection();
            Integer index = r.getNumber();
            HashMap value = (HashMap) partialSols.get(re);
            if (value == null) {   // first piece
                value = new HashMap();
                partialSols.put(re, value);
            }
            SmallSet evidences = value.get(index);
            if (evidences == null) { // A new piece
                evidences = new SmallSet(s);
                value.put(index, evidences);
                if (value.size() == re.getK()) { // have all pieces
                    // Add an edge from current node to re
                    // addEdge();
                }
            } else if (trackAll) {
                evidences.add(s);
            }
                        return;
        } 
        */
        if (forwardSolutions.putResultEvidence(r, s)) {
            Debug.debugInfo("Forward solution added to: " + this + 
                            " from: " + s + " value: " + r);
            propagateForwardSolution(r);
        }
    }

    /** propagate backward solutions to all listening nodes. */
    protected void propagateBackwardSolutionsTo(BackwardSolutionListener listener)
    {
        Object[] sols = backwardSolutions.resultSet().toArray();
        for (int i=0; i<sols.length; i++) {
            listener.backwardSolutionAdded(this, (BackwardSolution)(sols[i]));
        }
    }
    
    protected void propagateForwardSolutionsTo(ForwardSolutionListener listener)
    {
        Object[] sols = forwardSolutions.resultSet().toArray();
        for (int i=0; i<sols.length; i++) {
            listener.forwardSolutionAdded(this, (ForwardSolution)(sols[i]));
        }
    }
    
    protected void propagateBackwardSolution(BackwardSolution g)
    {
        Object[] listeners = backwardListeners.toArray();
        for (int i=0; i<listeners.length; i++) {
            ((BackwardSolutionListener)listeners[i]).backwardSolutionAdded(this, g);
        }
    }
    
    protected void propagateForwardSolution(ForwardSolution g)
    {
        Object[] listeners = forwardListeners.toArray();
        for (int i=0; i<listeners.length; i++) {
            ((ForwardSolutionListener)listeners[i]).forwardSolutionAdded(this, g);
        }
    }
    
    public String toString() 
    {
                  return "node " + _roleExp;
    }
    

    // boolean hasParent(ProofNode node) { return parents.containsResult(node._roleExp); }


        //////////// code for SelectiveProofNode
    /*
     * The following two fields store desired goals.  Only desired goals are 
     * passed through edges.  Setting them to null means all goals are 
     * desired.
     * In backward search, if child A.r only wants to see one solution, while 
     * child A.r1.r2 wants to see all solutions.  All goals are desired, so
     * they are passed to A.r as well.  But A.r should have only one desired
     * solution, and so A.r will not propagate them further.
     */
    // SmallSet  backwardGoals = new SmallSet(); 
    // SmallSet  forwardGoals = new SmallSet();

    /* 
    void enableBackwardGoal(EntityExpression g)
    {
        if (backwardGoals != null && ! backwardGoals.containsGoal(g)) { 
                // has not been enabled before
            backwardGoals.addGoal(g);
            if (backwardSoltuions.containsResult(g)) {
                        propagateBackwardSolution(g);
            }
            // Enable this backward goal for all parents
            Object[] list = parents.toArray();  // inform listeners
            for (int i=0; i<list.length; i++) {
                ((ProofNode)list[i]).enableBackwardGoal(g);
            }
        }
    }

    void enableAllBackwardGoals()
    {
        if (backwardGoals == null ) {
            backwardGoals = null;
            // if have been procesed, loop over all parents, and enable them
            // if haven't been processed, just enable it
        }
    }
    */
} // End of class ProofNode