// $Id: CrOperNameConflict.java,v 1.15 2004/09/21 19:03:26 mvw Exp $
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package org.argouml.uml.cognitive.critics;

import java.util.Iterator;
import java.util.Vector;
import javax.swing.Icon;
import org.argouml.cognitive.Designer;
import org.argouml.cognitive.critics.Critic;
import org.argouml.model.ModelFacade;

// Use Model through ModelFacade

/**
 * A critic to detect when a class has operations with two matching
 * signatures.

 *
 * Takes each operation in turn and compares its signature with all
 * earlier operations. This version corrects and earlier bug, which
 * checked for matching names as well as types in the parameter
 * list.

 *
 * Warning. The algorithm in is quadratic in the number of
 * operations. It could be computationally demanding on a design where
 * classes have a lot of operations. See the {@link #predicate2}
 * method for possible solutions.

 *
 * @see 
 * ArgoUML User Manual: Change Names or Signatures in <artifact>
 * 
 * @author jrobbins@ics.uci.edu
 */

public class CrOperNameConflict extends CrUML {

    /**
     * Constructor for the critic.

     *
     * Sets up the resource name, which will allow headline and
     * description to found for the current locale. Provides design
     * issue categories (METHODS, NAMING), sets a knowledge type
     * (SYNTAX) and adds triggers for metaclasses "behaviouralFeature"
     * and feature_name".

     */
    public CrOperNameConflict() {

        setResource("CrOperNameConflict");

        addSupportedDecision(CrUML.DEC_METHODS);
        addSupportedDecision(CrUML.DEC_NAMING);

        setKnowledgeTypes(Critic.KT_SYNTAX);

        // These may not actually make any difference at present (the code
        // behind addTrigger needs more work).

        addTrigger("behavioralFeature");
        addTrigger("feature_name");
    }


    /**
     * The trigger for the critic.

     *
     * Finds all the operations for the given classifier. Takes each
     * operation in turn and compares its signature with all earlier
     * operations. This version corrects an earlier bug, which checked
     * for matching names as well as types in the parameter list.

     *
     * Note. The signature ignores any return parameters in
     * looking for a match. This is in line with Java/C++.

     *
     * We do not need to worry about signature clashes that are
     * inherited (overloading). This is something encouraged in many
     * OO environments to facilitate polymorphism.

     *
     * This algorithm is quadratic in the number of operations. If
     * this became a problem, we would have to consider sorting the
     * operations vector and comparing only adjacent pairs
     * (potentially O(n log n) performance).

     *
     * @param  dm    the {@link Object} to be checked against the critic.
     *
     * @param  dsgr  the {@link Designer} creating the model. Not used,
     *               this is for future development of ArgoUML.
     *
     * @return       {@link #PROBLEM_FOUND PROBLEM_FOUND} if the critic is
     *               triggered, otherwise {@link #NO_PROBLEM NO_PROBLEM}.
     */
    public boolean predicate2(Object dm, Designer dsgr) {

        // Only do this for classifiers

        if (!(ModelFacade.isAClassifier(dm))) {
            return NO_PROBLEM;
        }

	Iterator ops = ModelFacade.getOperations(dm).iterator();

        // Get all the features (giving up if there are none). Then loop
        // through finding all operations. Each time we find one, we compare
        // its signature with all previous (held in vector operSeen), and then
        // if it doesn't match add it to the vector.

        Vector operSeen = new Vector();

        while (ops.hasNext()) {

	    Object op = ops.next();

            // Compare against all earlier operations. If there's a match we've
            // found the problem

            int        size = operSeen.size();

            for (int i = 0; i < size; i++) {
                if (signaturesMatch(op, operSeen.get(i))) {
                    return PROBLEM_FOUND;
                }
            }

            // Add to the vector and round to look at the next one

            operSeen.addElement(op);
        }

        // If we drop out here, there was no match and we have no problem

        return NO_PROBLEM;
    }


    /**
     * Return the icon to be used for the clarifier for this critic.

     *
     * A clarifier is the graphical highlight used to show the
     * presence of a critique. For example wavy colored underlines
     * beneath operations.

     *
     * In this case it will be a wavy line under the second of the
     * clashing operations.

     *
     * @return       The {@link javax.swing.Icon Icon} to use.
     */
    public Icon getClarifier() {
        return ClOperationCompartment.getTheInstance();
    }


    /**
     * Sees if the signatures of two Operations are the same.

     *
     * Checks for matching operation name, and list of parameter
     * types. The order of the parameters is significant.
     *
     * This version also checks for the parameter kind, since
     * otherwise, "op(int a)" and "op():int" appear to have the same
     * signature. Purists would probably suggest that the kind should
     * match exactly. However we only differentiate the return
     * parameter(s). It is unlikely that any practical OO language
     * would be able to distinguish instantiation of in from out from
     * inout parameters.

     *
     * We ignore return parameters completely. This is in line with
     * Java/C++ which regard int x(int, int) and
     * double x(int, int) as having the same
     * signature.

     *
     * If you need to modify this method, take care, since there are
     * numerous "telegraph pole" problems involved in working through
     * pairs of mixed lists.

     *
     * @param op1 the first operation whose signature is being compared.
     * @param op2 the second operation whose signature is being compared.
     *
     * @return    true if the signatures match, false
     *            otherwise.
     */
    private boolean signaturesMatch(Object op1, Object op2) {

	// Check that the names match.

	String name1 = ModelFacade.getName(op1);
	if (name1 == null)
	    return false;

	String name2 = ModelFacade.getName(op2);
	if (name2 == null)
	    return false;

	if (!name1.equals(name2))
	    return false;

	// Check that the parameter lists match.

	Iterator params1 = ModelFacade.getParameters(op1).iterator();
	Iterator params2 = ModelFacade.getParameters(op2).iterator();

	while (params1.hasNext() 
	       && params2.hasNext()) {

	    // Get the next non-return parameter. Null if non left.
	    Object p1 = null;
	    while (p1 == null && params1.hasNext()) {
		p1 = params1.next();
		if (ModelFacade.isReturn(p1))
		    p1 = null;
	    }

	    Object p2 = null;
	    while (p2 == null && params1.hasNext()) {
		p2 = params1.next();
		if (ModelFacade.isReturn(p2))
		    p2 = null;
	    }

	    if (p1 == null && p2 == null)
		return true;	// Both lists have the same length

	    // Different lengths:
	    if (p1 == null)
		return false;
	    if (p2 == null)
		return false;

	    // Compare the type of the parameters. If any of the types is
	    // null, then we have a match.
	    Object p1type = ModelFacade.getType(p1);
	    if (p1type == null)
		continue;

	    Object p2type = ModelFacade.getType(p2);
	    if (p2type == null)
		continue;

	    if (!p1type.equals(p2type))
		return false;

	    // This pair of params where the same. Lets check the next pair.
	}

	if (!params1.hasNext()
	    && !params2.hasNext()) {
	    // Both lists have the same length.
	    return true;
	}
	    
	return false;
    }

} /* end class CrOperNameConflict.java */