MarkerQuery.java

/*******************************************************************************
 * Copyright (c) 2000, 2008 IBM Corporation and others.
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 *
 * Contributors:
 *     IBM Corporation - initial API and implementation
 *******************************************************************************/
package org.eclipse.ui.internal.ide.registry;

import org.eclipse.core.resources.IMarker;
import org.eclipse.core.runtime.CoreException;
import org.eclipse.ui.internal.ide.Policy;

/**
 * Instances of this class hold a marker type id and/or 
 * a series of marker attributes. This information may be used 
 * to determine if a given marker is of the same marker
 * type and determine its values for the attributes.
 */
public class MarkerQuery {
    /**
     * The marker type targetted by this query. 
     * May be <code>null</code>.
     */
    private String type;

    /**
     * A sorted list of the attributes targetted by this query.
     * The list is sorted from least to greatest according to
     * <code>Sting.compare</code>
     */
    private String[] attributes;

    /**
     * Cached hash code value
     */
    private int hashCode;

    /**
     * Creates a new marker query with the given type
     * and attributes.
     * <p>
     * The type may be <code>null</code>. The attributes may 
     * be empty, but not <code>null</code>.
     * </p>
     * 
     * @param markerType the targetted marker type
     * @param markerAttributes the targetted marker attributes
     */
    public MarkerQuery(String markerType, String[] markerAttributes) {
        if (markerAttributes == null) {
            throw new IllegalArgumentException();
        }

        type = markerType;
        attributes = markerAttributes;
        computeHashCode();
    }

    /**
     * Performs a query against the given marker.
     * <p>
     * Returns a <code>MarkerQueryResult</code> if the marker
     * is appropriate for this query (correct type and has
     * all of the query attributes), otherwise <code>null</code>
     * is returned.
     * 
     * @param marker the marker to perform the query against
     * @return a marker query result or <code>null</code>
     */
    public MarkerQueryResult performQuery(IMarker marker) {
        // Check type
        try {
            if (type != null && !type.equals(marker.getType())) {
				return null;
			}
        } catch (CoreException e) {
        	Policy.handle(e);
            return null;
        }

        // Check attributes
        String[] values = new String[attributes.length];
        for (int i = 0; i < attributes.length; i++) {
            try {
                Object value = marker.getAttribute(attributes[i]);
                if (value == null) {
					return null;
				}
                values[i] = value.toString();
            } catch (CoreException e) {
            	Policy.handle(e);
            	return null;
            }
        }

        // Create and return the result
        return new MarkerQueryResult(values);
    }

    /* (non-Javadoc)
     * Method declared on Object.
     */
    public boolean equals(Object o) {
        if (!(o instanceof MarkerQuery)) {
			return false;
		}

        if (o == this) {
			return true;
		}

        MarkerQuery mq = (MarkerQuery) o;
        if (!(type == null ? mq.type == null : type.equals(mq.type))) {
			return false;
		}

        if (attributes.length != mq.attributes.length) {
			return false;
		}

        for (int i = 0; i < attributes.length; i++) {
            if (!(attributes[i].equals(mq.attributes[i]))) {
				return false;
			}
        }

        return true;
    }

    /* (non-Javadoc)
     * Method declared on Object.
     */
    public int hashCode() {
        return hashCode;
    }

    /**
     * Computes the hash code for this instance.
     */
    public void computeHashCode() {
        hashCode = 19;

        if (type != null) {
			hashCode = hashCode * 37 + type.hashCode();
		}

        for (int i = 0; i < attributes.length; i++) {
            hashCode = hashCode * 37 + attributes[i].hashCode();
        }
    }

    /**
     * Returns the targetted marker type. May be 
     * <code>null</code>
     * 
     * @return the targetted marker type
     */
    public String getType() {
        return type;
    }

    /**
     * Returns the targetted attributes.
     * The array may be empty.
     * 
     * @return the targetted attributes
     */
    public String[] getAttributes() {
        return attributes;
    }
}