/*******************************************************************************
 * Copyright (c) 2000, 2003 IBM Corporation and others.
 * All rights reserved. This program and the accompanying materials 
 * are made available under the terms of the Common Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/cpl-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.IDEWorkbenchPlugin;

/**
 * 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) {
			IDEWorkbenchPlugin.log("Error accessing marker type", e.getStatus()); //$NON-NLS-1$
			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) {
				IDEWorkbenchPlugin.log("Error accessing marker attribute", e.getStatus()); //$NON-NLS-1$
				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;
	}
}