/*******************************************************************************
 * Copyright (c) 2006 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.jdt.ui.text.java;

import java.util.Comparator;

import org.eclipse.core.runtime.IConfigurationElement;

import org.eclipse.jface.text.contentassist.ICompletionProposal;

/**
 * Abstract base class for sorters contributed to the
 * <code>org.eclipse.jdt.ui.javaCompletionProposalSorters</code> extension point.
 * <p>
 * Subclasses need to implement {@link #compare(ICompletionProposal, ICompletionProposal)} and may
 * override {@link #beginSorting(ContentAssistInvocationContext) beginSorting} and
 * {@link #endSorting() endSorting}.
 * </p>
 * <p>
 * The orderings imposed by a subclass need not be consistent with equals.
 * </p>
 * 
 * @since 3.2
 */
public abstract class AbstractProposalSorter implements Comparator {

	/**
	 * Creates a new sorter. Note that subclasses must provide a zero-argument constructor to be
	 * instantiatable via {@link IConfigurationElement#createExecutableExtension(String)}.
	 */
	protected AbstractProposalSorter() {
	}

	/**
	 * Called once before sorting.
	 * <p>
	 * Clients may override, the default implementation does nothing.
	 * </p>
	 * 
	 * @param context the context of the content assist invocation
	 */
	public void beginSorting(ContentAssistInvocationContext context) {
	}

	/**
	 * Implements the same contract as {@link Comparator#compare(Object, Object)} but with
	 * completion proposals as parameters. This method will implement the {@link Comparator}
	 * interface if this class is ever converted to extend
	 * <code>Comparator&lt;ICompletionProposal&gt;</code>.
	 * <p>
	 * The orderings imposed by an implementation need not be consistent with equals.
	 * </p>
	 * 
	 * @param p1 the first proposal to be compared
	 * @param p2 the second proposal to be compared
	 * @return a negative integer, zero, or a positive integer as the first argument is less than,
	 *         equal to, or greater than the second.
	 */
	public abstract int compare(ICompletionProposal p1, ICompletionProposal p2);

	/**
	 * Called once after sorting.
	 * <p>
	 * Clients may override, the default implementation does nothing.
	 * </p>
	 */
	public void endSorting() {
	}

	/**
	 * This method delegates to {@link #compare(ICompletionProposal, ICompletionProposal)} and may
	 * be removed if the class is ever converted to extend
	 * <code>Comparator&lt;ICompletionProposal&gt;</code>.
	 * 
	 * @see java.util.Comparator#compare(java.lang.Object, java.lang.Object)
	 */
	public final int compare(Object o1, Object o2) {
		ICompletionProposal p1= (ICompletionProposal) o1;
		ICompletionProposal p2= (ICompletionProposal) o2;

		return compare(p1, p2);
	}
}