/*******************************************************************************
 * 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.jface.viewers;

import java.util.*;

import org.eclipse.jface.resource.JFaceResources;
import org.eclipse.jface.util.Assert;

/**
 * A concrete implementation of the <code>IStructuredSelection</code> interface,
 * suitable for instantiating.
 * <p>
 * This class is not intended to be subclassed.
 * </p>
 */
public class StructuredSelection implements IStructuredSelection {

	/**
	 * The element that make up this structured selection.
	 */
	private Object[] elements;
	
	/**
	 * The canonical empty selection. This selection should be used instead of
	 * <code>null</code>.
	 */
	public static final StructuredSelection EMPTY = new StructuredSelection();
/**
 * Creates a new empty selection.  
 * See also the static field <code>EMPTY</code> which contains an empty selection singleton.
 *
 * @see #EMPTY
 */
public StructuredSelection() {
}
/**
 * Creates a structured selection from the given elements.
 *
 * @param elements an array of elements
 */
public StructuredSelection(Object[] elements) {
	this.elements= new Object[elements.length];
	System.arraycopy(elements, 0, this.elements, 0, elements.length);
}
/**
 * Creates a structured selection containing a single object.
 * The object must not be <code>null</code>.
 *
 * @param element the element
 */
public StructuredSelection(Object element) {
	Assert.isNotNull(element);
	elements= new Object[] { element };
}
/**
 * Creates a structured selection from the given <code>List</code>.
 */
public StructuredSelection(List elements) {
	Assert.isNotNull(elements);
	this.elements = elements.toArray();
}
/**
 * Returns whether this structured selection is equal to the given object.
 * Two structured selections are equal iff they contain the same elements
 * in the same order.
 *
 * @param o the other object
 * @return <code>true</code> if they are equal, and <code>false</code> otherwise
 */
public boolean equals(Object o) {
	if (this == o) {
		return true;
	}
	//null and other classes
	if (!(o instanceof StructuredSelection)) {
		return false;
	}
	StructuredSelection s2 = (StructuredSelection)o;

	// either or both empty?
	if (isEmpty()) {
		return s2.isEmpty();
	}
	if (s2.isEmpty()) {
		return false;
	}

	//size
	int myLen = elements.length;
	if (myLen != s2.elements.length) {
		return false;
	}
	//element comparison
	for (int i = 0; i < myLen; i++) {
		if (!elements[i].equals(s2.elements[i])) {
			return false;
		}
	}
	return true;
}
/* (non-Javadoc)
 * Method declared in IStructuredSelection.
 */
public Object getFirstElement() {
	return isEmpty() ? null : elements[0];
}
/* (non-Javadoc)
 * Method declared in ISelection.
 */
public boolean isEmpty() {
	return elements == null || elements.length == 0;
}
/* (non-Javadoc)
 * Method declared in IStructuredSelection.
 */
public Iterator iterator() {
	return Arrays.asList(elements == null ? new Object[0] : elements).iterator();
}
/* (non-Javadoc)
 * Method declared in IStructuredSelection.
 */
public int size() {
	return elements == null ? 0 : elements.length;
}
/* (non-Javadoc)
 * Method declared in IStructuredSelection.
 */
public Object[] toArray() {
	return elements == null ? new Object[0] : (Object[]) elements.clone();
}
/* (non-Javadoc)
 * Method declared in IStructuredSelection.
 */
public List toList() {
	return Arrays.asList(elements == null ? new Object[0] : elements);
}
/**
 * Internal method which returns a string representation of this
 * selection suitable for debug purposes only.
 *
 * @return debug string
 */
public String toString() {
	return isEmpty() ? JFaceResources.getString("<empty_selection>") : toList().toString(); //$NON-NLS-1$
}
}
