package de.faktorlogik.eclipse.ui;

import java.util.Collection;
import java.util.HashSet;
import java.util.Iterator;
import java.util.Set;

import org.eclipse.core.databinding.observable.Diffs;
import org.eclipse.core.databinding.observable.set.WritableSet;

/**
 * A writable set that allows to replace all the values of the set in one
 * step.
 */
final class ReplacableWritableSet extends WritableSet {
    /**
     * Replaces the elements of this set with the specified elements.
     *
     * @param elements
     *            the elements to replace this collection with
     * @return <code>true</code> if this set has been changed,
     *         <code>false</code> otherwise
     */
    boolean replaceWith(final Collection elements) {
        getterCalled();
        Set removes = new HashSet();
        Iterator wrappedIterator = wrappedSet.iterator();
        while (wrappedIterator.hasNext()) {
            Object element = wrappedIterator.next();
            if (!elements.contains(element)) {
                wrappedIterator.remove();
                removes.add(element);
            }
        }
        
        Set additions = new HashSet();
        Iterator elementsIterator = elements.iterator();
        while (elementsIterator.hasNext()) {
            Object element = elementsIterator.next();
            if (wrappedSet.add(element)) {
                additions.add(element);
            }
        }
        
        if (!additions.isEmpty() || !removes.isEmpty()) {
            fireSetChange(Diffs.createSetDiff(additions, removes));
            
            return true;
        }
        return false;
    }
}