/*******************************************************************************
 * Copyright (c) 2010-2018, Gabor Bergmann, IncQuery Labs Ltd.
 * This program and the accompanying materials are made available under the
 * terms of the Eclipse Public License v. 2.0 which is available at
 * http://www.eclipse.org/legal/epl-v20.html.
 * 
 * SPDX-License-Identifier: EPL-2.0
 *******************************************************************************/
package tools.refinery.viatra.runtime.matchers.util;

import java.util.Collections;
import java.util.Iterator;
import java.util.Set;

/**
 * A singleton immutable empty memory. 
 * @author Gabor Bergmann
 * @since 2.0
 *
 */
public class EmptyMemory<T> implements IMemoryView<T> {

    @SuppressWarnings("rawtypes")
    private static final EmptyMemory INSTANCE = new EmptyMemory();
    
    @SuppressWarnings("unchecked")
    public static <T> EmptyMemory<T> instance() {
        return INSTANCE;
    }
    
    
    
    /**
     * Singleton; hidden constructor
     */
    private EmptyMemory() {
        super();
    }

    @Override
    public Iterator<T> iterator() {
        return Collections.<T>emptySet().iterator();
    }

    @Override
    public int getCount(T value) {
        return 0;
    }

    @Override
    public int getCountUnsafe(Object value) {
        return 0;
    }

    @Override
    public boolean containsNonZero(T value) {
        return false;
    }

    @Override
    public boolean containsNonZeroUnsafe(Object value) {
        return false;
    }

    @Override
    public int size() {
        return 0;
    }

    @Override
    public boolean isEmpty() {
        return true;
    }

    @Override
    public Set<T> distinctValues() {
        return Collections.emptySet();
    }
    
    @Override
    public int hashCode() {
        return IMemoryView.hashCode(this);
    }
    @Override
    public boolean equals(Object obj) {
        return IMemoryView.equals(this, obj);
    }

    @Override
    public String toString() {
        return "{}";
    }
}