Copyright (c) 2000, 2008 IBM Corporation and others.
This program and the accompanying materials
are made available under the terms of the Eclipse Public License 2.0
which accompanies this distribution, and is available at
https://www.eclipse.org/legal/epl-2.0/
SPDX-License-Identifier: EPL-2.0
Contributors:
    IBM Corporation - initial API and implementation
/*******************************************************************************
 * Copyright (c) 2000, 2008 IBM Corporation and others.
 *
 * This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License 2.0
 * which accompanies this distribution, and is available at
 * https://www.eclipse.org/legal/epl-2.0/
 *
 * SPDX-License-Identifier: EPL-2.0
 *
 * Contributors:
 *     IBM Corporation - initial API and implementation
 *******************************************************************************/
package org.eclipse.core.internal.expressions;

import org.w3c.dom.Element;

import org.eclipse.core.expressions.EvaluationResult;
import org.eclipse.core.expressions.Expression;
import org.eclipse.core.expressions.ExpressionInfo;
import org.eclipse.core.expressions.IEvaluationContext;

import org.eclipse.core.runtime.Assert;
import org.eclipse.core.runtime.CoreException;
import org.eclipse.core.runtime.IConfigurationElement;

public class EqualsExpression extends Expression {
	
The seed for the hash code for all equals expressions.
/**
	 * The seed for the hash code for all equals expressions.
	 */
	private static final int HASH_INITIAL= EqualsExpression.class.getName().hashCode();

	private Object fExpectedValue;

	public EqualsExpression(Object expectedValue) {
		Assert.isNotNull(expectedValue);
		fExpectedValue= expectedValue;
	}

	public EqualsExpression(IConfigurationElement element) throws CoreException {
		String value= element.getAttribute(ATT_VALUE);
		Expressions.checkAttribute(ATT_VALUE, value);
		fExpectedValue= Expressions.convertArgument(value);
	}

	public EqualsExpression(Element element) throws CoreException {
		String value= element.getAttribute(ATT_VALUE);
		Expressions.checkAttribute(ATT_VALUE, value.isEmpty() ? null : value);
		fExpectedValue= Expressions.convertArgument(value);
	}

	@Override
	public EvaluationResult evaluate(IEvaluationContext context) throws CoreException {
		Object element= context.getDefaultVariable();
		return EvaluationResult.valueOf(element.equals(fExpectedValue));
	}

	@Override
	public void collectExpressionInfo(ExpressionInfo info) {
		info.markDefaultVariableAccessed();
	}

	@Override
	public boolean equals(final Object object) {
		if (!(object instanceof EqualsExpression))
			return false;

		final EqualsExpression that= (EqualsExpression)object;
		return this.fExpectedValue.equals(that.fExpectedValue);
	}

	@Override
	protected int computeHashCode() {
		return HASH_INITIAL * HASH_FACTOR + fExpectedValue.hashCode();
	}

	@Override
	public String toString() {
		StringBuilder builder = new StringBuilder(getClass().getSimpleName());
		builder.append(" [expected="); //$NON-NLS-1$
		builder.append(fExpectedValue);
		builder.append("]"); //$NON-NLS-1$
		return builder.toString();
	}
}