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/*******************************************************************
 * © 2020 SAP SE or an SAP affiliate company. All rights reserved. *
 *******************************************************************/
package com.sap.cds.ql.cqn;

import java.util.Collection;

/**
 * The {@code in} predicate tests wether an {@link #value() actual value} is
 * equal to any value from a defined {@link #valueSet() value set}.
 *
 * It evaluates to {@code false} if the value set is empty.
 */
public interface CqnInPredicate extends CqnPredicate {

	/**
	 * The actual {@link CqnValue} that is tested against the values given by
	 * {@link #valueSet()}.
	 *
	 * @return the actual {@link CqnValue}
	 */
	CqnValue value();

	/**
	 * Returns the collection of expected values in case {@link #valueSet()} is a
	 * {@link CqnListValue}, otherwise a {@link ClassCastException} is thrown.
	 *
	 * @throws ClassCastException if this value is not a {@link CqnListValue}
	 * @return the expected values
	 */
	default Collection values() {
		return valueSet().asList().values().toList();
	}

	/**
	 * Defines the set of expected values the {@link #value() actual value} is
	 * tested against. The returned {@link CqnValue} can either be a
	 * {@link CqnListValue} containing all expected values, a {@link CqnReference}
	 * pointing to a collection-valued element, or a {@link CqnParameter} pointing
	 * to a collection of values.
	 *
	 * @return the set of expected values
	 */
	CqnValue valueSet();

	@Override
	default void accept(CqnVisitor visitor) {
		value().accept(visitor);
		valueSet().accept(visitor);

		visitor.visit(this);
	}

}