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/*******************************************************************
 * © 2019 SAP SE or an SAP affiliate company. All rights reserved. *
 *******************************************************************/
package com.sap.cds.ql.cqn;

import java.util.stream.Collectors;

public interface CqnExpression extends CqnValue {

	@Override
	default boolean isExpression() {
		return true;
	}

	@Override
	default CqnExpression asExpression() {
		return this;
	}

	/**
	 * Returns {@code true} if this is a {@link CqnArithmeticExpression}.
	 * 
	 * @return {@code true} if this is an arithmetic expression, otherwise
	 *         {@code false}
	 */
	default boolean isArithmeticExpression() {
		return false;
	}

	/**
	 * Returns {@code true} if this is a {@link CqnCaseExpression}.
	 * 
	 * @return {@code true} if this is a case expression, otherwise
	 *         {@code false}
	 */
	default boolean isCaseExpression() {
		return false;
	}
	
	/**
	 * Casts this expression to a {@code CqnArithmeticExpression}.
	 * 
	 * @throws ClassCastException if this expression is not an arithmetic expression
	 * @return this as an arithmetic expression
	 */
	default CqnArithmeticExpression asArithmeticExpression() {
		throw new ClassCastException("Cannot cast to CqnArithmeticExpression");
	}

	/**
	 * Casts this expression to a {@code CqnCaseExpression}.
	 * 
	 * @throws ClassCastException if this expression is not a case expression
	 * @return this as a case expression
	 */
	default CqnCaseExpression asCaseExpression() {
		throw new ClassCastException("Cannot cast to CqnArithmeticExpression");
	}
	
	/**
	 * Returns {@code true} if this is a {@link CqnArithmeticNegation}.
	 * 
	 * @return {@code true} if this is a negation expression, otherwise
	 *         {@code false}
	 */
	default boolean isNegation() {
		return false;
	}

	/**
	 * Casts this expression to a {@code CqnArithmeticNegation}.
	 * 
	 * @throws ClassCastException if this expression is not an arithmetic negation
	 * @return this as a negation expression
	 */
	default CqnArithmeticNegation asNegation() {
		throw new ClassCastException("Cannot cast to CqnArithmeticNegation");
	}

	/**
	 * Returns {@code true} if this is a {@link CqnPredicate}.
	 * 
	 * @return {@code true} if this is a predicate, otherwise {@code false}
	 */
	default boolean isPredicate() {
		return false;
	}

	/**
	 * Casts this expression to a {@code CqnPredicate}.
	 * 
	 * @throws ClassCastException if this expression is not a predicate
	 * @return this as a predicate
	 */
	default CqnPredicate asPredicate() {
		throw new ClassCastException("Cannot cast to CqnPredicate");
	}

	@Override
	default String toJson() {
		return "[" + tokens().map(CqnToken::toJson).collect(Collectors.joining(", ")) + "]";
	}

	@Override
	default void accept(CqnVisitor visitor) {
		visitor.visit(this);
	}

}