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/************************************************************************
 * © 2019-2024 SAP SE or an SAP affiliate company. All rights reserved. *
 ************************************************************************/
package com.sap.cds.ql.cqn;

import java.util.stream.Stream;

import com.google.common.annotations.Beta;

/**
 * A CQN literal value of type {@link T}. Use {@link #value} to get the value.
 */
public interface CqnLiteral extends CqnValue {

	/**
	 * Returns the literal value.
	 * 
	 * @return the literal value
	 */
	T value();

	/**
	 * Specifies if this {@link CqnLiteral} should be handled as a constant value
	 * during query execution.
	 *
	 * @return true if the literal can be handled as a constant value
	 */
	default boolean isConstant() {
		return true;
	}

	@Override
	default CqnLiteral asLiteral() {
		return this;
	}

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

	@Override
	default Stream> ofLiteral() {
		return Stream.of(this);
	}

	/**
	 * Returns {@code true} if this is a {@link CqnBooleanLiteral}.
	 * 
	 * @return {@code true} if this is a boolean literal, otherwise {@code false}
	 */
	default boolean isBoolean() {
		return false;
	}

	/**
	 * Returns {@code true} if this is a {@link CqnNumericLiteral}.
	 * 
	 * @return {@code true} if this is a numeric literal, otherwise {@code false}
	 */
	default boolean isNumeric() {
		return false;
	}

	/**
	 * Returns {@code true} if this is a {@link CqnStringLiteral}.
	 * 
	 * @return {@code true} if this is a string literal, otherwise {@code false}
	 */
	default boolean isString() {
		return false;
	}

	/**
	 * Returns {@code true} if this is a {@link CqnTemporalLiteral}.
	 * 
	 * @return {@code true} if this is a temporal literal, otherwise {@code false}
	 */
	default boolean isTemporal() {
		return false;
	}

	/**
	 * Returns {@code true} if this is a {@link CqnStructuredLiteral}.
	 * 
	 * @return {@code true} if this is a structured literal, otherwise {@code false}
	 */
	default boolean isStructured() {
		return false;
	}

	/**
	 * Returns {@code true} if this is a {@link CqnVector}.
	 * 
	 * @return {@code true} if this is a vector, otherwise {@code false}
	 */
	@Beta
	default boolean isVector() {
		return false;
	}

	/**
	 * Casts this literal to {@code CqnBooleanLiteral}.
	 * 
	 * @throws ClassCastException if this literal is not boolean
	 * @return this literal as a boolean literal
	 */
	default CqnBooleanLiteral asBoolean() {
		return as(CqnBooleanLiteral.class);
	}

	/**
	 * Casts this literal to {@code CqnStringLiteral}.
	 * 
	 * @throws ClassCastException if this literal is not a string literal
	 * @return this literal as a string literal
	 */
	default CqnStringLiteral asString() {
		return as(CqnStringLiteral.class);
	}

	/**
	 * Casts this literal to {@code CqnNumericLiteral}.
	 * 
	 * @throws ClassCastException if this literal is not numeric
	 * @return this literal as a numeric literal
	 */
	default CqnNumericLiteral asNumber() {
		return as(CqnNumericLiteral.class);
	}

	/**
	 * Casts this literal to {@code CqnTemporalLiteral}.
	 * 
	 * @throws ClassCastException if this literal is not temporal
	 * @return this literal as a temporal literal
	 */
	default CqnTemporalLiteral asTemporal() {
		return as(CqnTemporalLiteral.class);
	}

	/**
	 * Casts this literal to {@code CqnStructuredLiteral}.
	 * 
	 * @throws ClassCastException if this literal is not structured
	 * @return this literal as a structured literal
	 */
	default CqnStructuredLiteral asStructured() {
		return as(CqnStructuredLiteral.class);
	}

	/**
	 * Casts this literal to {@code CqnVector}.
	 * 
	 * @throws ClassCastException if this literal is no vector
	 * @return this literal as a vector
	 */
	default CqnVector asVector() {
		return as(CqnVector.class);
	}

}