/*
 * Copyright (c) 2015 Cisco Systems, Inc. and others.  All rights reserved.
 *
 * This program and the accompanying materials are made available under the
 * terms of the Eclipse Public License v1.0 which accompanies this distribution,
 * and is available at http://www.eclipse.org/legal/epl-v10.html
 */
package org.opendaylight.yangtools.yang.model.api.meta;

import org.eclipse.jdt.annotation.NonNull;
import org.opendaylight.yangtools.yang.common.Empty;

/**
 * Model statement. There are two base types of model statements:
 * <ul>
 *   <li>{@link DeclaredStatement} - Statement representation as was defined in original source. This representation
 *       could be used during computation of effective model or during transforming YANG model from one serialization
 *       format to another.
 *   </li>
 *   <li>{@link EffectiveStatement} - Representation of effective statement - this statement may be different from
 *       declared, in such way, that it contains additional substatements, provides access to model namespaces. Some
 *       effective statements may be not directly declared in YANG source, but could be inferred by semantic processing
 *       of other statements (for example {@code uses}, {@code augment} and others).
 *   </li>
 * </ul>
 *
 * @param <A> Argument type ({@link Empty} if statement does not have argument.)
 */
public sealed interface ModelStatement<A> permits DeclaredStatement, EffectiveStatement, AbstractModelStatement {
    /**
     * Statement Definition of this statement.
     *
     * @return definition of this statement.
     */
    @NonNull StatementDefinition statementDefinition();

    /**
     * Returns statement argument.
     *
     * @return statement argument.
     */
    @NonNull A argument();
}