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// $Id: AbstractRestrictableStatement.java 7460 2005-07-12 20:27:29Z steveebersole $
package org.hibernate.hql.ast.tree;

import org.hibernate.hql.antlr.HqlSqlTokenTypes;
import org.hibernate.hql.ast.util.ASTUtil;

import antlr.collections.AST;

import org.apache.commons.logging.Log;

/**
 * Convenience implementation of RestrictableStatement to centralize common functionality.
 *
 * @author Steve Ebersole
 */
public abstract class AbstractRestrictableStatement extends AbstractStatement implements RestrictableStatement {

	private FromClause fromClause;
	private AST whereClause;

	protected abstract int getWhereClauseParentTokenType();
	protected abstract Log getLog();

	/**
	 * @see org.hibernate.hql.ast.tree.RestrictableStatement#getFromClause
	 */
	public final FromClause getFromClause() {
		if ( fromClause == null ) {
			fromClause = ( FromClause ) ASTUtil.findTypeInChildren( this, HqlSqlTokenTypes.FROM );
		}
		return fromClause;
	}

	/**
	 * @see RestrictableStatement#hasWhereClause
	 */
	public final boolean hasWhereClause() {
		AST whereClause = locateWhereClause();
		return whereClause != null && whereClause.getNumberOfChildren() > 0;
	}

	/**
	 * @see org.hibernate.hql.ast.tree.RestrictableStatement#getWhereClause
	 */
	public final AST getWhereClause() {
		if ( whereClause == null ) {
			whereClause = locateWhereClause();
			// If there is no WHERE node, make one.
			if ( whereClause == null ) {
				getLog().debug( "getWhereClause() : Creating a new WHERE clause..." );
				whereClause = ASTUtil.create( getWalker().getASTFactory(), HqlSqlTokenTypes.WHERE, "WHERE" );
				// inject the WHERE after the parent
				AST parent = ASTUtil.findTypeInChildren( this, getWhereClauseParentTokenType() );
				whereClause.setNextSibling( parent.getNextSibling() );
				parent.setNextSibling( whereClause );
			}
		}
		return whereClause;
	}

	protected AST locateWhereClause() {
		return ASTUtil.findTypeInChildren( this, HqlSqlTokenTypes.WHERE );
	}
}