/*
 * Copyright (c) 2006, 2021 Oracle and/or its affiliates. All rights reserved.
 *
 * This program and the accompanying materials are made available under the
 * terms of the Eclipse Public License v. 2.0 which is available at
 * http://www.eclipse.org/legal/epl-2.0,
 * or the Eclipse Distribution License v. 1.0 which is available at
 * http://www.eclipse.org/org/documents/edl-v10.php.
 *
 * SPDX-License-Identifier: EPL-2.0 OR BSD-3-Clause
 */

// Contributors:
//     Oracle - initial API and implementation
//
package org.eclipse.persistence.jpa.jpql.parser;

import java.util.Collection;
import java.util.List;
import org.eclipse.persistence.jpa.jpql.WordParser;

/**
 * The <b>UPDATE</b> clause of a query consists of a conditional expression used to select objects
 * or values that satisfy the expression. The <b>UPDATE</b> clause restricts the result of a select
 * statement or the scope of an update operation.
 *
 * <div><b>BNF:</b> <code>update_statement ::= update_clause [where_clause]</code><p></p></div>
 *
 * @see JPQLExpression
 * @see UpdateClause
 * @see WhereClause
 *
 * @version 2.5
 * @since 2.3
 * @author Pascal Filion
 */
public final class UpdateStatement extends AbstractExpression {

    /**
     * Determines whether a whitespace was parsed after the <b>UPDATE</b> clause.
     */
    private boolean hasSpaceAfterUpdateClause;

    /**
     * The expression representing the <b>UPDATE</b> clause.
     */
    private UpdateClause updateClause;

    /**
     * The expression representing the <b>WHERE</b> clause.
     */
    private AbstractExpression whereClause;

    /**
     * Creates a new <code>UpdateStatement</code>.
     *
     * @param parent The parent of this expression
     */
    public UpdateStatement(AbstractExpression parent) {
        super(parent);
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public void accept(ExpressionVisitor visitor) {
        visitor.visit(this);
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public void acceptChildren(ExpressionVisitor visitor) {
        getUpdateClause().accept(visitor);
        getWhereClause().accept(visitor);
    }

    /**
     * {@inheritDoc}
     */
    @Override
    protected void addChildrenTo(Collection<Expression> children) {
        children.add(getUpdateClause());
        children.add(getWhereClause());
    }

    /**
     * {@inheritDoc}
     */
    @Override
    protected void addOrderedChildrenTo(List<Expression> children) {

        // Update clause
        children.add(updateClause);

        if (hasSpaceAfterUpdateClause) {
            children.add(buildStringExpression(SPACE));
        }

        // Where clause
        if (whereClause != null) {
            children.add(whereClause);
        }
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public JPQLQueryBNF findQueryBNF(Expression expression) {

        if (updateClause.isAncestor(expression)) {
            return getQueryBNF(UpdateClauseBNF.ID);
        }

        if ((whereClause != null) && whereClause.isAncestor(expression)) {
            return getQueryBNF(WhereClauseBNF.ID);
        }

        return super.findQueryBNF(expression);
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public JPQLQueryBNF getQueryBNF() {
        return getQueryBNF(UpdateStatementBNF.ID);
    }

    /**
     * Returns the {@link UpdateClause} representing the <b>UPDATE</b> clause.
     *
     * @return The section of the update statement representing the <b>UPDATE</b> clause
     */
    public UpdateClause getUpdateClause() {
        return updateClause;
    }

    /**
     * Returns the {@link Expression} representing the <b>WHERE</b> clause.
     *
     * @return The section of the update statement representing the <b>WHERE</b> clause
     */
    public Expression getWhereClause() {
        if (whereClause == null) {
            whereClause = buildNullExpression();
        }
        return whereClause;
    }

    /**
     * Determines whether a whitespace was parsed after the <b>UPDATE</b> clause.
     *
     * @return <code>true</code> if a whitespace was parsed after the <b>UPDATE</b> clause;
     * <code>false</code> otherwise
     */
    public boolean hasSpaceAfterUpdateClause() {
        return hasSpaceAfterUpdateClause;
    }

    /**
     * Determines whether the <b>WHERE</b> clause is defined or not.
     *
     * @return <code>true</code> if this statement has a <b>WHERE</b> clause; <code>false</code> if
     * it was not parsed
     */
    public boolean hasWhereClause() {
        return whereClause != null &&
              !whereClause.isNull();
    }

    /**
     * {@inheritDoc}
     */
    @Override
    protected void parse(WordParser wordParser, boolean tolerant) {

        // Parse 'UPDATE'
        updateClause = new UpdateClause(this);
        updateClause.parse(wordParser, tolerant);

        hasSpaceAfterUpdateClause = wordParser.skipLeadingWhitespace() > 0;

        // Parse 'WHERE'
        if (wordParser.startsWithIdentifier(WHERE)) {
            whereClause = new WhereClause(this);
            whereClause.parse(wordParser, tolerant);
        }

        // Now fully qualify attribute names with a virtual identification variable
        accept(new FullyQualifyPathExpressionVisitor());
    }

    /**
     * {@inheritDoc}
     */
    @Override
    protected void toParsedText(StringBuilder writer, boolean actual) {

        // Update clause
        updateClause.toParsedText(writer, actual);

        if (hasSpaceAfterUpdateClause) {
            writer.append(SPACE);
        }

        // Where clause
        if (whereClause != null) {
            whereClause.toParsedText(writer, actual);
        }
    }
}