jpa/org.eclipse.persistence.jpa.jpql/src/main/java/org/eclipse/persistence/jpa/jpql/parser/ConstructorExpression.java

/*
 * 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.ArrayList;
import java.util.Collection;
import java.util.List;
import org.eclipse.persistence.jpa.jpql.ExpressionTools;
import org.eclipse.persistence.jpa.jpql.WordParser;

/**
 * In the <b>SELECT</b> clause a constructor may be used in the <b>SELECT</b> list to return one or
 * more Java instances. The specified class is not required to be an entity or to be mapped to the
 * database. The constructor name must be fully qualified.
 *
 * <div><b>BNF:</b> <code>constructor_expression ::= NEW constructor_name(constructor_item {, constructor_item}*)</code><p></p></div>
 *
 * @version 2.5
 * @since 2.3
 * @author Pascal Filion
 */
public final class ConstructorExpression extends AbstractExpression {

    /**
     * The fully qualified class name of this expression.
     */
    private String className;

    /**
     * The list of constructor items.
     */
    private AbstractExpression constructorItems;

    /**
     * Flag used to determine if the closing parenthesis is present in the query.
     */
    private boolean hasLeftParenthesis;

    /**
     * Flag used to determine if the opening parenthesis is present in the query.
     */
    private boolean hasRightParenthesis;

    /**
     * When the expression is not valid and the left parenthesis is missing, then a space might have
     * been parsed.
     */
    private boolean hasSpaceAfterConstructorName;

    /**
     * Determines whether there is a whitespace after the identifier <b>NEW</b>.
     */
    private boolean hasSpaceAfterNew;

    /**
     * The actual <b>NEW</b> identifier found in the string representation of the JPQL query.
     */
    private String identifier;

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

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

    @Override
    public void acceptChildren(ExpressionVisitor visitor) {
        getConstructorItems().accept(visitor);
    }

    @Override
    protected void addChildrenTo(Collection<Expression> children) {
        children.add(getConstructorItems());
    }

    @Override
    protected void addOrderedChildrenTo(List<Expression> children) {

        // 'NEW'
        children.add(buildStringExpression(NEW));

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

        // Class name
        if (className.length() > 0) {
            children.add(buildStringExpression(className));
        }

        // '('
        if (hasLeftParenthesis) {
            children.add(buildStringExpression(LEFT_PARENTHESIS));
        }
        else if (hasSpaceAfterConstructorName) {
            children.add(buildStringExpression(SPACE));
        }

        // Constructor items
        if (hasConstructorItems()) {
            children.add(constructorItems);
        }

        // ')'
        if (hasRightParenthesis) {
            children.add(buildStringExpression(RIGHT_PARENTHESIS));
        }
    }

    /**
     * Creates a new {@link CollectionExpression} that will wrap the single constructor item.
     *
     * @return The single constructor item represented by a temporary collection
     */
    public CollectionExpression buildCollectionExpression() {

        List<AbstractExpression> children = new ArrayList<AbstractExpression>(1);
        children.add((AbstractExpression) getConstructorItems());

        List<Boolean> commas = new ArrayList<Boolean>(1);
        commas.add(Boolean.FALSE);

        List<Boolean> spaces = new ArrayList<Boolean>(1);
        spaces.add(Boolean.FALSE);

        return new CollectionExpression(this, children, commas, spaces, true);
    }

    @Override
    public JPQLQueryBNF findQueryBNF(Expression expression) {

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

        return super.findQueryBNF(expression);
    }

    /**
     * Returns the actual <b>NEW</b> identifier found in the string representation of the JPQL query,
     * which has the actual case that was used.
     *
     * @return The <b>NEW</b> identifier that was actually parsed
     */
    public String getActualIdentifier() {
        return identifier;
    }

    /**
     * Returns the fully qualified class name that will be used to retrieve the constructor.
     *
     * @return The fully qualified class name or an empty string if it is not defined
     */
    public String getClassName() {
        return className;
    }

    /**
     * Returns the constructor items aggregated into a single expression and separated by commas or
     * a single expression.
     *
     * @return The constructor item or items or an invalid or "<code>null</code>" expression
     */
    public Expression getConstructorItems() {
        if (constructorItems == null) {
            constructorItems = buildNullExpression();
        }
        return constructorItems;
    }

    @Override
    public JPQLQueryBNF getQueryBNF() {
        return getQueryBNF(ConstructorExpressionBNF.ID);
    }

    /**
     * Determines whether the constructor items were parsed.
     *
     * @return <code>true</code> if the query had at least one constructor item; <code>false</code>
     * otherwise
     */
    public boolean hasConstructorItems() {
        return constructorItems != null &&
              !constructorItems.isNull();
    }

    /**
     * Determines whether the open parenthesis was parsed or not.
     *
     * @return <code>true</code> if the open parenthesis was present in the string version of the
     * query; <code>false</code> otherwise
     */
    public boolean hasLeftParenthesis() {
        return hasLeftParenthesis;
    }

    /**
     * Determines whether the close parenthesis was parsed or not.
     *
     * @return <code>true</code> if the close parenthesis was present in the string version of the
     * query; <code>false</code> otherwise
     */
    public boolean hasRightParenthesis() {
        return hasRightParenthesis;
    }

    /**
     * Determines whether a whitespace was parsed after <b>NEW</b>.
     *
     * @return <code>true</code> if there was a whitespace after <b>NEW</b>; <code>false</code>
     * otherwise
     */
    public boolean hasSpaceAfterNew() {
        return hasSpaceAfterNew;
    }

    @Override
    protected boolean isParsingComplete(WordParser wordParser, String word, Expression expression) {
        return wordParser.character() == RIGHT_PARENTHESIS ||
               super.isParsingComplete(wordParser, word, expression);
    }

    @Override
    protected void parse(WordParser wordParser, boolean tolerant) {

        // Parse 'NEW'
        identifier = wordParser.moveForward(NEW);

        hasSpaceAfterNew = wordParser.skipLeadingWhitespace() > 0;

        // Parse the class name
        String className = wordParser.word();

        if (tolerant && isIdentifier(className)) {
            this.className = ExpressionTools.EMPTY_STRING;
            return;
        }

        this.className = className;
        wordParser.moveForward(className);

        int count = wordParser.skipLeadingWhitespace();

        // Parse '('
        hasLeftParenthesis = wordParser.startsWith(LEFT_PARENTHESIS);

        if (hasLeftParenthesis) {
            wordParser.moveForward(1);
            count = wordParser.skipLeadingWhitespace();
        }
        else {
            hasSpaceAfterConstructorName = (count > 0);
        }

        // Parse the constructor items
        constructorItems = parse(wordParser, ConstructorItemBNF.ID, tolerant);

        if (constructorItems != null) {
            count = wordParser.skipLeadingWhitespace();
        }

        // Parse ')'
        hasRightParenthesis = wordParser.character() == RIGHT_PARENTHESIS;

        if (hasRightParenthesis) {
            wordParser.moveForward(1);
        }
        else {
            wordParser.moveBackward(count);
        }
    }

    @Override
    protected boolean shouldSkipLiteral(AbstractExpression expression) {
        return false;
    }

    @Override
    protected void toParsedText(StringBuilder writer, boolean actual) {

        // 'NEW'
        writer.append(actual ? identifier : getText());

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

        // Class name
        writer.append(className);

        // '('
        if (hasLeftParenthesis) {
            writer.append(LEFT_PARENTHESIS);
        }
        else if (hasSpaceAfterConstructorName) {
            writer.append(SPACE);
        }

        // Constructor items
        if (constructorItems != null) {
            constructorItems.toParsedText(writer, actual);
        }

        // ')'
        if (hasRightParenthesis) {
            writer.append(RIGHT_PARENTHESIS);
        }
    }
}