/*
 * 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 java.util.StringTokenizer;

import org.eclipse.persistence.jpa.jpql.WordParser;

/**
 * A <b>JOIN</b> enables the fetching of an association as a side effect of the execution of a query.
 * A <b>JOIN</b> is specified over an entity and its related entities.
 *
 * <div><b>BNF:</b> <code>join ::= join_spec join_association_path_expression [AS] identification_variable</code></div>
 * <p>
 * A <b>JOIN FETCH</b> enables the fetching of an association as a side effect of the execution of
 * a query. A <b>JOIN FETCH</b> is specified over an entity and its related entities.
 *
 * <div><b>BNF:</b> <code>fetch_join ::= join_spec FETCH join_association_path_expression</code></div>
 * <p>
 * EclipseLink 2.4
 *
 * <div><b>BNF:</b> <code>join_spec { abstract_schema_name | join_association_path_expression } [AS] identification_variable [join_condition]</code></div>
 *
 * @version 2.5
 * @since 2.3
 * @author Pascal Filion
 */
@SuppressWarnings("nls")
public final class Join extends AbstractExpression {

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

    /**
     * Determines whether a whitespace was parsed after <b>AS</b>.
     */
    private boolean hasSpaceAfterAs;

    /**
     * Determines whether a whitespace was parsed after the identification variable.
     */
    private boolean hasSpaceAfterIdentificationVariable;

    /**
     * Determines whether a whitespace was parsed after <b>JOIN</b>.
     */
    private boolean hasSpaceAfterJoin;

    /**
     * Determines whether a whitespace was parsed after the join association path expression.
     */
    private boolean hasSpaceAfterJoinAssociation;

    /**
     * The {@link Expression} representing the identification variable.
     */
    private AbstractExpression identificationVariable;

    /**
     * The {@link Expression} representing the join association path expression.
     */
    private AbstractExpression joinAssociationPath;

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

    /**
     * The {@link Expression} representing the join <b>ON</b> clause.
     */
    private AbstractExpression onClause;

    /**
     * Make sure when parsing the identification variable with tolerance turned on, a the join
     * condition identifier <b>ON</b> is not parsed.
     */
    private boolean parsingIdentificationVariable;

    /**
     * Creates a new <code>Join</code>.
     *
     * @param parent The parent of this expression
     * @param identifier The full <b>JOIN</b> identifier
     */
    public Join(AbstractExpression parent, String identifier) {
        super(parent, identifier);
    }

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

    @Override
    public void acceptChildren(ExpressionVisitor visitor) {
        getJoinAssociationPath().accept(visitor);
        getIdentificationVariable().accept(visitor);
        getOnClause().accept(visitor);
    }

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

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

        String join = getText();

        // Break the identifier into multiple identifiers
        if (join.indexOf(SPACE) != -1) {
            StringTokenizer tokenizer = new StringTokenizer(join, " ", true);

            while (tokenizer.hasMoreTokens()) {
                String token = tokenizer.nextToken();
                children.add(buildStringExpression(token));
            }
        }
        else {
            children.add(buildStringExpression(join));
        }

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

        // Join association path
        if (joinAssociationPath != null) {
            children.add(joinAssociationPath);
        }

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

        // 'AS'
        if (asIdentifier != null) {
            children.add(buildStringExpression(AS));

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

        // Identification variable
        if (identificationVariable != null) {
            children.add(identificationVariable);
        }

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

        // ON clause
        if (onClause != null) {
            children.add(onClause);
        }
    }

    @Override
    public JPQLQueryBNF findQueryBNF(Expression expression) {

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

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

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

        return super.findQueryBNF(expression);
    }

    /**
     * Returns the actual <b>AS</b> found in the string representation of the JPQL query, which has
     * the actual case that was used.
     *
     * @return The <b>AS</b> identifier that was actually parsed, or an empty string if it was not
     * parsed
     */
    public String getActualAsIdentifier() {
        return asIdentifier;
    }

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

    /**
     * Returns the {@link Expression} that represents the identification variable.
     *
     * @return The expression that was parsed representing the identification variable
     */
    public Expression getIdentificationVariable() {
        if (identificationVariable == null) {
            identificationVariable = buildNullExpression();
        }
        return identificationVariable;
    }

    /**
     * Returns the identifier this expression represents.
     *
     * @return Either <b>JOIN</b>, <b>INNER JOIN</b>, <b>LEFT JOIN</b> or <b>LEFT OUTER JOIN</b>.
     * Although it's possible to have an incomplete identifier if the query is not complete
     */
    public String getIdentifier() {
        return getText();
    }

    /**
     * Returns the {@link Expression} that represents the join association path expression.
     *
     * @return The expression that was parsed representing the join association path expression
     */
    public Expression getJoinAssociationPath() {
        if (joinAssociationPath == null) {
            joinAssociationPath = buildNullExpression();
        }
        return joinAssociationPath;
    }

    /**
     * Returns the {@link Expression} that represents the <b>ON</b> clause if present.
     *
     * @return The expression that was parsed representing the identification variable
     */
    public Expression getOnClause() {
        if (onClause == null) {
            onClause = buildNullExpression();
        }
        return onClause;
    }

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

    /**
     * Determines whether the identifier <b>AS</b> was parsed.
     *
     * @return <code>true</code> if the identifier <b>AS</b> was parsed; <code>false</code> otherwise
     */
    public boolean hasAs() {
        return asIdentifier != null;
    }

    /**
     * Determines whether the identifier <b>FETCH</b> was parsed.
     *
     * @return <code>true</code> if the identifier <b>FETCH</b> was parsed; <code>false</code> otherwise
     */
    public boolean hasFetch() {
        String identifier = getText();
        return identifier == JOIN_FETCH       ||
               identifier == INNER_JOIN_FETCH ||
               identifier == LEFT_JOIN_FETCH  ||
               identifier == LEFT_OUTER_JOIN_FETCH;
    }

    /**
     * Determines whether the identification variable was parsed.
     *
     * @return <code>true</code> if the identification variable was parsed; <code>false</code> otherwise
     */
    public boolean hasIdentificationVariable() {
        return identificationVariable != null  &&
              !identificationVariable.isNull() &&
              !identificationVariable.isVirtual();
    }

    /**
     * Determines whether the join association path expression was parsed.
     *
     * @return <code>true</code> if the join association path expression was parsed; <code>false</code>
     * otherwise
     */
    public boolean hasJoinAssociationPath() {
        return joinAssociationPath != null &&
              !joinAssociationPath.isNull();
    }

    /**
     * Determines whether the <b>ON</b> clause was parsed.
     *
     * @return <code>true</code> if the <b>ON</b> clause was parsed; <code>false</code> otherwise
     */
    public boolean hasOnClause() {
        return onClause != null &&
              !onClause.isNull();
    }

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

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

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

    /**
     * Determines whether a whitespace was parsed after the join association path expression.
     *
     * @return <code>true</code> if there was a whitespace after join association path expression;
     * <code>false</code> otherwise
     */
    public boolean hasSpaceAfterJoinAssociation() {
        return hasSpaceAfterJoinAssociation;
    }

    /**
     * Determines whether this {@link Join} is a left join, i.e. {@link Expression#LEFT_JOIN},
     * {@link Expression#LEFT_JOIN_FETCH},  {@link Expression#LEFT_OUTER_JOIN}, {@link
     * Expression#LEFT_OUTER_JOIN_FETCH}.
     *
     * @return <code>true</code> if this {@link Join} expression is a {@link Expression#LEFT_JOIN},
     * {@link Expression#LEFT_JOIN_FETCH},  {@link Expression#LEFT_OUTER_JOIN}, {@link
     * Expression#LEFT_OUTER_JOIN_FETCH}; <code>false</code> otherwise
     */
    public boolean isLeftJoin() {
        String identifier = getIdentifier();
        return identifier == LEFT_JOIN ||
               identifier == LEFT_OUTER_JOIN ||
               identifier == LEFT_JOIN_FETCH ||
               identifier == LEFT_OUTER_JOIN_FETCH;
    }

    @Override
    protected boolean isParsingComplete(WordParser wordParser, String word, Expression expression) {

        // Make sure when parsing the identification variable with tolerance turned on,
        // a the join condition identifier ON is not parsed
        if (parsingIdentificationVariable &&
            word.equalsIgnoreCase(ON)) {

            return true;
        }

        return word.equalsIgnoreCase(AS)    ||
               word.equalsIgnoreCase(INNER) ||
               word.equalsIgnoreCase(JOIN)  ||
               word.equalsIgnoreCase(LEFT)  ||
               word.equalsIgnoreCase(OUTER) ||
               super.isParsingComplete(wordParser, word, expression);
    }

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

        // Parse the JOIN identifier
        joinIdentifier = wordParser.moveForward(getText());

        hasSpaceAfterJoin = wordParser.skipLeadingWhitespace() > 0;

        // Parse the join association path expression
        if (tolerant) {
            joinAssociationPath = parse(wordParser, JoinAssociationPathExpressionBNF.ID, tolerant);
        }
        // TREAT expression
        else if (wordParser.startsWithIdentifier(TREAT)) {
            joinAssociationPath = new TreatExpression(this);
            joinAssociationPath.parse(wordParser, tolerant);
        }
        // Abstract schema name, Collection-valued path expression or state field path expression
        else {
            String path = wordParser.word();

            if (path.indexOf('.') == -1) {
                joinAssociationPath = new AbstractSchemaName(this, path);
                joinAssociationPath.parse(wordParser, tolerant);
            }
            else {
                joinAssociationPath = new CollectionValuedPathExpression(this, path);
                joinAssociationPath.parse(wordParser, tolerant);
            }
        }

        int count = wordParser.skipLeadingWhitespace();
        hasSpaceAfterJoinAssociation = count > 0;

        // Parse 'AS'
        if (wordParser.startsWithIdentifier(AS)) {
            asIdentifier = wordParser.moveForward(AS);
            hasSpaceAfterAs = wordParser.skipLeadingWhitespace() > 0;
        }

        // Parse the identification variable
        parsingIdentificationVariable = true;

        if (tolerant) {
            identificationVariable = parse(wordParser, IdentificationVariableBNF.ID, tolerant);
        }
        else {
            String word = wordParser.word();

            if ((word.length() > 0) && !isParsingComplete(wordParser, word, null)) {
                identificationVariable = new IdentificationVariable(this, word);
                identificationVariable.parse(wordParser, tolerant);
            }
        }

        parsingIdentificationVariable = false;

        // A JOIN FETCH without '[AS] identification_variable' will not keep the
        // whitespace after the join association for backward compatibility (for now)
        if (asIdentifier == null           &&
            hasSpaceAfterJoinAssociation   &&
            identificationVariable == null &&
            hasFetch() &&
           !wordParser.startsWithIdentifier(ON)) {

            hasSpaceAfterJoinAssociation = false;
            wordParser.moveBackward(count);
            count = 0;
        }
        else {
            count = wordParser.skipLeadingWhitespace();
        }

        // Parse the ON clause
        if (tolerant) {
            onClause = parse(wordParser, OnClauseBNF.ID, tolerant);
        }
        else if (wordParser.startsWithIdentifier(ON)) {
            onClause = new OnClause(this);
            onClause.parse(wordParser, tolerant);
        }

        if (onClause != null) {
            hasSpaceAfterIdentificationVariable = (count > 0);
        }
        else {
            wordParser.moveBackward(count);
        }
    }

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

        // Join identifier
        writer.append(actual ? joinIdentifier : getText());

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

        // Join association path
        if (joinAssociationPath != null) {
            joinAssociationPath.toParsedText(writer, actual);
        }

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

        // 'AS'
        if (asIdentifier != null) {
            writer.append(actual ? asIdentifier : AS);

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

        // Identification variable
        if (identificationVariable != null) {
            identificationVariable.toParsedText(writer, actual);
        }

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

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