/*******************************************************************************
 * Copyright (c) 2006, 2014 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 v1.0 and Eclipse Distribution License v. 1.0
 * which accompanies this distribution.
 * The Eclipse Public License is available at http://www.eclipse.org/legal/epl-v10.html
 * and the Eclipse Distribution License is available at
 * http://www.eclipse.org/org/documents/edl-v10.php.
 *
 * 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);
	}

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

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

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

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

		String join = getText();
		String space = " ";

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

	/**
	 * {@inheritDoc}
	 */
	@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;
	}

	/**
	 * {@inheritDoc}
	 */
	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;
	}

	/**
	 * {@inheritDoc}
	 */
	@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);
	}

	/**
	 * {@inheritDoc}
	 */
	@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);
		}
	}

	/**
	 * {@inheritDoc}
	 */
	@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);
		}
	}
}