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

/**
 * This is the delete clause of the delete statement.
 * <p>
 * A <b>DELETE</b> statement provides bulk operations over sets of entities of a single entity class
 * (together with its subclasses, if any). Only one entity abstract schema type may be specified in
 * the <b>UPDATE</b> clause.
 *
 * <div><b>BNF:</b> <code>delete_clause ::= DELETE FROM abstract_schema_name [[AS] identification_variable]</code></div>
 * <p>
 * Example: <code>DELETE FROM Employee e</code>
 *
 * @version 2.5
 * @since 2.3
 * @author Pascal Filion
 */
public final class DeleteClause extends AbstractExpression {

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

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

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

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

	/**
	 * The {@link Expression} representing the range variable declaration.
	 */
	private AbstractExpression rangeVariableDeclaration;

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

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

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

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

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

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

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

		// 'FROM'
		if (fromIdentifier != null) {
			children.add(buildStringExpression(FROM));
		}

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

		// Range declaration variable
		if (rangeVariableDeclaration != null) {
			children.add(rangeVariableDeclaration);
		}
	}

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

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

		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);
	}

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

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

		return super.findQueryBNF(expression);
	}

	/**
	 * Returns the actual <b>DELETE</b> found in the string representation of the JPQL query, which
	 * has the actual case that was used.
	 *
	 * @return The <b>DELETE</b> identifier that was actually parsed, or an empty string if it was
	 * not parsed
	 */
	public String getActualDeleteIdentifier() {
		return (deleteIdentifier != null) ? deleteIdentifier : ExpressionTools.EMPTY_STRING;
	}

	/**
	 * Returns the actual <b>FROM</b> identifier found in the string representation of the JPQL
	 * query, which has the actual case that was used.
	 *
	 * @return The <b>FROM</b> identifier that was actually parsed, or an empty string if it was
	 * not parsed
	 */
	public String getActualFromIdentifier() {
		return (fromIdentifier != null) ? fromIdentifier : ExpressionTools.EMPTY_STRING;
	}

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

	/**
	 * Returns the {@link Expression} representing the range variable declaration.
	 *
	 * @return The expression representing the range variable declaration
	 */
	public Expression getRangeVariableDeclaration() {
		if (rangeVariableDeclaration == null) {
			rangeVariableDeclaration = buildNullExpression();
		}
		return rangeVariableDeclaration;
	}

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

	/**
	 * Determines whether the range variable declaration was parsed.
	 *
	 * @return <code>true</code> if the range variable declaration was parsed; <code>false</code> otherwise
	 */
	public boolean hasRangeVariableDeclaration() {
		return rangeVariableDeclaration != null &&
		      !rangeVariableDeclaration.isNull();
	}

	/**
	 * Determines whether a whitespace was found after the identifier <b>DELETE</b>.
	 *
	 * @return <code>true</code> if there was a whitespace after the identifier <b>DELETE</b>;
	 * <code>false</code> otherwise
	 */
	public boolean hasSpaceAfterDelete() {
		return hasSpaceAfterDelete;
	}

	/**
	 * Determines whether a whitespace was found after the identifier <b>FROM</b>.
	 *
	 * @return <code>true</code> if there was a whitespace after the identifier <b>FROM</b>;
	 * <code>false</code> otherwise
	 */
	public boolean hasSpaceAfterFrom() {
		return hasSpaceAfterFrom;
	}

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

		// Parse 'DELETE'
		deleteIdentifier = wordParser.moveForward(DELETE);

		hasSpaceAfterDelete = wordParser.skipLeadingWhitespace() > 0;

		// Parse 'FROM'
		if (!tolerant || wordParser.startsWithIdentifier(FROM)) {
			fromIdentifier = wordParser.moveForward(FROM);
			hasSpaceAfterFrom = wordParser.skipLeadingWhitespace() > 0;
		}

		// Parse the range variable declaration
		if (tolerant) {
			rangeVariableDeclaration = parse(
				wordParser,
				DeleteClauseRangeVariableDeclarationBNF.ID,
				tolerant
			);
		}
		else {
			rangeVariableDeclaration = new RangeVariableDeclaration(this);
			rangeVariableDeclaration.parse(wordParser, tolerant);
		}
	}

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

		// 'DELETE'
		writer.append(actual ? deleteIdentifier : DELETE);

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

		// 'FROM'
		if (fromIdentifier != null) {
			writer.append(actual ? fromIdentifier : FROM);
		}

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

		// Range variable declaration
		if (rangeVariableDeclaration != null) {
			rangeVariableDeclaration.toParsedText(writer, actual);
		}
	}
}