/*******************************************************************************
 * 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.WordParser;

/**
 * Conditional expressions are composed of other conditional expressions, comparison operations,
 * logical operations, path expressions that evaluate to boolean values, boolean literals, and
 * boolean input parameters. Arithmetic expressions can be used in comparison expressions.
 * Arithmetic expressions are composed of other arithmetic expressions, arithmetic operations, path
 * expressions that evaluate to numeric values, numeric literals, and numeric input parameters.
 * Arithmetic operations use numeric promotion. Standard bracketing () for ordering expression
 * evaluation is supported.
 *
 * <div><b>BNF:</b> <code>expression ::= identifier conditional_expression</code><p></div>
 *
 * @see HavingClause
 * @see OnClause
 * @see StartWithClause
 * @see WhereClause
 *
 * @version 2.5
 * @since 2.3
 * @author Pascal Filion
 */
public abstract class AbstractConditionalClause extends AbstractExpression {

	/**
	 * The expression representing the composition of the conditional expressions.
	 */
	private AbstractExpression conditionalExpression;

	/**
	 * Determines whether a whitespace was parsed after the identifier.
	 */
	private boolean hasSpaceAfterIdentifier;

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

	/**
	 * Creates a new <code>AbstractConditionalClause</code>.
	 *
	 * @param parent The parent of this expression
	 * @param identifier The identifier of this conditional clause
	 */
	protected AbstractConditionalClause(AbstractExpression parent, String identifier) {
		super(parent, identifier);
	}

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

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

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

		// Identifier
		children.add(buildStringExpression(getText()));

		// Space
		if (hasSpaceAfterIdentifier) {
			children.add(buildStringExpression(SPACE));
		}

		// Conditional Expression
		if (conditionalExpression != null) {
			children.add(conditionalExpression);
		}
	}

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

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

		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 ((conditionalExpression != null) && conditionalExpression.isAncestor(expression)) {
			return getQueryBNF(ConditionalExpressionBNF.ID);
		}

		return super.findQueryBNF(expression);
	}

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

	/**
	 * Returns the expression representing the composition of the conditional expressions.
	 *
	 * @return The actual conditional expression
	 */
	public final Expression getConditionalExpression() {
		if (conditionalExpression == null) {
			conditionalExpression = buildNullExpression();
		}
		return conditionalExpression;
	}

	/**
	 * Returns the JPQL identifier of this expression.
	 *
	 * @return The JPQL identifier
	 */
	public final String getIdentifier() {
		return getText();
	}

	/**
	 * Determines whether the conditional expression was parsed.
	 *
	 * @return <code>true</code> if there is a conditional expression; <code>false</code> otherwise
	 */
	public final boolean hasConditionalExpression() {
		return conditionalExpression != null &&
		      !conditionalExpression.isNull();
	}

	/**
	 * Determines whether a whitespace was parsed after the identifier or not.
	 *
	 * @return <code>true</code> if there was a whitespace after the identifier; <code>false</code>
	 * otherwise
	 */
	public final boolean hasSpaceAfterIdentifier() {
		return hasSpaceAfterIdentifier;
	}

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

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

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

		hasSpaceAfterIdentifier = wordParser.skipLeadingWhitespace() > 0;

		// Parse the conditional expression
		conditionalExpression = parse(wordParser, ConditionalExpressionBNF.ID, tolerant);
	}

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

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

		writer.append(actual ? identifier : getText());

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

		if (conditionalExpression != null) {
			conditionalExpression.toParsedText(writer, actual);
		}
	}
}