/*******************************************************************************
 * Copyright (c) 2012, 2013 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.tools;

import java.util.LinkedList;
import java.util.List;
import org.eclipse.persistence.jpa.jpql.Assert;
import org.eclipse.persistence.jpa.jpql.utility.iterable.ListIterable;
import org.eclipse.persistence.jpa.jpql.utility.iterable.SnapshotCloneListIterable;

/**
 * The default implementation of {@link RefactoringDelta} which contains the {@link TextEdit} that
 * were creating during the refactoring of a JPQL query.
 *
 * @version 2.5
 * @since 2.4
 * @author Pascal Filion
 */
@SuppressWarnings("nls")
public class DefaultRefactoringDelta implements RefactoringDelta {

	/**
	 * The JPQL query or JPQL fragment that will be traversed when refactoring operations will be executed.
	 */
	private CharSequence jpqlQuery;

	/**
	 * The list of {@link TextEdit} objects that have been added by refactoring operations.
	 */
	private List<TextEdit> textEdits;

	/**
	 * Creates a new <code>DefaultRefactoringDelta</code>.
	 *
	 * @param jpqlQuery The JPQL query or JPQL fragment that will be traversed when refactoring
	 * operations will be executed
	 * @exception NullPointerException The JPQL query cannot be <code>null</code>
	 */
	public DefaultRefactoringDelta(CharSequence jpqlQuery) {
		super();
		initialize(jpqlQuery);
	}

	/**
	 * Adds the given {@link TextEdit} at the right position. The list will be kept ordered, meaning
	 * the insertion index is based on the offset, from the biggest value to the smallest value.
	 *
	 * @param textEdit The {@link TextEdit} to add
	 * @exception NullPointerException The {@link TextEdit} cannot be <code>null</code>
	 */
	public void addTextEdit(TextEdit textEdit) {

		Assert.isNotNull(textEdit, "The TextEdit cannot be null");

		if (textEdits.isEmpty()) {
			textEdits.add(textEdit);
		}
		else {
			int position = calculateInsertionPosition(textEdit);
			textEdits.add(position, textEdit);
		}
	}

	/**
	 * Adds the given collection of {@link TextEdit} objects. The list will be kept ordered, meaning
	 * the insertion index is based on the offset, from the biggest value to the smallest value.
	 *
	 * @param textEdits The collection of {@link TextEdit} objects to add
	 * @exception NullPointerException The given {@link Iterable} or one of the child {@link TextEdit}
	 * was <code>null</code>
	 */
	public void addTextEdits(Iterable<? extends TextEdit> textEdits) {
		Assert.isNotNull(textEdits, "The Iterable<TextEdit> cannot be null");
		for (TextEdit textEdit : textEdits) {
			addTextEdit(textEdit);
		}
	}

	/**
	 * {@inheritDoc}
	 */
	public String applyChanges() {

		// Nothing to apply
		if (textEdits.isEmpty()) {
			return jpqlQuery.toString();
		}

		StringBuilder result = new StringBuilder(jpqlQuery);

		// The TextEdits are already in the right order (biggest offset to smallest offset),
		// so simply iterate them in order and replace the segments
		for (int index = 0, count = size(); index < count; index++) {
			TextEdit textEdit = textEdits.get(index);
			int offset = textEdit.getOffset();
			result.replace(offset, offset + textEdit.getLength(), textEdit.getNewValue());
		}

		textEdits.clear();
		return result.toString();
	}

	/**
	 * Calculates the insertion position for the given {@link TextEdit} based on those already registered
	 *
	 * @param textEdit The {@link TextEdit} for which its insertion position will be calculated
	 * @return The insertion position for the given {@link TextEdit}
	 */
	protected int calculateInsertionPosition(TextEdit textEdit) {

		int position = size();

		for (int index = position; --index >= 0; ) {
			TextEdit edit = textEdits.get(index);
			if (textEdit.getOffset() > edit.getOffset()) {
				position = index;
			}
			else {
				break;
			}
		}

		return position;
	}

	/**
	 * {@inheritDoc}
	 */
	public boolean hasTextEdits() {
		return !textEdits.isEmpty();
	}

	/**
	 * Initializes this <code>DefaultRefactoringDelta</code>.
	 *
	 * @param jpqlQuery The JPQL query or JPQL fragment that will be traversed when refactoring
	 * operations will be executed
	 * @exception NullPointerException The JPQL query cannot be <code>null</code>
	 */
	protected void initialize(CharSequence jpqlQuery) {
		Assert.isNotNull(jpqlQuery, "The JPQL query cannot be null");
		this.jpqlQuery = jpqlQuery;
		this.textEdits = new LinkedList<TextEdit>();
	}

	/**
	 * {@inheritDoc}
	 */
	public int size() {
		return textEdits.size();
	}

	/**
	 * {@inheritDoc}
	 */
	public ListIterable<TextEdit> textEdits() {
		return new SnapshotCloneListIterable<TextEdit>(textEdits);
	}

	/**
	 * {@inheritDoc}
	 */
	@Override
	public String toString() {
		return textEdits.toString();
	}
}