/*******************************************************************************
 * Copyright (c) 2000, 2008 IBM Corporation and others.
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 *
 * Contributors:
 *     IBM Corporation - initial API and implementation
 *******************************************************************************/
package org.eclipse.jface.text.projection;


import org.eclipse.jface.text.BadLocationException;
import org.eclipse.jface.text.BadPositionCategoryException;
import org.eclipse.jface.text.DefaultPositionUpdater;
import org.eclipse.jface.text.DocumentEvent;
import org.eclipse.jface.text.IDocument;
import org.eclipse.jface.text.Position;


/**
 * The position updater used to adapt the fragments of a master document. If an
 * insertion happens at a fragment's offset, the fragment is extended rather
 * than shifted. Also, the last fragment is extended if an insert operation
 * happens at the end of the fragment.
 *
 * @since 3.0
 */
class FragmentUpdater extends DefaultPositionUpdater {

	/** Indicates whether the position being updated represents the last fragment. */
	private boolean fIsLast= false;

	/**
	 * Creates the fragment updater for the given category.
	 *
	 * @param fragmentCategory the position category used for managing the fragments of a document
	 */
	protected FragmentUpdater(String fragmentCategory) {
		super(fragmentCategory);
	}

	@Override
	public void update(DocumentEvent event) {

		try {

			Position[] category= event.getDocument().getPositions(getCategory());

			fOffset= event.getOffset();
			fLength= event.getLength();
			fReplaceLength= (event.getText() == null ? 0 : event.getText().length());
			fDocument= event.getDocument();

			for (int i= 0; i < category.length; i++) {

				fPosition= category[i];
				fIsLast= (i == category.length -1);

				fOriginalPosition.offset= fPosition.offset;
				fOriginalPosition.length= fPosition.length;

				if (notDeleted())
					adaptToReplace();
			}

		} catch (BadPositionCategoryException x) {
			// do nothing
		}
	}

	@Override
	protected void adaptToInsert() {
		int myStart= fPosition.offset;
		int myEnd= Math.max(myStart, fPosition.offset + fPosition.length - (fIsLast || isAffectingReplace() ? 0 : 1));

		if (myEnd < fOffset)
			return;

		if (fLength <= 0) {

			if (myStart <= fOffset)
				fPosition.length += fReplaceLength;
			else
				fPosition.offset += fReplaceLength;

		} else {

			if (myStart <= fOffset && fOriginalPosition.offset <= fOffset)
				fPosition.length += fReplaceLength;
			else
				fPosition.offset += fReplaceLength;
		}
	}

	/**
	 * Returns whether this updater considers any position affected by the given document event. A
	 * position is affected if <code>event</code> {@link Position#overlapsWith(int, int) overlaps}
	 * with it but not if the position is only shifted.
	 *
	 * @param event the event
	 * @return <code>true</code> if there is any affected position, <code>false</code> otherwise
	 */
	public boolean affectsPositions(DocumentEvent event) {
		IDocument document= event.getDocument();
		try {

			int index= document.computeIndexInCategory(getCategory(), event.getOffset());
			Position[] fragments= document.getPositions(getCategory());

			if (0 < index) {
				Position fragment= fragments[index - 1];
				if (fragment.overlapsWith(event.getOffset(), event.getLength()))
					return true;
				if (index == fragments.length && fragment.offset + fragment.length == event.getOffset())
					return true;
			}

			if (index < fragments.length) {
				Position fragment= fragments[index];
				return fragment.overlapsWith(event.getOffset(), event.getLength());
			}

		} catch (BadLocationException x) {
		} catch (BadPositionCategoryException x) {
		}

		return false;
	}
}