/*******************************************************************************
 * Copyright (c) 2005 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
 * Port to the D programming language:
 *     Frank Benoit <benoit@tionex.de>
 *******************************************************************************/
module dwtx.jface.internal.text.NonDeletingPositionUpdater;

import dwt.dwthelper.utils;

import dwtx.jface.text.BadPositionCategoryException;
import dwtx.jface.text.DocumentEvent;
import dwtx.jface.text.IPositionUpdater;
import dwtx.jface.text.Position;


/**
 * A position updater that never deletes a position. If the region containing
 * the position is deleted, the position is moved to the beginning/end (falling
 * together) of the change. If the region containing the position is replaced,
 * the position is placed at the same location inside the replacement text, but
 * always inside the replacement text.
 *
 * @since 3.1
 */
public final class NonDeletingPositionUpdater : IPositionUpdater {
    /** The position category. */
    private final String fCategory;

    /**
     * Creates a new updater for the given <code>category</code>.
     *
     * @param category the new category.
     */
    public NonDeletingPositionUpdater(String category) {
        fCategory= category;
    }

    /*
     * @see dwtx.jface.text.IPositionUpdater#update(dwtx.jface.text.DocumentEvent)
     */
    public void update(DocumentEvent event) {

        int eventOffset= event.getOffset();
        int eventOldEndOffset= eventOffset + event.getLength();
        int eventNewLength= event.getText() is null ? 0 : event.getText().length();
        int eventNewEndOffset= eventOffset + eventNewLength;
        int deltaLength= eventNewLength - event.getLength();

        try {
            Position[] positions= event.getDocument().getPositions(fCategory);

            for (int i= 0; i !is positions.length; i++) {

                Position position= positions[i];

                if (position.isDeleted())
                    continue;

                int offset= position.getOffset();
                int length= position.getLength();
                int end= offset + length;

                if (offset > eventOldEndOffset) {
                    // position comes way after change - shift
                    position.setOffset(offset + deltaLength);
                } else if (end < eventOffset) {
                    // position comes way before change - leave alone
                } else if (offset <= eventOffset && end >= eventOldEndOffset) {
                    // event completely internal to the position - adjust length
                    position.setLength(length + deltaLength);
                } else if (offset < eventOffset) {
                    // event extends over end of position - include the
                    // replacement text into the position
                    position.setLength(eventNewEndOffset - offset);
                } else if (end > eventOldEndOffset) {
                    // event extends from before position into it - adjust
                    // offset and length, including the replacement text into
                    // the position
                    position.setOffset(eventOffset);
                    int deleted= eventOldEndOffset - offset;
                    position.setLength(length - deleted + eventNewLength);
                } else {
                    // event comprises the position - keep it at the same
                    // position, but always inside the replacement text
                    int newOffset= Math.min(offset, eventNewEndOffset);
                    int newEndOffset= Math.min(end, eventNewEndOffset);
                    position.setOffset(newOffset);
                    position.setLength(newEndOffset - newOffset);
                }
            }
        } catch (BadPositionCategoryException e) {
            // ignore and return
        }
    }

    /**
     * Returns the position category.
     *
     * @return the position category
     */
    public String getCategory() {
        return fCategory;
    }
}