/*
 * $Id$
 *
 * Copyright (C) 2003-2015 JNode.org
 *
 * This library is free software; you can redistribute it and/or modify it
 * under the terms of the GNU Lesser General Public License as published
 * by the Free Software Foundation; either version 2.1 of the License, or
 * (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful, but 
 * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
 * or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public 
 * License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with this library; If not, write to the Free Software Foundation, Inc., 
 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 */
 
package org.jnode.fs.ntfs.index;

import java.util.Iterator;
import java.util.NoSuchElementException;
import org.jnode.fs.ntfs.FileRecord;
import org.jnode.fs.ntfs.NTFSStructure;


/**
 * Iterator used to iterate over all IndexEntry's in an index block
 * or index_root attribute.
 *
 * @author Ewout Prangsma (epr@users.sourceforge.net)
 */
public final class IndexEntryIterator implements Iterator<IndexEntry> {
    private int offset;
    private IndexEntry nextEntry;
    private final NTFSStructure parent;
    private final FileRecord parentFileRecord;

    /**
     * Initialize this instance.
     */
    public IndexEntryIterator(FileRecord parentFileRecord, NTFSStructure parent, int firstOffset) {
        this.offset = firstOffset;
        this.parentFileRecord = parentFileRecord;
        this.parent = parent;
        readNext();
    }

    /**
     * @see java.util.Iterator#hasNext()
     */
    public boolean hasNext() {
        if (nextEntry == null) {
            return false;
        }
        return !nextEntry.isLastIndexEntryInSubnode() || nextEntry.hasSubNodes();
    }

    /**
     * @see java.util.Iterator#next()
     */
    public IndexEntry next() {
        if (nextEntry == null) {
            throw new NoSuchElementException();
        } else {
            final IndexEntry result = nextEntry;
            final int size = nextEntry.getSize();

            // Prevents an infinite loop.  Seen on images where the size of the index entry has been zeroed out.
            if (size <= 0) {
                throw new IllegalStateException(String.format(
                    "Index entry size is 0, filesystem is corrupt.  Parent directory: '%s', reference number '%d'",
                    nextEntry.getParentFileRecord().getFileName(),
                    nextEntry.getParentFileRecord().getReferenceNumber()));
            }

            offset += size;
            // Now read the next next entry
            readNext();
            return result;
        }
    }

    /**
     * @see java.util.Iterator#remove()
     */
    public void remove() {
        throw new UnsupportedOperationException();
    }

    private void readNext() {
        nextEntry = new IndexEntry(parentFileRecord, parent, offset);

        try {
            if (nextEntry.isLastIndexEntryInSubnode() && !nextEntry.hasSubNodes()) {
                nextEntry = null;
            }
        } catch (ArrayIndexOutOfBoundsException e) {
            // If the last entry in the sub-node doesn't have the right flags set, an out-of-bounds exception can be
            // raised trying to read the next entry that isn't there. E.g. offset 4088 in a 4096 block. Just ignore this
            // for now
            nextEntry = null;
        }
    }
}