/*******************************************************************************
 * Copyright (c) 2000, 2003 IBM Corporation and others.
 * All rights reserved. This program and the accompanying materials 
 * are made available under the terms of the Common Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/cpl-v10.html
 * 
 * Contributors:
 *     IBM Corporation - initial API and implementation
 *     MetaMatrix, Inc - repackaging and updates for use as a metadata store
 *******************************************************************************/
package org.teiid.designer.core.index;

import java.io.IOException;
import java.util.ArrayList;
import org.teiid.core.designer.util.StringUtilities;

/**
 * @since 8.0
 */
public class FileListBlock extends Block {

    protected int offset = 0;
    protected String prevPath = null;
    protected String[] paths = null;

    public FileListBlock( int blockSize ) {
        super(blockSize);
    }

    /**
     * add the name of the indexedfile to the buffr of the field. The name is not the entire name of the indexedfile, but the
     * difference between its name and the name of the previous indexedfile ...
     */
    public boolean addFile( IndexedFile indexedFile ) {
        int offset = this.offset;
        if (isEmpty()) {
            field.putInt4(offset, indexedFile.getFileNumber());
            offset += 4;
        }
        String path = indexedFile.getPath();
        int prefixLen = prevPath == null ? 0 : StringUtilities.prefixLength(prevPath, path);
        int sizeEstimate = 2 + 2 + (path.length() - prefixLen) * 3;
        if (offset + sizeEstimate > blockSize - 2)
            return false;
        field.putInt2(offset, prefixLen);
        offset += 2;
        char[] chars = new char[path.length() - prefixLen];
        path.getChars(prefixLen, path.length(), chars, 0);
        offset += field.putUTF(offset, chars);
        this.offset = offset;
        prevPath = path;
        return true;
    }

    @Override
    public void clear() {
        reset();
        super.clear();
    }

    @Override
    public void flush() {
        if (offset > 0) {
            field.putInt2(offset, 0);
            field.putInt2(offset + 2, 0);
            offset = 0;
        }
    }

    public IndexedFile getFile( int fileNum ) {
        IndexedFile resp = null;
        try {
            String[] paths = getPaths();
            int i = fileNum - field.getInt4(0);
            resp = new IndexedFile(paths[i], fileNum);
        } catch (Exception e) {
            // fileNum too big
        }
        return resp;
    }

    /**
     * Creates a vector of paths reading the buffer of the field.
     */
    protected String[] getPaths() throws IOException {
        if (paths == null) {
            ArrayList v = new ArrayList();
            int offset = 4;
            char[] prevPath = null;
            for (;;) {
                int prefixLen = field.getUInt2(offset);
                offset += 2;
                int utfLen = field.getUInt2(offset);
                char[] path = field.getUTF(offset);
                offset += 2 + utfLen;
                if (prefixLen != 0) {
                    char[] temp = new char[prefixLen + path.length];
                    System.arraycopy(prevPath, 0, temp, 0, prefixLen);
                    System.arraycopy(path, 0, temp, prefixLen, path.length);
                    path = temp;
                }
                if (path.length == 0) break;
                v.add(new String(path));
                prevPath = path;
            }
            paths = new String[v.size()];
            v.toArray(paths);
        }
        return paths;
    }

    public boolean isEmpty() {
        return offset == 0;
    }

    public void reset() {
        offset = 0;
        prevPath = null;
    }
}