/*******************************************************************************
 * 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;


/**
 * This class provides an input on an index, after it has been generated. You can access all the files of an index via
 * getNextFile(), getCurrentFile() and moveToNextFile() (idem for the word entries). The usage is the same for every subclass:
 * creation (constructor), opening (the open() method), usage, and closing (the close() method), to release the data source used
 * by this input.
 *
 * @since 8.0
 */
public abstract class IndexInput {
    protected int filePosition;
    protected WordEntry currentWordEntry;
    protected int wordPosition;

    // Cache the open state of the Index
    private boolean openState;

    public IndexInput() {
        super();
        wordPosition = 1;
        filePosition = 1;
    }

    /**
     * clears the cache of this indexInput, if it keeps track of the information already read.
     */
    public abstract void clearCache();

    /**
     * Closes the IndexInput. For example, if the input is on a RandomAccessFile, it calls the close() method of RandomAccessFile.
     */
    public abstract void close() throws IOException;

    /**
     * Returns the current file the indexInput is pointing to in the index.
     */
    public abstract IndexedFile getCurrentFile() throws IOException;

    /**
     * Returns the current file the indexInput is pointing to in the index.
     */
    public WordEntry getCurrentWordEntry() {
        if (!hasMoreWords()) return null;
        return currentWordEntry;
    }

    /**
     * Returns the position of the current file the input is pointing to in the index.
     */
    public int getFilePosition() {
        return filePosition;
    }

    /**
     * Set the open state of the Index
     * 
     * @since 5.0
     */
    public void setOpen( boolean state ) {
        this.openState = state;
    }

    /**
     * returns the open state of the index
     * 
     * @since 5.0
     */
    public boolean isOpen() {
        return this.openState;
    }

    /**
     * Returns the indexedFile corresponding to the given document number in the index the input reads in, or null if such
     * indexedFile does not exist.
     */
    public abstract IndexedFile getIndexedFile( int fileNum ) throws IOException;

    /**
     * Returns the indexedFile corresponding to the given document in the index the input reads in (e.g. the indexedFile with the
     * same path in this index), or null if such indexedFile does not exist.
     */
    public abstract IndexedFile getIndexedFile( IDocument document ) throws IOException;

    /**
     * Returns the number of files in the index.
     */
    public abstract int getNumFiles();

    /**
     * Returns the number of unique words in the index.
     */
    public abstract int getNumWords();

    /**
     * Returns the Object the input is reading from. It can be an IIndex, a File, ...
     */
    public abstract Object getSource();

    /**
     * Returns true if the input has not reached the end of the index for the files.
     */
    public boolean hasMoreFiles() {
        return getFilePosition() <= getNumFiles();
    }

    /**
     * Returns true if the input has not reached the end of the index for the files.
     */
    public boolean hasMoreWords() {
        return wordPosition <= getNumWords();
    }

    /**
     * Moves the pointer on the current file to the next file in the index.
     */
    public abstract void moveToNextFile() throws IOException;

    /**
     * Moves the pointer on the current word to the next file in the index.
     */
    public abstract void moveToNextWordEntry() throws IOException;

    /**
     * Open the Source where the input gets the information from.
     */
    public abstract void open() throws IOException;

    /**
     * Returns the list of the files containing the given word in the index.
     */
    public abstract IEntryResult[] queryEntriesPrefixedBy( char[] prefix ) throws IOException;

    public abstract IQueryResult[] queryFilesReferringToPrefix( char[] prefix ) throws IOException;

    /**
     * Returns the list of the files whose name contain the given word in the index.
     */
    public abstract IQueryResult[] queryInDocumentNames( String word ) throws IOException;

    /**
     * Set the pointer on the current file to the first file of the index.
     */
    protected abstract void setFirstFile() throws IOException;

    /**
     * Set the pointer on the current word to the first word of the index.
     */
    protected abstract void setFirstWord() throws IOException;
}