source: trunk/indexers/mg/java/org/greenstone/mg/MGWrapper.java@ 3744

/*
 *    MGWrapper.java
 *    Copyright (C) 2002 New Zealand Digital Library, http://www.nzdl.org
 *
 *    This program is free software; you can redistribute it and/or modify
 *    it under the terms of the GNU General Public License as published by
 *    the Free Software Foundation; either version 2 of the License, or
 *    (at your option) any later version.
 *
 *    This program 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 General Public License for more details.
 *
 *    You should have received a copy of the GNU General Public License
 *    along with this program; if not, write to the Free Software
 *    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 */
package org.greenstone.mg;


/** java wrapper class for access to mg in C
 *
 * the native side implemented in MGWrapperImpl.c
 * uses MGQueryResult to hold the result of a query.
 * the result of a getDocument is a String
 * uses the jni
 *
 *@see MGQueryResult
 */
public class MGWrapper
{
    /** the query result, filled in by runQuery */
    protected MGQueryResult mg_query_result_ = null;

    /** pointer to c MGWrapperData class - cached indexData and queryInfo */
    protected long mg_data_ptr_ = 0;

    static {
    System.loadLibrary("mgjni");
    initIDs();
    }

    public MGWrapper() {
    mg_query_result_ = new MGQueryResult();
    initCSide();
    }

    /** initialises field and method IDs for java side to enable access on C side */
    private static native void initIDs();

    /** initialises the mg_data_ptr_ */
    private native boolean initCSide();

    /** returns a document: number docnum at level level 
     * the base_dir and text_path paths should join together to provide
     * the absolute location of the mg text files eg ..../index/text/demo
     * returns the doc in utf-8
     */
    public native String getDocument(String base_dir, String text_dir, long docnum);

    /** unloads the data */
    public native boolean unloadIndexData();

    // query param methods

    /** if on=true, sets default casefolding on - it's off by default */
    public native void setCase(boolean on);
    /** if on=true, sets default stemming on - it's off by default */
    public native void setStem(boolean on);
    /** default is 50 */
    public native void setMaxDocs(int num);
    /** if on=true, sorts by rank, otherwise returns in build order - 
    default is on */
    public native void setSortByRank(boolean on);
    /** if on=true, a query returns term freq info - default is on */
    public native void setReturnTerms(boolean on);
    /** sets the index to search - default is 'dtx' */
    public native void setIndex(String index);
    /** sets the default boolean operator - AND(=1)/OR(=0) */
    public native void setMatchMode(int mode);

    /** returns a string with all the current query param settings */
    public native String getQueryParams();

    /** actually carry out the query.
    Use the set methods to set query results.
    Writes the result to query_result.
     * - maintains state between requests as can be slow  
     * base_dir and index_path should join together to provide
     * the absolute location of the mg index files eg ..../index/dtx/demo 
     * base_dir must end with a file separator (OS dependant)
     */
    public native void runQuery(String base_dir, String text_dir, String query_string);


    /** get the result out of the wrapper */
    public MGQueryResult getQueryResult()
    {
    return mg_query_result_;
    }
}