package org.greenstone.gsdl3.util;

import au.com.pharos.gdbm.GdbmFile;
import au.com.pharos.packing.*;
import au.com.pharos.gdbm.GdbmException;

import org.apache.log4j.*;

/** java wrapper class for gdbm - uses Java-GDBM written by Martin Pool
 * replaces gdbmclass in the old version
 */

public class GDBMWrapper {

      static Logger logger = Logger.getLogger(org.greenstone.gsdl3.util.GDBMWrapper.class.getName());


    // Values must match those from gdbm.h - uses the definitions from GdbmFile !
    /** Indicates that the caller will just read the database.  Many
     * readers may share a database. */
    public final static int READER = GdbmFile.READER;
 
    /** The caller wants read/write access to an existing database and
     * requires exclusive access. */
    public final static int WRITER = GdbmFile.WRITER;
 
    /** The caller wants exclusive read/write access, and the database
     * should be created if it does not already exist. */
    public final static int WRCREAT = GdbmFile.WRCREAT;
 
    /** The caller wants exclusive read/write access, and the database
     * should be replaced if it already exists. */
    public final static int NEWDB = GdbmFile.NEWDB;

    protected GdbmFile db_=null;

    /** open the database filename, with mode mode - uses the constants
	above, eg GdbmFile.WRITER */
    public boolean openDatabase(String filename, int mode){
	try {
	    if (db_!=null) {
		db_.close();
	    }
	    db_ = new GdbmFile(filename, mode);
	} catch ( GdbmException e) { // the database wasn't opened or created
	    logger.error("couldn't open database "+filename);
	    return false;
	} 
	db_.setKeyPacking(new StringPacking());
	db_.setValuePacking(new StringPacking());
	return true;
    }

    /** cloase the database associated with this wrapper */
    public void closeDatabase() {
	try {
	    if (db_ != null) {
		db_.close();
		db_ = null;
	    }
	} catch (GdbmException e) {
	    // should never get here - close never actually throws an exception
	    logger.error("error on close()");
	}
    }

    /** returns a DBInfo object containing all the name-value pairs for 
     * main_key 
     * @see DBInfo
     */
    public DBInfo getInfo(String main_key) {
	if (db_==null) {
	    return null;
	}
	String s_info;
	try {
	    s_info = (String)db_.fetch(main_key);
	} catch (GdbmException e) {
	    logger.error("couldn't get record");
	    return null;
	}
	if (s_info==null) {
	    // record not present
	    logger.error("key "+main_key+" not present in db");
	    return null;
	}
	DBInfo info = new DBInfo();

	String [] lines = s_info.split("\n");
	String key;
	String value;
	for (int i=0; i<lines.length; i++) {
	    logger.debug("line:"+lines[i]);
	    int a = lines[i].indexOf('<');
	    int b= lines[i].indexOf('>');
	    if (a==-1 || b==-1) {
		logger.error("bad format in db");
	    }
	    else {
		key=lines[i].substring(a+1, b);
		value=lines[i].substring(b+1);
		logger.debug("key="+key+", val="+value);
		info.addInfo(key, value);

	    }
	}
	return info;
    }

    /** sets all the name-value pairs in info as the content for key key 
     * TODO - not implemented yet */
    public boolean setInfo(String key, DBInfo info) {
	if (db_==null) {
	    return false;
	}
	return true;
    }
    /** sets the key value as info 
     * TODO - not implemented yet */
    public boolean setInfo (String key, String info) {
	if (db_==null) {
	    return false;
	}
	return true;
    }
    /** deletes the entry for key 
     * TODO - not implemented yet */
    public boolean deleteKey(String key) {
	if (db_==null) {
	    return false;
	}
	return true;
    }

    // greenstone convenience methods - should these go into a separate class?
    // yes I think so.
    /** converts a greenstone OID to internal docnum */
    public long OID2Docnum(String OID) {
	DBInfo info = getInfo(OID);
	if (info != null) {
	    long real_num = Long.parseLong(info.getInfo("docnum"));
	    return real_num;
	}
	return -1;
    }
    /** converts a docnum to greenstone OID */
    public String docnum2OID(long docnum) {
	return docnum2OID(Long.toString(docnum));
    }
    
    /** converts a docnum to greenstone OID */
    public String docnum2OID(String docnum) {
	DBInfo info = getInfo(docnum);
	if (info!=null){
	    String oid = info.getInfo("section");
	    return oid;
	}else{
	    return null;
	}
    }

    /** converts an external id to greenstone OID */
    public String externalId2OID(String extid) {
	DBInfo info = getInfo(extid);
	if (info != null) {
	    String oid = info.getInfo("section");
	    return oid;
	}
	return null;
    }
    /** translates relative oids into proper oids:
     * .pr (parent), .rt (root) .fc (first child), .lc (last child),
     * .ns (next sibling), .ps (previous sibling) 
     * .np (next page), .pp (previous page) : links sections in the order that you'd read the document
     * a suffix is expected to be present so test before using 
     */
    public String translateOID(String oid) {

	int p = oid.lastIndexOf('.');
	if (p != oid.length()-3) {
	    logger.info("translateoid error: '.' is not the third to last char!!");
	    return oid;
	}
	
	String top = oid.substring(0, p);
	String suff = oid.substring(p+1);
	// just in case we have multiple extensions, we must translate
	// we process inner ones first
	if (OID.needsTranslating(top)) {
	    top = translateOID(top);
	}
	if (suff.equals("pr")) {
	    return OID.getParent(top);
	} 
	if (suff.equals("rt")) {
	    return OID.getTop(top);
	} 
	if (suff.equals("np")) {
	    // try first child
	    String node_id = translateOID(top+".fc");
	    if (!node_id.equals(top)) {
		return node_id;
	    }
	    // try next sibling
	    node_id = translateOID(top+".ns");
	    if (!node_id.equals(top)) {
		return node_id;
	    }
	    // otherwise we keep trying parents sibling
	    String child_id = top;
	    String parent_id = OID.getParent(child_id);
	    while(!parent_id.equals(child_id)) {
		node_id = translateOID(parent_id+".ns");
		if (!node_id.equals(parent_id)) {
		    return node_id;
		}
		child_id = parent_id;
		parent_id = OID.getParent(child_id);
	    }
	    return top; // we couldn't get a next page, so just return the original
	} 
	if (suff.equals("pp")) {
	    String prev_sib = translateOID(top+".ps");
	    if (prev_sib.equals(top)) {
		// no previous sibling, so return the parent
		return OID.getParent(top);
	    }
	    // there is a previous sibling, so its either this section, or the last child of the last child..
	    String last_child = translateOID(prev_sib+".lc");
	    while (!last_child.equals(prev_sib)) {
		prev_sib = last_child;
		last_child = translateOID(prev_sib+".lc");
	    }
	    return last_child;
	} 
	
	int sibling_num = 0;
	if (suff.equals("ss")) {
	    // we have to remove the sib num before we get top
	    p = top.lastIndexOf('.');
	    sibling_num = Integer.parseInt(top.substring(p+1));
	    top = top.substring(0, p);
	}
	
	// need to get info out of gdbm db -
	String doc_id = top;
	if (suff.endsWith("s")) {
	    doc_id = OID.getParent(top);
	    if (doc_id.equals(top)) {
		// i.e. we are already at the top
		return top;
	    }
	}
	DBInfo info = getInfo(doc_id);
	if (info==null) {
	    logger.info("info is null!!");
	    return top;
	}
	
	String contains = info.getInfo("contains");
	if (contains.equals("")) {
	    // something is wrong
	    return top;
	}
	contains = contains.replaceAll("\"", doc_id);
	String [] children = contains.split(";");
	if (suff.equals("fc")) {
	    return children[0];
	} else if (suff.equals("lc")) {
	    return children[children.length-1];
	} else {
	    if (suff.equals("ss")) {
		return children[sibling_num-1];
	    }
	    // find the position that we are at.
	    int i=0;
	    while (i<children.length) {
		if (children[i].equals(top)) {
		    break;
		}
		i++;
	    }
	    
	    if (suff.equals("ns")) {
		if (i==children.length-1) {
		    return children[i];
		}
		return children[i+1];
	    } else if (suff.equals("ps")) {
		if (i==0) {
		    return children[i];
		}
		return children[i-1];
	    }
	}
	
	return top;
    }
}