/*
 * RDFresource.java
 *
 * Version: $Revision: 0.1 $
 *
 * Date: $Date: 2007/11/23 12:40:00 $
 *
 */

package nl.leidenuniv.dspace.rdf;

import java.sql.SQLException;

import org.apache.log4j.Logger;
import org.dspace.core.Context;
import org.dspace.core.LogManager;
import org.dspace.content.DCValue;
import org.dspace.content.Item;
import org.dspace.storage.rdbms.DatabaseManager;
import org.dspace.storage.rdbms.TableRow;
import org.dspace.storage.rdbms.TableRowIterator;
import org.dspace.handle.HandleManager;

import org.dspace.core.Utils;

import java.io.IOException;

import java.util.ArrayList;
import java.util.List;

/**
 * Class representing a Resource Description Framework resource
 *
 * @author Lucas van Schaik
 * @version $Revision: 0.1 $
 */
public class RDFresource
{
  /** log4j logger */
  private static Logger log = Logger.getLogger(RDFresource.class);

  /** Our context */
  private Context myContext;

  /** The row in the table representing this eperson */
  private TableRow myRow;

  RDFresource(Context context, TableRow row) {
    myContext = context;
    myRow = row;

    myContext.cache(this, this.getID());
  }

  RDFresource(Context context, String uri) throws SQLException {
    myContext = context;
    myRow = DatabaseManager.create(context, "RDFresource"); 

    this.setURI(uri);
 
    context.cache(this, getID());
    this.update();
  }

  RDFresource(Context context, Object resource) throws IOException, SQLException {
    String uri = RDFresource.getURIforObject(context,resource);
    myContext = context;
    myRow = DatabaseManager.create(context, "RDFresource"); 

    this.setURI(uri);
 
    context.cache(this, getID());
    this.update();
  }

  public static RDFresource create(Context context, Object resource) throws IOException, SQLException {
    RDFresource result = RDFresource.find(context, resource);

    if (result == null) {
      result = new RDFresource(context, resource);
    }

    return result;
  }

  public int getID()
  {
    return myRow.getIntColumn("rdf_resource_id");
  }

  public String getURI() {
    return myRow.getStringColumn("URI");
  }

  public void setURI(String aString) {

    myRow.setColumn("URI", aString);    
  } 

  public Object getResource() {
    // dit moet anders... URI 'uitpakken' en herleiden naar object
    Object result = null;
    try {
      result = RDFresource.find(myContext,getURI());
    }
    catch (SQLException e) {
      // do nothing
    }
    return result;
  }

  public static RDFresource find(Context context, int id) throws SQLException
  {
    RDFresource fromCache = (RDFresource) context.fromCache(RDFresource.class, id);

    if (fromCache != null) {
      return fromCache;
    }

    TableRow row = DatabaseManager.find(context, "RDFresource", id);

    if (row == null) {
      if (log.isDebugEnabled()) {
        log.debug(LogManager.getHeader(context, "find_RDFresource", "not_found,rdf_resource_id=" + id));
      }
      return null;
    }
    else {
      if (log.isDebugEnabled()) {
        log.debug(LogManager.getHeader(context, "find_RDFresource", "rdf_resource_id=" + id));
      }
      return new RDFresource(context,row);
    }
  }

  public static RDFresource find(Context context, Object anObject) throws IOException, SQLException
  {
    String uri = RDFresource.getURIforObject(context,anObject);
    return find(context,uri);
  }

  public static RDFresource find(Context context, String anURI) throws SQLException
  {
    String query = "SELECT * from RDFresource where URI like '"+anURI+"'";
    TableRow row = DatabaseManager.querySingle(context, "RDFresource", query);

    if (row == null) {
      return null;
    }
    else {
      // First check the cache
      RDFresource fromCache = (RDFresource) context.fromCache(RDFresource.class, row.getIntColumn("rdf_resource_id"));

      if (fromCache != null) {
        return fromCache;
      }
      else {
        return new RDFresource(context, row);
      }
    }
  }

  public static RDFresource[] findAll(Context context, String partOfURI)
                             throws SQLException {
    String query = "SELECT * from  RDFresource";
   
    if (partOfURI != null && partOfURI.length() > 0) {
      query += " WHERE URI like '%"+partOfURI+"%'";
    }

    TableRowIterator tri = DatabaseManager.query(context,"RDFresource",query);
    List resource = new ArrayList();
    while (tri.hasNext()) {
      TableRow r = (TableRow) tri.next();
      RDFresource fromCache = (RDFresource) context.fromCache(
                    RDFresource.class, r.getIntColumn("rdf_resource_id"));
      if (fromCache != null) {
        resource.add(fromCache);
      }
      else {
        resource.add(new RDFresource(context, r));
      }
    }
    tri.close();
    return (RDFresource[])resource.toArray(new RDFresource[resource.size()]);
  }

  public static RDFresource[] findAll(Context context) throws SQLException {
    return findAll(context, null);
  }

  public void update() throws SQLException {
    // FIXME: Check authorisation
    DatabaseManager.update(myContext, myRow);
  }

  public void delete() throws SQLException {
    // FIXME: Check authorisation
    // Remove from cache
    myContext.removeCached(this, getID());

    // Remove ourself
    DatabaseManager.delete(myContext, myRow);

    log.info(LogManager.getHeader(myContext, "delete_rdf_resource", "rdf_resource_id=" + getID()));
  }


  private static String getURIforObject(Context c, Object anObject) 
        throws SQLException, IOException {
    String result = null;

    // only do dcvalue for now
    if (anObject instanceof DCValue) {
      DCValue dcv = (DCValue)anObject;
      Item item = dcv.item;
      String dcq = "dc." + dcv.element;
      if (dcv.qualifier != null) {
        dcq += "." + dcv.qualifier;
      }
      String handle = null;
      if ((item == null) || (handle = HandleManager.findHandle(c, item)) == null) {
        throw new IOException("Cannot make URI for DCValue '"+dcv.value+"' ("+dcv.element+(dcv.qualifier==null?"":"."+dcv.qualifier)+") if item does not have handle");
      }
      result = "hdl:"+handle+"#"+dcq+":"+Utils.getMD5(dcv.value+dcv.language);
    }

    return result;
  }
}