/**
 * 
 */
package uk.ac.vamsas.client;

import java.io.IOException;
import java.io.PrintWriter;
import java.io.Reader;
import java.io.Writer;
import java.lang.reflect.Field;
import java.util.Hashtable;
import java.util.Iterator;
import java.util.Vector;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.exolab.castor.mapping.FieldHandler;
import org.exolab.castor.mapping.GeneralizedFieldHandler;
import org.exolab.castor.mapping.ValidityException;
import org.exolab.castor.xml.IDResolver;
import org.exolab.castor.xml.MarshalException;
import org.exolab.castor.xml.MarshalListener;
import org.exolab.castor.xml.Marshaller;
import org.exolab.castor.xml.UnmarshalListener;
import org.exolab.castor.xml.Unmarshaller;
import org.exolab.castor.xml.ValidationException;

import uk.ac.vamsas.objects.core.VamsasDocument;
/**
 * Implements the Vamsas Vobject ID machinery for translating 
 * between non-volatile XML IDs and Vobject references. Use the
 * marshalling and unmarshalling methods in this class in order
 * to add automatically computed values for required fields in objects,
 * so as to avoid validation exceptions when marshalling new objects
 * into the vamsas document.
 */
public class VorbaXmlBinder implements UnmarshalListener {
  private static Log log = LogFactory.getLog(VorbaXmlBinder.class);
  private final IVorbaIdFactory vorbafactory;

  private final Vector obj;
  private final Hashtable oldobjhashes;
  private final Hashtable objrefs;
  private final Vector updatedobjs; // not yet used elswhere ?
  public VorbaXmlBinder(IVorbaIdFactory vorbafactory2, Vector unrefedObj, Hashtable objrefs2, Hashtable oldobjhashes, Vector updatedObj) {
    this.vorbafactory = vorbafactory2;
    this.obj = unrefedObj;
    this.objrefs = objrefs2;
    this.oldobjhashes = oldobjhashes;
    this.updatedobjs = updatedObj;
  }

  /*
   * (non-Javadoc)
   * 
   * @see org.exolab.castor.xml.UnmarshalListener#attributesProcessed(java.lang.Object)
   */
  public void attributesProcessed(Object object) {

  }

  /*
   * (non-Javadoc)
   * 
   * @see org.exolab.castor.xml.UnmarshalListener#fieldAdded(java.lang.String,
   *      java.lang.Object, java.lang.Object)
   */
  public void fieldAdded(String fieldName, Object parent, Object child) {
    if (parent instanceof Vobject && child instanceof Vobject) {
      if (((Vobject) child).V_parent==null) {
        // System.err.println("Setting parent of "+fieldName);
        ((Vobject) child).setV_parent((Vobject) parent);
      }
    }
  }

  /*
   * (non-Javadoc)
   * 
   * @see org.exolab.castor.xml.UnmarshalListener#initialized(java.lang.Object)
   */
  public void initialized(Object object) {
    if (object instanceof Vobject) {
      Vobject nobj = (Vobject) object;
    }
  }

  /*
   * Check if the object has an 'id' field - if it does, copy the value into
   * the VorbaId field of Vobject, and add the Vobject to the VorbaId hash.
   * 
   * @see org.exolab.castor.xml.UnmarshalListener#unmarshalled(java.lang.Object)
   */
  public void unmarshalled(Object newobj) {
    if (newobj instanceof Vobject) {
      Vobject nobj = (Vobject) newobj;
      nobj.set__stored_in_document(true);
      try {
        if (nobj.isRegisterable() && nobj.___id_field!=null) {
          VorbaId nobj_id=null;
          // look for the id field (should be an NCName string)
          nobj.__vorba = vorbafactory;
          // use the Vobject accessor method to avoid unpleasant security exceptions.
          String idstring = nobj.__getInstanceIdField();
          if (idstring!=null) { 
            if (idstring.length() > 0) {
              nobj.setVorbaId(VorbaId.newId(idstring));
              nobj_id=nobj.getVorbaId();
              if (objrefs.containsKey(nobj_id) && !objrefs.get(nobj_id).equals(nobj)) {
                System.err.println("Serious problem : duplicate id '"+idstring+"' found! expect badness.");
                // TODO: HANDLE duplicate XML ids correctly
              }
              objrefs.put(nobj_id, nobj);
            } else {
              // add to list of objects without a valid vorbaId
              obj.add(nobj);
            }
          } else {
            // TODO: add to list of objects without a valid vorbaId
            obj.add(nobj);
          }
          nobj.doHash(); // updates detected by comparing with last hash when marshalling
          // check to see if new object was present in old object hash
          if (nobj_id!=null) {
            if (oldobjhashes.containsKey(nobj_id)) {
              Vobjhash oldhash = (Vobjhash) oldobjhashes.get(nobj_id);
              if (oldhash.isUpdated(nobj)) {
                // mark the object as updated in this document read.
                nobj.set__updated_since_last_read(true);
                updatedobjs.addElement(nobj);
              }
            } else {
              // object has no entry in the oldhashvalue list but
              // there is a valid vorbaId so
              nobj.set__added_since_last_read(true);
            }
            // and record the just-unmarshalled hash value
            oldobjhashes.put(nobj_id, new Vobjhash(nobj));
          } else {
            // for objects yet to get a valid vorba_id
            nobj.set__added_since_last_read(true);
          }
        }

      } catch (Exception e) {
        return;
      };

    }
  }

  /**
   * writes the VamsasDocument to the given stream.
   * TODO: ensure that (at least) default provenance entries are written for objects.
   * @param outstream
   * @param vorba valid VorbaIdFactory to construct any missing IDs 
   * @param doc
   * @throws IOException
   * @throws MarshalException
   * @throws ValidationException
   */
  public static void putVamsasDocument(PrintWriter outstream, VorbaIdFactory vorba, VamsasDocument doc)
  throws IOException, MarshalException, ValidationException {
    // Ensure references
    if (vorba==null)
      throw new Error("Null VorbaIdFactory Parameter");
    if (doc.__vorba==null)
      doc.__vorba = vorba;
    doc.__ensure_instance_ids(); // this may take a while. Do we allow for cyclic references ? 
    Marshaller mshl = new Marshaller(outstream);
    mshl.marshal(doc);

  }
  /**
   * creates new VorbaId references where necessary for newly unmarshalled objects
   * @param unrefed
   * @param objrefs
   * @return false if any new object references were made
   */
  private static boolean ensure_references(Vector unrefed, Hashtable objrefs) {
    boolean sync=true;
    if (unrefed.size()>0) {
      sync=false; // document is out of sync - ids have been created.
      java.util.Iterator newobj = unrefed.listIterator();
      while (newobj.hasNext()) {
        Vobject o = (Vobject) newobj.next();
        // forces registration and id field update.
        VorbaId id = o.getVorbaId();
        if (!objrefs.containsKey(id)) {
          objrefs.put(id, o);
        } else {
          if (!objrefs.get(id).equals(o))
            throw new Error("Serious! Duplicate reference made by vorbaIdFactory!");
        }
      }
    }
    return sync;
  }
  /**
   * Unmarshals a vamsasDocument Vobject from a stream, registers
   * unregistered objects, records existing VorbaIds, and completes 
   * the uk.ac.vamsas.client.Vobject housekeeping fields.
   * For a valid unmarshalling, the array of returned objects also includes
   * a <return>sync</return> parameter which is true if new VorbaIds
   * were created. If sync is false, then the caller should ensure that the
   * vamsasDocument is written back to disk to propagate the new VorbaIds.
   *  TODO: ensure that provenance is correct for newly registered objects
   * as getVamsasObjects but will detect updated objects based on differing hash values
   * obtained from the VorbaIdFactory's VorbaId, Vobject.get__last_Hash() pairs (if any) 
   * @param instream - the XML input stream 
   * @param factory - the SimpleClient's properly configured VorbaId factory to make new references.
   * @param root the root element's uk.ac.vamsas.objects.core Vobject.
   * @return null or {(Object) VamsasDocument Vobject, (Object) Hashtable of Vobject references, (Object) Boolean(sync), (Object) Vector of updated objects in document }
   */
  public static Object[] getVamsasObjects(Reader instream,
      VorbaIdFactory factory, Vobject root) {  
    Unmarshaller unmarshaller = new Unmarshaller(root);
    unmarshaller.setIDResolver(new IDResolver() {
      public Object resolve(String id) {
        // TODO: allow for external ID resolution
        VorbaXmlBinder.log.warn("Warning - id " + id
            + " is not found in the Vamsas XML! (TODO: Ignore if this is a forward reference!)");
        return null;
      }
    });
    final Hashtable objrefs = new Hashtable();
    if (factory.extanthashv==null)
      factory.extanthashv=new Hashtable();
    final Hashtable oobjhashes=factory.extanthashv;
    final VorbaIdFactory vorbafactory = factory;
    final Vector unrefedObj =  new Vector();
    final Vector updatedObj = new Vector();
    unmarshaller.setUnmarshalListener(new VorbaXmlBinder(vorbafactory, unrefedObj, objrefs, oobjhashes,updatedObj));
    // Call the unmarshaller.
    try {
      while (instream.ready()) {
        // TODO: mark objects in oobjhash prior to unmarshalling, to detect when objects have been lost through an update.
        //tohere
        Object obj = unmarshaller.unmarshal(instream);
        boolean sync=ensure_references(unrefedObj, objrefs);
        if (!(obj instanceof Vobject))
          return null;
        vorbafactory.setNewIdHash(objrefs); // update the Document IO Handler's set of vorbaId<>Object bindings.
        return new Object[] { obj, objrefs, new Boolean(sync),updatedObj};
      }
    } catch (MarshalException e) {
      // TODO Auto-generated catch block
      e.printStackTrace();
    } catch (ValidationException e) {
      // TODO Auto-generated catch block
      e.printStackTrace();
    } catch (IOException e) {
      // TODO Auto-generated catch block
      e.printStackTrace();
    }
    return null;
  }
}