/**
 * 
 */
package org.vamsas.client;

import java.lang.reflect.Field;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.util.Iterator;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.exolab.castor.mapping.FieldDescriptor;
import org.exolab.castor.mapping.FieldHandler;
import org.exolab.castor.xml.util.XMLClassDescriptorImpl;
import org.vamsas.test.simpleclient.VamsasArchive;

/**
 * Base class for all Vamsas objects extracted from an IClientDocument. An
 * Vobject maybe registered or unregistered.
 * 
 * @author jimp
 * 
 */
public abstract class Vobject {
  static Log log = LogFactory.getLog(Vobject.class);
  
  /**
   * true if Vobject was stored in a vamsas Document or has been retrieved from it
   */
  protected boolean __stored_in_document = false;
  /**
   * memory of the last doHash() value computed for the Vobject 
   * @see doHash()
   */
  protected long __last_hash = 0; 
  /**
   * set by testInstanceForIdField() if Vobject should have a VorbaId
   */
  protected boolean registerable = false; 


  /**
   * unique id for all vamsas objects allows unambiguous referencing to any
   * Vobject in the vamsas document
   */
  protected VorbaId vorbaId = null;

  /**
   * the source of unique VorbaIds.
   */
  protected IVorbaIdFactory __vorba = null;

  /**
   * 
   */
  protected Vobject() {
    super();
    testInstanceForIdField();
  }

  /**
   * set the isRegisterable flag based on the presence of a 'private String _id' field in
   * the reflected class instance.
   */
  private void testInstanceForIdField() {
    // look for the id field (should be an NCName string)
    // TODO: decide if 'id' is an appropriate reserved attribute name for the VorbaId
    try {
      java.lang.reflect.Field fd = this.getClass().getDeclaredField("_id");
      if (String.class.isAssignableFrom(fd.getType())) {
        this.setRegisterable(true);
      }
    } catch (SecurityException e) {
      e.printStackTrace();
    } catch (NoSuchFieldException e) {
      this.setRegisterable(false);
    }
  }

  /**
   * update the Vobject instance's _id field, based on the contents of the
   * VorbaId. Only call this if you mean to do it!
   */
  protected void setInstanceIdField() {
    if (registerable) {
      if (__vorba != null)
        try {
          Method fd = this.getClass().getMethod("setId", new Class[] { String.class });
          fd.invoke((Object) this, new Object[] {new String(this.getVorbaId().id)});
          log.debug(this.getClass().getName()+" called setInstanceIdField!");
        } catch (InvocationTargetException e) { 
          log.error("SourceGeneration of "
              + this.getClass().toString()
              + "\n has resulted in an inaccessible 'setId' method!\nCannot set ID from the vorbaId Vobject.", e);
        }
        catch (IllegalAccessException e) {
          log.error("SourceGeneration of "
                  + this.getClass().toString()
                  + "\n has resulted in an inaccessible 'setId' method!\nCannot set ID from the vorbaId Vobject.", e);
        } catch (SecurityException e) {
          log.error("Security access violation for "+this.getClass().toString(),e);
        } catch (NoSuchMethodException e) {
          log.warn(this.getClass().toString()+" was erroneously marked as a Vorba Vobject class (Implementation error?)");
          this.setRegisterable(false);
        }
    } else {
      System.err.println("Client error. Trying to setInstanceIdField on a "
          + this.getClass().toString() + " (which cannot be given a vorbaId)");
    }
  }

  /**
   * calculate a hash for the Vobject with all housekeeping fields at standard
   * values. (isRegisterable is an immutable attribute property)
   * TODO: decide if __stored_in_document should be included in the hash or not.
   * @return true if new hash different to last hash
   */
  synchronized protected boolean doHash() {
    long __old_hash = __last_hash;
    __last_hash = 0;
    VorbaId thisid = vorbaId;
    IVorbaIdFactory factory = __vorba;
    boolean stored = __stored_in_document;
    vorbaId = null;
    __vorba = null;
    __last_hash = this.hashCode();
    vorbaId = thisid;
    __vorba = factory;
    __stored_in_document = stored;
    return (__old_hash==0) || (__old_hash == __last_hash);
  }

  /**
   * TODO: combine two versions of the same collection Vobject to resolve
   * asynchronous updates to the same vamsas Vobject Merges two vamsas objects,
   * one of which is a later version of the earlier (ie they have the same
   * vorbaId but one is a later version recently read from the vamsasDocument
   * collection.
   * 
   * @return
   */
  protected boolean merge(Vobject laterCopy) {
    log.warn(this.getClass().getName()+".merge() not implemented.");
    return true;
  }

  /**
   * 
   * @return true if Vobject is registered
   */
  public boolean isRegistered() {
    return (registerable) ? (vorbaId != null) : false;
  }

  /**
   * Method to get fixed reference for the Vobject in the vamsas document.
   * 
   * @returns null if Vobject is neither registered or not associated with a
   *          properly instantiated VorbaIdFactory.
   */
  public VorbaId getVorbaId() {
    if (registerable && vorbaId == null) {
      // Try to use the associated factory.
      if (__vorba != null)
        if ((vorbaId = __vorba.makeVorbaId(this)) == null)
          return null; // Factory not valid.
        else {
          this.setInstanceIdField();
          return vorbaId;
        }
    }
    return vorbaId;
  }

  /**
   * used by the IClient implementation to generate unique Id based on client
   * applications current namespace.
   */
  protected void setVorbaId(VorbaId newid) {
    vorbaId = newid;
  }

  /**
   * @return true if Vobject is present in Vamsas Document.
   */
  public boolean is__stored_in_document() {
    return __stored_in_document;
  }

  /**
   * for use by Vorba agent to reflect state of vamsas Vobject to client
   * application.
   * Setting stored_in_document on a registerable Vobject without a 
   * vorbaId will mean is will *never* get a vorbaId and 
   * horrible things will happen.
   * @param __stored_in_document true if Vobject has been marshalled into current document.
   */
  protected void set__stored_in_document(boolean __stored_in_document) {
    this.__stored_in_document = __stored_in_document;
  }

  /**
   * __last_hash is the hash value computed when the Vobject was last checked
   * against a IClientDocument generated by the Vobject's parent IClient
   * instance.
   * 
   * @return Returns the __last_hash.
   */
  public long get__last_hash() {
    return __last_hash;
  }

  /**
   * @return true if Vobject can have a vorbaId
   */
  public boolean isRegisterable() {
    return registerable;
  }

  /**
   * Called by __testInstanceForidField and the post-unmarshalling handler
   * to indicate if Vobject will have a vorbaId.
   * @param registerable 
   */
  protected void setRegisterable(boolean registerable) {
    this.registerable = registerable;
  }
  /**
   * ensure's internal id field corresponds to vorbaId and
   * cascade through all fields referring to an instance of Vobject
   * calling the same method on them.
   * TODO: LATER: properly apply castors own field mechanisms to get at accessors
   * TODO: FIX CYCLIC __ensure+instance_ids
   * Implementation note for the todo:
   * this works like a depth-first search over all vamsas objects in an vamsasDocument. 
   * The doHash() function is used as the 'visited' flag - 
   * this *is not* a valid heuristic, although it will work "most of the time".
   * TODO: LATER? Add another method for setDefaultProvenanceField (in the spirit of setInstanceIdField) using the info from the __vorba.getClient/User/Session methods 
   */
  protected void __ensure_instance_ids() {
    if (__vorba==null)
      throw new Error("Improperly intialised org.vamsas.client.Vobject - no VorbaFactory given.");
    log.debug("doing "+this.getClass()+".__ensure_instance_ids()");
    if (!__stored_in_document && registerable)
      setInstanceIdField();
    if (!doHash())
      return; // nothing has changed in this Vobject - probably visited it before.
    Class descriptor = null;
    XMLClassDescriptorImpl descimpl = null;
    try {
      // castor descriptor resolver magic
      descriptor = this.getClass().getClassLoader().loadClass(this.getClass().getName()+"Descriptor");
      descimpl = (XMLClassDescriptorImpl) descriptor.getConstructor(null).newInstance(null);
    } catch (Exception e) {
      log.fatal("Source Generation Error!: Couldn't resolve descriptor for "
          +this.getClass().getName()
          +" was 'generate descriptors' set for castorbuilder.properties?");
      return;
    }
    FieldDescriptor fields[] = descimpl.getFields();
    for (int i=0,j=fields.length; i<j; i++) {
      Class type= fields[i].getFieldType();
      if (type.isArray()) {
        if (Vobject[].class.isAssignableFrom(type)) {
          try {
            Object val = fields[i].getHandler().getValue(this);
            if (val!=null) {
              Vobject vals[] = (Vobject[]) val; 
              for (int k=0, l=vals.length; k<l; k++) {
                if (vals[k].__vorba==null)
                  vals[k].__vorba = __vorba; // propagate IVorbaIdFactory
                vals[k].__ensure_instance_ids();
              }
            }
          }
          catch (Exception e) {
            log.error("Client error - could not access array "+type.getName()+" in "+this.getClass().getName(), e);
          }
        }
      } else
        if (Vobject.class.isAssignableFrom(type)) {
          try {
            FieldHandler fh = fields[i].getHandler();
            Vobject rf = null;
            if (fh != null) {
              Object fval = fh.getValue(this);
              if (fval!=null) {
                if (fval.getClass().isArray()) {
                  //if (Vobject[].class.isAssignableFrom(type)) {
                    try {
                      Vobject vals[] = (Vobject[]) fval; 
                      for (int k=0, l=vals.length; k<l; k++) {
                        if (vals[k].__vorba==null)
                          vals[k].__vorba = __vorba; // propagate IVorbaIdFactory
                        vals[k].__ensure_instance_ids();
                      }
                    }
                    catch (Exception e) {
                      log.error("Client error - could not access (fhval)array "+type.getName()+" in "+this.getClass().getName(), e);
                    }
                  //}
                } else {
                  rf = (Vobject) fval;
                  log.debug("Got value for "+fields[i].getFieldName());
                }
              }
            } else {
              // fuck around, fuck around, jump up jump up and get down! */
              Object o = fields[i].getClassDescriptor();
              if (o!=null) {
                // XMLClassDescriptorImpl fclasdes = (XMLClassDescriptorImpl) o;
                String methname = "get"+fields[i].getFieldName();
                Method fgetmeth = this.getClass().getMethod(methname,null);
                if (fgetmeth!=null) {
                  Object fval = fgetmeth.invoke(this,null);
                  if (fval!=null)
                    rf = (Vobject) fval;
                } else {
                  log.warn("Couldn't find "+this.getClass().getName()+"."+methname);
                }
              }
            }
            if (rf!=null) {
              if (rf.__vorba==null)
                rf.__vorba = __vorba; // propagate IVorbaIdFactory
              rf.__ensure_instance_ids();
            }
          }
          catch (Exception e) {
            log.error("Client error - could not access "+type.getName()+" in "+this.getClass().getName(), e);
          }
        }
    }
    
  }
}