package org.greenstone.gatherer.msm;
/**
 *#########################################################################
 *
 * A component of the Gatherer application, part of the Greenstone digital
 * library suite from the New Zealand Digital Library Project at the
 * University of Waikato, New Zealand.
 *
 * <BR><BR>
 *
 * Author: John Thompson, Greenstone Digital Library, University of Waikato
 *
 * <BR><BR>
 *
 * Copyright (C) 1999 New Zealand Digital Library Project
 *
 * <BR><BR>
 *
 * 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.
 *
 * <BR><BR>
 *
 * 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.
 *
 * <BR><BR>
 *
 * 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.
 *########################################################################
 */
import java.io.*;
import org.greenstone.gatherer.Gatherer;
import org.greenstone.gatherer.collection.Collection;
import org.greenstone.gatherer.collection.CollectionManager;
import org.greenstone.gatherer.msm.ElementWrapper;
import org.greenstone.gatherer.msm.MetadataSetManager;
import org.greenstone.gatherer.valuetree.GValueModel;
import org.greenstone.gatherer.valuetree.GValueNode;
import org.w3c.dom.Element;
/** Stores a mapping between a particular metadata element, and a certain value node. 
 * @author John Thompson, Greenstone Digital Library, University of Waikato
 * @version 2.3
 */
public class Metadata 
    implements Comparable {
    /** Is this an accumulating piece of metadata? */
    transient private boolean accumulate = false;
    /** Indicates what level of metadata this is, relative to the file it was retrieved for. */
    transient private boolean file_level = true;
    /** The file for which this metadata was retrieved. This allows us to determine the source of folder level metadata. */
    transient private File file;
    /** The value node this metadata maps to. */
    private GValueNode value = null;
    /** Used to count the number of references to this piece of metadata within the metadata table. */
    private int count = 1;
    /** The metadata element this metadata maps to. */
    private ElementWrapper element = null;
    /** Constructs a new Metadata object with no current value.
     * @param element The <strong>ElementWrapper</strong> associated with this metadata.
	  */
    public Metadata(ElementWrapper element) {
	super();
	this.element = element;
	this.value = null;
    }
    /** Default constructor simply creates a new Metadata object based on the given parameters.
	  * @param element The <strong>ElementWrapper</strong> associated with this metadata. 
	  * @param value The assigned value for the given element, as a <strong>GValueNode</strong>.
	  */
    public Metadata(ElementWrapper element, GValueNode value) {
	super();
	this.element = element;
	this.value = value;
    }
    /** Constructs a new Metadata object, given the value. The metadata element is extracted from the value tree information.
	  * @param value The assigned value for the given element, as a <strong>GValueNode</strong>.
	  * @see org.greenstone.gatherer.Gatherer
	  * @see org.greenstone.gatherer.collection.CollectionManager
	  * @see org.greenstone.gatherer.msm.MetadataSetManager
	  */
    public Metadata(GValueNode value) {
	super();
	this.element = Gatherer.c_man.getCollection().msm.getElement(value.getMetadataElementName());
	this.value = value;
    }
    /** Determine if this metadata overwrites or accumulates. */
    public boolean accumulates() {
	return accumulate;
    }
    /** Compares two Metadata objects for ordering purposes.
	  * @param object The other metadata as an <strong>Object</strong>.
	  * @return An <i>int</i> value as specified in java.lang.String#compareTo
	  * @see java.lang.String#compareTo
	  */
    public int compareTo(Object object) {
	return toString().compareTo(object.toString());
    }
    /** Decrease the reference count by 1. */
    public void dec() {
	count--;
    }
    /** Tests to metadata objects for equality.
	  * @param object The other metadata as an <strong>Object</strong>.
	  * @return <i>true</i> if the metadata are equal, <i>false</i> otherwise.
	  */
    public boolean equals(Object object) {
	if(compareTo(object) == 0) {
	    return true;
	}
	return false;
    }
    /** Determine the absolute path value of this metadata, taking into account whether this value is hierarchical. */
    public String getAbsoluteValue() {
	String abs_value = getValue();
	// What actually gets written as the value depends on whether this is a hierarchy based element.
	GValueModel model = Gatherer.c_man.getCollection().msm.getValueTree(element);
	if(model != null && model.isHierarchy()) {
	    if(value != null) {
		GValueNode node = (GValueNode)value.getParent();
		while(node != null) {
		    GValueNode next = (GValueNode)node.getParent();
		    if(next != null) {
			abs_value = node.toString() + "\\" + abs_value;
		    }
		    node = next;
		}
	    }
	    abs_value = model.getHIndex(abs_value);
	}
	// Return the result
	return abs_value;
    }
    /** Retrieve the reference count.
	  * @return The count as an <i>int</i>.
	  */
    public int getCount() {
	return count;
    }
    /** Retrieve the element associated with this metadata.
	  * @return An <strong>ElementWrapper</strong>.
	  */
    public ElementWrapper getElement() {
	return element;
    }

    /** Retrieve the source file if any. */
    public File getFile() {
	return file;
    }

    /** Get the textual value of this metadata.
	  * @return A <strong>String</strong> representing the value of this Metadata. Note that if the value node is null, then the String returned is "".
	  */
    public String getValue() {
	String result = "";
	if(value != null) {
	    result = value.toString();
	}
	return result;
    }
    /** Retrieve the value node associated with this metadata.
	  * @return A <strong>GValueNode</strong>.
	  */
    public GValueNode getValueNode() {
	return value;
    }
    /** Increase the reference count by 1. */
    public void inc() {
	count++;
    }
	 
    /** Determine if this metadata is file level or folder level. */
    public boolean isFileLevel() {
	return file_level;
    }

    /** Inform this metadata whether it will accumulate with any other metadata of the same type. */
    public void setAccumulate(boolean accumulate) {
	this.accumulate = accumulate;
    }
    /** Sets the reference count. 
	  * @param value The new value of count as an <i>int</i>.
	  */
    public void setCount(int value) {
	count = value;
    }
    /** Set the level of this metadata (whether it is associated with this file explicitly or found in some folder above this file). */
    public void setFileLevel(boolean file_level) {
	this.file_level = file_level;
    }

    /** Set the current source file for this metadata to the given collection. This value should not be counted are remaining valid at any time other than immediately after a getMetadata call as it is relative the the file that metadata call was for. */
    public void setFile(File file) {
	this.file = file;
    }

    /** Translates this object into a string representation.
	  * @return A <strong>String</strong>.
	  */
    public String toString() {
	return element.toString() + "=" + getValue();
    }
    /** Retrieve the value node associated with a certain value string. */
    static final public GValueNode getDefaultValueNode(ElementWrapper element, String value) {
	// Retrieve the GValueNode
	GValueModel model = Gatherer.c_man.getCollection().msm.getValueTree(element);
	GValueNode value_node;
	if(model != null) {
	    value_node = model.getValue(value);
	}
	else {
	    value_node = new GValueNode(element.getName(), value);
	}
	model = null;
	return value_node;
    }
}