// Copyright 2001 freehep
package org.freehep.graphicsio.pdf;

import java.io.IOException;
import java.util.Collection;
import java.util.Hashtable;
import java.util.Iterator;
import java.util.LinkedList;
import java.util.Map;
import java.util.Vector;

/**
 * This class keeps track of all kinds of objects written to a pdf file and
 * avoids to write them several times instead of referencing the same object
 * several times. Right now only encoding tables are supported.
 * 
 * An implementation for images and paint would be possible.
 * 
 * @author Simon Fischer
 * @version $Id: PDFRedundanceTracker.java,v 1.5 2009-08-17 21:44:44 murkle Exp
 *          $
 */
public class PDFRedundanceTracker {

	/**
	 * To be implemented by Writers which write objects that may already have
	 * been written.
	 */
	public interface Writer {
		public void writeObject(Object o, PDFRef reference, PDFWriter pdf)
				throws IOException;
	}

	private class Entry {
		private static final String REF_PREFIX = "PDF_RTObj";

		private Object object;

		private Writer writer;

		private boolean written;

		private PDFRef reference;

		private Object groupID;

		private Entry(Object o, Object groupID, Writer w) {
			this.object = o;
			this.groupID = groupID;
			this.writer = w;
			this.written = false;
			this.reference = pdf.ref(REF_PREFIX + (refCount++));
		}
	}

	private static int refCount = 1;

	private PDFWriter pdf;

	private Map objects;

	private Vector orderedObjects; // to keep order

	public PDFRedundanceTracker(PDFWriter pdf) {
		this.pdf = pdf;
		objects = new Hashtable();
		orderedObjects = new Vector();
	}

	/**
	 * Returns a reference that points to <tt>object</tt>. When this method is
	 * called several times for the same object (according to its hash code) the
	 * same reference is returned. When <tt>writeAll()</tt> is called the
	 * writer's <tt>writeObject()</tt> method will be called once with
	 * <tt>object</tt> as argument.<br>
	 * The groupID is only used for <tt>getGroup()</tt>
	 */
	public PDFRef getReference(Object object, Object groupID, Writer writer) {
		Object o = objects.get(object);
		if (o != null) {
			return ((Entry) o).reference;
		}
		Entry entry = new Entry(object, groupID, writer);
		objects.put(object, entry);
		orderedObjects.add(entry);
		return entry.reference;
	}

	public PDFRef getReference(Object object, Writer writer) {
		return getReference(object, null, writer);
	}

	/**
	 * Writes all objects that are not yet written. If the method is called
	 * several times then each times only the new objects are written.
	 */
	public void writeAll() {
		Iterator i = orderedObjects.iterator();
		while (i.hasNext()) {
			Entry entry = (Entry) i.next();
			if (!entry.written) {
				try {
					// System.out.println("PDFRT: Writing: " + entry.object);
					entry.writer.writeObject(entry.object, entry.reference,
							pdf);
					entry.written = true;
				} catch (IOException e) {
					e.printStackTrace();
				}
			}
		}
	}

	/** Returns all objects belonging to a particular group. */
	public Collection getGroup(Object groupID) {
		Collection result = new LinkedList();
		Iterator i = orderedObjects.iterator();
		while (i.hasNext()) {
			Entry entry = (Entry) i.next();
			if (groupID.equals(entry.groupID)) {
				result.add(entry.object);
			}
		}
		return result;
	}
}