/************************************************************************
 *         Copyright (C) 2004 The University of Sheffield               *
 *       Developed by Mark Greenwood <m.greenwood@dcs.shef.ac.uk>       *
 *                                                                      *
 * This program is free software; you can redistribute it and/or modify *
 * it under the terms of the GNU Lesser General Public License as       *
 * published by the Free Software Foundation; either version 2.1 of the *
 * License, or (at your option) any later version.                      *
 *                                                                      *
 * 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.                         *
 *                                                                      *
 * You should have received a copy of the GNU Lesser General Public     *
 * License along with this program; if not, write to the Free Software  *
 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.            *
 ************************************************************************/

package mark.chunking;

import java.io.*;
import java.net.*;
import java.util.*;
import java.text.NumberFormat;

import gate.*;
import gate.creole.*;
import gate.util.GateRuntimeException;

public class GATEWrapper extends AbstractLanguageAnalyser implements ProcessingResource, Serializable
{
	private Chunker c = null;
	private Map chunkTags = null;

	private URL posTagURL;
	public void setPosTagURL(URL posTagURL) { this.posTagURL = posTagURL; }
	public URL getPosTagURL() { return posTagURL; }

	private URL rulesURL;
	public void setRulesURL(URL rulesURL) { this.rulesURL = rulesURL; }
	public URL getRulesURL() { return rulesURL; }

	private String posFeature;
	public void setPosFeature(String posFeature) { this.posFeature = posFeature; }
	public String getPosFeature() { return posFeature; }

	private String unknownTag;
	public void setUnknownTag(String unknownTag) { this.unknownTag = unknownTag; }
	public String getUnknownTag() { return unknownTag; }

	private String inputASName;
	public void setInputASName(String inputASName) { this.inputASName = inputASName; }
	public String getInputASName() { return inputASName; }

	private String outputASName;
	public void setOutputASName(String outputASName) { this.outputASName = outputASName; }
	public String getOutputASName() { return outputASName; }

	private String annotationName;
	public void setAnnotationName(String annotationName) { this.annotationName = annotationName; }
	public String getAnnotationName() { return annotationName; }

	public Resource init() throws ResourceInstantiationException
	{
		if (rulesURL == null) {
      throw new ResourceInstantiationException(
          "Rules URL must be specified");
    }

		if (posTagURL == null) {
      throw new ResourceInstantiationException(
          "POS tag dictionary URL must be specified");
    }

		try
		{
			//lets create a new Chunker using the URL provided (which we know
			//is not null as we already checked it).
			c = new Chunker(rulesURL);

			//Open a reader over the pos_tag_dict file so we can load
			//the database
			BufferedReader in = new BufferedReader(new InputStreamReader(posTagURL.openStream()));

			//read in the first line of the file
			String line = in.readLine();

			//create a new empty map to hold the pos and chunk tags
			chunkTags = new HashMap();

			while (line != null)
			{
				//while there is still data in the file...

				//split the current line into two parts
				String[] tags = line.split(" ");

				//put the data in the map, POS tags as key
				//chunk tag as value
				chunkTags.put(tags[0],tags[1]);

				//get the next line from the data file
				line = in.readLine();
			}

			//close the data file now we have finished with it
			in.close();
		}
		catch (Exception e)
		{
			//if an error occurred then throw an exception so that the user knows
			throw new ResourceInstantiationException("Unable to correctly init the chunker: " + e.getMessage());
		}

		//if we get to here then everything has initialised correctly
		//so return this instance
		return this;
	}

	public void execute() throws ExecutionException
	{
		//lets get the AnnotationSet we are using as input. Get either the
		//set the user has asked for or if they haven't specified use the default set
		if(inputASName != null && inputASName.equals("")) inputASName = null;
		AnnotationSet inputAS = (inputASName == null) ? document.getAnnotations() : document.getAnnotations(inputASName);

		//lets get the AnnotationSet we are using as output. Get either the
		//set the user has asked for or if they haven't specified use the default set
		if(outputASName != null && outputASName.equals("")) outputASName = null;
		AnnotationSet outputAS = (outputASName == null) ? document.getAnnotations() : document.getAnnotations(outputASName);

		//Get the set of sentences contained within the current document
		AnnotationSet sentences = inputAS.get(SENTENCE_ANNOTATION_TYPE);

		if (sentences != null && sentences.size() > 0)
		{
			//assuming there are sentences...

			//get the current time to use as part of the progress feedback
			long startTime = System.currentTimeMillis();

			//tell the user we are just starting to chunk the document
			fireStatusChanged("Chunking " + document.getName());
        	fireProgressChanged(0);

			//we are just starting so we haven't processed a document yet
			//so remember this ready for the progress feedback
			int i = 0;

        	//Loop through all the sentences
        	Iterator sit = sentences.iterator();
        	while(sit.hasNext())
        	{
				//get the current sentence to process
				Annotation sentence = (Annotation)sit.next();

				//Get a sorted list of the tokens within the current sentence
				List tokens = new ArrayList();
				tokens.addAll(inputAS.get(TOKEN_ANNOTATION_TYPE,sentence.getStartNode().getOffset(), sentence.getEndNode().getOffset()));
				Collections.sort(tokens);

				//Create three empty lists to hold the words, pos and chunk
				//tags of the tokens in the current sentence
				List wl = new ArrayList();
				List tl = new ArrayList();
				List pl = new ArrayList();

				//Loop through all the tokens in the current sentence
				Iterator tit = tokens.iterator();
				while(tit.hasNext())
				{
					//get the current token to process
					Annotation token = (Annotation)tit.next();

					//add the string spanned by the current token to the list of words
					wl.add(token.getFeatures().get("string"));

					//get the POS tag for the current token
					String pos = (String)token.getFeatures().get(posFeature);

					//add the POS tag to the list of POS tags
					pl.add(pos);

					//get the initial chunk tag for this POS tag
					String chunkTag = (String)chunkTags.get(pos);

					//if the chunk tag is null then use the unknown chunk tag
					if (chunkTag == null) chunkTag = unknownTag;

					//now add the chunk tag to the list of chunk tags
					tl.add(chunkTag);
				}

				//run the chunker over the current sentence and get back
				//an updated list of chunk tags
				tl = c.chunkSentence(wl,tl,pl);

				//a variable to hold the index of the token which
				//starts the current noun chunk
				int start = 0;

				//a flag so we know if we are in an NP or not
				boolean inBaseNP = false;

				//Loop through all the chunk tags in the current sentence
				//so we can find the noun chunks
				for (int tIndex = 0 ; tIndex < tl.size() ; ++tIndex)
				{
					//get the current chunk tag
					String ct = (String)tl.get(tIndex);

					if (inBaseNP)
					{
						//if we are currently inside a noun chunk then...

						if (ct.equals("B"))
						{
							//if the chunk tag is "B" then we are about to start a
							//new chunk so record the one that has just finished
							addAnnotation(outputAS, tokens, start, tIndex-1);

							//now reset the beginning of the chunk to the current token
							start = tIndex;
						}
						else if (ct.equals("O"))
						{
							//if the chunk tag is "O" then we have dropped out
							//the end of a chunk so add the chunk we just finished
							addAnnotation(outputAS, tokens, start, tIndex-1);

							//now flag that we are outside of any chunk
							inBaseNP = false;
						}
					}
					else
					{
						//we aren't currently in a noun chunk so...

						if (ct.equals("B") || ct.equals("I"))
						{
							//if the chunk tag is "B" or "I" then we have found
							//the beginning of a chunk, so....

							//record the start index
							start = tIndex;

							//and flag that we are now inside a chunk
							inBaseNP = true;
						}
					}
				}

				if (inBaseNP)
				{
					//if we got to the end of a sentence and we are still in a
					//noun chunk then we need to close the end and add the annotation
					addAnnotation(outputAS, tokens, start, tl.size()-1);
				}

				//update the progress stuff to show the precentage of sentences
				//we have processed so far
				fireProgressChanged(i++ * 100 / sentences.size());
			}

			//we have finished! so update the progress and tell
			//the user how long it took to chunk the document
			fireProcessFinished();
			fireStatusChanged(document.getName() + " chunked in " + NumberFormat.getInstance().format((double)(System.currentTimeMillis() - startTime) / 1000) + " seconds!");
		}
		else
		{
			//if there are no sentence annotations then throw an exception as theres
			//not much we can do
			throw new GateRuntimeException("No sentences to process! Please run a sentence splitter first!");
		}
	}

	private void addAnnotation(AnnotationSet outputAS, List tokens, int start, int end)
	{
		//Create a new FeatureMap to act as the features for the new annotation
		//but we will leave it blank for now as we don't have anything to add
		FeatureMap params = Factory.newFeatureMap();

		//Get the token annotation from the beginning of the chunk
		Annotation aStart = (Annotation)tokens.get(start);

		//Get the token annotation from the end of the chunk
		Annotation aEnd = (Annotation)tokens.get(end);

		//This spots errors where the start is after the end. What
		//we should do is figure out why this occurs in the first place
		if (aStart.getStartNode().getOffset().longValue() >= aEnd.getEndNode().getOffset().longValue()) return;

		//add a new annotation to mark the noun chunk
		outputAS.add(aStart.getStartNode(), aEnd.getEndNode(), annotationName, params);
	}
}