/**
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.lucene.xmlparser.webdemo;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.util.Enumeration;
import java.util.Properties;
import java.util.StringTokenizer;

import javax.servlet.RequestDispatcher;
import javax.servlet.ServletConfig;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.apache.lucene.analysis.Analyzer;
import org.apache.lucene.analysis.standard.StandardAnalyzer;
import org.apache.lucene.document.Document;
import org.apache.lucene.document.Field;
import org.apache.lucene.index.CorruptIndexException;
import org.apache.lucene.index.IndexWriter;
import org.apache.lucene.search.IndexSearcher;
import org.apache.lucene.search.Query;
import org.apache.lucene.search.ScoreDoc;
import org.apache.lucene.search.TopDocs;
import org.apache.lucene.store.RAMDirectory;
import org.apache.lucene.xmlparser.CorePlusExtensionsParser;
import org.apache.lucene.xmlparser.QueryTemplateManager;

public class FormBasedXmlQueryDemo extends HttpServlet {

	private QueryTemplateManager queryTemplateManager;
	private CorePlusExtensionsParser xmlParser;
	private IndexSearcher searcher;
	private Analyzer analyzer=new StandardAnalyzer(org.apache.lucene.util.Version.LUCENE_CURRENT);

	@Override
	public void init(ServletConfig config) throws ServletException {
		super.init(config);
		try {
			openExampleIndex();

			//load servlet configuration settings
			String xslFile=config.getInitParameter("xslFile");
			String defaultStandardQueryParserField = config.getInitParameter("defaultStandardQueryParserField");


			//Load and cache choice of XSL query template using QueryTemplateManager
			queryTemplateManager=new QueryTemplateManager(
					getServletContext().getResourceAsStream("/WEB-INF/"+xslFile));

			//initialize an XML Query Parser for use by all threads
			xmlParser=new CorePlusExtensionsParser(defaultStandardQueryParserField,analyzer);
		} catch (Exception e) {
			throw new ServletException("Error loading query template",e);
		}
	}

	@Override
	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		//Take all completed form fields and add to a Properties object
		Properties completedFormFields=new Properties();
		Enumeration pNames = request.getParameterNames();
		while(pNames.hasMoreElements()){
			String propName=(String) pNames.nextElement();
			String value=request.getParameter(propName);
			if((value!=null)&&(value.trim().length()>0)){
				completedFormFields.setProperty(propName, value);
			}
		}

		try{

			//Create an XML query by populating template with given user criteria
			org.w3c.dom.Document xmlQuery=queryTemplateManager.getQueryAsDOM(completedFormFields);

			//Parse the XML to produce a Lucene query
			Query query=xmlParser.getQuery(xmlQuery.getDocumentElement());

			//Run the query
			TopDocs topDocs = searcher.search(query,10);

			//and package the results and forward to JSP
			if(topDocs!=null)	{
				ScoreDoc[] sd = topDocs.scoreDocs;
				Document[] results=new Document[sd.length];
				for (int i = 0; i < results.length; i++) {
					results[i]=searcher.doc(sd[i].doc);
					request.setAttribute("results", results);
				}
			}
			RequestDispatcher dispatcher = getServletContext().getRequestDispatcher("/index.jsp");
			dispatcher.forward(request,response);
		}
		catch(Exception e){
			throw new ServletException("Error processing query",e);
		}
	}

	private void openExampleIndex() throws CorruptIndexException, IOException {

		//Create a RAM-based index from our test data file
		RAMDirectory rd=new RAMDirectory();
		IndexWriter writer=new IndexWriter (rd,analyzer,IndexWriter.MaxFieldLength.LIMITED);
		InputStream dataIn=getServletContext().getResourceAsStream("/WEB-INF/data.tsv");
		BufferedReader br = new BufferedReader(new InputStreamReader(dataIn));
		String line = br.readLine();
		while(line!=null)
		{
			line=line.trim();
			if(line.length()>0)
			{
				//parse row and create a document
				StringTokenizer st=new StringTokenizer(line,"\t");
				Document doc=new Document();
				doc.add(new Field("location",st.nextToken(),Field.Store.YES,
						Field.Index.ANALYZED_NO_NORMS));
				doc.add(new Field("salary",st.nextToken(),Field.Store.YES,
						Field.Index.ANALYZED_NO_NORMS));
				doc.add(new Field("type",st.nextToken(),Field.Store.YES,
						Field.Index.ANALYZED_NO_NORMS));
				doc.add(new Field("description",st.nextToken(),Field.Store.YES,
						Field.Index.ANALYZED));
				writer.addDocument(doc);
			}
			line=br.readLine();
		}
		writer.close();

		//open searcher
		searcher=new IndexSearcher(rd, true);
	}
}