package org.gcube.data.analysis.nlphub;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.net.HttpURLConnection;
import java.net.URL;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.xml.stream.FactoryConfigurationError;
import javax.xml.stream.XMLInputFactory;
import javax.xml.stream.XMLStreamConstants;
import javax.xml.stream.XMLStreamException;
import javax.xml.stream.XMLStreamReader;

import org.gcube.data.analysis.nlphub.session.SessionUtils;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * Servlet implementation class NLPHub
 */
@WebServlet(asyncSupported = true, name = "DiscoverDataMinerServlet", urlPatterns = { "/discover-dataminer-servlet" })
public class DiscoverDataMinerService extends HttpServlet {
	private static final long serialVersionUID = 1L;
	private static final Logger logger = LoggerFactory.getLogger(DiscoverDataMinerService.class);

	/**
	 * @see HttpServlet#HttpServlet()
	 */
	public DiscoverDataMinerService() {
		super();
		// TODO Auto-generated constructor stub
	}

	/**
	 * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse
	 *      response)
	 */
	protected void doGet(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		doWork(request, response);
	}

	/**
	 * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse
	 *      response)
	 */
	protected void doPost(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		doWork(request, response);
	}

	private void doWork(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		logger.debug("Discover DataMinerService");
		String token = SessionUtils.getToken(request);

		discoverDataMinerService(request, response, token);

	}

	private void discoverDataMinerService(HttpServletRequest request, HttpServletResponse response, String token)
			throws ServletException, IOException {

		HttpURLConnection connection = null;
		String dataMinerServiceUrl = "";
		response.setContentType("text/plain;charset=UTF-8");
		try (PrintWriter writer = response.getWriter()) {

			try {
				String urlInformationSystem = "http://registry.d4science.org/icproxy/gcube/service/ServiceEndpoint/DataAnalysis/DataMiner?";

				logger.debug("Request url: " + urlInformationSystem);
				urlInformationSystem += "gcube-token=" + token;
				URL url = new URL(urlInformationSystem);

				connection = (HttpURLConnection) url.openConnection();
				connection.setRequestMethod("GET");
				connection.setDoInput(true);
				connection.setDoOutput(false);
				connection.setUseCaches(false);

				try (BufferedReader r = new BufferedReader(new InputStreamReader(connection.getInputStream()))) {
					dataMinerServiceUrl = readProfileInfo(r);
				}

			} catch (Exception e) {
				logger.error("Discover DataMiner Service error: " + e.getLocalizedMessage(), e);
			} finally {
				try {
					if (connection != null)
						connection.disconnect();
				} catch (Exception e) {
					logger.error("Discover DataMiner Service error: " + e.getLocalizedMessage(), e);
				}
			}

			writer.println(dataMinerServiceUrl);
			

		} catch (Throwable e) {
			logger.error("Error discovering DataMiner Service Url: " + e.getLocalizedMessage(), e);
		}
	}

	private String readProfileInfo(BufferedReader r) throws FactoryConfigurationError, XMLStreamException {
		String dataMinerServiceUrl = null;
		XMLInputFactory xmlInFact = XMLInputFactory.newInstance();
		XMLStreamReader reader = xmlInFact.createXMLStreamReader(r);
		while (reader.hasNext()) {
			int eventType = reader.next();
			if (eventType == XMLStreamConstants.START_ELEMENT) {
				logger.debug("Read Element: " + reader.getLocalName());
				if (reader.getLocalName().compareToIgnoreCase("EndPoint") == 0) {
					logger.debug("Attribute count:" + reader.getAttributeCount());
					for (int i = 0; i < reader.getAttributeCount(); i++) {
						logger.debug("Attribute Name: " + reader.getAttributeName(i));
						logger.debug("Attribute Value: " + reader.getAttributeValue(i));
						if (reader.getAttributeName(i).toString().compareToIgnoreCase("EntryName") == 0
								&& reader.getAttributeValue(i).toString()
										.compareToIgnoreCase("dataminer-prototypes.d4science.org") == 0) {
							dataMinerServiceUrl = reader.getElementText();
							dataMinerServiceUrl=dataMinerServiceUrl.trim();
							dataMinerServiceUrl = dataMinerServiceUrl.replace("\\n", "").replace("\\r", "");
							logger.debug("url lenght: "+dataMinerServiceUrl.length());
							logger.debug("DataMiner service url retrieved: " + dataMinerServiceUrl);
							return dataMinerServiceUrl;
						}

					} 

				}
			}
		}
		return dataMinerServiceUrl;
	}

}