package org.openslx.dozmod.util;

import java.io.IOException;
import java.io.InputStream;
import java.net.MalformedURLException;
import java.net.URL;
import java.net.URLConnection;
import java.sql.Date;

import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.ParserConfigurationException;

import org.apache.log4j.Logger;
import org.openslx.bwlp.thrift.iface.SessionData;
import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.Node;
import org.w3c.dom.NodeList;
import org.xml.sax.SAXException;

/**
 *	Class representing the news given by the satellite
 *	Makes use of the News-API of the webservice slx-admin:
 *		http://satellite.ip/slx-admin/api.php?do=news
 *
 *	Access the data through the public getters:
 *		String newsHeadline = News.getHeadline();
 *		String newsContent = News.getContent();
 *		Date newsLatestDate = News.getDate();
 */

public class News {

	// Logger instance for this class
	private final static Logger LOGGER = Logger.getLogger(News.class);

	// Private members representing the news
	private static String headline = null;
	private static String content = null;
	private static Date date = null;

	/**
	 * Gets the headline as String.
	 *
	 * @return String Contains the headline text.
	 */
	public static String getHeadline() {
		if (headline != null)
			return headline;
		else {
			init();
			// check if it is still null
			if (headline != null)
				return headline;
			else
				return null;
		}
	}

	/**
	 * Gets the content as String.
	 *
	 * @return String Contains the content text.
	 */
	public static String getContent() {
		if (content != null)
			return content;
		else {
			init();
			if (content != null)
				return content;
			else
				return null;
		}
	}

	/**
	 * Gets the date of the latest news as Date.
	 *
	 * @return Date Represent last modification date.
	 */
	public static Date getDate() {
		if (date != null)
			return date;
		else {
			init();
			if (date != null)
				return date;
			else
				return null;
		}
	}

	/**
	 *	Private 'init' function doing the main work.
	 *	It is called by getters if their object is null.
	 *	Follows these steps:
	 *	- Opens URL as stream
	 *	- Parse stream as (XML-)Document
	 *	- Check validity of the news format:
	 *		<news>
	 *			<headline>...</headline>
	 *			<content>...</content>
	 *			<date>...</date>
	 *		</news>
	 *
	 *	- Sets private members
	 */

	private static void init(){
		// Document representing the XML
		Document doc = null;
		String satIp = SessionData._Fields.SERVER_ADDRESS.toString();
		// sanity check to see if we have the satellite IP
		if (satIp == null || satIp.isEmpty()) {
			LOGGER.error("No satellite IP adress is set in SessionData, aborting news fetching...");
			return;
		}
		
		// URL to news API
		URL url = null;
		try {
			url = new URL("http://" + SessionData._Fields.SERVER_ADDRESS.toString() + "/slx-admin/api.php?do=news");
		} catch (MalformedURLException e) {
			LOGGER.error("Malformated URL to News-API, see trace: ", e);
		}
		
		// check is the url got created.
		if (url == null) {
			// no URL, log it and return
			LOGGER.error("URL to the News-API not defined!");
			return;
		}
				
		// set timeout for URLConnection
		URLConnection urlCon = null;
		try {
			urlCon = url.openConnection();
			// 5 seconds timeout for connection
			urlCon.setConnectTimeout(5000);
			// 10 seconds timeout for reading the stream
			urlCon.setReadTimeout(10000);
		} catch (IOException e) {
			LOGGER.error("IO error while requesting News URL, see trace: ", e);
			return;
		}

		InputStream is = null;
		try {
			is = urlCon.getInputStream();
		} catch (IOException e1) {
			LOGGER.error("Could not open stream to URL '" + url.toString() + "', see trace: ", e1);
			return;
		}
		
		// use java's DocumentBuilder engine to parse the XML
		DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
		DocumentBuilder builder = null;
		
		try {
			builder = factory.newDocumentBuilder();
		} catch (ParserConfigurationException e) {
			LOGGER.error("XML parsing configuration error, see trace: ", e);
			return;
		}
		
		// try the parsing
		try {
			doc = builder.parse(is);
		} catch (SAXException e) {
			LOGGER.error("XML parsing error, see trace: ", e);
			return;
		} catch (IOException e) {
			LOGGER.error("IO-Error, see trace: ", e);
			return;
		}

		// now that we have parsed the XML, check if it is valid
		Element docRoot = doc.getDocumentElement();
		
		// first element has to be name "news"
		if (docRoot.getNodeName().equals("news")) {
			Node headlineNode = null;
			Node contentNode = null;
			Node dateNode = null;
			
			// get list of every child
			NodeList nList = docRoot.getElementsByTagName("*");		
			
			// fail if the list is empty
			if (nList == null) return;
			
			// now we go through the list looking for our elements
			// TODO: get definition of tags externally/through static api?
			for (int i = 0; i < nList.getLength(); i++) {
				Node current = nList.item(i);
				if (current.getNodeType() == Node.ELEMENT_NODE) {
					if (current.getNodeName().equals("headline") && 
							current.getFirstChild().getNodeType() == Node.TEXT_NODE) headlineNode = current.getFirstChild();
					// FIXME: temporary workaround for possibly different slx-admin versions!
					if ((current.getNodeName().equals("info") || current.getNodeName().equals("content")) &&
							current.getFirstChild().getNodeType() == Node.TEXT_NODE) contentNode = current.getFirstChild();
					if (current.getNodeName().equals("date") &&
							current.getFirstChild().getNodeType() == Node.TEXT_NODE) dateNode = current.getFirstChild();
				}
			}
			
			// set what the elements we found
			if (headlineNode != null) headline = headlineNode.getNodeValue().trim();
			if (contentNode != null) content = contentNode.getNodeValue().trim();
			if (dateNode != null) {
				// for the date we need a bit more stuff
				Date tmpDate = null;
				try {
					tmpDate = new Date(Long.parseLong(dateNode.getNodeValue().trim()) * 1000);
				} catch (NumberFormatException nfe) {
					LOGGER.error("Date format is invalid, see trace: ", nfe);
				}
				// Date creation worked, save it
				if (tmpDate != null) date = tmpDate;
			}
		} else {
			LOGGER.error("No valid news in the response!");
			return;
		}
	}	
}