/*

* Copyright (c) 2010 Nokia Corporation and/or its subsidiary(-ies).

* All rights reserved.

* This component and the accompanying materials are made available

* under the terms of the License "Eclipse Public License v1.0"

* which accompanies this distribution, and is available

* at the URL "http://www.eclipse.org/legal/epl-v10.html".

*

* Initial Contributors:

* Nokia Corporation - initial contribution.

*

* Contributors:

*

* Description: 

*

*/

package com.nokia.carbide.internal.discovery.ui.editor;

import java.io.IOException;

import java.io.InputStream;

import java.net.MalformedURLException;

import java.net.URL;

import java.net.URLConnection;

import java.text.ParseException;

import java.text.SimpleDateFormat;

import java.util.ArrayList;

import java.util.Date;

import java.util.HashSet;

import java.util.List;

import java.util.Set;

import javax.xml.parsers.ParserConfigurationException;

import javax.xml.parsers.SAXParser;

import javax.xml.parsers.SAXParserFactory;

import org.xml.sax.Attributes;

import org.xml.sax.SAXException;

import org.xml.sax.helpers.DefaultHandler;

import com.nokia.carbide.discovery.ui.Activator;

import com.nokia.carbide.discovery.ui.Messages;

/**

 * A simple RSS reader

 * @see http://www.rssboard.org/rss-specification

 */

public class SimpleRSSReader {

	public static class Rss {

		private List<Channel> channels = new ArrayList<Channel>();

		public List<Channel> getChannels() {

			return channels;

		}

		protected void addChannel(Channel channel) {

			channels.add(channel);

		}

	}

	public static class Container {

		private String title;

		private URL link;

		private String description;

		private Date pubDate;

		private List<String> categories = new ArrayList<String>();

		public String getTitle() {

			return title;

		}

		public URL getLink() {

			return link;

		}

		public String getDescription() {

			return description;

		}

		public Date getPubDate() {

			return pubDate;

		}

		public String[] getCategories() {

			return (String[]) categories.toArray(new String[categories.size()]);

		}

		public boolean isValid() {

			return title != null && link != null && description != null;

		}

		protected void setField(String element, String value) {

			if (RSSHandler.TITLE.equalsIgnoreCase(element))

				title = value;

			else if (RSSHandler.LINK.equalsIgnoreCase(element)) {

				try {

					link = new URL(value);

				} catch (MalformedURLException e) {

					// don't store malformed URLs

					Activator.logError(Messages.SimpleRSSReader_BadURLError, e);

				}

			}

			else if (RSSHandler.DESCRIPTION.equalsIgnoreCase(element) || RSSHandler.SUMMARY.equalsIgnoreCase(element))

				description = value;

			else if (RSSHandler.PUBDATE.equalsIgnoreCase(element)) {

				pubDate = parseRFC822Date(value);

			}

			else if (RSSHandler.CATEGORY.equalsIgnoreCase(element))

				categories.add(value);

		}

		private Date parseRFC822Date(String value) {

	        SimpleDateFormat format = new SimpleDateFormat("EEE, d MMM yyyy HH:mm:ss Z"); //$NON-NLS-1$

	        try {

				return format.parse(value);

			} catch (ParseException e) {

			}

			return null;

		}

	}

	public static class Channel extends Container {

		List<Item> items = new ArrayList<Item>();

		public List<Item> getItems() {

			return items;

		}

		protected void addItem(Item item) {

			items.add(item);

		}

		public boolean hasItems() {

			return !items.isEmpty();

		}

	}

	public static class Item extends Container {

		private Channel channel;

		public Item(Channel channel) {

			this.channel = channel;

		}

		public Channel getChannel() {

			return channel;

		}

	}

	private static class RSSHandler extends DefaultHandler {

		private static final String CHANNEL = "channel"; //$NON-NLS-1$

		private static final String TITLE = "title"; //$NON-NLS-1$

		private static final String LINK = "link"; //$NON-NLS-1$

		private static final String DESCRIPTION = "description"; //$NON-NLS-1$

		private static final String SUMMARY = "atom:summary"; //$NON-NLS-1$

		private static final String ITEM = "item"; //$NON-NLS-1$

		private static final String PUBDATE = "pubDate"; //$NON-NLS-1$

		private static final String CATEGORY = "category"; //$NON-NLS-1$

		private static final Set<String> charsElements = new HashSet<String>();

		static {

			charsElements.add(TITLE.toLowerCase());

			charsElements.add(LINK.toLowerCase());

			charsElements.add(DESCRIPTION.toLowerCase());

			charsElements.add(SUMMARY.toLowerCase());

			charsElements.add(PUBDATE.toLowerCase());

			charsElements.add(CATEGORY.toLowerCase());

		}

		private Channel curChannel;

		private Item curItem;

		private StringBuffer charsBuf;

		private Rss rss;

		public RSSHandler(Rss rss) {

			this.rss = rss;

		}

		@Override

		public void startElement(String uri, String localName, String qName, Attributes attributes) throws SAXException {

			if (charsElements.contains(qName.toLowerCase())) {

				charsBuf = new StringBuffer();

			}

			if (CHANNEL.equalsIgnoreCase(qName)) {

				curChannel = new Channel();

			}

			else if (ITEM.equalsIgnoreCase(qName) && curChannel != null) {

				curItem = new Item(curChannel);

			}

		}

		@Override

		public void endElement(String uri, String localName, String qName) throws SAXException {

			if (CHANNEL.equalsIgnoreCase(qName)) {

				if (curChannel != null && curChannel.isValid() && curChannel.hasItems())

					rss.addChannel(curChannel);

				curChannel = null;

				curItem = null;

			}

			else if (ITEM.equalsIgnoreCase(qName)) {

				if (curChannel != null && curItem != null && curItem.isValid())

					curChannel.addItem(curItem);

				curItem = null;

			}

			else if (charsBuf != null && curChannel != null) {

				if (curItem != null)

					curItem.setField(qName, charsBuf.toString().trim());

				else

					curChannel.setField(qName, charsBuf.toString().trim());

				charsBuf = null;

			} 

		}

		@Override

		public void characters(char[] ch, int start, int length) throws SAXException {

			if (charsBuf != null) {

				charsBuf.append(new String(ch, start, length));

			}

		}

	}

	public static Rss readRSS(URL url) throws SAXException, IOException, ParserConfigurationException {

		Rss rss = new Rss();

		URLConnection connection = url.openConnection();

		connection.connect();

		InputStream inputStream = url.openStream();

		SAXParser parser = SAXParserFactory.newInstance().newSAXParser();

		parser.parse(inputStream, new RSSHandler(rss));

		return rss;

	}

}