/*******************************************************************************
 * Copyright (c) 2011 IBM Corporation and others.
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 *
 * Contributors:
 *     IBM Corporation - initial API and implementation
 *******************************************************************************/
package org.eclipse.wst.css.ui.internal.text.hover;

import java.io.IOException;
import java.net.URL;
import java.util.HashMap;
import java.util.Map;

import javax.xml.parsers.ParserConfigurationException;
import javax.xml.parsers.SAXParserFactory;

import org.eclipse.core.runtime.FileLocator;
import org.eclipse.core.runtime.Path;
import org.eclipse.swt.graphics.RGB;
import org.eclipse.wst.css.ui.internal.CSSUIPlugin;
import org.eclipse.wst.css.ui.internal.Logger;
import org.xml.sax.Attributes;
import org.xml.sax.InputSource;
import org.xml.sax.SAXException;
import org.xml.sax.XMLReader;
import org.xml.sax.helpers.DefaultHandler;

import com.ibm.icu.util.StringTokenizer;

/**
 * Associates css color names to the appropriate {@link RGB} values.
 * These associations are defined in org.eclipse.wst.css.ui/csscolors/extended-color-mapping.xml
 *
 */
class CSSColorNames {

	private static CSSColorNames instance;
	private static final Map colors = new HashMap();

	private CSSColorNames() {
		try {
			URL url = FileLocator.find(CSSUIPlugin.getDefault().getBundle(), new Path("csscolors/extended-color-mapping.xml"), null); //$NON-NLS-1$
			final XMLReader xmlReader = SAXParserFactory.newInstance().newSAXParser().getXMLReader();
			xmlReader.setContentHandler(new ColorMappingHandler());
			xmlReader.parse(new InputSource(url.openStream()));
		}
		catch (IOException e) {
			Logger.logException(e);
		}
		catch (SAXException e) {
			Logger.logException(e);
		}
		catch (ParserConfigurationException e) {
			Logger.logException(e);
		}
	}

	public static synchronized CSSColorNames getInstance() {
		if (instance == null) {
			instance = new CSSColorNames();
		}
		return instance;
	}

	/**
	 * Returns the {@link RGB} value associated with this color name.
	 * @param name the color name
	 * @return {@link RGB} associated with <code>name</code>, null if it is an unknown name or invalid RGB value
	 */
	public RGB getRGB(String name) {
		return (RGB) colors.get(name);
	}

	class ColorMappingHandler extends DefaultHandler {
		private final String COLOR_ELEM = "color"; //$NON-NLS-1$
		private final String NAME_ATTR = "name"; //$NON-NLS-1$
		private final String RGB_ATTR = "rgb"; //$NON-NLS-1$

		public void startElement(String uri, String localName, String qName, Attributes attributes) throws SAXException {
			if (COLOR_ELEM.equals(qName)) {
				final String name = attributes.getValue(NAME_ATTR);
				final String rgb = attributes.getValue(RGB_ATTR);
				if (name != null && rgb != null) {
					final RGB rgbValue = getRGB(rgb);
					if (rgbValue != null) {
						colors.put(name, rgbValue);
					}
				}
			}
		}

		/**
		 * Converts an rgb string into an {@link RGB}
		 * @param rgb the color string
		 * @return an {@link RGB} if one can be created from the string; otherwise, null
		 */
		private RGB getRGB(String rgb) {
			final StringTokenizer tokenizer = new StringTokenizer(rgb, ","); //$NON-NLS-1$
			int[] weights = new int[3];
			for (int i = 0; tokenizer.hasMoreTokens(); i++) {
				if (i > 2)
					return null;
				try {
					weights[i] = Integer.parseInt(tokenizer.nextToken().trim());
				}
				catch (NumberFormatException e) {
					return null;
				}
				if (weights[i] > 255 || weights[i] < 0)
					return null;
			}
			return new RGB(weights[0], weights[1], weights[2]);
		}
	}
	
	
}