/*******************************************************************************
 * Copyright (c) 2008 Jesper Steen Moeller 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:
 * Jesper Steen Moeller - XSL core plugin
 * Doug Satchwell - bug 225304
 *******************************************************************************/

package org.eclipse.wst.xsl.core.resolver;

import java.io.IOException;
import java.net.URL;

import javax.xml.parsers.ParserConfigurationException;

import org.eclipse.core.resources.IFile;
import org.eclipse.core.runtime.CoreException;
import org.eclipse.core.runtime.FileLocator;
import org.eclipse.core.runtime.IStatus;
import org.eclipse.core.runtime.Path;
import org.eclipse.core.runtime.Status;
import org.eclipse.wst.common.uriresolver.internal.provisional.URIResolverExtension;
import org.eclipse.wst.sse.core.StructuredModelManager;
import org.eclipse.wst.sse.core.internal.provisional.IModelManager;
import org.eclipse.wst.sse.core.internal.provisional.IStructuredModel;
import org.eclipse.wst.xml.core.internal.provisional.document.IDOMModel;
import org.eclipse.wst.xsl.core.Messages;
import org.eclipse.wst.xsl.core.XSLCore;
import org.eclipse.wst.xsl.core.internal.XSLCorePlugin;
import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.xml.sax.InputSource;
import org.xml.sax.SAXException;

/**
 * TODO: Javadoc
 * 
 * @author Jesper Steen Moeller
 * 
 */
public class ResolverExtension implements URIResolverExtension
{
	private static final Double DEFAULT_XSLT_VERSION = 1.0;
	private static final String XSLT_STYLESHEET = "stylesheet"; //$NON-NLS-1$
	private static final String XSLT_TEMPLATE = "template"; //$NON-NLS-1$
	private static final String XSLT_VERSION = "version"; //$NON-NLS-1$

	private boolean initialised;
	private String xslt_1_0_fileURL;
	private String xslt_2_0_fileURL;

	public String resolve(IFile file, String baseLocation, String publicId, String systemId)
	{

		// Is someone looking for "our" schema?
		if (!XSLCore.XSL_NAMESPACE_URI.equals(publicId))
		{
			// Not this time, return right away
			return null;
		}

		String version = null;

		if (file != null)
			version = peekVersionAttributeFromSSE(file);
		if (version == null)
			version = peekVersionFromFile(file, baseLocation);

		if (version == null)
			return null;

		Double versionNumber = null;
		try
		{
			versionNumber = Double.valueOf(version);
		}
		catch (Throwable t)
		{
			// Not interested
		}

		if (versionNumber == null)
		{
			versionNumber = DEFAULT_XSLT_VERSION;
		}

		// We carelessly ditch the fraction part
		int intVersion = versionNumber.intValue();
		checkInitialised();
		if (intVersion == 1)
		{
			return xslt_1_0_fileURL;
		}
		else if (intVersion == 2)
		{
			return xslt_2_0_fileURL;
		}
		else
			return null;
	}

	private void checkInitialised()
	{
		if (!initialised)
		{
			initialised = true;
			try
			{
				URL pluginURL = FileLocator.find(XSLCorePlugin.getDefault().getBundle(), new Path("/xslt-schemas/xslt-1.0.xsd"), null); //$NON-NLS-1$
				xslt_1_0_fileURL = FileLocator.toFileURL(pluginURL).toExternalForm();
				pluginURL = FileLocator.find(XSLCorePlugin.getDefault().getBundle(), new Path("/xslt-schemas/xslt-2.0.xsd"), null); //$NON-NLS-1$
				xslt_2_0_fileURL = FileLocator.toFileURL(pluginURL).toExternalForm();
			}
			catch (IOException e)
			{
				XSLCorePlugin.log(e);
			}
		}
	}

	private String peekVersionFromFile(IFile file, String baseLocation)
	{
		XSLVersionHandler handler = new XSLVersionHandler();
		try
		{
			handler.parseContents(file != null ? createInputSource(file) : createInputSource(baseLocation));
		}
		catch (SAXException se)
		{
			XSLCorePlugin.log(se);
			// drop through, since this is almost to be expected
		}
		catch (IOException ioe)
		{
			XSLCorePlugin.log(new CoreException(XSLCorePlugin.newErrorStatus("Can't parse XSL document", ioe))); //$NON-NLS-1$
			// drop through, since this is not really a show-stopper
		}
		catch (ParserConfigurationException pce)
		{
			// some bad thing happened - force this describer to be disabled
			String message = Messages.XSLCorePlugin_parserConfiguration;
			XSLCorePlugin.log(new Status(IStatus.ERROR, XSLCorePlugin.PLUGIN_ID, 0, message, pce));
			throw new RuntimeException(message);
			// drop through, since this is not really a show-stopper
		}
		catch (CoreException ce)
		{
			XSLCorePlugin.log(ce);
			// drop through, since this is not really a show-stopper
		}

		String versionX = handler.getVersionAttribute();
		return versionX;
	}

	private String peekVersionAttributeFromSSE(IFile file)
	{
		IModelManager manager = StructuredModelManager.getModelManager();

		if (manager != null)
		{
			String id = manager.calculateId(file);
			IStructuredModel model = manager.getExistingModelForRead(id);
			try
			{
				if (model instanceof IDOMModel)
				{
					Document doc = ((IDOMModel) model).getDocument();
					if (doc != null && doc.getDocumentElement() != null)
					{
						Element documentElement = doc.getDocumentElement();
						if (XSLT_STYLESHEET.equals(documentElement.getLocalName()) || XSLT_TEMPLATE.equals(documentElement.getLocalName()))
						{
							return documentElement.getAttribute(XSLT_VERSION);
						}
						else
							return ""; //$NON-NLS-1$
					}
				}
			}
			finally
			{
				// bug 225304
				if (model != null)
					model.releaseFromRead();
			}
		}
		return null;
	}

	private InputSource createInputSource(String systemId) throws CoreException
	{
		return new InputSource(systemId);
	}

	private InputSource createInputSource(IFile file) throws CoreException
	{
		InputSource src = new InputSource(file.getContents());
		src.setSystemId(file.getLocationURI().toString());
		return src;
	}
}