Copyright (c) 2003, 2012 IBM Corporation and others.
This program and the accompanying materials
are made available under the terms of the Eclipse Public License 2.0
which accompanies this distribution, and is available at
https://www.eclipse.org/legal/epl-2.0/
SPDX-License-Identifier: EPL-2.0
Contributors:
    IBM Corporation - initial API and implementation
/*******************************************************************************
 * Copyright (c) 2003, 2012 IBM Corporation and others.
 *
 * This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License 2.0
 * which accompanies this distribution, and is available at
 * https://www.eclipse.org/legal/epl-2.0/
 *
 * SPDX-License-Identifier: EPL-2.0
 * 
 * Contributors:
 *     IBM Corporation - initial API and implementation
 *******************************************************************************/

package org.eclipse.osgi.storage.url.reference;

import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStream;
import java.net.URL;
import java.net.URLConnection;
import org.eclipse.osgi.framework.util.FilePath;
import org.eclipse.osgi.internal.location.LocationHelper;
import org.eclipse.osgi.internal.messages.Msg;
import org.eclipse.osgi.util.NLS;

URLConnection for the reference protocol.
/**
 * URLConnection for the reference protocol.
 */

public class ReferenceURLConnection extends URLConnection {
	private final String installPath;
	private volatile File reference;

	protected ReferenceURLConnection(URL url, String installPath) {
		super(url);
		this.installPath = installPath;
	}

	@Override
	public synchronized void connect() throws IOException {
		if (!connected) {
			// TODO assumes that reference URLs are always based on file: URLs.
			// There are not solid usecases to the contrary. Yet.
			// Construct the ref File carefully so as to preserve UNC paths etc.
			String path = url.getPath();
			if (!path.startsWith("file:")) { //$NON-NLS-1$
				throw new IOException(NLS.bind(Msg.ADAPTOR_URL_CREATE_EXCEPTION, path));
			}
			path = url.getPath().substring(5);
			File file = new File(path);

			if (!file.isAbsolute()) {
				if (installPath != null)
					file = makeAbsolute(installPath, file);
			}

			file = LocationHelper.decodePath(file);

			checkRead(file);

			reference = file;
			connected = true;
		}
	}

	private void checkRead(File file) throws IOException {
		if (!file.exists())
			throw new FileNotFoundException(file.toString());
		if (file.isFile()) {
			// Try to open the file to ensure that this is possible: see bug 260217
			// If access is denied, a FileNotFoundException with (access denied) message is thrown
			// Here file.canRead() cannot be used, because on Windows it does not 
			// return correct values - bug 6203387 in Sun's bug database
			InputStream is = new FileInputStream(file);
			is.close();
		} else if (file.isDirectory()) {
			// There is no straightforward way to check if a directory
			// has read permissions - same issues for File.canRead() as above; 
			// try to list the files in the directory
			File[] files = file.listFiles();
			// File.listFiles() returns null if the directory does not exist 
			// (which is not the current case, because we check that it exists and is directory),
			// or if an IO error occurred during the listing of the files, including if the
			// access is denied 
			if (files == null)
				throw new FileNotFoundException(file.toString() + " (probably access denied)"); //$NON-NLS-1$
		} else {
			// TODO not sure if we can get here.
		}
	}

	@Override
	public boolean getDoInput() {
		return true;
	}

	@Override
	public boolean getDoOutput() {
		return false;
	}

	@Override
	public InputStream getInputStream() throws IOException {
		if (!connected) {
			connect();
		}

		return new ReferenceInputStream(reference);
	}

	private static File makeAbsolute(String base, File relative) {
		if (relative.isAbsolute())
			return relative;
		return new File(new FilePath(base + relative.getPath()).toString());
	}
}