/*
 * The Apache Software License, Version 1.1
 *
 * Copyright (c) 2002 The Apache Software Foundation.  All rights
 * reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 *
 * 3. The end-user documentation included with the redistribution, if
 *    any, must include the following acknowlegement:
 *       "This product includes software developed by the
 *        Apache Software Foundation (http://www.apache.org/)."
 *    Alternately, this acknowlegement may appear in the software itself,
 *    if and wherever such third-party acknowlegements normally appear.
 *
 * 4. The names "The Jakarta Project", "Ant", and "Apache Software
 *    Foundation" must not be used to endorse or promote products derived
 *    from this software without prior written permission. For written
 *    permission, please contact apache@apache.org.
 *
 * 5. Products derived from this software may not be called "Apache"
 *    nor may "Apache" appear in their names without prior written
 *    permission of the Apache Group.
 *
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED.  IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR
 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
 * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 * ====================================================================
 *
 * This software consists of voluntary contributions made by many
 * individuals on behalf of the Apache Software Foundation.  For more
 * information on the Apache Software Foundation, please see
 * <http://www.apache.org/>.
 */
package org.apache.ant.init;
import java.io.BufferedReader;
import java.io.File;
import java.io.FilenameFilter;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintStream;
import java.net.MalformedURLException;
import java.net.URL;
import java.net.URLClassLoader;
import java.util.ArrayList;
import java.util.List;

/**
 * LoaderUtils is a utility class with methods for configuring a class
 * loader from a URL.
 *
 * @author Conor MacNeill
 * @created 9 January 2002
 */
public class LoaderUtils {

    /**
     * This is the file that is consulted on remote systems to specify
     * available jars
     */
    public static final String LIST_FILE = "file.list";


    /**
     * Get the URLs of a set of libraries in the given location
     *
     * @param location the location to be searched
     * @param defaultFile default file if none can be found
     * @return an array of URLs for the relevant jars
     * @exception MalformedURLException the URLs cannot be created
     */
    public static URL[] getLocationURLs(URL location, String defaultFile)
         throws MalformedURLException {
        return getLocationURLs(location, defaultFile, new String[]{".jar"});
    }

    /**
     * Get the URLs of a set of libraries in the given location
     *
     * @param location the location to be searched
     * @param extensions array of allowable file extensions
     * @param defaultFile default file if none can be found
     * @return an array of URLs for the relevant jars
     * @exception MalformedURLException if the URL to the jars could not be
     *      formed
     */
    public static URL[] getLocationURLs(URL location, String defaultFile,
                                        String[] extensions)
         throws MalformedURLException {
        URL[] urls = null;
        if (location.getProtocol().equals("file")) {
            // URL is local filesystem.
            urls = getLocalURLs(new File(location.getFile()), extensions);
        } else {
            // URL is remote - try to read a file with the list of jars
            URL jarListURL = new URL(location, LIST_FILE);
            BufferedReader reader = null;
            List jarList = new ArrayList();
            try {
                InputStreamReader isr
                     = new InputStreamReader(jarListURL.openStream());
                reader = new BufferedReader(isr);
                String line = null;
                while ((line = reader.readLine().trim()) != null) {
                    for (int i = 0; i < extensions.length; ++i) {
                        if (line.endsWith(extensions[i])) {
                            jarList.add(new URL(location, line));
                            break;
                        }
                    }
                }
                urls = (URL[]) jarList.toArray(new URL[0]);
            } catch (IOException e) {
                // use the default location
                if (defaultFile != null) {
                    urls = new URL[]{new URL(location, defaultFile)};
                }
            } finally {
                if (reader != null) {
                    try {
                        reader.close();
                    } catch (IOException e) {
                    }
                }
            }
        }

        return urls;
    }

    /**
     * Get the classpath from a classloader. This can only extract path
     * components from the loaders which are instances of URLClassLoaders
     *
     * @param loader the loader whose path is required
     * @return the loader's configuration expressed as a classpath
     */
    public static String getClasspath(ClassLoader loader) {
        StringBuffer pathBuffer = null;
        if (loader instanceof URLClassLoader) {
            URLClassLoader urlLoader = (URLClassLoader) loader;
            URL[] urls = urlLoader.getURLs();
            for (int i = 0; i < urls.length; ++i) {
                if (!urls[i].getProtocol().equals("file")) {
                    continue;
                }
                String pathElement = urls[i].getFile();
                if (pathBuffer == null) {
                    pathBuffer = new StringBuffer(pathElement);
                } else {
                    pathBuffer.append(File.pathSeparatorChar);
                    pathBuffer.append(pathElement);
                }
            }
        }
        String path = pathBuffer == null ? "" : pathBuffer.toString();
        ClassLoader parentLoader = loader.getParent();
        if (parentLoader != null) {
            String parentPath = getClasspath(parentLoader);
            if (parentPath.length() != 0) {
                path = parentPath + File.pathSeparator + path;
            }
        }

        return path;
    }


    /**
     * Debug method to dump a class loader hierarchy to a PrintStream
     * URLClassLoaders dump their URLs
     *
     * @param loader the class loaders whose configuration is dumped
     * @param ps PrintStream to which info is sent
     */
    public static void dumpLoader(PrintStream ps, ClassLoader loader) {
        if (loader instanceof URLClassLoader) {
            URLClassLoader urlLoader = (URLClassLoader) loader;
            URL[] urls = urlLoader.getURLs();
            if (urls.length == 0) {
                ps.println("   No URLs");
            } else {
                for (int i = 0; i < urls.length; ++i) {
                    ps.println("   URL: " + urls[i]);
                }
            }
        } else {
            ps.println("Class Loader: " + loader.getClass().getName());
        }
        ps.println();

        ClassLoader parentLoader = loader.getParent();
        if (parentLoader != null) {
            ps.println("Parent Loader:");
            dumpLoader(ps, parentLoader);
        }
    }


    /**
     * Get an array of URLs for each file in the filesystem. If the given
     * location is a directory, it is searched for files of the given
     * extension. If it is a file, it is returned as a URL if it matches the
     * given extension list.
     *
     * @param location the location within the local filesystem to be
     *      searched
     * @param extensions an array of file extensions to be considered in the
     *      search
     * @return an array of URLs for the file found in the directory.
     * @exception MalformedURLException if the URLs to the jars cannot be
     *      formed
     */
    private static URL[] getLocalURLs(File location,
                                      final String[] extensions)
         throws MalformedURLException {
        URL[] urls = new URL[0];

        if (!location.exists()) {
            return urls;
        }

        if (!location.isDirectory()) {
            urls = new URL[1];
            String path = location.getPath();
            for (int i = 0; i < extensions.length; ++i) {
                if (path.endsWith(extensions[i])) {
                    urls[0] = InitUtils.getFileURL(location);
                    break;
                }
            }
            return urls;
        }

        File[] jars = location.listFiles(
            new FilenameFilter() {
                public boolean accept(File dir, String name) {
                    for (int i = 0; i < extensions.length; ++i) {
                        if (name.endsWith(extensions[i])) {
                            return true;
                        }
                    }
                    return false;
                }
            });
        urls = new URL[jars.length];
        for (int i = 0; i < jars.length; ++i) {
            urls[i] = InitUtils.getFileURL(jars[i]);
        }
        return urls;
    }

    /**
     * Set the context loader of the current thread and returns the existing
     * classloader
     *
     * @param newLoader the new context loader
     * @return the old context loader
     */
    public static ClassLoader setContextLoader(ClassLoader newLoader) {
        Thread thread = Thread.currentThread();
        ClassLoader currentLoader = thread.getContextClassLoader();
        thread.setContextClassLoader(newLoader);
        return currentLoader;
    }

}