/*
 * Copyright  2001-2004 The Apache Software Foundation
 *
 *  Licensed under the Apache License, Version 2.0 (the "License");
 *  you may not use this file except in compliance with the License.
 *  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 *
 */
package org.apache.tools.ant.taskdefs.optional.sitraka.bytecode;

import java.io.BufferedInputStream;
import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.FilenameFilter;
import java.io.IOException;
import java.io.InputStream;
import java.util.Enumeration;
import java.util.Hashtable;
import java.util.NoSuchElementException;
import java.util.StringTokenizer;
import java.util.Vector;
import java.util.zip.ZipEntry;
import java.util.zip.ZipFile;

/**
 * Core of the bytecode analyzer. It loads classes from a given classpath.
 *
 */
public class ClassPathLoader {

    public static final FileLoader NULL_LOADER = new NullLoader();

    /** the list of files to look for */
    private File[] files;

    /**
     * create a new instance with a given classpath. It must be urls
     * separated by the platform specific path separator.
     * @param classPath the classpath to load all the classes from.
     */
    public ClassPathLoader(String classPath) {
        StringTokenizer st = new StringTokenizer(classPath, File.pathSeparator);
        Vector entries = new Vector();
        while (st.hasMoreTokens()) {
            File file = new File(st.nextToken());
            entries.addElement(file);
        }
        files = new File[entries.size()];
        entries.copyInto(files);
    }

    /**
     * create a new instance with a given set of urls.
     * @param entries valid file urls (either .jar, .zip or directory)
     */
    public ClassPathLoader(String[] entries) {
        files = new File[entries.length];
        for (int i = 0; i < entries.length; i++) {
            files[i] = new File(entries[i]);
        }
    }

    /**
     * create a new instance with a given set of urls
     * @param entries file urls to look for classes (.jar, .zip or directory)
     */
    public ClassPathLoader(File[] entries) {
        files = entries;
    }

    /** the interface to implement to look up for specific resources */
    public interface FileLoader {
        /** the file url that is looked for .class files */
        File getFile();

        /** return the set of classes found in the file */
        ClassFile[] getClasses() throws IOException;
    }

    /**
     * @return the set of <tt>FileLoader</tt> loaders matching the given classpath.
     */
    public Enumeration loaders() {
        return new LoaderEnumeration();
    }

    /**
     * return the whole set of classes in the classpath. Note that this method
     * can be very resource demanding since it must load all bytecode from
     * all classes in all resources in the classpath at a time.
     * To process it in a less resource demanding way, it is maybe better to
     * use the <tt>loaders()</tt> that will return loader one by one.
     *
     * @return the hashtable containing ALL classes that are found in the given
     * classpath. Note that the first entry of a given classname will shadow
     * classes with the same name (as a classloader does)
     */
    public Hashtable getClasses() throws IOException {
        Hashtable map = new Hashtable();
        Enumeration e = loaders();
        while (e.hasMoreElements()) {
            FileLoader loader = (FileLoader) e.nextElement();
            System.out.println("Processing " + loader.getFile());
            long t0 = System.currentTimeMillis();
            ClassFile[] classes = loader.getClasses();
            long dt = System.currentTimeMillis() - t0;
            System.out.println("" + classes.length + " classes loaded in " + dt + "ms");
            for (int j = 0; j < classes.length; j++) {
                String name = classes[j].getFullName();
                // do not allow duplicates entries to preserve 'classpath' behavior
                // first class in wins
                if (!map.containsKey(name)) {
                    map.put(name, classes[j]);
                }
            }
        }
        return map;
    }

    /** the loader enumeration that will return loaders */
    private class LoaderEnumeration implements Enumeration {
        private int index = 0;

        public boolean hasMoreElements() {
            return index < files.length;
        }

        public Object nextElement() {
            if (index >= files.length) {
                throw new NoSuchElementException();
            }
            File file = files[index++];
            if (!file.exists()) {
                return new NullLoader(file);
            }
            if (file.isDirectory()) {
                // it's a directory
                return new DirectoryLoader(file);
            } else if (file.getName().endsWith(".zip") || file.getName().endsWith(".jar")) {
                // it's a jar/zip file
                return new JarLoader(file);
            }
            return new NullLoader(file);

        }
    }

    /**
     * useful methods to read the whole input stream in memory so that
     * it can be accessed faster. Processing rt.jar and tools.jar from JDK 1.3.1
     * brings time from 50s to 7s.
     */
    public static InputStream getCachedStream(InputStream is) throws IOException {
        final InputStream bis = new BufferedInputStream(is);
        final byte[] buffer = new byte[8192];
        final ByteArrayOutputStream bos = new ByteArrayOutputStream(2048);
        int n;
        bos.reset();
        while ((n = bis.read(buffer, 0, buffer.length)) != -1) {
            bos.write(buffer, 0, n);
        }
        is.close();
        return new ByteArrayInputStream(bos.toByteArray());
    }
}

/** a null loader to return when the file is not valid */
final class NullLoader implements ClassPathLoader.FileLoader {
    private File file;

    NullLoader() {
        this(null);
    }

    NullLoader(File file) {
        this.file = file;
    }

    public File getFile() {
        return file;
    }

    public ClassFile[] getClasses() throws IOException {
        return new ClassFile[0];
    }
}

/**
 * jar loader specified in looking for classes in jar and zip
 * @todo read the jar manifest in case there is a Class-Path
 * entry.
 */
final class JarLoader implements ClassPathLoader.FileLoader {
    private File file;

    JarLoader(File file) {
        this.file = file;
    }

    public File getFile() {
        return file;
    }

    public ClassFile[] getClasses() throws IOException {
        ZipFile zipFile = new ZipFile(file);
        Vector v = new Vector();
        Enumeration entries = zipFile.entries();
        while (entries.hasMoreElements()) {
            ZipEntry entry = (ZipEntry) entries.nextElement();
            if (entry.getName().endsWith(".class")) {
                InputStream is = ClassPathLoader.getCachedStream(zipFile.getInputStream(entry));
                ClassFile classFile = new ClassFile(is);
                is.close();
                v.addElement(classFile);
            }
        }
        ClassFile[] classes = new ClassFile[v.size()];
        v.copyInto(classes);
        return classes;
    }
}

/**
 * directory loader that will look all classes recursively
 * @todo should discard classes which package name does not
 * match the directory ?
 */
final class DirectoryLoader implements ClassPathLoader.FileLoader {
    private File directory;
    private static final FilenameFilter DIRECTORY_FILTER = new DirectoryFilter();
    private static final FilenameFilter CLASS_FILTER = new ClassFilter();

    DirectoryLoader(File dir) {
        directory = dir;
    }

    public File getFile() {
        return directory;
    }

    public ClassFile[] getClasses() throws IOException {
        Vector v = new Vector(127);
        Vector files = listFiles(directory, CLASS_FILTER, true);
        final int filesCount = files.size();
        for (int i = 0; i < filesCount; i++) {
            File file = (File) files.elementAt(i);
            InputStream is = null;
            try {
                is = ClassPathLoader.getCachedStream(new FileInputStream(file));
                ClassFile classFile = new ClassFile(is);
                is.close();
                is = null;
                v.addElement(classFile);
            } finally {
                if (is != null) {
                    try {
                        is.close();
                    } catch (IOException ignored) {
                    }
                }
            }
        }
        ClassFile[] classes = new ClassFile[v.size()];
        v.copyInto(classes);
        return classes;
    }

    /**
     * List files that obeys to a specific filter recursively from a given base
     * directory.
     * @param   directory   the directory where to list the files from.
     * @param   filter      the file filter to apply
     * @param   recurse     tells whether or not the listing is recursive.
     * @return  the list of <tt>File</tt> objects that applies to the given
     *          filter.
     */
    public static Vector listFiles(File directory, FilenameFilter filter, boolean recurse) {
        if (!directory.isDirectory()) {
            throw new IllegalArgumentException(directory + " is not a directory");
        }
        Vector list = new Vector(512);
        listFilesTo(list, directory, filter, recurse);
        return list;
    }

    /**
     * List and add files to a given list. As a convenience it sends back the
     * instance of the list given as a parameter.
     * @param   list    the list of files where the filtered files should be added
     * @param   directory   the directory where to list the files from.
     * @param   filter      the file filter to apply
     * @param   recurse     tells whether or not the listing is recursive.
     * @return  the list instance that was passed as the <tt>list</tt> argument.
     */
    private static Vector listFilesTo(Vector list, File directory,
                                      FilenameFilter filter, boolean recurse) {
        String[] files = directory.list(filter);
        for (int i = 0; i < files.length; i++) {
            list.addElement(new File(directory, files[i]));
        }
        files = null;   // we don't need it anymore
        if (recurse) {
            String[] subdirs = directory.list(DIRECTORY_FILTER);
            for (int i = 0; i < subdirs.length; i++) {
                listFilesTo(list, new File(directory, subdirs[i]), filter, recurse);
            }
        }
        return list;
    }

}

/** Convenient filter that accepts only directory <tt>File</tt> */
final class DirectoryFilter implements FilenameFilter {
    public boolean accept(File directory, String name) {
        File pathname = new File(directory, name);
        return pathname.isDirectory();
    }
}

/** convenient filter to accept only .class files */
final class ClassFilter implements FilenameFilter {
    public boolean accept(File dir, String name) {
        return name.endsWith(".class");
    }
}