/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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.myfaces.test.base.junit.runners;

import java.io.ByteArrayOutputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.net.URL;
import java.util.Enumeration;
import java.util.Properties;
import java.util.StringTokenizer;
import java.util.Vector;
import java.util.zip.ZipEntry;
import java.util.zip.ZipFile;

/**
 * A Classloader that delegates the loading of the classes to the parent if it is in the 
 * excluded list or does it itself otherwise.
 * Useful for a system that sets up a classloader per Test system.
 *  
 * @author Rudy De Busscher
 * @since 1.0.0
 */
public class TestClassLoader extends ClassLoader
{
    /** scanned class path */
    private Vector<String> fPathItems;
    /** default excluded paths */
    private String[] defaultExclusions = { "junit.framework.",
            "junit.extensions.", "junit.runner." };
    /** name of excluded properties file */
    static final String EXCLUDED_FILE = "excluded.properties";
    /** excluded paths */
    private Vector<String> fExcluded;

    /**
     * Constructs a TestCaseLoader. It scans the class path
     * and the excluded package paths
     */
    public TestClassLoader()
    {
        this(System.getProperty("java.class.path"));
    }

    /**
     * Constructs a TestCaseLoader. It scans the class path
     * and the excluded package paths
     */
    public TestClassLoader(String classPath)
    {
        scanPath(classPath);
        readExcludedPackages();
    }

    private void scanPath(String classPath)
    {
        String separator = System.getProperty("path.separator");
        fPathItems = new Vector<String>(10);
        StringTokenizer st = new StringTokenizer(classPath, separator);
        while (st.hasMoreTokens())
        {
            fPathItems.addElement(st.nextToken());
        }
    }

    @Override
    public URL getResource(String name)
    {
        return ClassLoader.getSystemResource(name);
    }

    @Override
    public InputStream getResourceAsStream(String name)
    {
        return ClassLoader.getSystemResourceAsStream(name);
    }

    /**
     * Checks if path is excluded.
     * 
     * @param name the name
     * 
     * @return true, if is excluded
     */
    public boolean isExcluded(String name)
    {
        for (int i = 0; i < fExcluded.size(); i++)
        {
            if (name.startsWith((String) fExcluded.elementAt(i)))
            {
                return true;
            }
        }
        return false;
    }

    @Override
    public synchronized Class loadClass(String name, boolean resolve)
            throws ClassNotFoundException
    {

        Class c = findLoadedClass(name);
        if (c != null)
        {
            return c;
        }
        //
        // Delegate the loading of excluded classes to the
        // standard class loader.
        //
        if (isExcluded(name))
        {
            try
            {
                c = findSystemClass(name);
                return c;
            }
            catch (ClassNotFoundException e)
            {
                // keep searching
            }
        }
        if (c == null)
        {
            byte[] data = lookupClassData(name);
            if (data == null)
            {
                throw new ClassNotFoundException();
            }
            c = defineClass(name, data, 0, data.length);
        }
        if (resolve)
        {
            resolveClass(c);
        }
        return c;
    }

    /**
     * Lookup class data in one of the classpath elements configured.
     * 
     * @param className the class name
     * 
     * @return the bytes making up the class
     * 
     * @throws ClassNotFoundException when class can't be found on the classpath elements.
     */
    private byte[] lookupClassData(String className)
            throws ClassNotFoundException
    {
        byte[] data = null;
        for (int i = 0; i < fPathItems.size(); i++)
        {
            String path = (String) fPathItems.elementAt(i);
            String fileName = className.replace('.', '/') + ".class";
            if (isJar(path))
            {
                data = loadJarData(path, fileName);
            }
            else
            {
                data = loadFileData(path, fileName);
            }
            if (data != null)
            {
                return data;
            }
        }
        throw new ClassNotFoundException(className);
    }

    /**
     * Checks if is jar.
     * 
     * @param pathEntry the path entry
     * 
     * @return true, if is jar
     */
    boolean isJar(String pathEntry)
    {
        return pathEntry.endsWith(".jar") || pathEntry.endsWith(".zip");
    }

    /**
     * Load class bytes from file.
     * 
     * @param path the path
     * @param fileName the file name
     * 
     * @return the bytes making up the class
     */
    private byte[] loadFileData(String path, String fileName)
    {
        File file = new File(path, fileName);
        if (file.exists())
        {
            return getClassData(file);
        }
        return null;
    }

    private byte[] getClassData(File f)
    {
        try
        {
            FileInputStream stream = new FileInputStream(f);
            ByteArrayOutputStream out = new ByteArrayOutputStream(1000);
            byte[] b = new byte[1000];
            int n;
            while ((n = stream.read(b)) != -1)
            {
                out.write(b, 0, n);
            }
            stream.close();
            out.close();
            return out.toByteArray();

        }
        catch (IOException e)
        {
        }
        return null;
    }

    /**
     * Load class bytes from jar.
     * 
     * @param path the path
     * @param fileName the file name
     * 
     * @return the bytes making up the class
     */
    private byte[] loadJarData(String path, String fileName)
    {
        ZipFile zipFile = null;
        InputStream stream = null;
        File archive = new File(path);
        if (!archive.exists())
        {
            return null;
        }
        try
        {
            zipFile = new ZipFile(archive);
        }
        catch (IOException io)
        {
            return null;
        }
        ZipEntry entry = zipFile.getEntry(fileName);
        if (entry == null)
        {
            return null;
        }
        int size = (int) entry.getSize();
        try
        {
            stream = zipFile.getInputStream(entry);
            byte[] data = new byte[size];
            int pos = 0;
            while (pos < size)
            {
                int n = stream.read(data, pos, data.length - pos);
                pos += n;
            }
            zipFile.close();
            return data;
        }
        catch (IOException e)
        {
        }
        finally
        {
            try
            {
                if (stream != null)
                {
                    stream.close();
                }
            }
            catch (IOException e)
            {
            }
        }
        return null;
    }

    /**
     * Read excluded packages for which classes are read by the parent class loader.
     */
    private void readExcludedPackages()
    {
        fExcluded = new Vector<String>(10);
        for (int i = 0; i < defaultExclusions.length; i++)
        {
            fExcluded.addElement(defaultExclusions[i]);
        }

        InputStream is = getClass().getResourceAsStream(EXCLUDED_FILE);
        if (is == null)
        {
            return;
        }
        Properties p = new Properties();
        try
        {
            p.load(is);
        }
        catch (IOException e)
        {
            return;
        }
        finally
        {
            try
            {
                is.close();
            }
            catch (IOException e)
            {
            }
        }
        for (Enumeration e = p.propertyNames(); e.hasMoreElements();)
        {
            String key = (String) e.nextElement();
            if (key.startsWith("excluded."))
            {
                String path = p.getProperty(key);
                path = path.trim();
                if (path.endsWith("*"))
                {
                    path = path.substring(0, path.length() - 1);
                }
                if (path.length() > 0)
                {
                    fExcluded.addElement(path);
                }
            }
        }
    }
}