/*
 *  This file is part of the Jikes RVM project (http://jikesrvm.org).
 *
 *  This file is licensed to You under the Eclipse Public License (EPL);
 *  You may not use this file except in compliance with the License. You
 *  may obtain a copy of the License at
 *
 *      http://www.opensource.org/licenses/eclipse-1.0.php
 *
 *  See the COPYRIGHT.txt file distributed with this work for information
 *  regarding copyright ownership.
 */
package org.jikesrvm.classloader;

import java.io.File;
import java.net.MalformedURLException;
import java.net.URL;
import java.net.URLClassLoader;
import java.util.StringTokenizer;

import org.jikesrvm.VM;
import org.jikesrvm.runtime.Magic;
import org.jikesrvm.util.Services;

/**
 * The class loader used by Jikes RVM to load the application program.  Since
 * version 1.2 of the Sun API docs, the Application ClassLoader  and the
 * System Class Loader are officially the same thing.  (What Jikes RVM used to
 * call the "System Class Loader" is officially the "Bootstrap Class
 * Loader".)
 * <p>
 * We use a two-link chain.  An ordinary user's class is loaded by this class
 * loader.  This class loader first delegates to its parent (the Bootstrap
 * Class Loader) before trying the class itself.
 * <p>
 *  Renamed the former "system class loader" to the "bootstrap class loader".
 */
public class ApplicationClassLoader extends URLClassLoader {

  static final boolean DBG = false;

  static int numInstantiations = 0;

  /** For status printing, to make sure that, if an application class loader is
   *  created at boot image writing time, it won't leak out into the next
   *  mode.   This is actually not used any more, but it should never hurt,
   *  and can give one a sense of confidence when debugging Jikes RVM's
   *  classloaders.
   *  */
  private final boolean createdAtBootImageWritingTime;
  private final boolean createdWithRunningVM;

  public ApplicationClassLoader(String specifiedClasspath) {
    super(new URL[0]);
    if (DBG) {
      VM.sysWriteln("The Application Class Loader has been instantiated ", numInstantiations, " times");
    }
    ++numInstantiations;

    createdAtBootImageWritingTime = VM.writingBootImage;
    createdWithRunningVM = VM.runningVM;

    try {
      if (specifiedClasspath == null) {
        addURL(new URL("file", null, -1, System.getProperty("user.dir") + File.separator));
      } else {
        StringTokenizer tok = new StringTokenizer(specifiedClasspath, File.pathSeparator);
        while (tok.hasMoreElements()) {
          String elt = tok.nextToken();

          if (!(elt.endsWith(".jar") || elt.endsWith(".zip"))) {
            if (!elt.endsWith(File.separator)) {
              elt += File.separator;
            }
          }

          if (elt.indexOf(File.pathSeparatorChar) != -1) {
            addURL(new URL(elt));
          } else if (elt.startsWith(File.separator)) {
            addURL(new URL("file", null, -1, elt));
          } else {
            addURL(new URL("file", null, -1, System.getProperty("user.dir") + File.separator + elt));
          }
        }
      }
    } catch (MalformedURLException e) {
      VM.sysFail(
          "JikesRVM: ApplicationClassLoader: Initialization Failed with a MalformedURLException; there was an error setting the application's classpath: " +
          e);
    }
  }

  /** Name of the Application Class Loader.  Actually used by Jikes RVM's
   * serialization code.
   * <P>
   * I intended this name to reflect both "SystemClassLoader" and
   * "ApplicationClassLoader".
   */
  public static final String myName = "SystemAppCL";

  @Override
  public String toString() {
    return myName +
           (createdAtBootImageWritingTime ? "-createdAtBootImageWritingTime" : "") +
           (createdWithRunningVM ? "" : "-NOTcreatedWithRunningVM") +
           (DBG ? "@" + Services.addressAsHexString(Magic.objectAsAddress(this)) : "");
  }

  @Override
  protected String findLibrary(String libName) {
    return null;
  }
}