package com.quantum.util;

import java.io.File;
import java.io.IOException;
import java.net.MalformedURLException;
import java.net.URL;
import java.net.URLClassLoader;
import java.sql.Driver;
import java.util.ArrayList;
import java.util.Enumeration;
import java.util.Hashtable;
import java.util.List;
import java.util.jar.JarEntry;
import java.util.jar.JarFile;


/**
 * @author BC Holmes
 */
public class JarUtil {

    private static Hashtable classLoaderCache = new Hashtable();
	
	public static Driver loadDriver(String driverFile, String className) {
		Driver result = null;
		try {
			Class driverClass = loadDriverClass(driverFile, className);
			if (driverClass != null) {
	            try {
	            	result = (Driver) driverClass.newInstance();
	            } catch (ClassCastException e) {
	            }
	        }
		} catch (InstantiationException e) {
		} catch (IllegalAccessException e) {
		}
		return result;
	}
	
	public static Class loadDriverClass(String driverFile, String className) {
		Class result = null;
		if (driverFile != null && className != null) {
			try {
	        	File file = new File(driverFile);
	        	if (file.exists() && file.isFile()) {
	        		URLClassLoader loader = getURLClassLoader(file);
			        Class driverClass = loader.loadClass(className);
			        result = Driver.class.isAssignableFrom(driverClass) ? driverClass : null;
		        }
			} catch (MalformedURLException e) {
			} catch (ClassNotFoundException e) {
			}
		}
		return result;
	}
	
	public static String[] getAllDriverNames(String driverFile) {
		List list = new ArrayList();
		try {
			File file = new File(driverFile);
			URLClassLoader loader = getURLClassLoader(file);
			JarFile jar = new JarFile(file);
			for (Enumeration e = jar.entries(); e.hasMoreElements(); ) {
				JarEntry entry = (JarEntry) e.nextElement();
				String className = getClassNameFromFileName(entry.getName());
				if (className != null) {
					try {
						Class driverClass = loader.loadClass(className);
						if (Driver.class.isAssignableFrom(driverClass)) {
							list.add(className);
						}
					} catch (ClassNotFoundException ex) {
					}
				}
			}
		} catch (IOException e) {
		}
		return (String[]) list.toArray(new String[list.size()]);
	}
	
	private static String getClassNameFromFileName(String name) {
		String result = null;
		if (name.endsWith(".class")) {
			result = name.substring(0, name.length()-6).replace('/', '.').replace('\\', '.' );
		}
		return result;
	}

	/**
	 * @param file
	 * @return
	 * @throws MalformedURLException
	 */
	private static URLClassLoader getURLClassLoader(File file) throws MalformedURLException {
		String driverFile = file.getAbsolutePath();
		URLClassLoader loader =
		    (URLClassLoader) classLoaderCache.get(driverFile);
		if (loader == null) {
		    URL urls[] = new URL[1];
		    urls[0] = file.toURL();
		    loader = new URLClassLoader(urls);
		    classLoaderCache.put(driverFile, loader);
		}
		return loader;
	}
}