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SEMOSS
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package prerna.util;

import java.io.DataInputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.util.Hashtable;
import java.util.Map;

import org.apache.logging.log4j.LogManager;
import org.apache.logging.log4j.Logger;

public class SemossClassloader extends ClassLoader {

	private static final Logger classLogger = LogManager.getLogger(SemossClassloader.class);
	
	private String folder = null;
	private Map projectLoaded = new Hashtable<>();

	public void setFolder(String folder)
	{
		this.folder = folder;
	}

	public SemossClassloader(ClassLoader parent)
	{
		super(parent);
	}

	public void commitEngine(String projectId)
	{
		projectLoaded.put(projectId, true);
	}

	public void uncommitEngine(String projectId)
	{
		projectLoaded.remove(projectId);
	}

	public boolean isCommitted(String projectId)
	{
		return projectLoaded.containsKey(projectId);
	}

	/**
	 * Loads a given class from .class file just like
	 * the default ClassLoader. This method could be
	 * changed to load the class over network from some
	 * other server or from the database.
	 *
	 * @param name Full class name
	 */
	private Class getClass(String name) throws ClassNotFoundException {
		// We are getting a name that looks like
		// javablogging.package.ClassToLoad
		// and we have to convert it into the .class file name
		// like javablogging/package/ClassToLoad.class
		String file = name.replace('.', File.separatorChar)	+ ".class";
		byte[] b = null;
		try {
			// This loads the byte code data from the file
			b = loadClassData(file);
			// defineClass is inherited from the ClassLoader class
			// and converts the byte array into a Class
			if(b != null) {
				Class c = defineClass(name, b, 0, b.length);
				resolveClass(c);
				return c;
			}
		} catch (IOException e) {
			classLogger.error(Constants.STACKTRACE, e);
		}
		return null;
	}

	/**
	 * Every request for a class passes through this method.
	 * If the requested class is in "javablogging" package,
	 * it will load it using the
	 * {@link CustomClassLoader#getClass()} method.
	 * If not, it will use the super.loadClass() method
	 * which in turn will pass the request to the parent.
	 *
	 * @param name
	 *            Full class name
	 */
	@Override
	public Class loadClass(String name) throws ClassNotFoundException {
		Class retClass = null;
		// see if it is already loaded or in the classpath
		try {
			retClass = super.loadClass(name);
		} catch(Exception e) {
			// ignore
			//classLogger.error(Constants.STACKTRACE, e);
		}

		if (retClass == null) {
			classLogger.info("Project Specific Class " + name);
			retClass = getClass(name);
		}
		return retClass;
	}

	/**
	 * Loads a given file (presumably .class) into a byte array.
	 * The file should be accessible as a resource, for example
	 * it could be located on the classpath.
	 * 
	 * TODO: Need to incorporate loading jars. Not right now
	 *
	 * @param name File name to load
	 * @return Byte array read from the file
	 * @throws IOException Is thrown when there
	 *               was some problem reading the file
	 */
	private byte[] loadClassData(String name) throws IOException {
		FileInputStream stream = null;
		DataInputStream in = null;
		byte buff[] = null;
		try {
			stream = new FileInputStream(new File(folder + "/" + name));
			int size = stream.available();
			buff = new byte[size];
			in = new DataInputStream(stream);
			// Reading the binary data
			in.readFully(buff);
		} finally {
			try{
				if(stream!=null)
					stream.close();
			}catch(IOException e) {
				classLogger.error(Constants.STACKTRACE, e);
			}
			try{
				if(in!=null)
					in.close();
			}catch(IOException e) {
				classLogger.error(Constants.STACKTRACE, e);
			}
		}
		return buff;
	}


	protected Class	findClass(String name) throws ClassNotFoundException {
		return super.findClass(name);
	}

}