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javaFMI is a Java Library for the functional mock-up interface (or FMI). FMI defines a standardized interface to be used in computer simulations. The FMI Standard has beed developed by a large number of software companies and research centers that have worked in a cooperation project under the name of MODELISAR. This library addresses the connection of a java application with a FMU (functional mock-up unit).

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/*
 *  Copyright 2013-2018 - Monentia
 *
 * Daccosim is a collaborative development effort between EDF (France),
 *  CentraleSupélec (France), EIFER Institute (Germany), SIANI institute (Spain)
 *  and Monentia S.L. (Spain)
 *
 *  This File is part of JavaFMI Project
 *
 *  JavaFMI Project is free software: you can redistribute it and/or modify
 *  it under the terms of the GNU Lesser General Public License as published by
 *  the Free Software Foundation, either version 3 of the License.
 *
 *  JavaFMI Project is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 *  GNU Lesser General Public License for more details.
 *
 *  You should have received a copy of the GNU Lesser General Public License
 *  along with JavaFMI. If not, see .
 */

package org.javafmi.kernel;

import java.io.ByteArrayOutputStream;
import java.io.File;
import java.io.IOException;
import java.io.InputStream;
import java.net.URL;
import java.net.URLConnection;
import java.nio.file.Files;
import java.nio.file.Path;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;

import static org.javafmi.kernel.Files.close;
import static org.javafmi.kernel.Files.copyFromTo;

public class JarClassLoader extends ClassLoader {
	private File jarFile;
	private File outFolder;
	private static List javaPackagePatterns = new ArrayList<>(Arrays.asList("java.", "sun.", "javax.", "com.sun.", "jdk."));

	public JarClassLoader(File jarFile) {
		this.jarFile = jarFile;
		this.outFolder = getTempDirectory().toFile();
	}

	public Path getTempDirectory() {
		try {
			return Files.createTempDirectory(getClass().getName());
		} catch (IOException e) {
			throw new RuntimeException("Impossible to create temp directory to extract " + jarFile.getName());
		}
	}

	public Class loadClass(String className) {
		if (isAFrameworkClass(className) || isAJavaClass(className)) return loadCLassUsingSuperClassLoader(className);
		byte[] classData = getClassBytes(getClassUrl(replaceDotWithSlash(className)));
		return defineClass(className, classData, 0, classData.length);
	}

	public boolean isAFrameworkClass(String className) {
		return className.startsWith("org.javafmi.framework");
	}

	public boolean isAJavaClass(String className) {
		for (String javaPackagePattern : javaPackagePatterns) if (className.startsWith(javaPackagePattern)) return true;
		return false;
	}

	public static void registerJavaPackage(String aPackage) {
		javaPackagePatterns.add(aPackage);
	}

	public URL getResource(String name) {
		try {
			return new Unzipper(jarFile).unzip(name, outFolder).toURI().toURL();
		} catch (Exception e) {
			return super.getResource(name);
		}
	}

	private Class loadCLassUsingSuperClassLoader(String className) {
		try {
			return super.loadClass(className);
		} catch (ClassNotFoundException e) {
			try {
				return this.getClass().getClassLoader().loadClass(className);
			} catch (ClassNotFoundException ignored) {
			}
			throw new RuntimeException(e);
		}
	}

	private String replaceDotWithSlash(String className) {
		while (className.indexOf('.') > 0)
			className = className.replace('.', '/');
		return className;
	}

	public URL getClassUrl(String className) {
		try {
			return new Unzipper(jarFile).unzip(className + ".class", outFolder).toURI().toURL();
		} catch (IOException e) {
			throw new RuntimeException("Problem getting the class URL " + className);
		}
	}

	private byte[] getClassBytes(URL classUrl) {
		InputStream input = getInputStreamFromConnection(classUrl);
		ByteArrayOutputStream buffer = new ByteArrayOutputStream();
		copyFromTo(input, buffer);
		close(input);
		close(buffer);
		return buffer.toByteArray();
	}

	private URLConnection openConnection(URL classUrl) {
		try {
			return classUrl.openConnection();
		} catch (IOException e) {
			throw new RuntimeException(e);
		}
	}

	private InputStream getInputStreamFromConnection(URL classUrl) {
		try {
			return openConnection(classUrl).getInputStream();
		} catch (IOException e) {
			throw new RuntimeException(e);
		}
	}
}