/*
 * Copyright (c) 2017-2018 The Regents of the University of California
 *
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are
 * met:
 *
 * 1. Redistributions of source code must retain the above copyright
 * notice, this list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright
 * notice, this list of conditions and the following disclaimer in the
 * documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
 * HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */
package edu.berkeley.cs.jqf.instrument;

import java.io.BufferedInputStream;
import java.io.File;
import java.io.IOException;
import java.io.InputStream;
import java.lang.instrument.ClassFileTransformer;
import java.lang.instrument.IllegalClassFormatException;
import java.net.MalformedURLException;
import java.net.URL;
import java.net.URLClassLoader;

import janala.instrument.SnoopInstructionTransformer;

/**
 * @author Rohan Padhye
 */
public class InstrumentingClassLoader extends URLClassLoader {

    private ClassFileTransformer transformer = new SnoopInstructionTransformer();

    public InstrumentingClassLoader(URL[] urls, ClassLoader parent) {
        super(urls, parent);
    }

    public InstrumentingClassLoader(String[] paths, ClassLoader parent) throws MalformedURLException {
        this(stringsToUrls(paths), parent);
    }

    public static URL[] stringsToUrls(String[] paths) throws MalformedURLException {
        URL[] urls = new URL[paths.length];
        for (int i = 0; i < paths.length; i++) {
            urls[i] = new File(paths[i]).toURI().toURL();
        }
        return urls;
    }

    @Override
    public Class<?> findClass(String name) throws ClassNotFoundException {
        byte[] originalBytecode;

        // Try to read the class file in as a resource
        String internalName = name.replace('.', '/');
        String path = internalName.concat(".class");
        try (InputStream in = super.getResourceAsStream(path)) {
            if (in == null) {
                throw new ClassNotFoundException("Cannot find class " + name);
            }
            originalBytecode = in.readAllBytes();
        } catch (IOException e) {
            throw new ClassNotFoundException("I/O exception while loading class.", e);
        }

        assert (originalBytecode != null);

        byte[] bytesToLoad;
        try {
            byte[] instrumented = transformer.transform(this, internalName, null, null, originalBytecode);
            if (instrumented != null) {
                bytesToLoad = instrumented;
            } else {
                bytesToLoad = originalBytecode;
            }
        } catch (IllegalClassFormatException e) {
            bytesToLoad = originalBytecode;
        }
        return defineClass(name, bytesToLoad, 0, bytesToLoad.length);

    }

}
