/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.catalina.tribes.io;

import java.io.IOException;
import java.io.InputStream;
import java.io.ObjectInputStream;
import java.io.ObjectStreamClass;
import java.lang.reflect.Modifier;
import java.lang.reflect.Proxy;

import org.apache.catalina.tribes.util.StringManager;

/**
 * Custom subclass of <code>ObjectInputStream</code> that loads from the class loader for this web application. This
 * allows classes defined only with the web application to be found correctly.
 */
public final class ReplicationStream extends ObjectInputStream {

    static final StringManager sm = StringManager.getManager(ReplicationStream.class);

    /**
     * The class loader we will use to resolve classes.
     */
    private ClassLoader[] classLoaders;

    /**
     * Construct a new instance of CustomObjectInputStream
     *
     * @param stream       The input stream we will read from
     * @param classLoaders The class loader array used to instantiate objects
     *
     * @exception IOException if an input/output error occurs
     */
    public ReplicationStream(InputStream stream, ClassLoader[] classLoaders) throws IOException {

        super(stream);
        this.classLoaders = classLoaders;
    }

    /**
     * Load the local class equivalent of the specified stream class description, by using the class loader assigned to
     * this Context.
     *
     * @param classDesc Class description from the input stream
     *
     * @exception ClassNotFoundException if this class cannot be found
     * @exception IOException            if an input/output error occurs
     */
    @Override
    public Class<?> resolveClass(ObjectStreamClass classDesc) throws ClassNotFoundException, IOException {
        String name = classDesc.getName();
        try {
            return resolveClass(name);
        } catch (ClassNotFoundException e) {
            return super.resolveClass(classDesc);
        }
    }

    /**
     * Resolve a class by name using the configured class loaders.
     *
     * @param name the class name
     * @return the resolved class
     * @exception ClassNotFoundException if this class cannot be found
     */
    public Class<?> resolveClass(String name) throws ClassNotFoundException {

        boolean tryRepFirst = name.startsWith("org.apache.catalina.tribes");
        try {
            if (tryRepFirst) {
                return findReplicationClass(name);
            } else {
                return findExternalClass(name);
            }
        } catch (Exception e) {
            if (tryRepFirst) {
                return findExternalClass(name);
            } else {
                return findReplicationClass(name);
            }
        }
    }

    /**
     * ObjectInputStream.resolveProxyClass has some funky way of using the incorrect class loader to resolve proxy
     * classes, let's do it our way instead
     */
    @Override
    protected Class<?> resolveProxyClass(String[] interfaces) throws IOException, ClassNotFoundException {

        ClassLoader latestLoader;
        if (classLoaders.length > 0) {
            latestLoader = classLoaders[0];
        } else {
            latestLoader = null;
        }
        ClassLoader nonPublicLoader = null;
        boolean hasNonPublicInterface = false;

        // define proxy in class loader of non-public interface(s), if any
        Class<?>[] classObjs = new Class[interfaces.length];
        for (int i = 0; i < interfaces.length; i++) {
            Class<?> cl = this.resolveClass(interfaces[i]);
            if (latestLoader == null) {
                latestLoader = cl.getClassLoader();
            }
            if ((cl.getModifiers() & Modifier.PUBLIC) == 0) {
                if (hasNonPublicInterface) {
                    if (nonPublicLoader != cl.getClassLoader()) {
                        throw new IllegalAccessError(sm.getString("replicationStream.conflict"));
                    }
                } else {
                    nonPublicLoader = cl.getClassLoader();
                    hasNonPublicInterface = true;
                }
            }
            classObjs[i] = cl;
        }
        try {
            // @SuppressWarnings("deprecation") Java 9
            Class<?> proxyClass =
                    Proxy.getProxyClass(hasNonPublicInterface ? nonPublicLoader : latestLoader, classObjs);
            return proxyClass;
        } catch (IllegalArgumentException e) {
            throw new ClassNotFoundException(null, e);
        }
    }


    /**
     * Find a replication class by name using the class loader of this class.
     *
     * @param name the class name
     * @return the resolved class
     * @exception ClassNotFoundException if this class cannot be found
     */
    public Class<?> findReplicationClass(String name) throws ClassNotFoundException {
        return Class.forName(name, false, getClass().getClassLoader());
    }

    /**
     * Find an external class by name using the configured class loaders.
     *
     * @param name the class name
     * @return the resolved class
     * @exception ClassNotFoundException if this class cannot be found
     */
    public Class<?> findExternalClass(String name) throws ClassNotFoundException {
        ClassNotFoundException cnfe = null;
        for (ClassLoader classLoader : classLoaders) {
            try {
                return Class.forName(name, false, classLoader);
            } catch (ClassNotFoundException x) {
                cnfe = x;
            }
        }
        if (cnfe != null) {
            throw cnfe;
        } else {
            throw new ClassNotFoundException(name);
        }
    }

    @Override
    public void close() throws IOException {
        this.classLoaders = null;
        super.close();
    }


}
