/*
 * Copyright (c) 2000, 2017 Oracle and/or its affiliates. All rights reserved.
 *
 * This program and the accompanying materials are made available under the
 * terms of the Eclipse Public License v. 2.0, which is available at
 * http://www.eclipse.org/legal/epl-2.0.
 *
 * This Source Code may also be made available under the following Secondary
 * Licenses when the conditions for such availability set forth in the
 * Eclipse Public License v. 2.0 are satisfied: GNU General Public License,
 * version 2 with the GNU Classpath Exception, which is available at
 * https://www.gnu.org/software/classpath/license.html.
 *
 * SPDX-License-Identifier: EPL-2.0 OR GPL-2.0 WITH Classpath-exception-2.0
 */

package javax.xml.messaging;

import java.io.InputStream;
import java.io.File;
import java.io.FileInputStream;

import java.util.Properties;
import java.util.MissingResourceException;
import java.io.BufferedReader;
import java.io.InputStreamReader;
import com.sun.messaging.jmq.resources.SharedResources;

class FactoryFinder {

    private static final transient SharedResources cr = SharedResources.getResources();

    /**
     * Creates an instance of the specified class using the specified <code>ClassLoader</code> object.
     *
     * @exception JAXMException if the given class could not be found or could not be instantiated
     */
    private static Object newInstance(String className, ClassLoader classLoader) throws JAXMException {

        String emsg = "";
        try {
            emsg = cr.getKString(cr.X_NO_FACTORY_CLASS, className);
        } catch (MissingResourceException mre) {
        }

        try {
            Class spiClass;
            if (classLoader == null) {
                spiClass = Class.forName(className);
            } else {
                spiClass = classLoader.loadClass(className);
            }
            return spiClass.newInstance();
        } catch (ClassNotFoundException x) {
            throw new JAXMException(emsg);
            // "Provider " + className + " not found", x);
        } catch (Exception x) {
            throw new JAXMException(emsg);
            // "Provider " + className + " could not be instantiated: " + x,
            // x);
        }
    }

    /**
     * Finds the implementation <code>Class</code> object for the given factory name, or if that fails, finds the
     * <code>Class</code> object for the given fallback class name. The arguments supplied must be used in order. If using
     * the first argument is successful, the second one will not be used.
     * <P>
     * This method is package private so that this code can be shared.
     *
     * @return the <code>Class</code> object of the specified message factory; may not be <code>null</code>
     *
     * @param factoryId the name of the factory to find, which is a system property
     * @param fallbackClassName the implementation class name, which is to be used only if nothing else is found;
     * <code>null</code> to indicate that there is no fallback class name
     * @exception JAXMException if there is a SOAP error
     */
    static Object find(String factoryId, String fallbackClassName) throws JAXMException {
        ClassLoader classLoader;
        try {
            classLoader = Thread.currentThread().getContextClassLoader();
        } catch (Exception x) {
            throw new JAXMException(x.toString(), x);
        }

        // Use the system property first
        try {
            String systemProp = System.getProperty(factoryId);
            if (systemProp != null) {
                return newInstance(systemProp, classLoader);
            }
        } catch (SecurityException se) {
        }

        // try to read from $java.home/lib/jaxm.properties
        try {
            String javah = System.getProperty("java.home");
            String configFile = javah + File.separator + "lib" + File.separator + "jaxm.properties";
            File f = new File(configFile);
            if (f.exists()) {
                Properties props = new Properties();
                props.load(new FileInputStream(f));
                String factoryClassName = props.getProperty(factoryId);
                return newInstance(factoryClassName, classLoader);
            }
        } catch (Exception ex) {
        }

        String serviceId = "META-INF/services/" + factoryId;
        // try to find services in CLASSPATH
        try {
            InputStream is = null;
            if (classLoader == null) {
                is = ClassLoader.getSystemResourceAsStream(serviceId);
            } else {
                is = classLoader.getResourceAsStream(serviceId);
            }

            if (is != null) {
                BufferedReader rd = new BufferedReader(new InputStreamReader(is, "UTF-8"));

                String factoryClassName = rd.readLine();
                rd.close();

                if (factoryClassName != null && !"".equals(factoryClassName)) {
                    return newInstance(factoryClassName, classLoader);
                }
            }
        } catch (Exception ex) {
        }

        if (fallbackClassName == null) {
            throw new JAXMException("Provider for " + factoryId + " cannot be found", null);
        }

        return newInstance(fallbackClassName, classLoader);
    }
}
