/*
 * Copyright (c) 2008-2012, Hazel Bilisim Ltd. All Rights Reserved.
 *
 * Licensed 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 com.hazelcast.impl.base;

import com.hazelcast.logging.ILogger;
import com.hazelcast.logging.Logger;
import com.hazelcast.nio.AbstractSerializer;

import java.io.BufferedReader;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.URL;
import java.util.Enumeration;
import java.util.logging.Level;

public final class NodeInitializerFactory {

    private static final ILogger logger = Logger.getLogger(NodeInitializerFactory.class.getName());
    private static final String FACTORY_ID = "com.hazelcast.NodeInitializer";

    public static NodeInitializer create() {
        NodeInitializer initializer = null;
        final String initializerClassname = ServiceLoader.load(FACTORY_ID);
        if (initializerClassname != null) {
            try {
                Class klass = AbstractSerializer.loadClass(initializerClassname);
                initializer = (NodeInitializer) AbstractSerializer.newInstance(klass);
            } catch (Exception e) {
                logger.log(Level.WARNING, "Initializer instance of class[" + initializerClassname + "] " +
                        "could not be instantiated! => "
                        + e.getClass().getName() + ": " + e.getMessage());
            }
        }
        return initializer != null ? initializer : createDefault();
    }

    public static NodeInitializer createDefault() {
        return new DefaultNodeInitializer();
    }

    /**
     * ServiceLoader utility similar to Java 6 ServiceLoader
     */
    private static class ServiceLoader {
        public static String load(String factoryId) {
            final ClassLoader cl = Thread.currentThread().getContextClassLoader();
            final String resourceName = "META-INF/services/" + factoryId;
            try {
                final Enumeration<URL> configs;
                if (cl != null) {
                    configs = cl.getResources(resourceName);
                } else {
                    configs = ClassLoader.getSystemResources(resourceName);
                }
                while (configs.hasMoreElements()) {
                    URL url = configs.nextElement();
                    InputStream in = url.openStream();
                    try {
                        BufferedReader r = new BufferedReader(new InputStreamReader(in, "UTF-8"));
                        while (true) {
                            String line = r.readLine();
                            if (line == null) {
                                break;
                            }
                            int comment = line.indexOf('#');
                            if (comment >= 0) {
                                line = line.substring(0, comment);
                            }
                            String name = line.trim();
                            if (name.length() == 0) {
                                continue;
                            }
                            return name;
                        }
                    } finally {
                        in.close();
                    }
                }
            } catch (Exception e) {
                logger.log(Level.WARNING, e.getMessage(), e);
            }
            return null;
        }
    }
}