/*
 * 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.tamaya.core.internal;

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

import org.apache.tamaya.spisupport.PriorityServiceComparator;
import org.osgi.framework.Bundle;
import org.osgi.framework.BundleContext;
import org.osgi.framework.BundleEvent;
import org.osgi.framework.BundleListener;
import org.osgi.framework.Constants;
import org.osgi.framework.ServiceFactory;
import org.osgi.framework.ServiceReference;
import org.osgi.framework.ServiceRegistration;

/**
 * A bundle listener that registers services defined in META-INF/services, when
 * a bundle is starting.
 *
 * @author anatole@apache.org
 */
@SuppressWarnings("rawtypes")
public class OSGIServiceLoader implements BundleListener {
    // Provide logging
    private static final Logger LOG = Logger.getLogger(OSGIServiceLoader.class.getName());
    private static final String META_INF_SERVICES = "META-INF/services/";

    private BundleContext context;

    private Set<Bundle> resourceBundles = Collections.synchronizedSet(new HashSet<Bundle>());

    public OSGIServiceLoader(BundleContext context) {
        this.context = Objects.requireNonNull(context);
        // Check for matching bundles already installed...
        for (Bundle bundle : context.getBundles()) {
            if (bundle.getState() == Bundle.ACTIVE) {
                checkAndLoadBundle(bundle);
            }
        }
    }

    public BundleContext getBundleContext() {
        return context;
    }

    public Set<Bundle> getResourceBundles() {
        synchronized (resourceBundles) {
            return new HashSet<>(resourceBundles);
        }
    }

    @Override
    public void bundleChanged(BundleEvent bundleEvent) {
        // Parse and createObject metadata when installed
        if (bundleEvent.getType() == BundleEvent.STARTED) {
            Bundle bundle = bundleEvent.getBundle();
            checkAndLoadBundle(bundle);
        } else if (bundleEvent.getType() == BundleEvent.STOPPED) {
            Bundle bundle = bundleEvent.getBundle();
            checkAndUnloadBundle(bundle);
        }
    }

    private void checkAndUnloadBundle(Bundle bundle) {
        if (bundle.getEntry(META_INF_SERVICES) == null) {
            return;
        }
        synchronized (resourceBundles) {
            resourceBundles.remove(bundle);
            LOG.fine("Unregistered ServiceLoader bundle: " + bundle.getSymbolicName());
        }
        Enumeration<String> entryPaths = bundle.getEntryPaths(META_INF_SERVICES);
        while (entryPaths.hasMoreElements()) {
            String entryPath = entryPaths.nextElement();
            if (!entryPath.endsWith("/")) {
                removeEntryPath(bundle, entryPath);
            }
        }
    }

    private void checkAndLoadBundle(Bundle bundle) {
        if (bundle.getEntry(META_INF_SERVICES) == null) {
            return;
        }
        synchronized (resourceBundles) {
            resourceBundles.add(bundle);
            LOG.info("Registered ServiceLoader bundle: " + bundle.getSymbolicName());
        }
        Enumeration<String> entryPaths = bundle.getEntryPaths(META_INF_SERVICES);
        while (entryPaths.hasMoreElements()) {
            String entryPath = entryPaths.nextElement();
            if (!entryPath.endsWith("/")) {
                processEntryPath(bundle, entryPath);
            }
        }
    }

    private void processEntryPath(Bundle bundle, String entryPath) {
        try {
            String serviceName = entryPath.substring(META_INF_SERVICES.length());
            if (!serviceName.startsWith("org.apache.tamaya")) {
                // Ignore non Tamaya entries...
                return;
            }
            Class<?> serviceClass = bundle.loadClass(serviceName);
            URL child = bundle.getEntry(entryPath);
            InputStream inStream = child.openStream();
            LOG.info("Loading Services " + serviceClass.getName() + " from bundle...: " + bundle.getSymbolicName());
            try (BufferedReader br = new BufferedReader(new InputStreamReader(inStream, "UTF-8"))) {
                String implClassName = br.readLine();
                while (implClassName != null) {
                    int hashIndex = implClassName.indexOf("#");
                    if (hashIndex > 0) {
                        implClassName = implClassName.substring(0, hashIndex - 1);
                    } else if (hashIndex == 0) {
                        implClassName = "";
                    }
                    implClassName = implClassName.trim();
                    if (implClassName.length() > 0) {
                        try {
                            // Load the service class
                            LOG.fine("Loading Class " + implClassName + " from bundle...: " + bundle.getSymbolicName());
                            Class<?> implClass = bundle.loadClass(implClassName);
                            if (!serviceClass.isAssignableFrom(implClass)) {
                                LOG.warning("Configured service: " + implClassName + " is not assignable to "
                                        + serviceClass.getName());
                                continue;
                            }
                            LOG.info("Loaded Service Factory (" + serviceName + "): " + implClassName);
                            // Provide service properties
                            Hashtable<String, String> props = new Hashtable<>();
                            props.put(Constants.VERSION_ATTRIBUTE, bundle.getVersion().toString());
                            String vendor = bundle.getHeaders().get(Constants.BUNDLE_VENDOR);
                            props.put(Constants.SERVICE_VENDOR, (vendor != null ? vendor : "anonymous"));
                            // Translate annotated @Priority into a service ranking
                            props.put(Constants.SERVICE_RANKING,
                                    String.valueOf(PriorityServiceComparator.getPriority(implClass)));

                            // Register the service factory on behalf of the intercepted bundle
                            JDKUtilServiceFactory factory = new JDKUtilServiceFactory(implClass);
                            BundleContext bundleContext = bundle.getBundleContext();
                            bundleContext.registerService(serviceName, factory, props);
                            LOG.info("Registered Tamaya service class: " + implClassName + "(" + serviceName + ")");
                        } catch (Exception e) {
                            LOG.log(Level.SEVERE, "Failed to load service: " + implClassName, e);
                        } catch (NoClassDefFoundError err) {
                            LOG.log(Level.SEVERE, "Failed to load service: " + implClassName, err);
                        }
                    }
                    implClassName = br.readLine();
                }
            }
        } catch (RuntimeException rte) {
            throw rte;
        } catch (Exception e) {
            LOG.log(Level.SEVERE, "Failed to read services from: " + entryPath, e);
        }
    }

    private void removeEntryPath(Bundle bundle, String entryPath) {
        try {
            String serviceName = entryPath.substring(META_INF_SERVICES.length());
            if (!serviceName.startsWith("org.apache.tamaya")) {
                // Ignore non Tamaya entries...
                return;
            }
            Class<?> serviceClass = bundle.loadClass(serviceName);

            URL child = bundle.getEntry(entryPath);
            InputStream inStream = child.openStream();

            BufferedReader br = new BufferedReader(new InputStreamReader(inStream, "UTF-8"));
            String implClassName = br.readLine();
            while (implClassName != null) {
                int hashIndex = implClassName.indexOf("#");
                if (hashIndex > 0) {
                    implClassName = implClassName.substring(0, hashIndex - 1);
                } else if (hashIndex == 0) {
                    implClassName = "";
                }
                implClassName = implClassName.trim();
                if (implClassName.length() > 0) {
                    LOG.fine("Unloading Service (" + serviceName + "): " + implClassName);
                    try {
                        // Load the service class
                        Class<?> implClass = bundle.loadClass(implClassName);
                        if (!serviceClass.isAssignableFrom(implClass)) {
                            LOG.warning("Configured service: " + implClassName + " is not assignable to "
                                    + serviceClass.getName());
                            continue;
                        }
                        ServiceReference<?> ref = bundle.getBundleContext().getServiceReference(implClass);
                        if (ref != null) {
                            bundle.getBundleContext().ungetService(ref);
                        }
                    } catch (Exception e) {
                        LOG.log(Level.SEVERE, "Failed to unload service: " + implClassName, e);
                    } catch (NoClassDefFoundError err) {
                        LOG.log(Level.SEVERE, "Failed to unload service: " + implClassName, err);
                    }
                }
                implClassName = br.readLine();
            }
            br.close();
        } catch (RuntimeException rte) {
            throw rte;
        } catch (Exception e) {
            LOG.log(Level.SEVERE, "Failed to read services from: " + entryPath, e);
        }
    }

    /**
     * Service factory simply instantiating the configured service.
     */
    static class JDKUtilServiceFactory implements ServiceFactory {
        private final Class<?> serviceClass;

        public JDKUtilServiceFactory(Class<?> serviceClass) {
            this.serviceClass = serviceClass;
        }

        @Override
        public Object getService(Bundle bundle, ServiceRegistration registration) {
            try {
                LOG.fine("Creating Service...:" + serviceClass.getName());
                return serviceClass.getConstructor().newInstance();
            } catch (Exception ex) {
                throw new IllegalStateException("Failed to createObject service: " + serviceClass.getName(), ex);
            }
        }

        @Override
        public void ungetService(Bundle bundle, ServiceRegistration registration, Object service) {
        }
    }
}