package org.eclipse.aether.impl;
   
   /*
    * 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.
   */
  
  import java.lang.reflect.Constructor;
  import java.lang.reflect.Modifier;
  import java.util.ArrayList;
  import java.util.Collection;
  import java.util.Collections;
  import java.util.HashMap;
  import java.util.LinkedHashSet;
  import java.util.List;
  import java.util.Map;
  import static java.util.Objects.requireNonNull;
  
  import org.eclipse.aether.RepositorySystem;
  import org.eclipse.aether.internal.impl.DefaultArtifactResolver;
  import org.eclipse.aether.internal.impl.DefaultChecksumPolicyProvider;
  import org.eclipse.aether.internal.impl.collect.DefaultDependencyCollector;
  import org.eclipse.aether.internal.impl.DefaultDeployer;
  import org.eclipse.aether.internal.impl.DefaultFileProcessor;
  import org.eclipse.aether.internal.impl.DefaultInstaller;
  import org.eclipse.aether.internal.impl.DefaultLocalRepositoryProvider;
  import org.eclipse.aether.internal.impl.DefaultMetadataResolver;
  import org.eclipse.aether.internal.impl.DefaultOfflineController;
  import org.eclipse.aether.internal.impl.DefaultRemoteRepositoryManager;
  import org.eclipse.aether.internal.impl.DefaultRepositoryConnectorProvider;
  import org.eclipse.aether.internal.impl.DefaultRepositoryEventDispatcher;
  import org.eclipse.aether.internal.impl.DefaultRepositoryLayoutProvider;
  import org.eclipse.aether.internal.impl.DefaultRepositorySystem;
  import org.eclipse.aether.internal.impl.DefaultSyncContextFactory;
  import org.eclipse.aether.internal.impl.DefaultTransporterProvider;
  import org.eclipse.aether.internal.impl.DefaultUpdateCheckManager;
  import org.eclipse.aether.internal.impl.DefaultUpdatePolicyAnalyzer;
  import org.eclipse.aether.internal.impl.EnhancedLocalRepositoryManagerFactory;
  import org.eclipse.aether.internal.impl.Maven2RepositoryLayoutFactory;
  import org.eclipse.aether.internal.impl.SimpleLocalRepositoryManagerFactory;
  import org.eclipse.aether.internal.impl.slf4j.Slf4jLoggerFactory;
  import org.eclipse.aether.spi.connector.checksum.ChecksumPolicyProvider;
  import org.eclipse.aether.spi.connector.layout.RepositoryLayoutFactory;
  import org.eclipse.aether.spi.connector.layout.RepositoryLayoutProvider;
  import org.eclipse.aether.spi.connector.transport.TransporterProvider;
  import org.eclipse.aether.spi.io.FileProcessor;
  import org.eclipse.aether.spi.localrepo.LocalRepositoryManagerFactory;
  import org.eclipse.aether.spi.locator.Service;
  import org.eclipse.aether.spi.locator.ServiceLocator;
  import org.eclipse.aether.spi.log.LoggerFactory;
  
  /**
   * A simple service locator that is already setup with all components from this library. To acquire a complete
   * repository system, clients need to add an artifact descriptor reader, a version resolver, a version range resolver
   * and optionally some repository connector and transporter factories to access remote repositories. Once the locator is
   * fully populated, the repository system can be created like this:
   * 
   * <pre>
   * RepositorySystem repoSystem = serviceLocator.getService( RepositorySystem.class );
   * </pre>
   * 
   * <em>Note:</em> This class is not thread-safe. Clients are expected to create the service locator and the repository
   * system on a single thread.
   */
  public final class DefaultServiceLocator
      implements ServiceLocator
  {
  
      private class Entry<T>
      {
  
          private final Class<T> type;
  
          private final Collection<Object> providers;
  
          private List<T> instances;
  
          Entry( Class<T> type )
          {
              this.type = requireNonNull( type, "service type cannot be null" );
              providers = new LinkedHashSet<>( 8 );
          }
  
          public synchronized void setServices( T... services )
          {
             providers.clear();
             if ( services != null )
             {
                 for ( T service : services )
                 {
                     providers.add( requireNonNull( service, "service instance cannot be null" ) );
                 }
             }
             instances = null;
         }
 
         public synchronized void setService( Class<? extends T> impl )
         {
             providers.clear();
             addService( impl );
         }
 
         public synchronized void addService( Class<? extends T> impl )
         {
             providers.add( requireNonNull( impl, "implementation class cannot be null" ) );
             instances = null;
         }
 
         public T getInstance()
         {
             List<T> instances = getInstances();
             return instances.isEmpty() ? null : instances.get( 0 );
         }
 
         public synchronized List<T> getInstances()
         {
             if ( instances == null )
             {
                 instances = new ArrayList<>( providers.size() );
                 for ( Object provider : providers )
                 {
                     T instance;
                     if ( provider instanceof Class )
                     {
                         instance = newInstance( (Class<?>) provider );
                     }
                     else
                     {
                         instance = type.cast( provider );
                     }
                     if ( instance != null )
                     {
                         instances.add( instance );
                     }
                 }
                 instances = Collections.unmodifiableList( instances );
             }
             return instances;
         }
 
         private T newInstance( Class<?> impl )
         {
             try
             {
                 Constructor<?> constr = impl.getDeclaredConstructor();
                 if ( !Modifier.isPublic( constr.getModifiers() ) )
                 {
                     constr.setAccessible( true );
                 }
                 Object obj = constr.newInstance();
 
                 T instance = type.cast( obj );
                 if ( instance instanceof Service )
                 {
                     ( (Service) instance ).initService( DefaultServiceLocator.this );
                 }
                 return instance;
             }
             catch ( Exception | LinkageError e )
             {
                 serviceCreationFailed( type, impl, e );
             }
             return null;
         }
 
     }
 
     private final Map<Class<?>, Entry<?>> entries;
 
     private ErrorHandler errorHandler;
 
     /**
      * Creates a new service locator that already knows about all service implementations included this library.
      */
     public DefaultServiceLocator()
     {
         entries = new HashMap<>();
 
         addService( RepositorySystem.class, DefaultRepositorySystem.class );
         addService( ArtifactResolver.class, DefaultArtifactResolver.class );
         addService( DependencyCollector.class, DefaultDependencyCollector.class );
         addService( Deployer.class, DefaultDeployer.class );
         addService( Installer.class, DefaultInstaller.class );
         addService( MetadataResolver.class, DefaultMetadataResolver.class );
         addService( RepositoryLayoutProvider.class, DefaultRepositoryLayoutProvider.class );
         addService( RepositoryLayoutFactory.class, Maven2RepositoryLayoutFactory.class );
         addService( TransporterProvider.class, DefaultTransporterProvider.class );
         addService( ChecksumPolicyProvider.class, DefaultChecksumPolicyProvider.class );
         addService( RepositoryConnectorProvider.class, DefaultRepositoryConnectorProvider.class );
         addService( RemoteRepositoryManager.class, DefaultRemoteRepositoryManager.class );
         addService( UpdateCheckManager.class, DefaultUpdateCheckManager.class );
         addService( UpdatePolicyAnalyzer.class, DefaultUpdatePolicyAnalyzer.class );
         addService( FileProcessor.class, DefaultFileProcessor.class );
         addService( SyncContextFactory.class, DefaultSyncContextFactory.class );
         addService( RepositoryEventDispatcher.class, DefaultRepositoryEventDispatcher.class );
         addService( OfflineController.class, DefaultOfflineController.class );
         addService( LocalRepositoryProvider.class, DefaultLocalRepositoryProvider.class );
         addService( LocalRepositoryManagerFactory.class, SimpleLocalRepositoryManagerFactory.class );
         addService( LocalRepositoryManagerFactory.class, EnhancedLocalRepositoryManagerFactory.class );
         addService( LoggerFactory.class, Slf4jLoggerFactory.class );
     }
 
     private <T> Entry<T> getEntry( Class<T> type, boolean create )
     {
         @SuppressWarnings( "unchecked" )
         Entry<T> entry = (Entry<T>) entries.get( requireNonNull( type, "service type cannot be null" ) );
         if ( entry == null && create )
         {
             entry = new Entry<>( type );
             entries.put( type, entry );
         }
         return entry;
     }
 
     /**
      * Sets the implementation class for a service. The specified class must have a no-arg constructor (of any
      * visibility). If the service implementation itself requires other services for its operation, it should implement
      * {@link Service} to gain access to this service locator.
      * 
      * @param <T> The service type.
      * @param type The interface describing the service, must not be {@code null}.
      * @param impl The implementation class of the service, must not be {@code null}.
      * @return This locator for chaining, never {@code null}.
      */
     public <T> DefaultServiceLocator setService( Class<T> type, Class<? extends T> impl )
     {
         getEntry( type, true ).setService( impl );
         return this;
     }
 
     /**
      * Adds an implementation class for a service. The specified class must have a no-arg constructor (of any
      * visibility). If the service implementation itself requires other services for its operation, it should implement
      * {@link Service} to gain access to this service locator.
      * 
      * @param <T> The service type.
      * @param type The interface describing the service, must not be {@code null}.
      * @param impl The implementation class of the service, must not be {@code null}.
      * @return This locator for chaining, never {@code null}.
      */
     public <T> DefaultServiceLocator addService( Class<T> type, Class<? extends T> impl )
     {
         getEntry( type, true ).addService( impl );
         return this;
     }
 
     /**
      * Sets the instances for a service.
      * 
      * @param <T> The service type.
      * @param type The interface describing the service, must not be {@code null}.
      * @param services The instances of the service, may be {@code null} but must not contain {@code null} elements.
      * @return This locator for chaining, never {@code null}.
      */
     public <T> DefaultServiceLocator setServices( Class<T> type, T... services )
     {
         getEntry( type, true ).setServices( services );
         return this;
     }
 
     public <T> T getService( Class<T> type )
     {
         Entry<T> entry = getEntry( type, false );
         return ( entry != null ) ? entry.getInstance() : null;
     }
 
     public <T> List<T> getServices( Class<T> type )
     {
         Entry<T> entry = getEntry( type, false );
         return ( entry != null ) ? entry.getInstances() : null;
     }
 
     private void serviceCreationFailed( Class<?> type, Class<?> impl, Throwable exception )
     {
         if ( errorHandler != null )
         {
             errorHandler.serviceCreationFailed( type, impl, exception );
         }
     }
 
     /**
      * Sets the error handler to use.
      * 
      * @param errorHandler The error handler to use, may be {@code null} to ignore/swallow errors.
      */
     public void setErrorHandler( ErrorHandler errorHandler )
     {
         this.errorHandler = errorHandler;
     }
 
     /**
      * A hook to customize the handling of errors encountered while locating a service implementation.
      */
     public abstract static class ErrorHandler
     {
 
         /**
          * Handles errors during creation of a service. The default implemention does nothing.
          * 
          * @param type The interface describing the service, must not be {@code null}.
          * @param impl The implementation class of the service, must not be {@code null}.
          * @param exception The error that occurred while trying to instantiate the implementation class, must not be
          *            {@code null}.
          */
         public void serviceCreationFailed( Class<?> type, Class<?> impl, Throwable exception )
         {
         }
 
     }
 
 }