/*
    * ====================================================================
    * 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.
   * ====================================================================
   *
   * This software consists of voluntary contributions made by many
   * individuals on behalf of the Apache Software Foundation.  For more
   * information on the Apache Software Foundation, please see
   * <http://www.apache.org/>.
   *
   */
  
  package org.apache.hc.client5.http.impl.nio;
  
  import java.io.IOException;
  import java.net.InetAddress;
  import java.net.InetSocketAddress;
  import java.net.SocketAddress;
  import java.net.UnknownHostException;
  import java.util.List;
  import java.util.concurrent.Future;
  import java.util.concurrent.atomic.AtomicInteger;
  
  import org.apache.hc.client5.http.ConnectExceptionSupport;
  import org.apache.hc.client5.http.DnsResolver;
  import org.apache.hc.client5.http.SystemDefaultDnsResolver;
  import org.apache.hc.core5.concurrent.ComplexFuture;
  import org.apache.hc.core5.concurrent.FutureCallback;
  import org.apache.hc.core5.net.NamedEndpoint;
  import org.apache.hc.core5.reactor.ConnectionInitiator;
  import org.apache.hc.core5.reactor.IOSession;
  import org.apache.hc.core5.util.Timeout;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  final class MultihomeIOSessionRequester {
  
      private static final Logger LOG = LoggerFactory.getLogger(MultihomeIOSessionRequester.class);
      private final DnsResolver dnsResolver;
  
      MultihomeIOSessionRequester(final DnsResolver dnsResolver) {
          this.dnsResolver = dnsResolver != null ? dnsResolver : SystemDefaultDnsResolver.INSTANCE;
      }
  
      public Future<IOSession> connect(
              final ConnectionInitiator connectionInitiator,
              final NamedEndpoint remoteEndpoint,
              final SocketAddress remoteAddress,
              final SocketAddress localAddress,
              final Timeout connectTimeout,
              final Object attachment,
              final FutureCallback<IOSession> callback) {
  
          final ComplexFuture<IOSession> future = new ComplexFuture<>(callback);
          if (remoteAddress != null) {
              if (LOG.isDebugEnabled()) {
                  LOG.debug("{}:{} connecting {} to {} ({})",
                          remoteEndpoint.getHostName(), remoteEndpoint.getPort(), localAddress, remoteAddress, connectTimeout);
              }
              final Future<IOSession> sessionFuture = connectionInitiator.connect(remoteEndpoint, remoteAddress, localAddress, connectTimeout, attachment, new FutureCallback<IOSession>() {
                  @Override
                  public void completed(final IOSession session) {
                      future.completed(session);
                  }
  
                  @Override
                  public void failed(final Exception cause) {
                      if (LOG.isDebugEnabled()) {
                          LOG.debug("{}:{} connection to {} failed ({}); terminating operation",
                                  remoteEndpoint.getHostName(), remoteEndpoint.getPort(), remoteAddress, cause.getClass());
                      }
                      if (cause instanceof IOException) {
                          future.failed(ConnectExceptionSupport.enhance((IOException) cause, remoteEndpoint,
                                  (remoteAddress instanceof InetSocketAddress) ?
                                          new InetAddress[] { ((InetSocketAddress) remoteAddress).getAddress() } :
                                          new InetAddress[] {}));
                      } else {
                          future.failed(cause);
                      }
                  }
  
                  @Override
                  public void cancelled() {
                      future.cancel();
                 }
 
             });
             future.setDependency(sessionFuture);
             return future;
         }
 
         if (LOG.isDebugEnabled()) {
             LOG.debug("{} resolving remote address", remoteEndpoint.getHostName());
         }
 
         final List<InetSocketAddress> remoteAddresses;
         try {
             remoteAddresses = dnsResolver.resolve(remoteEndpoint.getHostName(), remoteEndpoint.getPort());
             if (remoteAddresses == null || remoteAddresses.isEmpty()) {
                 throw new UnknownHostException(remoteEndpoint.getHostName());
             }
         } catch (final UnknownHostException ex) {
             future.failed(ex);
             return future;
         }
 
         if (LOG.isDebugEnabled()) {
             LOG.debug("{} resolved to {}", remoteEndpoint.getHostName(), remoteAddresses);
         }
 
         final Runnable runnable = new Runnable() {
 
             private final AtomicInteger attempt = new AtomicInteger(0);
 
             void executeNext() {
                 final int index = attempt.getAndIncrement();
                 final InetSocketAddress remoteAddress = remoteAddresses.get(index);
 
                 if (LOG.isDebugEnabled()) {
                     LOG.debug("{}:{} connecting {}->{} ({})",
                             remoteEndpoint.getHostName(), remoteEndpoint.getPort(), localAddress, remoteAddress, connectTimeout);
                 }
 
                 final Future<IOSession> sessionFuture = connectionInitiator.connect(
                         remoteEndpoint,
                         remoteAddress,
                         localAddress,
                         connectTimeout,
                         attachment,
                         new FutureCallback<IOSession>() {
 
                             @Override
                             public void completed(final IOSession session) {
                                 if (LOG.isDebugEnabled()) {
                                     LOG.debug("{}:{} connected {}->{} as {}",
                                             remoteEndpoint.getHostName(), remoteEndpoint.getPort(), localAddress, remoteAddress, session.getId());
                                 }
                                 future.completed(session);
                             }
 
                             @Override
                             public void failed(final Exception cause) {
                                 if (attempt.get() >= remoteAddresses.size()) {
                                     if (LOG.isDebugEnabled()) {
                                         LOG.debug("{}:{} connection to {} failed ({}); terminating operation",
                                                 remoteEndpoint.getHostName(), remoteEndpoint.getPort(), remoteAddress, cause.getClass());
                                     }
                                     if (cause instanceof IOException) {
                                         final InetAddress[] addresses = remoteAddresses.stream()
                                                 .filter(addr -> addr instanceof InetSocketAddress)
                                                 .map(addr -> ((InetSocketAddress) addr).getAddress())
                                                 .toArray(InetAddress[]::new);
                                         future.failed(ConnectExceptionSupport.enhance((IOException) cause, remoteEndpoint, addresses));
                                     } else {
                                         future.failed(cause);
                                     }
                                 } else {
                                     if (LOG.isDebugEnabled()) {
                                         LOG.debug("{}:{} connection to {} failed ({}); retrying connection to the next address",
                                                 remoteEndpoint.getHostName(), remoteEndpoint.getPort(), remoteAddress, cause.getClass());
                                     }
                                     executeNext();
                                 }
                             }
 
                             @Override
                             public void cancelled() {
                                 future.cancel();
                             }
 
                         });
                 future.setDependency(sessionFuture);
             }
 
             @Override
             public void run() {
                 executeNext();
             }
 
         };
         runnable.run();
         return future;
     }
 
     public Future<IOSession> connect(
             final ConnectionInitiator connectionInitiator,
             final NamedEndpoint remoteEndpoint,
             final SocketAddress localAddress,
             final Timeout connectTimeout,
             final Object attachment,
             final FutureCallback<IOSession> callback) {
         return connect(connectionInitiator, remoteEndpoint, null, localAddress, connectTimeout, attachment, callback);
     }
 
 }