/*
    * Copyright 2013 The Netty Project
    *
    * The Netty Project 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:
    *
    *   https://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 io.netty5.channel.group;
  
  import io.netty5.buffer.api.Buffer;
  import io.netty5.util.Resource;
  import io.netty5.channel.Channel;
  import io.netty5.channel.ChannelId;
  import io.netty5.channel.ServerChannel;
  import io.netty5.util.ReferenceCountUtil;
  import io.netty5.util.concurrent.EventExecutor;
  import io.netty5.util.concurrent.Future;
  import io.netty5.util.concurrent.FutureContextListener;
  import io.netty5.util.internal.StringUtil;
  
  import java.util.AbstractSet;
  import java.util.ArrayList;
  import java.util.Collection;
  import java.util.Iterator;
  import java.util.LinkedHashMap;
  import java.util.Map;
  import java.util.concurrent.ConcurrentHashMap;
  import java.util.concurrent.ConcurrentMap;
  import java.util.concurrent.atomic.AtomicInteger;
  
  import static java.util.Objects.requireNonNull;
  
  /**
   * The default {@link ChannelGroup} implementation.
   */
  public class DefaultChannelGroup extends AbstractSet<Channel> implements ChannelGroup {
  
      private static final AtomicInteger nextId = new AtomicInteger();
      private final String name;
      final EventExecutor executor;
      private final ConcurrentMap<ChannelId, Channel> serverChannels = new ConcurrentHashMap<>();
      private final ConcurrentMap<ChannelId, Channel> nonServerChannels = new ConcurrentHashMap<>();
      private final FutureContextListener<Channel, Void> remover = (channel, future) -> remove(channel);
      private final boolean stayClosed;
      private volatile boolean closed;
  
      /**
       * Creates a new group with a generated name and the provided {@link EventExecutor} to notify the
       * {@link ChannelGroupFuture}s.
       */
      public DefaultChannelGroup(EventExecutor executor) {
          this(executor, false);
      }
  
      /**
       * Creates a new group with the specified {@code name} and {@link EventExecutor} to notify the
       * {@link ChannelGroupFuture}s.  Please note that different groups can have the same name, which means no
       * duplicate check is done against group names.
       */
      public DefaultChannelGroup(String name, EventExecutor executor) {
          this(name, executor, false);
      }
  
      /**
       * Creates a new group with a generated name and the provided {@link EventExecutor} to notify the
       * {@link ChannelGroupFuture}s. {@code stayClosed} defines whether or not, this group can be closed
       * more than once. Adding channels to a closed group will immediately close them, too. This makes it
       * easy, to shutdown server and child channels at once.
       */
      public DefaultChannelGroup(EventExecutor executor, boolean stayClosed) {
          this("group-0x" + Integer.toHexString(nextId.incrementAndGet()), executor, stayClosed);
      }
  
      /**
       * Creates a new group with the specified {@code name} and {@link EventExecutor} to notify the
       * {@link ChannelGroupFuture}s. {@code stayClosed} defines whether or not, this group can be closed
       * more than once. Adding channels to a closed group will immediately close them, too. This makes it
       * easy, to shutdown server and child channels at once. Please note that different groups can have
       * the same name, which means no duplicate check is done against group names.
       */
      public DefaultChannelGroup(String name, EventExecutor executor, boolean stayClosed) {
          requireNonNull(name, "name");
          this.name = name;
          this.executor = executor;
          this.stayClosed = stayClosed;
      }
  
      @Override
      public String name() {
          return name;
      }
 
     @Override
     public Channel find(ChannelId id) {
         Channel c = nonServerChannels.get(id);
         if (c != null) {
             return c;
         } else {
             return serverChannels.get(id);
         }
     }
 
     @Override
     public boolean isEmpty() {
         return nonServerChannels.isEmpty() && serverChannels.isEmpty();
     }
 
     @Override
     public int size() {
         return nonServerChannels.size() + serverChannels.size();
     }
 
     @Override
     public boolean contains(Object o) {
         if (o instanceof ServerChannel) {
             return serverChannels.containsValue(o);
         } else if (o instanceof Channel) {
             return nonServerChannels.containsValue(o);
         }
         return false;
     }
 
     @Override
     public boolean add(Channel channel) {
         ConcurrentMap<ChannelId, Channel> map =
             channel instanceof ServerChannel? serverChannels : nonServerChannels;
 
         boolean added = map.putIfAbsent(channel.id(), channel) == null;
         if (added) {
             channel.closeFuture().addListener(channel, remover);
         }
 
         if (stayClosed && closed) {
 
             // First add channel, than check if closed.
             // Seems inefficient at first, but this way a volatile
             // gives us enough synchronization to be thread-safe.
             //
             // If true: Close right away.
             // (Might be closed a second time by ChannelGroup.close(), but this is ok)
             //
             // If false: Channel will definitely be closed by the ChannelGroup.
             // (Because closed=true always happens-before ChannelGroup.close())
             //
             // See https://github.com/netty/netty/issues/4020
             channel.close();
         }
 
         return added;
     }
 
     @Override
     public boolean remove(Object o) {
         Channel c = null;
         if (o instanceof ChannelId) {
             c = nonServerChannels.remove(o);
             if (c == null) {
                 c = serverChannels.remove(o);
             }
         } else if (o instanceof Channel) {
             c = (Channel) o;
             if (c instanceof ServerChannel) {
                 c = serverChannels.remove(c.id());
             } else {
                 c = nonServerChannels.remove(c.id());
             }
         }
 
         return c != null;
     }
 
     @Override
     public void clear() {
         nonServerChannels.clear();
         serverChannels.clear();
     }
 
     @Override
     public Iterator<Channel> iterator() {
         return new CombinedIterator<>(
                 serverChannels.values().iterator(),
                 nonServerChannels.values().iterator());
     }
 
     @Override
     public Object[] toArray() {
         Collection<Channel> channels = new ArrayList<>(size());
         channels.addAll(serverChannels.values());
         channels.addAll(nonServerChannels.values());
         return channels.toArray();
     }
 
     @Override
     public <T> T[] toArray(T[] a) {
         Collection<Channel> channels = new ArrayList<>(size());
         channels.addAll(serverChannels.values());
         channels.addAll(nonServerChannels.values());
         return channels.toArray(a);
     }
 
     @Override
     public ChannelGroupFuture close() {
         return close(ChannelMatchers.all());
     }
 
     @Override
     public ChannelGroupFuture disconnect() {
         return disconnect(ChannelMatchers.all());
     }
 
     @Override
     public ChannelGroupFuture deregister() {
         return deregister(ChannelMatchers.all());
     }
 
     @Override
     public ChannelGroupFuture write(Object message) {
         return write(message, ChannelMatchers.all());
     }
 
     // Create a safe duplicate of the message to write it to a channel but not affect other writes.
     // See https://github.com/netty/netty/issues/1461
     private static Object safeDuplicate(Object message) {
         if (message instanceof Buffer) {
             return ((Buffer) message).copy();
         } else {
             return ReferenceCountUtil.retain(message);
         }
     }
 
     @Override
     public ChannelGroupFuture write(Object message, ChannelMatcher matcher) {
         requireNonNull(message, "message");
         requireNonNull(matcher, "matcher");
 
         Map<Channel, Future<Void>> futures = new LinkedHashMap<>(nonServerChannels.size());
         for (Channel c: nonServerChannels.values()) {
             if (matcher.matches(c)) {
                 futures.put(c, c.write(safeDuplicate(message)));
             }
         }
         ChannelGroupFuture future = new DefaultChannelGroupFuture(this, futures, executor);
         Resource.dispose(message);
         return future;
     }
 
     @Override
     public ChannelGroup flush() {
         return flush(ChannelMatchers.all());
     }
 
     @Override
     public ChannelGroupFuture flushAndWrite(Object message) {
         return writeAndFlush(message);
     }
 
     @Override
     public ChannelGroupFuture writeAndFlush(Object message) {
         return writeAndFlush(message, ChannelMatchers.all());
     }
 
     @Override
     public ChannelGroupFuture disconnect(ChannelMatcher matcher) {
         requireNonNull(matcher, "matcher");
 
         Map<Channel, Future<Void>> futures =
                 new LinkedHashMap<>(size());
 
         for (Channel c: serverChannels.values()) {
             if (matcher.matches(c)) {
                 futures.put(c, c.disconnect());
             }
         }
         for (Channel c: nonServerChannels.values()) {
             if (matcher.matches(c)) {
                 futures.put(c, c.disconnect());
             }
         }
 
         return new DefaultChannelGroupFuture(this, futures, executor);
     }
 
     @Override
     public ChannelGroupFuture close(ChannelMatcher matcher) {
         requireNonNull(matcher, "matcher");
 
         Map<Channel, Future<Void>> futures =
                 new LinkedHashMap<>(size());
 
         if (stayClosed) {
             // It is important to set the closed to true, before closing channels.
             // Our invariants are:
             // closed=true happens-before ChannelGroup.close()
             // ChannelGroup.add() happens-before checking closed==true
             //
             // See https://github.com/netty/netty/issues/4020
             closed = true;
         }
 
         for (Channel c: serverChannels.values()) {
             if (matcher.matches(c)) {
                 futures.put(c, c.close());
             }
         }
         for (Channel c: nonServerChannels.values()) {
             if (matcher.matches(c)) {
                 futures.put(c, c.close());
             }
         }
 
         return new DefaultChannelGroupFuture(this, futures, executor);
     }
 
     @Override
     public ChannelGroupFuture deregister(ChannelMatcher matcher) {
         requireNonNull(matcher, "matcher");
 
         Map<Channel, Future<Void>> futures =
                 new LinkedHashMap<>(size());
 
         for (Channel c: serverChannels.values()) {
             if (matcher.matches(c)) {
                 futures.put(c, c.deregister());
             }
         }
         for (Channel c: nonServerChannels.values()) {
             if (matcher.matches(c)) {
                 futures.put(c, c.deregister());
             }
         }
 
         return new DefaultChannelGroupFuture(this, futures, executor);
     }
 
     @Override
     public ChannelGroup flush(ChannelMatcher matcher) {
         for (Channel c: nonServerChannels.values()) {
             if (matcher.matches(c)) {
                 c.flush();
             }
         }
         return this;
     }
 
     @Override
     public ChannelGroupFuture flushAndWrite(Object message, ChannelMatcher matcher) {
         return writeAndFlush(message, matcher);
     }
 
     @Override
     public ChannelGroupFuture writeAndFlush(Object message, ChannelMatcher matcher) {
         requireNonNull(message, "message");
 
         Map<Channel, Future<Void>> futures = new LinkedHashMap<>(nonServerChannels.size());
         for (Channel c: nonServerChannels.values()) {
             if (matcher.matches(c)) {
                 futures.put(c, c.writeAndFlush(safeDuplicate(message)));
             }
         }
         final ChannelGroupFuture future = new DefaultChannelGroupFuture(this, futures, executor);
         Resource.dispose(message);
         return future;
     }
 
     @Override
     public ChannelGroupFuture newCloseFuture() {
         return newCloseFuture(ChannelMatchers.all());
     }
 
     @Override
     public ChannelGroupFuture newCloseFuture(ChannelMatcher matcher) {
         Map<Channel, Future<Void>> futures =
                 new LinkedHashMap<>(size());
 
         for (Channel c: serverChannels.values()) {
             if (matcher.matches(c)) {
                 futures.put(c, c.closeFuture());
             }
         }
         for (Channel c: nonServerChannels.values()) {
             if (matcher.matches(c)) {
                 futures.put(c, c.closeFuture());
             }
         }
 
         return new DefaultChannelGroupFuture(this, futures, executor);
     }
 
     @Override
     public int hashCode() {
         return System.identityHashCode(this);
     }
 
     @Override
     public boolean equals(Object o) {
         return this == o;
     }
 
     @Override
     public int compareTo(ChannelGroup o) {
         int v = name().compareTo(o.name());
         if (v != 0) {
             return v;
         }
 
         return System.identityHashCode(this) - System.identityHashCode(o);
     }
 
     @Override
     public String toString() {
         return StringUtil.simpleClassName(this) + "(name: " + name() + ", size: " + size() + ')';
     }
 }