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/*
 * Copyright (c) 2011-2013 The original author or authors
 * ------------------------------------------------------
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * and Apache License v2.0 which accompanies this distribution.
 *
 *     The Eclipse Public License is available at
 *     http://www.eclipse.org/legal/epl-v10.html
 *
 *     The Apache License v2.0 is available at
 *     http://www.opensource.org/licenses/apache2.0.php
 *
 * You may elect to redistribute this code under either of these licenses.
 */

package io.vertx.core.net.impl;

import io.netty.channel.EventLoop;
import io.vertx.core.Handler;
import io.vertx.core.impl.ContextImpl;
import io.vertx.core.logging.Logger;
import io.vertx.core.logging.LoggerFactory;

import java.util.List;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentMap;
import java.util.concurrent.CopyOnWriteArrayList;

/**
 * @author Tim Fox
 */
public class HandlerManager {

  @SuppressWarnings("unused")
  private static final Logger log = LoggerFactory.getLogger(HandlerManager.class);

  private final VertxEventLoopGroup availableWorkers;
  private final ConcurrentMap> handlerMap = new ConcurrentHashMap<>();

  // We maintain a separate hasHandlers variable so we can implement hasHandlers() efficiently
  // As it is called for every HTTP message received
  private volatile boolean hasHandlers;

  public HandlerManager(VertxEventLoopGroup availableWorkers) {
    this.availableWorkers = availableWorkers;
  }

  public boolean hasHandlers() {
    return hasHandlers;
  }

  public HandlerHolder chooseHandler(EventLoop worker) {
    Handlers handlers = handlerMap.get(worker);
    return handlers == null ? null : handlers.chooseHandler();
  }

  public synchronized void addHandler(Handler handler, ContextImpl context) {
    EventLoop worker = context.nettyEventLoop();
    availableWorkers.addWorker(worker);
    Handlers handlers = new Handlers<>();
    Handlers prev = handlerMap.putIfAbsent(worker, handlers);
    if (prev != null) {
      handlers = prev;
    }
    handlers.addHandler(new HandlerHolder<>(context, handler));
    hasHandlers = true;
  }

  public synchronized void removeHandler(Handler handler, ContextImpl context) {
    EventLoop worker = context.nettyEventLoop();
    Handlers handlers = handlerMap.get(worker);
    if (!handlers.removeHandler(new HandlerHolder<>(context, handler))) {
      throw new IllegalStateException("Can't find handler");
    }
    if (handlers.isEmpty()) {
      handlerMap.remove(worker);
    }
    if (handlerMap.isEmpty()) {
      hasHandlers = false;
    }
    //Available workers does it's own reference counting -since workers can be shared across different Handlers
    availableWorkers.removeWorker(worker);
  }

  private static final class Handlers {
    private int pos;
    private final List> list = new CopyOnWriteArrayList<>();
    HandlerHolder chooseHandler() {
      HandlerHolder handler = list.get(pos);
      pos++;
      checkPos();
      return handler;
    }

    void addHandler(HandlerHolder handler) {
      list.add(handler);
    }

    boolean removeHandler(HandlerHolder handler) {
      if (list.remove(handler)) {
        checkPos();
        return true;
      } else {
        return false;
      }
    }

    boolean isEmpty() {
      return list.isEmpty();
    }

    void checkPos() {
      if (pos == list.size()) {
        pos = 0;
      }
    }
  }

}