/*
    * 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.util.concurrent;
  
  import io.netty5.util.internal.logging.InternalLogger;
  
  import java.util.Arrays;
  import java.util.EventListener;
  
  final class DefaultFutureListeners {
      private Object[] listeners;
      private int size;
  
      DefaultFutureListeners() {
          listeners = new Object[4];
      }
  
      public void add(Object listener, Object context) {
          Object[] listeners = this.listeners;
          int index = size << 1;
          if (index == listeners.length) {
              this.listeners = listeners = Arrays.copyOf(listeners, listeners.length << 1);
          }
          listeners[index] = listener;
          listeners[index + 1] = context;
          size++;
      }
  
      public void remove(EventListener listener) {
          final Object[] listeners = this.listeners;
          for (int i = 0, len = listeners.length; i < len; i += 2) {
              Object candidateListener = listeners[i]; // With associated context at listeners[i + 1]
              if (candidateListener == listener) {
                  int listenersToMove = len - i - 2;
                  if (listenersToMove > 0) {
                      System.arraycopy(listeners, i + 2, listeners, i, listenersToMove);
                  }
                  listeners[len - 2] = null;
                  listeners[len - 1] = null;
                  size--;
                  return;
              }
          }
      }
  
      @SuppressWarnings("unchecked")
      public <V> void notifyListeners(DefaultPromise<V> promise, InternalLogger logger) {
          int size = this.size;
          Object[] listeners = this.listeners;
          for (int i = 0, len = size << 1; i < len; i += 2) {
              Object listener = listeners[i];
              Object context = listeners[i + 1];
              try {
                  // Since a listener could in theory be both a FutureListener and a FutureContextListener,
                  // we use the presence of a context object to determine which one was meant when the listener
                  // was added. The context reference will never be null if the FutureContextListener was intended,
                  // even if the context passed was null. In that case, the reference will point to the
                  // NULL_CONTEXT, and we have to convert it back to null here.
                  if (context != null) {
                      FutureContextListener<Object, V> fcl = (FutureContextListener<Object, V>) listener;
                      fcl.operationComplete(context == DefaultPromise.NULL_CONTEXT ? null : context, promise);
                  } else if (listener instanceof FutureListener) {
                      FutureListener<V> fl = (FutureListener<V>) listener;
                      fl.operationComplete(promise);
                  } else if (listener != null) {
                      logger.warn("Unknown future listener type: {} of type {}", listener, listener.getClass());
                  } else {
                      break; // Listeners are always densely packed in the array, so finding a null means we're done.
                  }
              } catch (Throwable t) {
                  if (logger.isWarnEnabled()) {
                      String className = listener.getClass().getName();
                      logger.warn("An exception was thrown by " + className + ".operationComplete()", t);
                  }
              }
          }
      }
  }