/*
    * 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.nio;
  
  import java.nio.channels.SelectionKey;
  import java.util.AbstractSet;
  import java.util.Arrays;
  import java.util.Iterator;
  import java.util.NoSuchElementException;
  
  final class SelectedSelectionKeySet extends AbstractSet<SelectionKey> {
  
      SelectionKey[] keys;
      int size;
  
      SelectedSelectionKeySet() {
          keys = new SelectionKey[1024];
      }
  
      @Override
      public boolean add(SelectionKey o) {
          if (o == null) {
              return false;
          }
  
          keys[size++] = o;
          if (size == keys.length) {
              increaseCapacity();
          }
  
          return true;
      }
  
      @Override
      public boolean remove(Object o) {
          return false;
      }
  
      @Override
      public boolean contains(Object o) {
          return false;
      }
  
      @Override
      public int size() {
          return size;
      }
  
      @Override
      public Iterator<SelectionKey> iterator() {
          return new Iterator<>() {
              private int idx;
  
              @Override
              public boolean hasNext() {
                  return idx < size;
              }
  
              @Override
              public SelectionKey next() {
                  if (!hasNext()) {
                      throw new NoSuchElementException();
                  }
                  return keys[idx++];
              }
  
              @Override
              public void remove() {
                  throw new UnsupportedOperationException();
              }
          };
      }
  
      void reset() {
          reset(0);
      }
  
      void reset(int start) {
          Arrays.fill(keys, start, size, null);
          size = 0;
      }
  
      private void increaseCapacity() {
          SelectionKey[] newKeys = new SelectionKey[keys.length << 1];
          System.arraycopy(keys, 0, newKeys, 0, size);
          keys = newKeys;
     }
 }