/*
    * This file is part of Waarp Project (named also Waarp or GG).
    *
    *  Copyright (c) 2019, Waarp SAS, and individual contributors by the @author
    *  tags. See the COPYRIGHT.txt in the distribution for a full listing of
    * individual contributors.
    *
    *  All Waarp Project is free software: you can redistribute it and/or
    * modify it under the terms of the GNU General Public License as published by
   * the Free Software Foundation, either version 3 of the License, or (at your
   * option) any later version.
   *
   * Waarp is distributed in the hope that it will be useful, but WITHOUT ANY
   * WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
   * A PARTICULAR PURPOSE. See the GNU General Public License for more details.
   *
   *  You should have received a copy of the GNU General Public License along with
   * Waarp . If not, see <http://www.gnu.org/licenses/>.
   */
  package org.waarp.common.utility;
  
  import java.io.InputStream;
  import java.io.OutputStream;
  import java.util.Collections;
  import java.util.List;
  import java.util.Map;
  import java.util.Set;
  
  /**
   * Singleton utility class
   */
  public final class SingletonUtils {
    private static final byte[] SINGLETON_BYTE_ARRAY = {};
    private static final InputStream SINGLETON_INPUTSTREAM =
        new NullInputStream();
    private static final OutputStream SINGLETON_OUTPUTSTREAM =
        new VoidOutputStream();
  
    private SingletonUtils() {
      // empty
    }
  
  
    /**
     * Immutable empty byte array
     *
     * @return a Byte Array Singleton
     */
    public static byte[] getSingletonByteArray() {
      return SINGLETON_BYTE_ARRAY;
    }
  
    /**
     * Immutable empty List
     *
     * @return an immutable empty List
     */
    public static <E> List<E> singletonList() {
      return Collections.emptyList();
    }
  
    /**
     * Immutable empty Set
     *
     * @return an immutable empty Set
     */
    public static <E> Set<E> singletonSet() {
      return Collections.emptySet();
    }
  
    /**
     * Immutable empty Map
     *
     * @return an immutable empty Map
     */
    public static <E, V> Map<E, V> singletonMap() {
      return Collections.emptyMap();
    }
  
    /**
     * Empty InputStream
     */
    private static final class NullInputStream extends InputStream {
      @Override
      public final int read() {
        return -1;
      }
  
      @Override
      public final int available() {
        return 0;
      }
  
      @Override
      public final void close() {
        // Empty
      }
  
      @Override
     public final void mark(final int arg0) {//NOSONAR
       // Empty
     }
 
     @Override
     public final boolean markSupported() {
       return true;
     }
 
     @Override
     public final int read(final byte[] arg0, final int arg1, final int arg2) {
       return -1;
     }
 
     @Override
     public final int read(final byte[] arg0) {
       return -1;
     }
 
     @Override
     public final void reset() {//NOSONAR
       // Empty
     }
 
     @Override
     public final long skip(final long arg0) {
       return 0;
     }
   }
 
   /**
    * Immutable empty InputStream
    *
    * @return an immutable empty InputStream
    */
   public static InputStream singletonInputStream() {
     return SINGLETON_INPUTSTREAM;
   }
 
   /**
    * OutputStream discarding all writed elements
    */
   private static final class VoidOutputStream extends OutputStream {
     @Override
     public final void close() {
       // Empty
     }
 
     @Override
     public final void flush() {
       // Empty
     }
 
     @Override
     public final void write(final byte[] arg0, final int arg1, final int arg2) {
       // Empty
     }
 
     @Override
     public final void write(final byte[] arg0) {
       // Empty
     }
 
     @Override
     public final void write(final int arg0) {
       // Empty
     }
   }
 
   /**
    * Immutable void OutputStream. Any write elements are discarder (equivalent
    * to /dev/null).
    *
    * @return an immutable empty OutputStream
    */
   public static OutputStream singletonOutputStream() {
     return SINGLETON_OUTPUTSTREAM;
   }
 
 }