/*
    * Licensed to the Apache Software Foundation (ASF) under one or more
    * contributor license agreements.  See the NOTICE file distributed with
    * this work for additional information regarding copyright ownership.
    * The ASF 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
    *
    *      http://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 org.apache.commons.io.output;
  
  import java.io.FilterWriter;
  import java.io.IOException;
  import java.io.Writer;
  import java.util.Arrays;
  import java.util.Collection;
  import java.util.Collections;
  import java.util.Objects;
  import java.util.stream.Stream;
  
  import org.apache.commons.io.IOExceptionList;
  import org.apache.commons.io.IOIndexedException;
  import org.apache.commons.io.function.IOConsumer;
  
  /**
   * Abstract class for writing filtered character streams to a {@link Collection} of writers. This is in contrast to
   * {@link FilterWriter} which is backed by a single {@link Writer}.
   * <p>
   * This abstract class provides default methods that pass all requests to the contained writers. Subclasses should
   * likely override some of these methods.
   * </p>
   * <p>
   * The class {@link Writer} defines method signatures with {@code throws} {@link IOException}, which in this class are
   * actually {@link IOExceptionList} containing a list of {@link IOIndexedException}.
   * </p>
   *
   * @since 2.7
   */
  public class FilterCollectionWriter extends Writer {
  
      /**
       * Empty and immutable collection of writers.
       */
      protected final Collection<Writer> EMPTY_WRITERS = Collections.emptyList();
  
      /**
       * The underlying writers.
       */
      protected final Collection<Writer> writers;
  
      /**
       * Constructs a new filtered collection writer.
       *
       * @param writers Writers to provide the underlying targets.
       */
      protected FilterCollectionWriter(final Collection<Writer> writers) {
          this.writers = writers == null ? EMPTY_WRITERS : writers;
      }
  
      /**
       * Constructs a new filtered collection writer.
       *
       * @param writers Writers to provide the underlying targets.
       */
      protected FilterCollectionWriter(final Writer... writers) {
          this.writers = writers == null ? EMPTY_WRITERS : Arrays.asList(writers);
      }
  
      @Override
      public Writer append(final char c) throws IOException {
          return forAllWriters(w -> w.append(c));
      }
  
      @Override
      public Writer append(final CharSequence csq) throws IOException {
          return forAllWriters(w -> w.append(csq));
      }
  
      @Override
      public Writer append(final CharSequence csq, final int start, final int end) throws IOException {
          return forAllWriters(w -> w.append(csq, start, end));
      }
  
      @SuppressWarnings("resource") // no allocation
      @Override
      public void close() throws IOException {
          forAllWriters(Writer::close);
      }
  
      /**
       * Flushes the stream.
      *
      * @throws IOException If an I/O error occurs
      */
     @SuppressWarnings("resource") // no allocation
     @Override
     public void flush() throws IOException {
         forAllWriters(Writer::flush);
     }
 
     private FilterCollectionWriter forAllWriters(final IOConsumer<Writer> action) throws IOExceptionList {
         IOConsumer.forAll(action, writers());
         return this;
     }
 
     @SuppressWarnings("resource") // no allocation
     @Override
     public void write(final char[] cbuf) throws IOException {
         forAllWriters(w -> w.write(cbuf));
     }
 
     /**
      * Writes a portion of an array of characters.
      *
      * @param cbuf Buffer of characters to be written
      * @param off  Offset from which to start reading characters
      * @param len  Number of characters to be written
      * @throws IOException If an I/O error occurs
      */
     @SuppressWarnings("resource") // no allocation
     @Override
     public void write(final char[] cbuf, final int off, final int len) throws IOException {
         forAllWriters(w -> w.write(cbuf, off, len));
     }
 
     /**
      * Writes a single character.
      *
      * @throws IOException If an I/O error occurs
      */
     @SuppressWarnings("resource") // no allocation
     @Override
     public void write(final int c) throws IOException {
         forAllWriters(w -> w.write(c));
     }
 
     @SuppressWarnings("resource") // no allocation
     @Override
     public void write(final String str) throws IOException {
         forAllWriters(w -> w.write(str));
     }
 
     /**
      * Writes a portion of a string.
      *
      * @param str String to be written
      * @param off Offset from which to start reading characters
      * @param len Number of characters to be written
      * @throws IOException If an I/O error occurs
      */
     @SuppressWarnings("resource") // no allocation
     @Override
     public void write(final String str, final int off, final int len) throws IOException {
         forAllWriters(w -> w.write(str, off, len));
     }
 
     private Stream<Writer> writers() {
         return writers.stream().filter(Objects::nonNull);
     }
 
 }