/*
    * 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.channels;
  
  import static java.nio.charset.StandardCharsets.US_ASCII;
  import static org.junit.jupiter.api.Assertions.assertFalse;
  import static org.junit.jupiter.api.Assertions.assertNotEquals;
  import static org.junit.jupiter.api.Assertions.assertTrue;
  
  import java.io.File;
  import java.io.FileInputStream;
  import java.io.IOException;
  import java.nio.channels.FileChannel;
  
  import org.apache.commons.io.FileUtils;
  import org.apache.commons.io.file.AbstractTempDirTest;
  import org.apache.commons.lang3.StringUtils;
  import org.junit.jupiter.api.Test;
  
  /**
   * Tests {@link FileChannels}.
   */
  public class FileChannelsTest extends AbstractTempDirTest {
  
      private static final int BUFFER_SIZE = 1024;
      private static final String CONTENT = StringUtils.repeat("x", BUFFER_SIZE);
  
      private boolean isEmpty(final File empty) {
          return empty.length() == 0;
      }
  
      private void testContentEquals(final String content1, final String content2) throws IOException {
          assertTrue(FileChannels.contentEquals(null, null, BUFFER_SIZE));
  
          // Prepare test files with same size but different content
          // (first 3 bytes are different, followed by a large amount of equal content)
          final File file1 = new File(tempDirFile, "test1.txt");
          final File file2 = new File(tempDirFile, "test2.txt");
          FileUtils.writeStringToFile(file1, content1, US_ASCII);
          FileUtils.writeStringToFile(file2, content2, US_ASCII);
  
          // File checksums are different
          assertNotEquals(FileUtils.checksumCRC32(file1), FileUtils.checksumCRC32(file2));
  
          try (FileInputStream stream1 = new FileInputStream(file1);
                  FileInputStream stream2 = new FileInputStream(file2);
                  FileChannel channel1 = stream1.getChannel();
                  FileChannel channel2 = stream2.getChannel()) {
              assertFalse(FileChannels.contentEquals(channel1, channel2, BUFFER_SIZE));
          }
          try (FileInputStream stream1 = new FileInputStream(file1);
                  FileInputStream stream2 = new FileInputStream(file2);
                  FileChannel channel1 = stream1.getChannel();
                  FileChannel channel2 = stream2.getChannel()) {
              assertTrue(FileChannels.contentEquals(channel1, channel1, BUFFER_SIZE));
              assertTrue(FileChannels.contentEquals(channel2, channel2, BUFFER_SIZE));
          }
      }
  
      @Test
      public void testContentEqualsDifferentPostfix() throws IOException {
          testContentEquals(CONTENT + "ABC", CONTENT + "XYZ");
      }
  
      @Test
      public void testContentEqualsDifferentPrefix() throws IOException {
          testContentEquals("ABC" + CONTENT, "XYZ" + CONTENT);
      }
  
      @Test
      public void testContentEqualsEmpty() throws IOException {
          assertTrue(FileChannels.contentEquals(null, null, BUFFER_SIZE));
  
          final File empty = new File(tempDirFile, "empty.txt");
          final File notEmpty = new File(tempDirFile, "not-empty.txt");
          FileUtils.writeStringToFile(empty, StringUtils.EMPTY, US_ASCII);
          FileUtils.writeStringToFile(notEmpty, "X", US_ASCII);
          assertTrue(isEmpty(empty));
          assertFalse(isEmpty(notEmpty));
  
          // File checksums are different
          assertNotEquals(FileUtils.checksumCRC32(empty), FileUtils.checksumCRC32(notEmpty));
  
          try (FileInputStream streamEmpty = new FileInputStream(empty);
                  FileInputStream streamNotEmpty = new FileInputStream(notEmpty);
                 FileChannel channelEmpty = streamEmpty.getChannel();
                 FileChannel channelNotEmpty = streamNotEmpty.getChannel()) {
             assertFalse(FileChannels.contentEquals(channelEmpty, channelNotEmpty, BUFFER_SIZE));
             assertFalse(FileChannels.contentEquals(null, channelNotEmpty, BUFFER_SIZE));
             assertFalse(FileChannels.contentEquals(channelNotEmpty, null, BUFFER_SIZE));
             assertTrue(FileChannels.contentEquals(channelEmpty, channelEmpty, BUFFER_SIZE));
             assertTrue(FileChannels.contentEquals(null, channelEmpty, BUFFER_SIZE));
             assertTrue(FileChannels.contentEquals(channelEmpty, null, BUFFER_SIZE));
             assertTrue(FileChannels.contentEquals(channelNotEmpty, channelNotEmpty, BUFFER_SIZE));
         }
     }
 
 }