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   *  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.causeway.commons.internal.base;
  
  import java.nio.charset.StandardCharsets;
  import java.util.Base64;
  
  import org.junit.jupiter.api.BeforeEach;
  import org.junit.jupiter.api.Test;
  import org.junit.jupiter.params.ParameterizedTest;
  import org.junit.jupiter.params.provider.ValueSource;
  
  import static org.hamcrest.MatcherAssert.assertThat;
  import static org.hamcrest.Matchers.lessThan;
  import static org.junit.jupiter.api.Assertions.assertArrayEquals;
  import static org.junit.jupiter.api.Assertions.assertEquals;
  import static org.junit.jupiter.api.Assertions.assertFalse;
  import static org.junit.jupiter.api.Assertions.assertNull;
  
  import org.apache.causeway.commons.internal._Constants;
  
  class BytesTest {
  
      final int n = 256;
      private final byte[] allBytes = new byte[n];
  
      private static final byte[] testimonial =
              _Strings.toBytes(
                      "https://docs.oracle.com/javase/8/docs/api/java/util/Base64.html#basic?"+
                              "0-theme-domainObjectContainer-entity-rows-2-rowContents-1-col-tabGroups-1-panel-"
                              + "tabPanel-rows-1-rowContents-1-col-fieldSets-1-memberGroup-properties-1-property-"
                              + "scalarTypeContainer-scalarIfRegular-associatedActionLinksBelow-additionalLinkList-"
                              + "additionalLinkItem-0-additionalLink",
                              StandardCharsets.UTF_8);
  
      @BeforeEach
      void before() {
          for(int i=0; i<n; ++i) {
              allBytes[i] = (byte)i;
          }
      }
  
      // -- PREPEND/APPEND
  
      @Test
      void concatNullWithNull() throws Exception {
          assertNull(_Bytes.append(null, null));
          assertNull(_Bytes.prepend(null, null));
      }
  
      @Test
      void concatNullWithEmpty() throws Exception {
          assertArrayEquals(_Constants.emptyBytes, _Bytes.append(null));
          assertArrayEquals(_Constants.emptyBytes, _Bytes.prepend(null));
      }
  
      @Test
      void concatWithNull() throws Exception {
          assertArrayEqualsButNotSame(allBytes, _Bytes.append(allBytes, null));
          assertArrayEqualsButNotSame(allBytes, _Bytes.prepend(allBytes, null));
      }
  
      @Test
      void concatWithEmpty() throws Exception {
          assertArrayEqualsButNotSame(allBytes, _Bytes.append(allBytes));
          assertArrayEqualsButNotSame(allBytes, _Bytes.prepend(allBytes));
      }
  
      @Test
      void concatHappyCase() throws Exception {
          assertArrayEqualsButNotSame(new byte[] {1,2,3,4,5}, _Bytes.append(new byte[] {1,2,3}, (byte)4, (byte)5));
          assertArrayEqualsButNotSame(new byte[] {4,5,1,2,3}, _Bytes.prepend(new byte[] {1,2,3}, (byte)4, (byte)5));
      }
  
      @Test
      void compressIdentityWithNull() throws Exception {
          assertNull(_Bytes.decompress(_Bytes.compress(null)));
      }
  
      @Test
      void compressIdentityWithByteRange() throws Exception {
          assertArrayEquals(allBytes,
                  _Bytes.decompress(_Bytes.compress(allBytes)));
      }
  
      @Test
      void compressIdentityWithTestimonial() throws Exception {
          assertArrayEquals(testimonial,
                  _Bytes.decompress(_Bytes.compress(testimonial)));
      }
  
      @Test
      void zlibCompressIdentityWithByteRange() throws Exception {
          assertArrayEquals(allBytes,
                  _Bytes.decompressZlib(_Bytes.compressZlib(allBytes)));
      }
  
      @Test
      void zlibCompressIdentityWithTestimonial() throws Exception {
          assertArrayEquals(testimonial,
                  _Bytes.decompressZlib(_Bytes.compressZlib(testimonial)));
      }
  
      @Test
      void compressionRatio() throws Exception {
          // lower is better
          final double compressionRatio = (double)_Bytes.compress(testimonial).length / testimonial.length;
          assertThat(compressionRatio, lessThan(0.7));
      }
  
      // -- COMPRESSION
  
      private static byte[] data(final int index) {
          return (byte[]) new Object[] {
                  null,
                  new byte[] { },
                  new byte[] { 0 },
                  new byte[] { 0, 1 },
                  new byte[] { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 }, // 17
                  new byte[] { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 }, // 18
                  new byte[] { 31, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 }, // 19
          }[index];
      }
  
      @ParameterizedTest
      @ValueSource(ints = {0, 1, 2, 3, 4, 5, 6}) // data indices
      void compressionRundtrip(final int dataIndex) throws Exception {
          var input = data(dataIndex);
          assertArrayEquals(input,
                  _Bytes.decompress(_Bytes.compress(input)));
      }
  
      // -- BASE-64
  
      @Test
      void base64IdentityWithNull() throws Exception {
          assertNull(_Bytes.decodeBase64(
                  Base64.getUrlDecoder(),
                  _Bytes.encodeToBase64(Base64.getUrlEncoder(), null)));
      }
  
      @Test
      void base64IdentityWithByteRange() throws Exception {
          assertArrayEquals(allBytes,
                  _Bytes.decodeBase64(
                          Base64.getUrlDecoder(),
                          _Bytes.encodeToBase64(Base64.getUrlEncoder(), allBytes)));
      }
  
      @Test
      void base64IdentityWithTestimonial() throws Exception {
          assertArrayEquals(testimonial,
                  _Bytes.decodeBase64(
                          Base64.getUrlDecoder(),
                          _Bytes.encodeToBase64(Base64.getUrlEncoder(), testimonial)));
      }
  
      // -- HEX
  
      @Test
      void hexDump(){
          final byte[] bytes = {Byte.MIN_VALUE, -1, 0, 1, Byte.MAX_VALUE};
          assertEquals("80 ff 00 01 7f", _Bytes.hexDump(bytes));
      }
  
      // -- OPERATOR COMPOSITION
  
      @Test
      void composedOperatorWithNull() throws Exception {
          assertNull(_Bytes.asCompressedUrlBase64.apply(null));
          assertNull(_Bytes.ofCompressedUrlBase64.apply(null));
          assertNull(_Bytes.asUrlBase64.apply(null));
          assertNull(_Bytes.ofUrlBase64.apply(null));
      }
  
      @Test
      void composedIdentityWithByteRange() throws Exception {
          assertArrayEquals(allBytes,
                  _Bytes.ofCompressedUrlBase64.apply(
                          _Bytes.asCompressedUrlBase64.apply(allBytes)));
      }
  
      @Test
      void composedIdentityWithTestimonial() throws Exception {
          assertArrayEquals(testimonial,
                  _Bytes.ofCompressedUrlBase64.apply(
                          _Bytes.asCompressedUrlBase64.apply(testimonial)));
      }
  
      // -- HELPER
  
      private void assertArrayEqualsButNotSame(final byte[] a, final byte[] b) {
          assertFalse(a == b);
          assertArrayEquals(a, b);
      }
  
  }
  