/*
    * 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
    *
    *      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 org.apache.commons.lang3.function;
  
  import static org.apache.commons.lang3.LangAssertions.assertNullPointerException;
  import static org.junit.jupiter.api.Assertions.assertEquals;
  import static org.junit.jupiter.api.Assertions.assertNotNull;
  import static org.junit.jupiter.api.Assertions.assertNull;
  import static org.junit.jupiter.api.Assertions.assertSame;
  import static org.junit.jupiter.api.Assertions.assertThrows;
  
  import java.io.IOException;
  
  import org.apache.commons.lang3.AbstractLangTest;
  import org.junit.jupiter.api.Test;
  
  /**
   * Tests {@link FailableFunction}.
   */
  class FailableFunctionTest extends AbstractLangTest {
  
      @Test
      void testAndThen_composesCorrectly() throws IOException {
          final FailableFunction<String, Integer, IOException> length = String::length;
          final FailableFunction<Integer, String, IOException> toStr = i -> "len=" + i;
          assertEquals("len=5", length.andThen(toStr).apply("hello"));
      }
  
      @Test
      void testAndThen_nullAfter_throwsNullPointerException() throws Throwable {
          final FailableFunction<String, String, IOException> f = s -> s;
          assertNullPointerException(() -> f.andThen(null));
      }
  
      @Test
      void testApply_returnsResult() throws IOException {
          final FailableFunction<String, Integer, IOException> f = String::length;
          assertEquals(5, f.apply("hello"));
      }
  
      @Test
      void testApply_throwsException() {
          final IOException expected = new IOException("fail");
          final FailableFunction<String, String, IOException> f = s -> {
              throw expected;
          };
          final IOException thrown = assertThrows(IOException.class, () -> f.apply("x"));
          assertEquals(expected, thrown);
      }
  
      @Test
      void testCompose_composesCorrectly() throws IOException {
          final FailableFunction<String, String, IOException> upper = String::toUpperCase;
          final FailableFunction<String, String, IOException> trim = String::trim;
          assertEquals("HELLO", upper.compose(trim).apply("  hello  "));
      }
  
      @Test
      void testCompose_nullBefore_throwsNullPointerException() throws Throwable {
          final FailableFunction<String, String, IOException> f = s -> s;
          assertNullPointerException(() -> f.compose(null));
      }
  
      @Test
      void testFunction_returnsArgument() throws IOException {
          final FailableFunction<String, String, IOException> f = String::toUpperCase;
          final FailableFunction<String, String, IOException> wrapped = FailableFunction.function(f);
          assertEquals("HELLO", wrapped.apply("hello"));
      }
  
      @Test
      void testIdentity_returnsInput() throws IOException {
          final String input = "hello";
          assertSame(input, FailableFunction.<String, IOException>identity().apply(input));
      }
  
      @Test
      void testNop_applyReturnsNull() throws Throwable {
          assertNull(FailableFunction.nop().apply("x"));
      }
  
      @Test
      void testNop_returnsNonNull() {
          assertNotNull(FailableFunction.nop());
     }
 }