/*
    * 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.time;
  
  import static org.junit.jupiter.api.Assertions.assertEquals;
  import static org.junit.jupiter.api.Assertions.assertNotNull;
  import static org.junit.jupiter.api.Assertions.assertSame;
  import static org.junit.jupiter.api.Assertions.assertThrows;
  
  import java.util.TimeZone;
  
  import org.apache.commons.lang3.SerializationUtils;
  import org.junit.jupiter.api.Test;
  
  /**
   * Tests {@link ImmutableTimeZone} and {@link TimeZones#GMT}.
   * <p>
   * TimeZones.GMT is a public static final mutable TimeZone. Callers can call setRawOffset() / setID() to globally corrupt time zone behavior.
   * </p>
   * <p>
   * Pre-patch: setRawOffset() / setID() succeed silently and mutate the shared singleton.
   * </p>
   * <p>
   * Post-patch: setRawOffset() / setID() throw UnsupportedOperationException.
   * </p>
   */
  public class TimeZonesGmtTest {
  
      @Test
      public void testCloneReturnsSelfForImmutableSingleton() {
          // For an immutable singleton, clone() should return the same instance,
          // and there must be no need to defensively copy the value.
          final Object copy = TimeZones.GMT.clone();
          assertSame(TimeZones.GMT, copy, "clone() of an immutable singleton should return the same instance");
      }
  
      @Test
      public void testGmtIdRemainsGmtAfterAttemptedMutation() {
          assertThrows(UnsupportedOperationException.class, () -> TimeZones.GMT.setID("Etc/UTC"));
          assertEquals("GMT", TimeZones.GMT.getID());
      }
  
      @Test
      public void testGmtOffsetRemainsZeroAfterAttemptedMutation() {
          assertThrows(UnsupportedOperationException.class, () -> TimeZones.GMT.setRawOffset(3600000));
          assertEquals(0, TimeZones.GMT.getRawOffset());
      }
  
      @Test
      public void testGmtTimeZoneIsImmutableSetId() {
          assertThrows(UnsupportedOperationException.class, () -> TimeZones.GMT.setID("Etc/UTC"));
      }
  
      @Test
      public void testGmtTimeZoneIsImmutableSetRawOffset() {
          assertThrows(UnsupportedOperationException.class, () -> TimeZones.GMT.setRawOffset(3600000));
      }
  
      @Test
      public void testSerializationRoundTripPreservesId() throws Exception {
          // Round-trip via Serializable to confirm the type is wire-format friendly.
          final TimeZone roundtrip = SerializationUtils.roundtrip(TimeZones.GMT);
          assertNotNull(roundtrip, "Round-tripped TimeZone must not be null");
          assertEquals("GMT", roundtrip.getID(), "Round-tripped TimeZone id must remain \"GMT\"");
          assertEquals(0, roundtrip.getRawOffset(), "Round-tripped TimeZone offset must remain 0");
      }
  
      @Test
      public void testSerializedFormUsesNamedClass() throws Exception {
          // Wire-format hazard guard: ensure the implementation class is a named static
          // nested type, not an anonymous inner class whose synthetic name (TimeZones$1)
          // is brittle across non-functional code reorderings.
          assertEquals(ImmutableTimeZone.class.getName(), TimeZones.GMT.getClass().getName());
      }
  }