/*
    * Copyright (C) 2011 The Guava Authors
    *
    * Licensed 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 com.google.common.base;
  
  import static com.google.common.truth.Truth.assertThat;
  
  import com.google.common.annotations.GwtCompatible;
  import com.google.common.collect.FluentIterable;
  import com.google.common.collect.ImmutableList;
  
  import junit.framework.TestCase;
  
  import java.util.Collections;
  import java.util.List;
  import java.util.Set;
  
  /**
   * Unit test for {@link Optional}.
   *
   * @author Kurt Alfred Kluever
   */
  @GwtCompatible(emulated = true)
  public final class OptionalTest extends TestCase {
    public void testAbsent() {
      Optional<String> optionalName = Optional.absent();
      assertFalse(optionalName.isPresent());
    }
  
    public void testOf() {
      assertEquals("training", Optional.of("training").get());
    }
  
    public void testOf_null() {
      try {
        Optional.of(null);
        fail();
      } catch (NullPointerException expected) {
      }
    }
  
    public void testFromNullable() {
      Optional<String> optionalName = Optional.fromNullable("bob");
      assertEquals("bob", optionalName.get());
    }
  
    public void testFromNullable_null() {
      // not promised by spec, but easier to test
      assertSame(Optional.absent(), Optional.fromNullable(null));
    }
  
    public void testIsPresent_no() {
      assertFalse(Optional.absent().isPresent());
    }
  
    public void testIsPresent_yes() {
      assertTrue(Optional.of("training").isPresent());
    }
  
    public void testGet_absent() {
      Optional<String> optional = Optional.absent();
      try {
        optional.get();
        fail();
      } catch (IllegalStateException expected) {
      }
    }
  
    public void testGet_present() {
      assertEquals("training", Optional.of("training").get());
    }
  
    public void testOr_T_present() {
      assertEquals("a", Optional.of("a").or("default"));
    }
  
    public void testOr_T_absent() {
      assertEquals("default", Optional.absent().or("default"));
    }
  
    public void testOr_supplier_present() {
      assertEquals("a", Optional.of("a").or(Suppliers.ofInstance("fallback")));
    }
  
    public void testOr_supplier_absent() {
      assertEquals("fallback", Optional.absent().or(Suppliers.ofInstance("fallback")));
   }
 
   public void testOr_nullSupplier_absent() {
     Supplier<Object> nullSupplier = Suppliers.ofInstance(null);
     Optional<Object> absentOptional = Optional.absent();
     try {
       absentOptional.or(nullSupplier);
       fail();
     } catch (NullPointerException expected) {
     }
   }
 
   public void testOr_nullSupplier_present() {
     Supplier<String> nullSupplier = Suppliers.ofInstance(null);
     assertEquals("a", Optional.of("a").or(nullSupplier));
   }
 
   public void testOr_Optional_present() {
     assertEquals(Optional.of("a"), Optional.of("a").or(Optional.of("fallback")));
   }
 
   public void testOr_Optional_absent() {
     assertEquals(Optional.of("fallback"), Optional.absent().or(Optional.of("fallback")));
   }
 
   public void testOrNull_present() {
     assertEquals("a", Optional.of("a").orNull());
   }
 
   public void testOrNull_absent() {
     assertNull(Optional.absent().orNull());
   }
 
   public void testAsSet_present() {
     Set<String> expected = Collections.singleton("a");
     assertEquals(expected, Optional.of("a").asSet());
   }
 
   public void testAsSet_absent() {
     assertTrue("Returned set should be empty", Optional.absent().asSet().isEmpty());
   }
 
   public void testAsSet_presentIsImmutable() {
     Set<String> presentAsSet = Optional.of("a").asSet();
     try {
       presentAsSet.add("b");
       fail();
     } catch (UnsupportedOperationException expected) {
     }
   }
 
   public void testAsSet_absentIsImmutable() {
     Set<Object> absentAsSet = Optional.absent().asSet();
     try {
       absentAsSet.add("foo");
       fail();
     } catch (UnsupportedOperationException expected) {
     }
   }
 
   public void testTransform_absent() {
     assertEquals(Optional.absent(), Optional.absent().transform(Functions.identity()));
     assertEquals(Optional.absent(), Optional.absent().transform(Functions.toStringFunction()));
   }
 
   public void testTransform_presentIdentity() {
     assertEquals(Optional.of("a"), Optional.of("a").transform(Functions.identity()));
   }
 
   public void testTransform_presentToString() {
     assertEquals(Optional.of("42"), Optional.of(42).transform(Functions.toStringFunction()));
   }
 
   public void testTransform_present_functionReturnsNull() {
     try {
       Optional.of("a").transform(
           new Function<String, String>() {
             @Override public String apply(String input) {
               return null;
             }
           });
       fail("Should throw if Function returns null.");
     } catch (NullPointerException expected) {
     }
   }
 
   public void testTransform_abssent_functionReturnsNull() {
     assertEquals(Optional.absent(),
         Optional.absent().transform(
           new Function<Object, Object>() {
             @Override public Object apply(Object input) {
               return null;
             }
           }));
   }
 
   // TODO(kevinb): use EqualsTester
 
   public void testEqualsAndHashCode_absent() {
     assertEquals(Optional.<String>absent(), Optional.<Integer>absent());
     assertEquals(Optional.absent().hashCode(), Optional.absent().hashCode());
   }
 
   public void testEqualsAndHashCode_present() {
     assertEquals(Optional.of("training"), Optional.of("training"));
     assertFalse(Optional.of("a").equals(Optional.of("b")));
     assertFalse(Optional.of("a").equals(Optional.absent()));
     assertEquals(Optional.of("training").hashCode(), Optional.of("training").hashCode());
   }
 
   public void testToString_absent() {
     assertEquals("Optional.absent()", Optional.absent().toString());
   }
 
   public void testToString_present() {
     assertEquals("Optional.of(training)", Optional.of("training").toString());
   }
 
   public void testPresentInstances_allPresent() {
     List<Optional<String>> optionals =
         ImmutableList.of(Optional.of("a"), Optional.of("b"), Optional.of("c"));
     assertThat(Optional.presentInstances(optionals)).iteratesAs("a", "b", "c");
   }
 
   public void testPresentInstances_allAbsent() {
     List<Optional<Object>> optionals =
         ImmutableList.of(Optional.absent(), Optional.absent());
     assertThat(Optional.presentInstances(optionals)).isEmpty();
   }
 
   public void testPresentInstances_somePresent() {
     List<Optional<String>> optionals =
         ImmutableList.of(Optional.of("a"), Optional.<String>absent(), Optional.of("c"));
     assertThat(Optional.presentInstances(optionals)).iteratesAs("a", "c");
   }
 
   public void testPresentInstances_callingIteratorTwice() {
     List<Optional<String>> optionals =
         ImmutableList.of(Optional.of("a"), Optional.<String>absent(), Optional.of("c"));
     Iterable<String> onlyPresent = Optional.presentInstances(optionals);
     assertThat(onlyPresent).iteratesAs("a", "c");
     assertThat(onlyPresent).iteratesAs("a", "c");
   }
 
   public void testPresentInstances_wildcards() {
     List<Optional<? extends Number>> optionals =
         ImmutableList.<Optional<? extends Number>>of(Optional.<Double>absent(), Optional.of(2));
     Iterable<Number> onlyPresent = Optional.presentInstances(optionals);
     assertThat(onlyPresent).iteratesAs(2);
   }
 
   private static Optional<Integer> getSomeOptionalInt() {
     return Optional.of(1);
   }
 
   private static FluentIterable<? extends Number> getSomeNumbers() {
     return FluentIterable.from(ImmutableList.<Number>of());
   }
 
   /*
    * The following tests demonstrate the shortcomings of or() and test that the casting workaround
    * mentioned in the method Javadoc does in fact compile.
    */
 
   @SuppressWarnings("unused") // compilation test
   public void testSampleCodeError1() {
     Optional<Integer> optionalInt = getSomeOptionalInt();
     // Number value = optionalInt.or(0.5); // error
   }
 
   @SuppressWarnings("unused") // compilation test
   public void testSampleCodeError2() {
     FluentIterable<? extends Number> numbers = getSomeNumbers();
     Optional<? extends Number> first = numbers.first();
     // Number value = first.or(0.5); // error
   }
 
   @SuppressWarnings("unused") // compilation test
   public void testSampleCodeFine1() {
     Optional<Number> optionalInt = Optional.of((Number) 1);
     Number value = optionalInt.or(0.5); // fine
   }
 
   @SuppressWarnings("unused") // compilation test
   public void testSampleCodeFine2() {
     FluentIterable<? extends Number> numbers = getSomeNumbers();
 
     // Sadly, the following is what users will have to do in some circumstances.
 
     @SuppressWarnings("unchecked") // safe covariant cast
     Optional<Number> first = (Optional) numbers.first();
     Number value = first.or(0.5); // fine
   }
 }