/*
 * Copyright (c) 2016 Google, Inc.
 *
 * 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.truth;

import static com.google.common.truth.Fact.fact;
import static com.google.common.truth.Fact.simpleFact;

import java.util.Optional;
import org.checkerframework.checker.nullness.compatqual.NullableDecl;

/**
 * Propositions for Java 8 {@link Optional} subjects.
 *
 * @author Christian Gruber
 */
public final class OptionalSubject extends Subject {
  private final Optional<?> actual;

  OptionalSubject(
      FailureMetadata failureMetadata,
      @NullableDecl Optional<?> subject,
      @NullableDecl String typeDescription) {
    super(failureMetadata, subject, typeDescription);
    this.actual = subject;
  }

  // TODO(cpovirk): Consider making OptionalIntSubject and OptionalLongSubject delegate to this.

  /** Fails if the {@link Optional}{@code <T>} is empty or the subject is null. */
  public void isPresent() {
    if (actual == null) {
      failWithActual(simpleFact("expected present optional"));
    } else if (!actual.isPresent()) {
      failWithoutActual(simpleFact("expected to be present"));
    }
  }

  /** Fails if the {@link Optional}{@code <T>} is present or the subject is null. */
  public void isEmpty() {
    if (actual == null) {
      failWithActual(simpleFact("expected empty optional"));
    } else if (actual.isPresent()) {
      failWithoutActual(
          simpleFact("expected to be empty"), fact("but was present with value", actual.get()));
    }
  }

  /**
   * Fails if the {@link Optional}{@code <T>} does not have the given value or the subject is null.
   *
   * <p>To make more complex assertions on the optional's value split your assertion in two:
   *
   * <pre>{@code
   * assertThat(myOptional).isPresent();
   * assertThat(myOptional.get()).contains("foo");
   * }</pre>
   */
  public void hasValue(Object expected) {
    if (expected == null) {
      throw new NullPointerException("Optional cannot have a null value.");
    }
    if (actual == null) {
      failWithActual("expected an optional with value", expected);
    } else if (!actual.isPresent()) {
      failWithoutActual(fact("expected to have value", expected), simpleFact("but was empty"));
    } else {
      checkNoNeedToDisplayBothValues("get()").that(actual.get()).isEqualTo(expected);
    }
  }

  public static Subject.Factory<OptionalSubject, Optional<?>> optionals() {
    return (metadata, subject) -> new OptionalSubject(metadata, subject, "optional");
  }
}
