// Copyright 2018 The Bazel Authors. All rights reserved.
//
// 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.devtools.build.lib.rules;

import static com.google.common.truth.Truth.assertThat;

import com.google.common.collect.ImmutableSet;
import com.google.devtools.build.lib.analysis.ConfiguredRuleClassProvider;
import com.google.devtools.build.lib.analysis.ConfiguredTarget;
import com.google.devtools.build.lib.analysis.config.BuildConfiguration.Fragment;
import com.google.devtools.build.lib.analysis.config.BuildOptions;
import com.google.devtools.build.lib.analysis.config.ConfigurationFragmentFactory;
import com.google.devtools.build.lib.analysis.config.FragmentOptions;
import com.google.devtools.build.lib.analysis.util.BuildViewTestCase;
import com.google.devtools.build.lib.cmdline.Label;
import com.google.devtools.build.lib.cmdline.LabelSyntaxException;
import com.google.devtools.build.lib.packages.Attribute.LateBoundDefault;
import com.google.devtools.build.lib.packages.AttributeMap;
import com.google.devtools.build.lib.packages.Rule;
import com.google.devtools.build.lib.rules.LateBoundAlias.CommonAliasRule;
import com.google.devtools.build.lib.testutil.TestRuleClassProvider;
import java.io.IOException;
import javax.annotation.Nullable;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.junit.runners.JUnit4;

/**
 * Tests that LateBoundAlias can resolve null actual reference.
 */
@RunWith(JUnit4.class)
public class LateBoundAliasTest extends BuildViewTestCase {

  private static final class TestFragment extends Fragment {}

  private static final class TestFragmentOptionFactory implements ConfigurationFragmentFactory {

    @Override
    public Class<? extends Fragment> creates() {
      return TestFragment.class;
    }

    @Override
    public ImmutableSet<Class<? extends FragmentOptions>> requiredOptions() {
      return ImmutableSet.of();
    }

    @Nullable
    @Override
    public Fragment create(BuildOptions buildOptions) {
      return new TestFragment();
    }
  }

  private static final class TestLateBoundDefault extends LateBoundDefault<TestFragment, Label> {

    private TestLateBoundDefault() {
      super(false, TestFragment.class, null);
    }

    @Override
    public Label resolve(Rule rule, AttributeMap attributes, TestFragment input) {
      return null;
    }
  }

  private static final class MyTestRule extends CommonAliasRule {
    public MyTestRule() {
      super("test_rule_name", env -> new TestLateBoundDefault(), TestFragment.class);
    }
  }

  @Override
  protected ConfiguredRuleClassProvider getRuleClassProvider() {
    ConfiguredRuleClassProvider.Builder builder = new ConfiguredRuleClassProvider.Builder();
    TestRuleClassProvider.addStandardRules(builder);
    builder.addConfigurationFragment(new TestFragmentOptionFactory());
    builder.addRuleDefinition(new MyTestRule());
    return builder.build();
  }

  @Test
  public void testResolveNullTarget() throws IOException, LabelSyntaxException {
    scratch.file("a/BUILD", "test_rule_name(name='alias')");

    ConfiguredTarget alias = getConfiguredTarget("//a:alias");

    assertThat(alias).isNotNull();
  }

  @Test
  public void testNullTargetCanBeDependant() throws IOException, LabelSyntaxException {
    scratch.file(
        "a/BUILD",
        "test_rule_name(name='alias')",
        "filegroup(",
        "    name = 'my_filegroup',",
        "    srcs = [':alias']",
        ")");

    ConfiguredTarget myFilegroup = getConfiguredTarget("//a:my_filegroup");

    assertThat(myFilegroup).isNotNull();
  }
}