// 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.analysis.test;

import com.google.common.annotations.VisibleForTesting;
import com.google.common.collect.ImmutableSet;
import com.google.devtools.build.lib.analysis.config.BuildOptions;
import com.google.devtools.build.lib.analysis.config.BuildOptionsCache;
import com.google.devtools.build.lib.analysis.config.BuildOptionsView;
import com.google.devtools.build.lib.analysis.config.CoreOptions;
import com.google.devtools.build.lib.analysis.config.FragmentOptions;
import com.google.devtools.build.lib.analysis.config.transitions.NoTransition;
import com.google.devtools.build.lib.analysis.config.transitions.PatchTransition;
import com.google.devtools.build.lib.analysis.config.transitions.TransitionFactory;
import com.google.devtools.build.lib.analysis.test.TestConfiguration.TestOptions;
import com.google.devtools.build.lib.events.EventHandler;
import com.google.devtools.build.lib.packages.NonconfigurableAttributeMapper;
import com.google.devtools.build.lib.packages.RuleClass;
import com.google.devtools.build.lib.packages.RuleTransitionData;
import com.google.devtools.build.lib.packages.TargetUtils;
import com.google.devtools.build.lib.packages.Type;
import com.google.devtools.common.options.Options;

/**
 * Trimming transition factory which removes the test config fragment when entering a non-test rule.
 */
public final class TestTrimmingTransitionFactory implements TransitionFactory<RuleTransitionData> {

  private static final ImmutableSet<String> TEST_OPTIONS =
      ImmutableSet.copyOf(Options.getDefaults(TestOptions.class).asMap().keySet());

  /**
   * Trimming transition which removes the test config fragment if --trim_test_configuration is on.
   *
   * <p>At the moment, need to know the value of the testonly attribute from the underlying rule. So
   * the factory, which has access to attributes but not the configuration, attaches the appropriate
   * TestTrimmingTransition, which will have access to the configuration.
   */
  public static class TestTrimmingTransition implements PatchTransition {
    // These are essentially a cache of the two versions of the transition depending on if
    // the associated rule is testonly = true or not.
    private static final TestTrimmingTransition TESTONLY_TRUE = new TestTrimmingTransition(true);
    private static final TestTrimmingTransition TESTONLY_FALSE = new TestTrimmingTransition(false);
    @VisibleForTesting public static final TestTrimmingTransition INSTANCE = TESTONLY_FALSE;

    private final boolean testonly;

    private TestTrimmingTransition(boolean testonly) {
      this.testonly = testonly;
    }

    // This cache is to prevent major slowdowns when using --trim_test_configuration. This
    // transition is always invoked on every target in the top-level invocation. Thus, a wide
    // invocation, like //..., will cause the transition to be invoked on a large number of targets
    // leading to significant performance degradation. (Notably, the transition itself is somewhat
    // fast; however, the post-processing of the BuildOptions into the actual BuildConfiguration
    // takes a significant amount of time).
    //
    // Test any caching changes for performance impact in a longwide scenario with
    // --trim_test_configuration on versus off.
    private static final BuildOptionsCache<Boolean> cache =
        new BuildOptionsCache<>(
            (options, unused) ->
                options.underlying().toBuilder().removeFragmentOptions(TestOptions.class).build());

    @Override
    public ImmutableSet<Class<? extends FragmentOptions>> requiresOptionFragments() {
      return ImmutableSet.of(TestOptions.class, CoreOptions.class);
    }

    @Override
    public BuildOptions patch(BuildOptionsView originalOptions, EventHandler eventHandler) {
      if (!originalOptions.contains(TestOptions.class)) {
        // nothing to do, already trimmed this fragment
        return originalOptions.underlying();
      }
      CoreOptions originalCoreOptions = originalOptions.get(CoreOptions.class);
      TestOptions originalTestOptions = originalOptions.get(TestOptions.class);
      if (!originalTestOptions.trimTestConfiguration
          || (originalTestOptions.experimentalRetainTestConfigurationAcrossTestonly && testonly)
          || !originalCoreOptions.useDistinctHostConfiguration) {
        // nothing to do, trimming is disabled
        // Due to repercussions of b/117932061, do not trim when `--nodistinct_host_configuration`
        // TODO(twigg): See if can remove distinct_host_configuration read here and thus
        // dependency on CoreOptions above.
        return originalOptions.underlying();
      }
      // No context needed, use the constant Boolean.TRUE.
      return cache.applyTransition(originalOptions, Boolean.TRUE);
    }
  }

  @Override
  public PatchTransition create(RuleTransitionData ruleData) {
    RuleClass ruleClass = ruleData.rule().getRuleClassObject();
    if (ruleClass
            .getConfigurationFragmentPolicy()
            .isLegalConfigurationFragment(TestConfiguration.class)
        || TargetUtils.isAlias(ruleData.rule())) {
      // If Test rule, no need to trim here.
      // If Alias rule, might point to test rule so don't trim yet.
      return NoTransition.INSTANCE;
    }

    for (String referencedOptions : ruleClass.getOptionReferenceFunction().apply(ruleData.rule())) {
      if (TEST_OPTIONS.contains(referencedOptions)) {
        // Test-option-referencing config_setting; no need to trim here.
        return NoTransition.INSTANCE;
      }
    }

    // Non-test rule. Trim it!
    // Use an attribute mapper to ensure testonly is resolved to an actual boolean value.
    // It is expected all rules should have a boolean testonly value so the `has` check is only
    //   there as an over-abundance of caution.
    NonconfigurableAttributeMapper attrs = NonconfigurableAttributeMapper.of(ruleData.rule());
    if (attrs.has("testonly", Type.BOOLEAN) && attrs.get("testonly", Type.BOOLEAN)) {
      return TestTrimmingTransition.TESTONLY_TRUE;
    }
    return TestTrimmingTransition.TESTONLY_FALSE;
  }

  @Override
  public TransitionType transitionType() {
    return TransitionType.RULE;
  }
}