// Copyright 2014 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.skyframe;

import static com.google.devtools.build.lib.skyframe.ConfiguredTargetFunction.getExecutionPlatformConstraints;

import com.google.common.base.Function;
import com.google.common.base.Preconditions;
import com.google.common.collect.ImmutableMap;
import com.google.common.collect.ImmutableSet;
import com.google.common.collect.Iterables;
import com.google.devtools.build.lib.actions.ActionAnalysisMetadata;
import com.google.devtools.build.lib.analysis.ConfiguredRuleClassProvider;
import com.google.devtools.build.lib.analysis.ConfiguredTarget;
import com.google.devtools.build.lib.analysis.Dependency;
import com.google.devtools.build.lib.analysis.DependencyResolver.DependencyKind;
import com.google.devtools.build.lib.analysis.DependencyResolver.InconsistentAspectOrderException;
import com.google.devtools.build.lib.analysis.PlatformConfiguration;
import com.google.devtools.build.lib.analysis.TargetAndConfiguration;
import com.google.devtools.build.lib.analysis.config.BuildConfiguration;
import com.google.devtools.build.lib.analysis.config.BuildOptions;
import com.google.devtools.build.lib.analysis.config.ConfigMatchingProvider;
import com.google.devtools.build.lib.analysis.config.ConfigurationResolver;
import com.google.devtools.build.lib.cmdline.Label;
import com.google.devtools.build.lib.packages.Attribute;
import com.google.devtools.build.lib.packages.BuildType;
import com.google.devtools.build.lib.packages.RawAttributeMapper;
import com.google.devtools.build.lib.packages.Rule;
import com.google.devtools.build.lib.packages.Target;
import com.google.devtools.build.lib.skyframe.SkyframeActionExecutor.ConflictException;
import com.google.devtools.build.lib.syntax.EvalException;
import com.google.devtools.build.lib.util.OrderedSetMultimap;
import com.google.devtools.build.skyframe.SkyFunction;
import com.google.devtools.build.skyframe.SkyFunctionException;
import com.google.devtools.build.skyframe.SkyKey;
import com.google.devtools.build.skyframe.SkyValue;
import java.util.LinkedHashMap;
import java.util.LinkedHashSet;
import java.util.Map;
import java.util.Set;
import javax.annotation.Nullable;

/**
 * Build a post-processed ConfiguredTarget, vetting it for action conflict issues.
 */
public class PostConfiguredTargetFunction implements SkyFunction {
  private static final Function<Dependency, SkyKey> TO_KEYS =
      new Function<Dependency, SkyKey>() {
        @Override
        public SkyKey apply(Dependency input) {
          return PostConfiguredTargetValue.key(
              ConfiguredTargetKey.of(input.getLabel(), input.getConfiguration()));
        }
      };

  private final SkyframeExecutor.BuildViewProvider buildViewProvider;
  private final ConfiguredRuleClassProvider ruleClassProvider;
  private final BuildOptions defaultBuildOptions;

  public PostConfiguredTargetFunction(
      SkyframeExecutor.BuildViewProvider buildViewProvider,
      ConfiguredRuleClassProvider ruleClassProvider,
      BuildOptions defaultBuildOptions) {
    this.buildViewProvider = Preconditions.checkNotNull(buildViewProvider);
    this.ruleClassProvider = ruleClassProvider;
    this.defaultBuildOptions = defaultBuildOptions;
  }

  @Nullable
  @Override
  public SkyValue compute(SkyKey skyKey, Environment env)
      throws SkyFunctionException, InterruptedException {
    ImmutableMap<ActionAnalysisMetadata, ConflictException> badActions =
        PrecomputedValue.BAD_ACTIONS.get(env);
    ConfiguredTargetValue ctValue =
        (ConfiguredTargetValue) env.getValue((ConfiguredTargetKey) skyKey.argument());
    if (env.valuesMissing()) {
      return null;
    }

    for (ActionAnalysisMetadata action : ctValue.getActions()) {
      if (badActions.containsKey(action)) {
        throw new ActionConflictFunctionException(badActions.get(action));
      }
    }

    ConfiguredTarget ct = ctValue.getConfiguredTarget();
    ConfiguredTargetAndData configuredTargetAndData =
        ConfiguredTargetAndData.fromConfiguredTargetInSkyframe(ct, env);
    if (configuredTargetAndData == null) {
      return null;
    }
    Target target = configuredTargetAndData.getTarget();
    BuildConfiguration configuration = configuredTargetAndData.getConfiguration();
    TargetAndConfiguration ctgValue = new TargetAndConfiguration(target, configuration);

    ImmutableMap<Label, ConfigMatchingProvider> configConditions =
        getConfigurableAttributeConditions(ctgValue, env);
    if (configConditions == null) {
      return null;
    }

    // Determine what toolchains are needed by this target.
    UnloadedToolchainContext unloadedToolchainContext = null;
    try {
      if (target instanceof Rule) {
        Rule rule = ((Rule) target);
        if (rule.getRuleClassObject().useToolchainResolution()) {
          ImmutableSet<Label> requiredToolchains =
              rule.getRuleClassObject().getRequiredToolchains();

          // Collect local (target, rule) constraints for filtering out execution platforms.
          ImmutableSet<Label> execConstraintLabels =
              getExecutionPlatformConstraints(
                  rule, configuration.getFragment(PlatformConfiguration.class));
          unloadedToolchainContext =
              (UnloadedToolchainContext)
                  env.getValueOrThrow(
                      UnloadedToolchainContext.key()
                          .configurationKey(BuildConfigurationValue.key(configuration))
                          .requiredToolchainTypeLabels(requiredToolchains)
                          .execConstraintLabels(execConstraintLabels)
                          .build(),
                      ToolchainException.class);
          if (env.valuesMissing()) {
            return null;
          }
        }
      }
    } catch (ToolchainException e) {
      throw new PostConfiguredTargetFunctionException(e.asConfiguredValueCreationException());
    }

    OrderedSetMultimap<DependencyKind, Dependency> deps;
    try {
      BuildConfiguration hostConfiguration =
          buildViewProvider.getSkyframeBuildView().getHostConfiguration(configuration);
      SkyframeDependencyResolver resolver =
          buildViewProvider.getSkyframeBuildView().createDependencyResolver(env);
      // We don't track root causes here - this function is only invoked for successfully analyzed
      // targets - as long as we redo the exact same steps here as in ConfiguredTargetFunction, this
      // can never fail.
      deps =
          resolver.dependentNodeMap(
              ctgValue,
              hostConfiguration,
              /*aspect=*/ null,
              configConditions,
              unloadedToolchainContext,
              ruleClassProvider.getTrimmingTransitionFactory());
      deps =
          ConfigurationResolver.resolveConfigurations(
              env, ctgValue, deps, hostConfiguration, ruleClassProvider, defaultBuildOptions);
    } catch (EvalException
        | ConfiguredTargetFunction.DependencyEvaluationException
        | InconsistentAspectOrderException e) {
      throw new PostConfiguredTargetFunctionException(e);
    }

    env.getValues(Iterables.transform(deps.values(), TO_KEYS));
    if (env.valuesMissing()) {
      return null;
    }

    return new PostConfiguredTargetValue(ct);
  }

  /**
   * Returns the configurable attribute conditions necessary to evaluate the given configured
   * target, or null if not all dependencies have yet been SkyFrame-evaluated.
   */
  @Nullable
  private static ImmutableMap<Label, ConfigMatchingProvider> getConfigurableAttributeConditions(
      TargetAndConfiguration ctg, Environment env) throws InterruptedException {
    if (!(ctg.getTarget() instanceof Rule)) {
      return ImmutableMap.of();
    }
    Rule rule = (Rule) ctg.getTarget();
    RawAttributeMapper mapper = RawAttributeMapper.of(rule);
    Set<SkyKey> depKeys = new LinkedHashSet<>();
    for (Attribute attribute : rule.getAttributes()) {
      for (Label label : mapper.getConfigurabilityKeys(attribute.getName(), attribute.getType())) {
        if (!BuildType.Selector.isReservedLabel(label)) {
          depKeys.add(ConfiguredTargetValue.key(label, ctg.getConfiguration()));
        }
      }
    }
    Map<SkyKey, SkyValue> cts = env.getValues(depKeys);
    if (env.valuesMissing()) {
      return null;
    }
    Map<Label, ConfigMatchingProvider> conditions = new LinkedHashMap<>();
    for (Map.Entry<SkyKey, SkyValue> entry : cts.entrySet()) {
      Label label = ((ConfiguredTargetKey) entry.getKey().argument()).getLabel();
      ConfiguredTarget ct = ((ConfiguredTargetValue) entry.getValue()).getConfiguredTarget();
      conditions.put(label, Preconditions.checkNotNull(
          ct.getProvider(ConfigMatchingProvider.class)));
    }
    return ImmutableMap.copyOf(conditions);
  }

  @Nullable
  @Override
  public String extractTag(SkyKey skyKey) {
    return Label.print(((ConfiguredTargetKey) skyKey.argument()).getLabel());
  }

  private static class ActionConflictFunctionException extends SkyFunctionException {
    public ActionConflictFunctionException(ConflictException e) {
      super(e, Transience.PERSISTENT);
    }
  }

  private static class PostConfiguredTargetFunctionException extends SkyFunctionException {
    public PostConfiguredTargetFunctionException(Exception e) {
      super(e, Transience.PERSISTENT);
    }
  }
}