// 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.skyframe;

import com.google.common.base.Predicates;
import com.google.common.collect.ArrayListMultimap;
import com.google.common.collect.ImmutableList;
import com.google.common.collect.ImmutableSet;
import com.google.common.collect.ImmutableSortedSet;
import com.google.common.collect.Multimap;
import com.google.devtools.build.lib.analysis.AnalysisUtils;
import com.google.devtools.build.lib.analysis.ConfiguredRuleClassProvider;
import com.google.devtools.build.lib.analysis.Dependency;
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.ConfigurationResolver;
import com.google.devtools.build.lib.analysis.config.HostTransition;
import com.google.devtools.build.lib.analysis.config.InvalidConfigurationException;
import com.google.devtools.build.lib.analysis.skylark.StarlarkTransition;
import com.google.devtools.build.lib.analysis.skylark.StarlarkTransition.TransitionException;
import com.google.devtools.build.lib.cmdline.Label;
import com.google.devtools.build.lib.cmdline.ResolvedTargets;
import com.google.devtools.build.lib.events.ErrorSensingEventHandler;
import com.google.devtools.build.lib.packages.NoSuchThingException;
import com.google.devtools.build.lib.packages.Target;
import com.google.devtools.build.lib.skyframe.PrepareAnalysisPhaseValue.PrepareAnalysisPhaseKey;
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 com.google.devtools.build.skyframe.ValueOrException;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.HashSet;
import java.util.LinkedHashMap;
import java.util.LinkedHashSet;
import java.util.List;
import java.util.Map;
import java.util.Set;
import javax.annotation.Nullable;

/**
 * Prepares for analysis - creates the top-level configurations and evaluates the transitions needed
 * for the top-level targets (including trimming).
 */
final class PrepareAnalysisPhaseFunction implements SkyFunction {
  private final ConfiguredRuleClassProvider ruleClassProvider;
  private final BuildOptions defaultBuildOptions;

  PrepareAnalysisPhaseFunction(
      ConfiguredRuleClassProvider ruleClassProvider, BuildOptions defaultBuildOptions) {
    this.ruleClassProvider = ruleClassProvider;
    this.defaultBuildOptions = defaultBuildOptions;
  }

  @Override
  public PrepareAnalysisPhaseValue compute(SkyKey key, Environment env)
      throws InterruptedException, PrepareAnalysisPhaseFunctionException {
    PrepareAnalysisPhaseKey options = (PrepareAnalysisPhaseKey) key.argument();

    BuildOptions targetOptions = defaultBuildOptions.applyDiff(options.getOptionsDiff());
    BuildOptions hostOptions =
        targetOptions.get(BuildConfiguration.Options.class).useDistinctHostConfiguration
            ? HostTransition.INSTANCE.patch(targetOptions)
            : targetOptions;

    ImmutableSortedSet<Class<? extends BuildConfiguration.Fragment>> allFragments =
        options.getFragments().fragmentClasses();
    BuildConfigurationValue.Key hostConfigurationKey =
        BuildConfigurationValue.key(
            allFragments,
            BuildOptions.diffForReconstruction(defaultBuildOptions, hostOptions));
    ImmutableList<BuildConfigurationValue.Key> targetConfigurationKeys =
        getTopLevelBuildOptions(targetOptions, options.getMultiCpu())
            .stream()
            .map(
                elem ->
                    BuildConfigurationValue.key(
                        allFragments,
                        BuildOptions.diffForReconstruction(defaultBuildOptions, elem)))
            .collect(ImmutableList.toImmutableList());

    // We don't need the host configuration below, but we call this to get the error, if any.
    try {
      env.getValueOrThrow(hostConfigurationKey, InvalidConfigurationException.class);
    } catch (InvalidConfigurationException e) {
      throw new PrepareAnalysisPhaseFunctionException(e);
    }

    Map<SkyKey, SkyValue> configs = env.getValues(targetConfigurationKeys);

    // We only report invalid options for the target configurations, and abort if there's an error.
    ErrorSensingEventHandler nosyEventHandler = new ErrorSensingEventHandler(env.getListener());
    targetConfigurationKeys
        .stream()
        .map(k -> configs.get(k))
        .filter(Predicates.notNull())
        .map(v -> ((BuildConfigurationValue) v).getConfiguration())
        .forEach(config -> config.reportInvalidOptions(nosyEventHandler));
    if (nosyEventHandler.hasErrors()) {
      throw new PrepareAnalysisPhaseFunctionException(
          new InvalidConfigurationException("Build options are invalid"));
    }

    // We get the list of labels from the TargetPatternPhaseValue, so we are reasonably certain that
    // there will not be an error loading these again.
    ResolvedTargets<Target> resolvedTargets =
        TestSuiteExpansionFunction.labelsToTargets(env, options.getLabels(), false);
    if (resolvedTargets == null) {
      return null;
    }
    ImmutableSet<Target> targets = resolvedTargets.getTargets();

    // We use a hash set here to remove duplicate nodes; this can happen for input files and package
    // groups.
    LinkedHashSet<TargetAndConfiguration> nodes = new LinkedHashSet<>(targets.size());
    for (Target target : targets) {
      if (target.isConfigurable()) {
        for (BuildConfigurationValue.Key configKey : targetConfigurationKeys) {
          BuildConfiguration config =
              ((BuildConfigurationValue) configs.get(configKey)).getConfiguration();
          nodes.add(new TargetAndConfiguration(target, config));
        }
      } else {
        nodes.add(new TargetAndConfiguration(target, null));
      }
    }

    // We'll get the configs from #resolveConfigurations below, which started out as a copy of the
    // same code in SkyframeExecutor, which gets configurations for deps including transitions. So,
    // for now, to satisfy its API we resolve transitions and repackage each target as a Dependency
    // (with a NONE transition if necessary).
    // Keep this in sync with AnalysisUtils#getTargetsWithConfigs.
    Multimap<BuildConfiguration, Dependency> asDeps =
        AnalysisUtils.targetsToDeps(nodes, ruleClassProvider);
    LinkedHashSet<TargetAndConfiguration> topLevelTargetsWithConfigs;
    try {
      topLevelTargetsWithConfigs = resolveConfigurations(env, nodes, asDeps);
    } catch (TransitionException e) {
      throw new PrepareAnalysisPhaseFunctionException(new InvalidConfigurationException(e));
    }
    if (env.valuesMissing()) {
      return null;
    }
    ImmutableList<ConfiguredTargetKey> topLevelCtKeys =
        topLevelTargetsWithConfigs
            .stream()
            .map(node -> ConfiguredTargetKey.of(node.getLabel(), node.getConfiguration()))
            .collect(ImmutableList.toImmutableList());
    return new PrepareAnalysisPhaseValue(
        hostConfigurationKey, targetConfigurationKeys, topLevelCtKeys);
  }

  /**
   * Returns the {@link BuildOptions} to apply to the top-level build configurations. This can be
   * plural because of {@code multiCpu}.
   */
  // Visible for SkyframeExecutor, which uses it for tests.
  static List<BuildOptions> getTopLevelBuildOptions(
      BuildOptions buildOptions, Set<String> multiCpu) {
    if (multiCpu.isEmpty()) {
      return ImmutableList.of(buildOptions);
    }
    ImmutableList.Builder<BuildOptions> multiCpuOptions = ImmutableList.builder();
    for (String cpu : multiCpu) {
      BuildOptions clonedOptions = buildOptions.clone();
      clonedOptions.get(BuildConfiguration.Options.class).cpu = cpu;
      multiCpuOptions.add(clonedOptions);
    }
    return multiCpuOptions.build();
  }

  // TODO(bazel-team): error out early for targets that fail - untrimmed configurations should
  // never make it through analysis (and especially not seed ConfiguredTargetValues)
  // Keep this in sync with {@link ConfigurationResolver#getConfigurationsFromExecutor}.
  private LinkedHashSet<TargetAndConfiguration> resolveConfigurations(
      SkyFunction.Environment env,
      Iterable<TargetAndConfiguration> nodes,
      Multimap<BuildConfiguration, Dependency> asDeps)
      throws InterruptedException, TransitionException {
    Map<Label, Target> labelsToTargets = new LinkedHashMap<>();
    for (TargetAndConfiguration node : nodes) {
      labelsToTargets.put(node.getTarget().getLabel(), node.getTarget());
    }

    // Maps <target, originalConfig> pairs to <target, finalConfig> pairs for targets that
    // could be successfully Skyframe-evaluated.
    Map<TargetAndConfiguration, TargetAndConfiguration> successfullyEvaluatedTargets =
        new LinkedHashMap<>();
    for (BuildConfiguration fromConfig : asDeps.keySet()) {
      Multimap<Dependency, BuildConfiguration> trimmedTargets =
          getConfigurations(
              env, fromConfig.getOptions(), asDeps.get(fromConfig));
      if (trimmedTargets == null) {
        continue;
      }
      for (Map.Entry<Dependency, BuildConfiguration> trimmedTarget : trimmedTargets.entries()) {
        Target target = labelsToTargets.get(trimmedTarget.getKey().getLabel());
        successfullyEvaluatedTargets.put(
            new TargetAndConfiguration(target, fromConfig),
            new TargetAndConfiguration(target, trimmedTarget.getValue()));
      }
    }

    if (env.valuesMissing()) {
      return null;
    }

    LinkedHashSet<TargetAndConfiguration> result = new LinkedHashSet<>();
    for (TargetAndConfiguration originalNode : nodes) {
      if (successfullyEvaluatedTargets.containsKey(originalNode)) {
        // The configuration was successfully trimmed.
        result.add(successfullyEvaluatedTargets.get(originalNode));
      } else {
        // Either the configuration couldn't be determined (e.g. loading phase error) or it's null.
        result.add(originalNode);
      }
    }
    return result;
  }

  /**
   * Returns whether configurations should trim their fragments to only those needed by
   * targets and their transitive dependencies.
   */
  private static boolean useUntrimmedConfigs(BuildOptions options) {
    return options.get(BuildConfiguration.Options.class).configsMode
        == BuildConfiguration.Options.ConfigsMode.NOTRIM;
  }

  // Keep in sync with {@link SkyframeExecutor#getConfigurations}.
  // Note: this implementation runs inside Skyframe, so it has access to SkyFunction.Environment.
  private Multimap<Dependency, BuildConfiguration> getConfigurations(
      SkyFunction.Environment env, BuildOptions fromOptions, Iterable<Dependency> keys)
      throws InterruptedException, TransitionException {
    Multimap<Dependency, BuildConfiguration> builder =
        ArrayListMultimap.<Dependency, BuildConfiguration>create();
    Set<Dependency> depsToEvaluate = new HashSet<>();

    ImmutableSortedSet<Class<? extends BuildConfiguration.Fragment>> allFragments = null;
    if (useUntrimmedConfigs(fromOptions)) {
      allFragments = ruleClassProvider.getAllFragments();
    }

    // Get the fragments needed for dynamic configuration nodes.
    final List<SkyKey> transitiveFragmentSkyKeys = new ArrayList<>();
    Map<Label, ImmutableSortedSet<Class<? extends BuildConfiguration.Fragment>>> fragmentsMap =
        new HashMap<>();
    Set<Label> labelsWithErrors = new HashSet<>();
    for (Dependency key : keys) {
      if (key.hasExplicitConfiguration()) {
        builder.put(key, key.getConfiguration());
      } else if (useUntrimmedConfigs(fromOptions)) {
        fragmentsMap.put(key.getLabel(), allFragments);
      } else {
        depsToEvaluate.add(key);
        transitiveFragmentSkyKeys.add(TransitiveTargetKey.of(key.getLabel()));
      }
    }
    Map<SkyKey, ValueOrException<NoSuchThingException>> fragmentsResult =
        env.getValuesOrThrow(transitiveFragmentSkyKeys, NoSuchThingException.class);
    if (env.valuesMissing()) {
      return null;
    }
    for (Dependency key : keys) {
      if (!depsToEvaluate.contains(key)) {
        // No fragments to compute here.
      } else {
        TransitiveTargetKey targetKey = TransitiveTargetKey.of(key.getLabel());
        try {
          TransitiveTargetValue ttv =
              (TransitiveTargetValue) fragmentsResult.get(targetKey).get();
          fragmentsMap.put(
              key.getLabel(),
              ImmutableSortedSet.copyOf(
                  BuildConfiguration.lexicalFragmentSorter,
                  ttv.getTransitiveConfigFragments().toSet()));
        } catch (NoSuchThingException e) {
          // We silently skip any labels with errors - they'll be reported in the analysis phase.
          labelsWithErrors.add(key.getLabel());
        }
      }
    }

    // Now get the configurations.
    final List<SkyKey> configSkyKeys = new ArrayList<>();
    for (Dependency key : keys) {
      if (labelsWithErrors.contains(key.getLabel()) || key.hasExplicitConfiguration()) {
        continue;
      }
      ImmutableSortedSet<Class<? extends BuildConfiguration.Fragment>> depFragments =
          fragmentsMap.get(key.getLabel());
      if (depFragments != null) {
        for (BuildOptions toOptions : ConfigurationResolver.applyTransition(
            fromOptions, key.getTransition(), depFragments, ruleClassProvider, true)) {
          StarlarkTransition.postProcessStarlarkTransitions(env.getListener(), key.getTransition());
          configSkyKeys.add(
              BuildConfigurationValue.key(
                  depFragments,
                  BuildOptions.diffForReconstruction(defaultBuildOptions, toOptions)));
        }
      }
    }
    Map<SkyKey, SkyValue> configsResult = env.getValues(configSkyKeys);
    if (env.valuesMissing()) {
      return null;
    }
    for (Dependency key : keys) {
      if (labelsWithErrors.contains(key.getLabel()) || key.hasExplicitConfiguration()) {
        continue;
      }
      ImmutableSortedSet<Class<? extends BuildConfiguration.Fragment>> depFragments =
          fragmentsMap.get(key.getLabel());
      if (depFragments != null) {
        for (BuildOptions toOptions : ConfigurationResolver.applyTransition(
            fromOptions, key.getTransition(), depFragments, ruleClassProvider, true)) {
          SkyKey configKey =
              BuildConfigurationValue.key(
                  depFragments, BuildOptions.diffForReconstruction(defaultBuildOptions, toOptions));
          BuildConfigurationValue configValue =
              ((BuildConfigurationValue) configsResult.get(configKey));
          // configValue will be null here if there was an exception thrown during configuration
          // creation. This will be reported elsewhere.
          if (configValue != null) {
            builder.put(key, configValue.getConfiguration());
          }
        }
      }
    }
    return builder;
  }

  @Nullable
  @Override
  public String extractTag(SkyKey skyKey) {
    return null;
  }

  /**
   * Used to declare all the exception types that can be wrapped in the exception thrown by
   * {@link PrepareAnalysisPhaseFunction#compute}.
   */
  private static final class PrepareAnalysisPhaseFunctionException extends SkyFunctionException {
    public PrepareAnalysisPhaseFunctionException(InvalidConfigurationException e) {
      super(e, Transience.PERSISTENT);
    }
  }
}