// 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 com.google.common.collect.Maps;
import com.google.devtools.build.lib.analysis.DependencyResolver;
import com.google.devtools.build.lib.analysis.TargetAndConfiguration;
import com.google.devtools.build.lib.causes.Cause;
import com.google.devtools.build.lib.causes.LoadingFailedCause;
import com.google.devtools.build.lib.cmdline.Label;
import com.google.devtools.build.lib.collect.nestedset.NestedSetBuilder;
import com.google.devtools.build.lib.events.Event;
import com.google.devtools.build.lib.packages.NoSuchPackageException;
import com.google.devtools.build.lib.packages.NoSuchTargetException;
import com.google.devtools.build.lib.packages.NoSuchThingException;
import com.google.devtools.build.lib.packages.Package;
import com.google.devtools.build.lib.packages.Target;
import com.google.devtools.build.lib.packages.TargetUtils;
import com.google.devtools.build.lib.util.OrderedSetMultimap;
import com.google.devtools.build.skyframe.SkyFunction.Environment;
import com.google.devtools.build.skyframe.SkyKey;
import com.google.devtools.build.skyframe.ValueOrException;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.stream.Collectors;
import javax.annotation.Nullable;

/**
 * A dependency resolver for use within Skyframe. Loads packages lazily when possible.
 */
public final class SkyframeDependencyResolver extends DependencyResolver {

  private final Environment env;

  public SkyframeDependencyResolver(Environment env) {
    this.env = env;
  }

  @Override
  protected void invalidPackageGroupReferenceHook(TargetAndConfiguration value, Label label) {
    env.getListener().handle(
        Event.error(TargetUtils.getLocationMaybe(value.getTarget()), String.format(
            "label '%s' does not refer to a package group", label)));
  }

  private void missingEdgeHook(
      Target from, DependencyKind dependencyKind, Label to, NoSuchThingException e) {
    boolean raiseError = false;
    if (e instanceof NoSuchTargetException) {
      NoSuchTargetException nste = (NoSuchTargetException) e;
      raiseError = to.equals(nste.getLabel());
    } else if (e instanceof NoSuchPackageException) {
      NoSuchPackageException nspe = (NoSuchPackageException) e;
      raiseError = nspe.getPackageId().equals(to.getPackageIdentifier());
    }

    if (!raiseError) {
      return;
    }

    String message;
    if (dependencyKind == TOOLCHAIN_DEPENDENCY) {
      message =
          String.format(
              "Target '%s' depends on toolchain '%s', which cannot be found: %s'",
              from.getLabel(), to, e.getMessage());
    } else {
      message = TargetUtils.formatMissingEdge(from, to, e);
    }

    env.getListener().handle(Event.error(TargetUtils.getLocationMaybe(from), message));
  }

  @Nullable
  @Override
  protected Map<Label, Target> getTargets(
      OrderedSetMultimap<DependencyKind, Label> labelMap,
      Target fromTarget,
      NestedSetBuilder<Cause> rootCauses)
      throws InterruptedException {

    List<PackageValue.Key> packageKeys =
        labelMap.entries().stream()
            .map(e -> e.getValue().getPackageIdentifier())
            .distinct()
            .map(i -> PackageValue.key(i))
            .collect(Collectors.toList());

    Map<SkyKey, ValueOrException<NoSuchPackageException>> packages =
        env.getValuesOrThrow(packageKeys, NoSuchPackageException.class);

    // As per the comment in SkyFunctionEnvironment.getValueOrUntypedExceptions(), we are supposed
    // to prefer reporting errors to reporting null, we first check for errors in our dependencies.
    // This, of course, results in some wasted work in case this will need to be restarted later.

    // Duplicates can occur, so we can't use ImmutableMap.
    HashMap<Label, Target> result = Maps.newHashMapWithExpectedSize(labelMap.size());
    for (Map.Entry<DependencyKind, Label> entry : labelMap.entries()) {
      Label label = entry.getValue();
      if (result.containsKey(label)) {
        continue;
      }

      PackageValue packageValue;
      try {
        packageValue =
            (PackageValue) packages.get(PackageValue.key(label.getPackageIdentifier())).get();
        if (packageValue == null) {
          // Dependency has not been computed yet. There will be a next iteration.
          continue;
        }
      } catch (NoSuchPackageException e) {
        rootCauses.add(new LoadingFailedCause(label, e.getMessage()));
        missingEdgeHook(fromTarget, entry.getKey(), label, e);
        continue;
      }

      Package pkg = packageValue.getPackage();
      try {
        Target target = pkg.getTarget(label.getName());
        if (pkg.containsErrors()) {
          NoSuchTargetException e = new NoSuchTargetException(target);
          missingEdgeHook(fromTarget, entry.getKey(), label, e);
          rootCauses.add(new LoadingFailedCause(label, e.getMessage()));
        }
        result.put(label, target);
      } catch (NoSuchTargetException e) {
        rootCauses.add(new LoadingFailedCause(label, e.getMessage()));
        missingEdgeHook(fromTarget, entry.getKey(), label, e);
      }
    }

    return env.valuesMissing() ? null : result;
  }
}