// Copyright 2016 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.ImmutableCollection;
import com.google.common.collect.ImmutableMap;
import com.google.common.collect.ImmutableSet;
import com.google.devtools.build.lib.analysis.BlazeDirectories;
import com.google.devtools.build.lib.cmdline.RepositoryName;
import com.google.devtools.build.lib.packages.Package;
import com.google.devtools.build.lib.skyframe.RecursivePkgValue.RecursivePkgKey;
import com.google.devtools.build.lib.vfs.PathFragment;
import com.google.devtools.build.lib.vfs.RootedPath;
import com.google.devtools.build.skyframe.SkyFunction;
import com.google.devtools.build.skyframe.SkyKey;
import com.google.devtools.build.skyframe.SkyValue;
import java.util.Map;
import javax.annotation.Nullable;

/**
 * <p>Computes {@link CollectPackagesUnderDirectoryValue} which describes whether the directory is a
 * package and whether non-excluded packages exist below each of the directory's subdirectories. As
 * a side effect, loads all of these packages, in order to interleave the disk-bound work of
 * checking for directories and the CPU-bound work of package loading.
 */
public class CollectPackagesUnderDirectoryFunction implements SkyFunction {
  private final BlazeDirectories directories;

  public CollectPackagesUnderDirectoryFunction(BlazeDirectories directories) {
    this.directories = directories;
  }

  @Override
  public SkyValue compute(SkyKey skyKey, Environment env) throws InterruptedException {
    return new MyTraversalFunction().visitDirectory((RecursivePkgKey) skyKey.argument(), env);
  }

  private class MyTraversalFunction
      extends RecursiveDirectoryTraversalFunction<MyVisitor, CollectPackagesUnderDirectoryValue> {

    private MyTraversalFunction() {
      super(directories);
    }

    @Override
    protected MyVisitor getInitialVisitor() {
      return new MyVisitor();
    }

    @Override
    protected SkyKey getSkyKeyForSubdirectory(
        RepositoryName repository,
        RootedPath subdirectory,
        ImmutableSet<PathFragment> excludedSubdirectoriesBeneathSubdirectory) {
      return CollectPackagesUnderDirectoryValue.key(
          repository, subdirectory, excludedSubdirectoriesBeneathSubdirectory);
    }

    @Override
    protected CollectPackagesUnderDirectoryValue aggregateWithSubdirectorySkyValues(
        MyVisitor visitor, Map<SkyKey, SkyValue> subdirectorySkyValues) {
      // Aggregate the child subdirectory package state.
      ImmutableMap.Builder<RootedPath, Boolean> builder = ImmutableMap.builder();
      for (SkyKey key : subdirectorySkyValues.keySet()) {
        RecursivePkgKey recursivePkgKey = (RecursivePkgKey) key.argument();
        CollectPackagesUnderDirectoryValue collectPackagesValue =
            (CollectPackagesUnderDirectoryValue) subdirectorySkyValues.get(key);
        boolean packagesInSubdirectory = collectPackagesValue.isDirectoryPackage();
        // If the subdirectory isn't a package, check to see if any of its subdirectories
        // transitively contain packages.
        if (!packagesInSubdirectory) {
          ImmutableCollection<Boolean> subdirectoryValues =
              collectPackagesValue.getSubdirectoryTransitivelyContainsPackages().values();
          for (Boolean pkgsInSubSub : subdirectoryValues) {
            if (pkgsInSubSub) {
              packagesInSubdirectory = true;
              break;
            }
          }
        }
        builder.put(recursivePkgKey.getRootedPath(), packagesInSubdirectory);
      }
      return CollectPackagesUnderDirectoryValue.of(visitor.isDirectoryPackage(), builder.build());
    }
  }

  private static class MyVisitor implements RecursiveDirectoryTraversalFunction.Visitor {

    private boolean isDirectoryPackage;

    private MyVisitor() {}

    @Override
    public void visitPackageValue(Package pkg, Environment env) {
      isDirectoryPackage = true;
    }

    boolean isDirectoryPackage() {
      return isDirectoryPackage;
    }
  }

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