// Copyright 2015 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.annotations.VisibleForTesting;
import com.google.common.collect.ImmutableSortedSet;
import com.google.common.collect.Interner;
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.FragmentClassSet;
import com.google.devtools.build.lib.concurrent.BlazeInterners;
import com.google.devtools.build.lib.concurrent.ThreadSafety.ThreadSafe;
import com.google.devtools.build.lib.skyframe.serialization.DeserializationContext;
import com.google.devtools.build.lib.skyframe.serialization.ObjectCodec;
import com.google.devtools.build.lib.skyframe.serialization.SerializationContext;
import com.google.devtools.build.lib.skyframe.serialization.SerializationException;
import com.google.devtools.build.lib.skyframe.serialization.autocodec.AutoCodec;
import com.google.devtools.build.skyframe.SkyFunctionName;
import com.google.devtools.build.skyframe.SkyKey;
import com.google.devtools.build.skyframe.SkyValue;
import com.google.protobuf.ByteString;
import com.google.protobuf.CodedInputStream;
import com.google.protobuf.CodedOutputStream;
import java.io.IOException;
import java.io.Serializable;
import java.util.Objects;
import java.util.Set;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentMap;
import java.util.logging.Logger;

/** A Skyframe value representing a {@link BuildConfiguration}. */
// TODO(bazel-team): mark this immutable when BuildConfiguration is immutable.
// @Immutable
@AutoCodec
@ThreadSafe
public class BuildConfigurationValue implements SkyValue {
  private static final Logger logger = Logger.getLogger(BuildConfigurationValue.class.getName());
  private final BuildConfiguration configuration;

  BuildConfigurationValue(BuildConfiguration configuration) {
    this.configuration = configuration;
  }

  public BuildConfiguration getConfiguration() {
    return configuration;
  }

  /**
   * Returns the key for a requested configuration.
   *
   * @param fragments the fragments the configuration should contain
   * @param optionsDiff the {@link BuildOptions.OptionsDiffForReconstruction} object the {@link
   *     BuildOptions} should be rebuilt from
   */
  @ThreadSafe
  public static Key key(
      Set<Class<? extends BuildConfiguration.Fragment>> fragments,
      BuildOptions.OptionsDiffForReconstruction optionsDiff) {
    return key(
        FragmentClassSet.of(
            ImmutableSortedSet.copyOf(BuildConfiguration.lexicalFragmentSorter, fragments)),
        optionsDiff);
  }

  public static Key key(
      FragmentClassSet fragmentClassSet, BuildOptions.OptionsDiffForReconstruction optionsDiff) {
    return Key.create(fragmentClassSet, optionsDiff);
  }

  public static Key key(BuildConfiguration buildConfiguration) {
    return key(buildConfiguration.fragmentClasses(), buildConfiguration.getBuildOptionsDiff());
  }

  /** {@link SkyKey} for {@link BuildConfigurationValue}. */
  public static final class Key implements SkyKey, Serializable {
    private static final Interner<Key> keyInterner = BlazeInterners.newWeakInterner();

    private final FragmentClassSet fragments;
    private final BuildOptions.OptionsDiffForReconstruction optionsDiff;
    // If hashCode really is -1, we'll recompute it from scratch each time. Oh well.
    private volatile int hashCode = -1;

    private static Key create(
        FragmentClassSet fragments, BuildOptions.OptionsDiffForReconstruction optionsDiff) {
      return keyInterner.intern(new Key(fragments, optionsDiff));
    }

    private Key(FragmentClassSet fragments, BuildOptions.OptionsDiffForReconstruction optionsDiff) {
      this.fragments = fragments;
      this.optionsDiff = optionsDiff;
    }

    @VisibleForTesting
    public ImmutableSortedSet<Class<? extends BuildConfiguration.Fragment>> getFragments() {
      return fragments.fragmentClasses();
    }

    public BuildOptions.OptionsDiffForReconstruction getOptionsDiff() {
      return optionsDiff;
    }

    @Override
    public SkyFunctionName functionName() {
      return SkyFunctions.BUILD_CONFIGURATION;
    }

    @Override
    public boolean equals(Object o) {
      if (this == o) {
        return true;
      }
      if (!(o instanceof Key)) {
        return false;
      }
      Key otherConfig = (Key) o;
      return optionsDiff.equals(otherConfig.optionsDiff)
          && Objects.equals(fragments, otherConfig.fragments);
    }

    @Override
    public int hashCode() {
      if (hashCode == -1) {
        hashCode = Objects.hash(fragments, optionsDiff);
      }
      return hashCode;
    }

    @Override
    public String toString() {
      return "BuildConfigurationValue.Key[" + optionsDiff.getChecksum() + "]";
    }

    private static class Codec implements ObjectCodec<Key> {
      @Override
      public Class<Key> getEncodedClass() {
        return Key.class;
      }

      @Override
      public void serialize(SerializationContext context, Key obj, CodedOutputStream codedOut)
          throws SerializationException, IOException {
        @SuppressWarnings("unchecked")
        ConcurrentMap<BuildConfigurationValue.Key, ByteString> cache =
            context.getDependency(KeyCodecCache.class).map;
        ByteString bytes = cache.get(obj);
        if (bytes == null) {
          context = context.getNewNonMemoizingContext();
          ByteString.Output byteStringOut = ByteString.newOutput();
          CodedOutputStream bytesOut = CodedOutputStream.newInstance(byteStringOut);
          context.serialize(obj.optionsDiff, bytesOut);
          bytesOut.flush();
          byteStringOut.flush();
          int optionsDiffSerializedSize = byteStringOut.size();
          context.serialize(obj.fragments, bytesOut);
          bytesOut.flush();
          byteStringOut.flush();
          bytes = byteStringOut.toByteString();
          cache.put(obj, bytes);
          logger.info(
              "Serialized "
                  + obj.optionsDiff
                  + " and "
                  + obj.fragments
                  + " to "
                  + bytes.size()
                  + " bytes (optionsDiff took "
                  + optionsDiffSerializedSize
                  + " bytes)");
        }
        codedOut.writeBytesNoTag(bytes);
      }

      @Override
      public Key deserialize(DeserializationContext context, CodedInputStream codedIn)
          throws SerializationException, IOException {
        codedIn = codedIn.readBytes().newCodedInput();
        context = context.getNewNonMemoizingContext();
        BuildOptions.OptionsDiffForReconstruction optionsDiff = context.deserialize(codedIn);
        FragmentClassSet fragmentClassSet = context.deserialize(codedIn);
        return key(fragmentClassSet, optionsDiff);
      }
    }
  }

  /**
   * Injected cache for {@code Codec}, so that we don't have to repeatedly serialize the same
   * object. We still incur the over-the-wire cost of the bytes, but we don't use CPU to repeatedly
   * compute it.
   *
   * <p>We provide the cache as an injected dependency so that different serializers' caches are
   * isolated.
   */
  public static class KeyCodecCache {
    private final ConcurrentMap<BuildConfigurationValue.Key, ByteString> map =
        new ConcurrentHashMap<>();

    public KeyCodecCache() {}
  }
}