// 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.actions;

import com.google.common.annotations.VisibleForTesting;
import com.google.devtools.build.lib.cmdline.Label;
import com.google.devtools.build.lib.skyframe.serialization.ObjectCodec;
import com.google.devtools.build.lib.skyframe.serialization.SingletonCodec;
import com.google.devtools.build.lib.skyframe.serialization.autocodec.AutoCodec;

/**
 * An interface for {@code ActionLookupKey}, or at least for a {@link Label}. Only tests and
 * internal {@link Artifact}-generators should implement this interface -- otherwise, {@code
 * ActionLookupKey} and its subclasses should be the only implementation.
 */
@AutoCodec(strategy = AutoCodec.Strategy.POLYMORPHIC)
public interface ArtifactOwner {
  ObjectCodec<ArtifactOwner> CODEC = new ArtifactOwner_AutoCodec();

  Label getLabel();

  /**
   * An {@link ArtifactOwner} that just returns null for its label. Only for use with resolved
   * source artifacts and tests.
   */
  class NullArtifactOwner implements ArtifactOwner {
    @VisibleForTesting public static final NullArtifactOwner INSTANCE = new NullArtifactOwner();

    static final ObjectCodec<NullArtifactOwner> CODEC = SingletonCodec.of(INSTANCE, "NULL_OWNER");

    private NullArtifactOwner() {}

    @Override
    public Label getLabel() {
      return null;
    }

    @Override
    public String toString() {
      return "NULL_OWNER";
    }
  }
}