// 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.skyframe;

import com.google.devtools.build.lib.util.StringUtil;
import com.google.devtools.build.skyframe.proto.GraphInconsistency.Inconsistency;
import java.util.Collection;
import javax.annotation.Nullable;

/**
 * A receiver that can be informed of inconsistencies detected in Skyframe. Such inconsistencies are
 * usually the result of external data loss (such as nodes in the graph, or the results of external
 * computations stored in a remote execution service).
 *
 * <p>The receiver can tolerate such inconsistencies, or throw hard if they are unexpected.
 */
public interface GraphInconsistencyReceiver {
  /**
   * How many child {@link SkyKey}s {@link #listChildren} will show for bulk inconsistency events.
   */
  int LOGGED_CHILDREN_LIMIT = 50;

  void noteInconsistencyAndMaybeThrow(
      SkyKey key, @Nullable Collection<SkyKey> otherKeys, Inconsistency inconsistency);

  /** A {@link GraphInconsistencyReceiver} that crashes on any inconsistency. */
  GraphInconsistencyReceiver THROWING =
      (key, otherKey, inconsistency) -> {
        throw new IllegalStateException(
            "Unexpected inconsistency: " + key + ", " + otherKey + ", " + inconsistency);
      };

  static String listChildren(Collection<SkyKey> children) {
    return StringUtil.listItemsWithLimit(new StringBuilder(), LOGGED_CHILDREN_LIMIT, children)
        .toString();
  }

  default boolean restartPermitted() {
    return false;
  }
}