// 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.skyframe;

import com.google.common.annotations.VisibleForTesting;
import com.google.devtools.build.skyframe.InvalidatingNodeVisitor.DeletingNodeVisitor;
import com.google.devtools.build.skyframe.InvalidatingNodeVisitor.DirtyingNodeVisitor;
import com.google.devtools.build.skyframe.InvalidatingNodeVisitor.InvalidationState;
import javax.annotation.Nullable;

/**
 * Utility class for performing eager invalidation on Skyframe graphs.
 *
 * <p>This is intended only for use in alternative {@code MemoizingEvaluator} implementations.
 */
public final class EagerInvalidator {

  private EagerInvalidator() {}

  /**
   * Deletes given values. The {@code traverseGraph} parameter controls whether this method deletes
   * (transitive) dependents of these nodes and relevant graph edges, or just the nodes themselves.
   * Deleting just the nodes is inconsistent unless the graph will not be used for incremental
   * builds in the future, but unfortunately there is a case where we delete nodes intra-build. As
   * long as the full upward transitive closure of the nodes is specified for deletion, the graph
   * remains consistent.
   */
  public static void delete(
      InMemoryGraph graph,
      Iterable<SkyKey> diff,
      DirtyTrackingProgressReceiver progressReceiver,
      InvalidatingNodeVisitor.DeletingInvalidationState state,
      boolean traverseGraph)
      throws InterruptedException {
    DeletingNodeVisitor visitor =
        createDeletingVisitorIfNeeded(
            graph, diff, progressReceiver, state, traverseGraph);
    if (visitor != null) {
      visitor.run();
    }
  }

  @VisibleForTesting
  @Nullable
  static DeletingNodeVisitor createDeletingVisitorIfNeeded(
      InMemoryGraph graph,
      Iterable<SkyKey> diff,
      DirtyTrackingProgressReceiver progressReceiver,
      InvalidatingNodeVisitor.DeletingInvalidationState state,
      boolean traverseGraph) {
    state.update(diff);
    return state.isEmpty() ? null
        : new DeletingNodeVisitor(graph, progressReceiver, state, traverseGraph);
  }

  @VisibleForTesting
  @Nullable
  static DirtyingNodeVisitor createInvalidatingVisitorIfNeeded(
      QueryableGraph graph,
      Iterable<SkyKey> diff,
      DirtyTrackingProgressReceiver progressReceiver,
      InvalidationState state) {
    state.update(diff);
    return state.isEmpty() ? null : new DirtyingNodeVisitor(graph, progressReceiver, state);
  }

  /** Invalidates given values and their upward transitive closure in the graph if necessary. */
  public static void invalidate(
      QueryableGraph graph,
      Iterable<SkyKey> diff,
      DirtyTrackingProgressReceiver progressReceiver,
      InvalidationState state)
      throws InterruptedException {
    DirtyingNodeVisitor visitor =
        createInvalidatingVisitorIfNeeded(graph, diff, progressReceiver, state);
    if (visitor != null) {
      visitor.run();
    }
  }
}