// 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.collect.ImmutableSet;
import com.google.devtools.build.lib.vfs.PathFragment;

import java.util.Set;

/**
 * A message sent conveying a set of changed files. This is sent over the event bus if a build is
 * discovered to have changed files. If many files have changed, the set of changed files will
 * be empty, but {@link #getChangedFileCount} will still return the correct number.
 */
public class ChangedFilesMessage {

  private final Set<PathFragment> changedFiles;
  private final int changedFileCount;

  public ChangedFilesMessage(Set<PathFragment> changedFiles, int changedFileCount) {
    this.changedFiles = ImmutableSet.copyOf(changedFiles);
    this.changedFileCount = changedFileCount;
  }

  /**
   * Returns a set with one PathFragment for each file that was changed since the last build, or
   * an empty set if the set is unknown or would be too big.
   */
  public Set<PathFragment> getChangedFiles() {
    return changedFiles;
  }

  /**
   * Returns the number of changed files. This will always be the correct number of files, even when
   * {@link #getChangedFiles} might return an empty set, because the actual set would be too big.
   */
  public int getChangedFileCount() {
    return changedFileCount;
  }
}