// 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.analysis;

import static com.google.common.base.MoreObjects.firstNonNull;

import com.google.devtools.build.lib.actions.Artifact;
import com.google.devtools.build.lib.actions.EmptyRunfilesSupplier;
import com.google.devtools.build.lib.actions.RunfilesSupplier;
import com.google.devtools.build.lib.collect.nestedset.NestedSet;
import com.google.devtools.build.lib.collect.nestedset.NestedSetBuilder;
import com.google.devtools.build.lib.collect.nestedset.Order;
import com.google.devtools.build.lib.concurrent.ThreadSafety.Immutable;
import com.google.devtools.build.lib.starlarkbuildapi.FilesToRunProviderApi;
import javax.annotation.Nullable;

/** Returns information about executables produced by a target and the files needed to run it. */
@Immutable
public final class FilesToRunProvider
    implements TransitiveInfoProvider, FilesToRunProviderApi<Artifact> {
  /** The name of the field in Starlark used to access this class. */
  public static final String STARLARK_NAME = "files_to_run";

  public static final FilesToRunProvider EMPTY =
      new FilesToRunProvider(NestedSetBuilder.emptySet(Order.STABLE_ORDER), null, null);

  private final NestedSet<Artifact> filesToRun;
  @Nullable private final RunfilesSupport runfilesSupport;
  @Nullable private final Artifact executable;

  public FilesToRunProvider(
      NestedSet<Artifact> filesToRun,
      @Nullable RunfilesSupport runfilesSupport,
      @Nullable Artifact executable) {
    this.filesToRun = filesToRun;
    this.runfilesSupport = runfilesSupport;
    this.executable  = executable;
  }

  /**
   * Creates an instance that contains one single executable and no other files.
   */
  public static FilesToRunProvider fromSingleExecutableArtifact(Artifact artifact) {
    return new FilesToRunProvider(
        NestedSetBuilder.create(Order.STABLE_ORDER, artifact), null, artifact);
  }

  @Override
  public boolean isImmutable() {
    return true; // immutable and Starlark-hashable
  }

  /** Returns artifacts needed to run the executable for this target. */
  public NestedSet<Artifact> getFilesToRun() {
    return filesToRun;
  }

  /**
   * Returns the {@link RunfilesSupport} object associated with the target or null if it does not
   * exist.
   */
  @Nullable
  public RunfilesSupport getRunfilesSupport() {
    return runfilesSupport;
  }

  /** Returns the Executable or null if it does not exist. */
  @Override
  @Nullable
  public Artifact getExecutable() {
    return executable;
  }

  /**
   * Returns the RunfilesManifest or null if it does not exist. It is a shortcut to
   * getRunfilesSupport().getRunfilesManifest().
   */
  @Override
  @Nullable
  public Artifact getRunfilesManifest() {
    return runfilesSupport != null ? runfilesSupport.getRunfilesManifest() : null;
  }

  /** Return a {@link RunfilesSupplier} encapsulating runfiles for this tool. */
  public RunfilesSupplier getRunfilesSupplier() {
    return firstNonNull(runfilesSupport, EmptyRunfilesSupplier.INSTANCE);
  }
}