// 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.skyframe;

import com.google.common.base.Objects;
import com.google.common.base.Optional;
import com.google.devtools.build.lib.cmdline.PackageIdentifier.RepositoryName;
import com.google.devtools.build.lib.vfs.Path;
import com.google.devtools.build.skyframe.SkyKey;
import com.google.devtools.build.skyframe.SkyValue;

/**
 * A local view of an external repository.
 */
public class RepositoryValue implements SkyValue {
  private final Path path;

  /**
   * This is the FileValue for the [output_base]/external/repo-name directory.
   *
   * <p>If path is a symlink, this will keep track of what the symlink actually points to (for
   * checking equality).</p>
   */
  private final FileValue details;

  /**
   * If this repository is using a user-created BUILD file (any of the new_* functions) then that
   * FileValue needs to be propagated up to the PackageLookup so it doesn't get pruned. The BUILD
   * file symlink will be under external/, thus assumed to be immutable, thus Skyframe will prune
   * it. Then user changes will be ignored (in favor of the cached version).
   */
  private final Optional<FileValue> overlaidBuildFile;

  private RepositoryValue(
      Path path, FileValue repositoryDirectory, Optional<FileValue> overlaidBuildFile) {
    this.path = path;
    this.details = repositoryDirectory;
    this.overlaidBuildFile = overlaidBuildFile;
  }

  /**
   * Creates an immutable external repository.
   */
  public static RepositoryValue create(FileValue repositoryDirectory) {
    return new RepositoryValue(
        repositoryDirectory.realRootedPath().asPath(), repositoryDirectory,
        Optional.<FileValue>absent());
  }

  /**
   * Creates an immutable external repository that's a symlink to elsewhere on the system.
   *
   * <p>For local repositories, the repository path is something like [output root]/external/repo
   * and the repository value resolves that to the actual symlink it points to. We don't want to
   * lose the repository path, so this constructor is used.</p>
   */
  public static RepositoryValue create(Path repositoryDirectory, FileValue details) {
    return new RepositoryValue(repositoryDirectory, details, Optional.<FileValue>absent());
  }

  /**
   * Creates an immutable external repository with a mutable BUILD file.
   */
  public static RepositoryValue createNew(
      FileValue repositoryDirectory, FileValue overlaidBuildFile) {
    return new RepositoryValue(
        repositoryDirectory.realRootedPath().asPath(), repositoryDirectory,
        Optional.of(overlaidBuildFile));
  }

  /**
   * Returns the path to the directory containing the repository's contents. This directory is
   * guaranteed to exist.  It may contain a full Bazel repository (with a WORKSPACE file,
   * directories, and BUILD files) or simply contain a file (or set of files) for, say, a jar from
   * Maven.
   */
  public Path getPath() {
    return path;
  }

  public FileValue getRepositoryDirectory() {
    return details;
  }

  public Optional<FileValue> getOverlaidBuildFile() {
    return overlaidBuildFile;
  }

  @Override
  public boolean equals(Object other) {
    if (this == other) {
      return true;
    }

    if (other instanceof RepositoryValue) {
      RepositoryValue otherValue = (RepositoryValue) other;
      return details.equals(otherValue.details)
          && overlaidBuildFile.equals(otherValue.overlaidBuildFile);
    }
    return false;
  }

  @Override
  public int hashCode() {
    return Objects.hashCode(details, overlaidBuildFile);
  }

  @Override
  public String toString() {
    return details + (overlaidBuildFile.isPresent()
        ? " (BUILD file: " + overlaidBuildFile.get() + ")" : "");
  }

  /**
   * Creates a key from the given repository name.
   */
  public static SkyKey key(RepositoryName repository) {
    return new SkyKey(SkyFunctions.REPOSITORY, repository);
  }
}