// Copyright 2016 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.rules.repository;

import com.google.devtools.build.lib.cmdline.RepositoryName;
import com.google.devtools.build.lib.skyframe.RepositoryValue;
import com.google.devtools.build.skyframe.SkyFunction;
import com.google.devtools.build.skyframe.SkyFunctionException;
import com.google.devtools.build.skyframe.SkyFunctionException.Transience;
import com.google.devtools.build.skyframe.SkyKey;
import com.google.devtools.build.skyframe.SkyValue;
import java.io.IOException;
import javax.annotation.Nullable;

/** Creates a local or remote repository. */
public class RepositoryLoaderFunction implements SkyFunction {

  @Nullable
  @Override
  public SkyValue compute(SkyKey skyKey, Environment env)
      throws SkyFunctionException, InterruptedException {
    // This cannot be combined with {@link RepositoryDelegatorFunction}. RDF fetches the
    // repository and must not have a Skyframe restart after writing it (otherwise the repository
    // would be re-downloaded).
    RepositoryName nameFromRule = (RepositoryName) skyKey.argument();
    SkyKey repositoryKey = RepositoryDirectoryValue.key(nameFromRule);
    RepositoryDirectoryValue repository = (RepositoryDirectoryValue) env.getValue(repositoryKey);
    if (repository == null) {
      return null;
    }
    if (!repository.repositoryExists()) {
      return RepositoryValue.notFound(nameFromRule);
    }
    return RepositoryValue.success(nameFromRule, repository);
  }

  @Nullable
  @Override
  public String extractTag(SkyKey skyKey) {
    return null;
  }

  /** An exception thrown by RepositoryLoaderFunction */
  public static class RepositoryLoaderFunctionException extends SkyFunctionException {

    /** Error reading or writing to the filesystem. */
    public RepositoryLoaderFunctionException(IOException cause, Transience transience) {
      super(cause, transience);
    }
  }
}