// Copyright 2015 Google Inc. 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.bazel.repository;

import com.google.devtools.build.lib.bazel.repository.DecompressorValue.DecompressorDescriptor;
import com.google.devtools.build.lib.bazel.repository.RepositoryFunction.RepositoryFunctionException;
import com.google.devtools.build.lib.vfs.FileSystemUtils;
import com.google.devtools.build.lib.vfs.Path;
import com.google.devtools.build.skyframe.SkyFunction;
import com.google.devtools.build.skyframe.SkyFunctionException.Transience;
import com.google.devtools.build.skyframe.SkyFunctionName;

import com.google.devtools.build.skyframe.SkyKey;
import com.google.devtools.build.skyframe.SkyValue;

import org.apache.commons.compress.archivers.tar.TarArchiveEntry;
import org.apache.commons.compress.archivers.tar.TarArchiveInputStream;

import java.io.FileInputStream;
import java.io.IOException;
import java.nio.file.Files;
import java.util.zip.GZIPInputStream;

import javax.annotation.Nullable;

/**
 * Creates a  repository by unarchiving a .tar.gz file.
 */
public class TarGzFunction implements SkyFunction {

  public static final SkyFunctionName NAME = SkyFunctionName.create("TAR_GZ_FUNCTION");

  @Nullable
  @Override
  public SkyValue compute(SkyKey skyKey, Environment env) throws RepositoryFunctionException {
    DecompressorDescriptor descriptor = (DecompressorDescriptor) skyKey.argument();

    try (GZIPInputStream gzipStream = new GZIPInputStream(
        new FileInputStream(descriptor.archivePath().getPathFile()))) {
      TarArchiveInputStream tarStream = new TarArchiveInputStream(gzipStream);
      TarArchiveEntry entry;
      while ((entry = tarStream.getNextTarEntry()) != null) {
        Path filename = descriptor.repositoryPath().getRelative(entry.getName());
        FileSystemUtils.createDirectoryAndParents(filename.getParentDirectory());
        if (entry.isDirectory()) {
          FileSystemUtils.createDirectoryAndParents(filename);
        } else {
          Files.copy(tarStream, filename.getPathFile().toPath());
          filename.chmod(entry.getMode());
        }
      }
    } catch (IOException e) {
      throw new RepositoryFunctionException(e, Transience.TRANSIENT);
    }
    return new DecompressorValue(descriptor.repositoryPath());
  }

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

}
