// 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.rules.repository;

import com.google.devtools.build.lib.analysis.BlazeDirectories;
import com.google.devtools.build.lib.analysis.RuleDefinition;
import com.google.devtools.build.lib.packages.Rule;
import com.google.devtools.build.lib.skyframe.FileSymlinkException;
import com.google.devtools.build.lib.skyframe.FileValue;
import com.google.devtools.build.lib.skyframe.InconsistentFilesystemException;
import com.google.devtools.build.lib.skyframe.PackageLookupValue;
import com.google.devtools.build.lib.vfs.Path;
import com.google.devtools.build.lib.vfs.PathFragment;
import com.google.devtools.build.lib.vfs.RootedPath;
import com.google.devtools.build.skyframe.SkyFunction.Environment;
import com.google.devtools.build.skyframe.SkyFunctionException.Transience;
import com.google.devtools.build.skyframe.SkyKey;
import java.io.IOException;
import java.util.Map;
import javax.annotation.Nullable;

/**
 * Access a repository on the local filesystem.
 */
public class LocalRepositoryFunction extends RepositoryFunction {

  @Override
  public boolean isLocal(Rule rule) {
    return true;
  }

  @Override
  public RepositoryDirectoryValue.Builder fetch(Rule rule, Path outputDirectory,
      BlazeDirectories directories, Environment env, Map<String, String> markerData)
      throws InterruptedException, RepositoryFunctionException {
    PathFragment pathFragment = RepositoryFunction.getTargetPath(rule, directories.getWorkspace());
    return LocalRepositoryFunction.symlink(outputDirectory, pathFragment, env);
  }

  public static RepositoryDirectoryValue.Builder symlink(
      Path source, PathFragment destination, Environment env)
      throws RepositoryFunctionException, InterruptedException {
    try {
      source.createSymbolicLink(destination);
    } catch (IOException e) {
      throw new RepositoryFunctionException(
          new IOException("Could not create symlink to repository " + destination + ": "
              + e.getMessage(), e), Transience.TRANSIENT);
    }
    FileValue repositoryValue = getRepositoryDirectory(source, env);
    if (repositoryValue == null) {
      // TODO(bazel-team): If this returns null, we unnecessarily recreate the symlink above on the
      // second execution.
      return null;
    }

    if (!repositoryValue.isDirectory()) {
      throw new RepositoryFunctionException(
          new IOException(source + " must be an existing directory"), Transience.PERSISTENT);
    }

    // Check that the repository contains a WORKSPACE file.
    // It's important to check the real path, otherwise this looks under the "external/[repo]" path
    // and cause a Skyframe cycle in the lookup.
    FileValue workspaceFileValue = getWorkspaceFile(repositoryValue.realRootedPath(), env);
    if (workspaceFileValue == null) {
      return null;
    }

    if (!workspaceFileValue.exists()) {
      throw new RepositoryFunctionException(
          new IOException("No WORKSPACE file found in " + source), Transience.PERSISTENT);
    }

    return RepositoryDirectoryValue.builder().setPath(source);
  }

  @Override
  public Class<? extends RuleDefinition> getRuleDefinition() {
    return LocalRepositoryRule.class;
  }

  @Nullable
  protected static FileValue getWorkspaceFile(RootedPath directory, Environment env)
      throws RepositoryFunctionException, InterruptedException {
    RootedPath workspaceRootedFile =
        RootedPath.toRootedPath(
            directory.getRoot(),
            directory
                .getRelativePath()
                .getRelative(PackageLookupValue.BuildFileName.WORKSPACE.getFilenameFragment()));

    SkyKey workspaceFileKey = FileValue.key(workspaceRootedFile);
    FileValue value;
    try {
      value =
          (FileValue)
              env.getValueOrThrow(
                  workspaceFileKey,
                  IOException.class,
                  FileSymlinkException.class,
                  InconsistentFilesystemException.class);
    } catch (IOException | FileSymlinkException | InconsistentFilesystemException e) {
      throw new RepositoryFunctionException(
          new IOException("Could not access " + workspaceRootedFile + ": " + e.getMessage()),
          Transience.PERSISTENT);
    }
    return value;
  }
}