// 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.common.collect.ImmutableMap;
import com.google.common.collect.Iterables;
import com.google.devtools.build.lib.actions.FileValue;
import com.google.devtools.build.lib.analysis.BlazeDirectories;
import com.google.devtools.build.lib.analysis.RuleDefinition;
import com.google.devtools.build.lib.bazel.ResolvedEvent;
import com.google.devtools.build.lib.bugreport.BugReport;
import com.google.devtools.build.lib.cmdline.Label;
import com.google.devtools.build.lib.io.InconsistentFilesystemException;
import com.google.devtools.build.lib.packages.BuildType;
import com.google.devtools.build.lib.packages.Rule;
import com.google.devtools.build.lib.skyframe.DirectoryListingValue;
import com.google.devtools.build.lib.vfs.FileSystem;
import com.google.devtools.build.lib.vfs.Path;
import com.google.devtools.build.lib.vfs.PathFragment;
import com.google.devtools.build.lib.vfs.Root;
import com.google.devtools.build.lib.vfs.RootedPath;
import com.google.devtools.build.lib.vfs.XattrProvider;
import com.google.devtools.build.skyframe.SkyFunction.Environment;
import com.google.devtools.build.skyframe.SkyFunctionException.Transience;
import com.google.devtools.build.skyframe.SkyKey;
import com.google.devtools.build.skyframe.SkyValue;
import com.google.devtools.build.skyframe.SkyframeLookupResult;
import java.io.IOException;
import java.util.Map;
import javax.annotation.Nullable;
import net.starlark.java.eval.Starlark;

/**
 * Create a repository from a directory on the local filesystem.
 */
public class NewLocalRepositoryFunction extends RepositoryFunction {

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

  @Override
  @Nullable
  public RepositoryDirectoryValue.Builder fetch(
      Rule rule,
      Path outputDirectory,
      BlazeDirectories directories,
      Environment env,
      Map<String, String> markerData,
      SkyKey key)
      throws InterruptedException, RepositoryFunctionException {

    NewRepositoryFileHandler fileHandler = new NewRepositoryFileHandler(directories.getWorkspace());
    if (!fileHandler.prepareFile(rule, env)) {
      return null;
    }

    String userDefinedPath = getPathAttr(rule);
    PathFragment pathFragment = getTargetPath(userDefinedPath, directories.getWorkspace());

    FileSystem fs = directories.getOutputBase().getFileSystem();
    Path path = fs.getPath(pathFragment);

    RootedPath dirPath = RootedPath.toRootedPath(Root.absoluteRoot(fs), path);

    try {
      FileValue dirFileValue =
          (FileValue) env.getValueOrThrow(FileValue.key(dirPath), IOException.class);
      if (dirFileValue == null) {
        return null;
      }

      if (!dirFileValue.exists()) {
        throw new RepositoryFunctionException(
            new IOException(
                String.format(
                    "The repository's path is \"%s\" (absolute: \"%s\") "
                        + "but this directory does not exist.",
                    userDefinedPath, dirPath.asPath().getPathString())),
            Transience.PERSISTENT);
      }
      if (!dirFileValue.isDirectory()) {
        // Someone tried to create a local repository from a file.
        throw new RepositoryFunctionException(
            new IOException(
                String.format(
                    "The repository's path is \"%s\" (absolute: \"%s\") "
                        + "but this is not a directory.",
                    userDefinedPath, dirPath.asPath().getPathString())),
            Transience.PERSISTENT);
      }
    } catch (IOException e) {
      throw new RepositoryFunctionException(e, Transience.PERSISTENT);
    }

    // fetch() creates symlinks to each child under 'path'.
    //
    // On Linux/macOS (i.e. where file symlinks are supported), DiffAwareness handles checking all
    // of these files and directories for changes.
    //
    // On Windows (when file symlinks are disabled), the supposed symlinks are actually copies and
    // DiffAwareness doesn't pick up changes of the "symlink" targets. To rectify that, we request
    // FileValues for each child of 'path'.
    // See https://github.com/bazelbuild/bazel/issues/7063
    //
    // Furthermore, if a new file/directory is added directly under 'path', Bazel doesn't know that
    // this has to be symlinked in. So we also create a dependency on the contents of the 'path'
    // directory.
    SkyKey dirKey = DirectoryListingValue.key(dirPath);
    DirectoryListingValue directoryValue;
    try {
      directoryValue = (DirectoryListingValue) env.getValueOrThrow(
          dirKey, InconsistentFilesystemException.class);
    } catch (InconsistentFilesystemException e) {
      throw new RepositoryFunctionException(new IOException(e), Transience.PERSISTENT);
    }
    if (directoryValue == null) {
      return null;
    }

    Root root = dirPath.getRoot();
    PathFragment rootRelativePath = dirPath.getRootRelativePath();
    Iterable<SkyKey> skyKeys =
        Iterables.transform(
            directoryValue.getDirents(),
            e ->
                FileValue.key(
                    RootedPath.toRootedPath(root, rootRelativePath.getRelative(e.getName()))));
    SkyframeLookupResult fileValuesResult = env.getValuesAndExceptions(skyKeys);
    if (env.valuesMissing()) {
      return null;
    }
    ImmutableMap.Builder<SkyKey, SkyValue> fileValues =
        ImmutableMap.builderWithExpectedSize(directoryValue.getDirents().size());
    for (SkyKey skyKey : skyKeys) {
      SkyValue value = fileValuesResult.get(skyKey);
      if (value == null) {
        BugReport.sendBugReport(
            new IllegalStateException(
                "SkyValue " + skyKey + " was missing, this should never happen"));
        return null;
      }
      fileValues.put(skyKey, value);
    }

    // Link x/y/z to /some/path/to/y/z.
    if (!symlinkLocalRepositoryContents(outputDirectory, path, userDefinedPath)) {
      return null;
    }

    fileHandler.finishFile(rule, outputDirectory, markerData);
    env.getListener().post(resolve(rule));

    return RepositoryDirectoryValue.builder()
        .setPath(outputDirectory)
        .setSourceDir(directoryValue)
        .setFileValues(fileValues.buildOrThrow());
  }

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

  private static ResolvedEvent resolve(Rule rule) {
    String name = rule.getName();
    Object pathObj = rule.getAttr("path");
    ImmutableMap.Builder<String, Object> origAttr =
        ImmutableMap.<String, Object>builder().put("name", name).put("path", pathObj);

    StringBuilder repr =
        new StringBuilder()
            .append("new_local_repository(name = ")
            .append(Starlark.repr(name))
            .append(", path = ")
            .append(Starlark.repr(pathObj));

    Label buildFile = (Label) rule.getAttr("build_file", BuildType.NODEP_LABEL);
    if (buildFile != null) {
      origAttr.put("build_file", buildFile);
      repr.append(", build_file = ").append(Starlark.repr(buildFile));
    } else {
      Object buildFileContentObj = rule.getAttr("build_file_content");
      if (buildFileContentObj != null) {
        origAttr.put("build_file_content", buildFileContentObj);
        repr.append(", build_file_content = ").append(Starlark.repr(buildFileContentObj));
      }
    }

    String nativeCommand = repr.append(")").toString();
    ImmutableMap<String, Object> orig = origAttr.buildOrThrow();

    return new ResolvedEvent() {
      @Override
      public String getName() {
        return name;
      }

      @Override
      public Object getResolvedInformation(XattrProvider xattrProvider) {
        return ImmutableMap.<String, Object>builder()
            .put(ResolvedFileValue.ORIGINAL_RULE_CLASS, "new_local_repository")
            .put(ResolvedFileValue.ORIGINAL_ATTRIBUTES, orig)
            .put(ResolvedFileValue.NATIVE, nativeCommand)
            .buildOrThrow();
      }
    };
  }
}