/*
 * Copyright 2014-present Facebook, Inc.
 *
 * 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.facebook.buck.cxx;

import com.facebook.buck.jvm.java.Javac;
import com.facebook.buck.log.Logger;
import com.facebook.buck.rules.SourcePathResolver;
import com.facebook.buck.rules.args.Arg;
import com.facebook.buck.rules.args.FileListableLinkerInputArg;
import com.facebook.buck.rules.args.StringArg;
import com.facebook.buck.step.Step;
import com.facebook.buck.util.MoreCollectors;
import com.google.common.collect.ImmutableList;
import java.nio.file.Path;
import java.util.Optional;

/**
 * Prepares argfile for the CxxLinkStep, so all arguments to the linker will be stored in a single
 * file. CxxLinkStep then would pass it to the linker via @path/to/the.argsfile command. This allows
 * us to break the constraints that command line sets for the maximum length of the commands.
 */
public class CxxPrepareForLinkStep {

  private static final Logger LOG = Logger.get(CxxPrepareForLinkStep.class);

  public static ImmutableList<Step> create(
      Path argFilePath,
      Path fileListPath,
      Iterable<Arg> linkerArgsToSupportFileList,
      Path output,
      ImmutableList<Arg> args,
      Linker linker,
      Path currentCellPath,
      SourcePathResolver resolver) {

    ImmutableList<Arg> allArgs =
        new ImmutableList.Builder<Arg>()
            .addAll(StringArg.from(linker.outputArgs(output.toString())))
            .addAll(args)
            .addAll(linkerArgsToSupportFileList)
            .build();

    boolean hasLinkArgsToSupportFileList = linkerArgsToSupportFileList.iterator().hasNext();

    LOG.debug(
        "Link command (pwd=%s): %s %s",
        currentCellPath.toString(),
        String.join("", linker.getCommandPrefix(resolver)),
        String.join(" ", CxxWriteArgsToFileStep.stringify(allArgs, currentCellPath, resolver)));

    CxxWriteArgsToFileStep createArgFileStep =
        CxxWriteArgsToFileStep.create(
            argFilePath,
            hasLinkArgsToSupportFileList
                ? allArgs
                    .stream()
                    .filter(input -> !(input instanceof FileListableLinkerInputArg))
                    .collect(MoreCollectors.toImmutableList())
                : allArgs,
            Optional.of(Javac.ARGFILES_ESCAPER),
            currentCellPath,
            resolver);

    if (!hasLinkArgsToSupportFileList) {
      LOG.verbose("linkerArgsToSupportFileList is empty, filelist feature is not supported");
      return ImmutableList.of(createArgFileStep);
    }

    CxxWriteArgsToFileStep createFileListStep =
        CxxWriteArgsToFileStep.create(
            fileListPath,
            allArgs
                .stream()
                .filter(input -> input instanceof FileListableLinkerInputArg)
                .collect(MoreCollectors.toImmutableList()),
            Optional.empty(),
            currentCellPath,
            resolver);

    return ImmutableList.of(createArgFileStep, createFileListStep);
  }

  private CxxPrepareForLinkStep() {}
}