/**
 * Copyright (c) Facebook, Inc. and its affiliates.
 *
 * This source code is licensed under the MIT license found in the
 * LICENSE file in the root directory of this source tree.
 */;
/**
 * Reads a file from disk. This returns a list containing each line of the file.
 */
let readLines = (file: string): list(string) => {
  let lines = ref([]);
  let chan = open_in(file);
  let finished_lines =
    try (
      {
        while (true) {
          lines := [input_line(chan), ...lines^];
        };
        [];
      }
    ) {
    | End_of_file =>
      close_in(chan);
      lines^ |> List.rev;
    };
  finished_lines;
};

/**
   * Reads a file from disk. This returns a single, new-line separated string
   * containing the contents of the file.
   */
let readFile = (file: string): string =>
  String.concat("\n", readLines(file));

/**
   * Recursively makes sure a directory exists.
   */
let rec mkdirp = (dirPath: string): unit =>
  if (Sys.file_exists(dirPath)) {
    /* The directory exists, stop recursing but check error cases */
    if (Sys.is_directory(dirPath)) {
      ();
        /* All good */
    } else {
      /* This means something like 'foo/bar' is a file, but we are trying
         to create the directory 'foo/bar/baz' since 'bar' is a file not a
         directory this will obviously fail. Here we call out the case
         explicitly and try to provide a helpful error message. */
      failwith(
        Printf.sprintf(
          "'%s' exists but is not a directory, aborting",
          dirPath,
        ),
      );
    };
  } else {
    mkdirp(Filename.dirname(dirPath));
    /* 493 = 0o755 */
    Unix.mkdir(dirPath, 493);
    ();
  };

/**
   * Implements `rm -rf <path>` behaviour.
   */
let rmrf = (path: string): unit => {
  let rec visit = path =>
    if (Sys.is_directory(path)) {
      Array.iter(
        name => visit(Filename.concat(path, name)),
        Sys.readdir(path),
      );
      Unix.rmdir(path);
    } else {
      Unix.unlink(path);
    };
  if (Sys.file_exists(path)) {
    visit(path);
  };
};

/**
   * Writes a file at the given path containing the given contents.
   */
let writeFile = (filePath: string, contents: string) => {
  let outFile = open_out(filePath);
  output_string(outFile, contents);
  close_out(outFile);
};

/**
   * TODO: Allow passing a serializer and file descriptor the child fn can write
   * its return value to.
   */
let captureOutput = (fn: unit => unit): (string, string, Unix.process_status) => {
  /* Capture normal stdout/stderr channels */
  let oldstdout = Unix.dup(Unix.stdout);
  let oldstderr = Unix.dup(Unix.stderr);
  /* Create tmpOut and tmpErr files */
  let (tmpOut, tmpOutChannel) =
    Filename.open_temp_file("reason-", ".stdout");
  let (tmpErr, tmpErrChannel) =
    Filename.open_temp_file("reason-", ".stderr");
  /* Redirect stdout/stderr channels to the tmp files */
  Unix.dup2(Unix.descr_of_out_channel(tmpOutChannel), Unix.stdout);
  Unix.dup2(Unix.descr_of_out_channel(tmpErrChannel), Unix.stderr);
  /**
     * Fork and call the function that may produce output. The fork is necessary
     * in case the function fatals. We do not want to crash the parent program.
     */
  let pid = Unix.fork();
  if (pid === 0) {
    fn();
    /*
     * Exit the child process, we don't care about the program anymore. We have
     * already captured the output.
     */
    exit(0);
  } else {
    /* Wait for the child process to finish */
    let (_, processStatus) = Unix.waitpid([], pid);
    /* Flush channels */
    flush(tmpOutChannel);
    flush(tmpErrChannel);
    /* Restore old channels */
    Unix.dup2(oldstdout, Unix.stdout);
    Unix.dup2(oldstderr, Unix.stderr);
    /* Read tmp files */
    let stdOutStr = readFile(tmpOut);
    let stdErrStr = readFile(tmpErr);
    /* Cleanup tmp files */
    Unix.unlink(tmpOut);
    Unix.unlink(tmpErr);
    /* Return outputs and exitStatus */
    (stdOutStr, stdErrStr, processStatus);
  };
};