open Fnm;

let symlinkExists = path => {
  try%lwt (Lwt_unix.lstat(path) |> Lwt.map(_ => true)) {
  | _ => Lwt.return(false)
  };
};

let rec makeTemporarySymlink = () => {
  let suggestedName =
    Filename.concat(
      Filename.get_temp_dir_name(),
      "fnm-shell-"
      ++ (Random.int32(9999999 |> Int32.of_int) |> Int32.to_string),
    );

  let%lwt exists = symlinkExists(suggestedName);

  if (exists) {
    let%lwt suggestedName = makeTemporarySymlink();
    Lwt.return(suggestedName);
  } else {
    let%lwt _ = Lwt_unix.symlink(Directories.defaultVersion, suggestedName);
    Lwt.return(suggestedName);
  };
};

let run = (~shell, ~multishell, ~nodeDistMirror, ~fnmDir) => {
  open Lwt;

  Random.self_init();

  let%lwt path =
    multishell
      ? makeTemporarySymlink() : Lwt.return(Directories.globalCurrentVersion);

  switch (shell) {
  | System.Shell.Bash =>
    Printf.sprintf("export PATH=%s/bin:$PATH", path) |> Console.log;
    Printf.sprintf("export %s=%s", Config.FNM_MULTISHELL_PATH.name, path)
    |> Console.log;
    Printf.sprintf("export %s=%s", Config.FNM_DIR.name, fnmDir) |> Console.log;
    Printf.sprintf(
      "export %s=%s",
      Config.FNM_NODE_DIST_MIRROR.name,
      nodeDistMirror,
    )
    |> Console.log;
  | System.Shell.Fish =>
    Printf.sprintf("set PATH %s/bin $PATH;", path) |> Console.log;
    Printf.sprintf("set %s %s;", Config.FNM_MULTISHELL_PATH.name, path)
    |> Console.log;
    Printf.sprintf("set %s %s;", Config.FNM_DIR.name, fnmDir) |> Console.log;
    Printf.sprintf(
      "set %s %s",
      Config.FNM_NODE_DIST_MIRROR.name,
      nodeDistMirror,
    )
    |> Console.log;
  };

  Lwt.return();
};