polly

-module(polly_ffi).
-export([
    readdir/1,
    lstat/1,
    repeatedly/3
]).
-include_lib("kernel/include/file.hrl").

readdir(Dir) ->
    case file:list_dir(Dir) of
        {ok, Filenames} ->
            {ok, [unicode:characters_to_binary(Filename) || Filename <- Filenames]};

        {error, Reason} ->
            {error, Reason}
    end.

lstat(Path) ->
    file:read_link_info(Path, [{time, posix}]).

repeatedly(Timeout, State, Callback) ->
    Pid = spawn(fun() -> do_repeatedly(Timeout, State, Callback) end),
    Stop = fun() -> Pid ! stop end,
    Stop.
    

do_repeatedly(Timeout, State, Callback) -> 
    receive
        stop -> ok
        after Timeout ->
            NewState = Callback(State),
            do_repeatedly(Timeout, NewState, Callback)
    end.