open Core;
module Unix = Core_unix;

let run_process = (name, args) => {
  /*** Run a process [name] with args [args], returning (exit_code, stdout text) */
  let stdout_chan = Unix.open_process_in(name ++ " " ++ (args |> String.concat(~sep=" ")));
  let stdout_content = stdout_chan |> In_channel.input_all;
  let exit_code = Unix.close_process_in(stdout_chan);
  (exit_code, stdout_content)
 };

let nix = (args) => run_process("nix", ["--extra-experimental-features", "\"nix-command flakes\" ", ...args]);

let hash_files = (filenames) => {
  /*** Hash all entries in [filenames], returning a hex-encoded string of the hash of their contents */
  let ctx = Sha1.init();
  let () = filenames
  |> Array.filter(~f=f => switch (Sys_unix.file_exists(f)) {
      | `Yes => true
      | _ => false
    })
  |> Array.iter(~f=(f) => {
      f |> In_channel.create |> In_channel.input_all |> Sha1.update_string(ctx);
    });
  Sha1.finalize(ctx) |> Sha1.to_hex
};

let rec rmrf = (path) => {
  switch (Unix.lstat(path).st_kind) {
  | exception Unix.Unix_error(_, _, _) => ()
  | S_REG => Unix.unlink(path)
  | S_LNK => Unix.unlink(path)
  | S_DIR => {
      Sys_unix.readdir(path) |> Array.iter(~f=name => rmrf(Filename.concat(path, name)));
      Unix.rmdir(path)
    }
  | S_CHR => Printf.eprintf("Don't know how to handle Character Device file\n")
  | S_BLK => Printf.eprintf("Don't know how to handle Block Device file\n")
  | S_FIFO => Printf.eprintf("Don't know how to handle FIFO file\n")
  | S_SOCK => Printf.eprintf("Don't know how to handle Socket file\n")
  }
};

let get_args = (argv) => {
  switch (Array.length(argv)) {
  | x when x >= 3 => {
      let layout_directory = argv[1];
      let flake_specifier = argv[2];
      let other_args = snd(List.split_n(List.of_array(argv), 3));
      Ok((layout_directory, flake_specifier, other_args))
    }
  | _ => Error()
  }
};