open Printf

module CLI = struct
  type t = {
    verbose: bool;
    max_files: int;
    dir_to_list: string;
    sort_order: [`alpha | `chrono | `owner] option;
    args: string list;
  }

  let default = {
    verbose=false;
    max_files=100;
    dir_to_list=".";
    sort_order=None;
    args=[];
  }

  let sort_order_of_string = function
    | "alpha" -> Some `alpha
    | "chrono" -> Some `chrono
    | "owner" -> Some `owner
    | _ -> None

  let usage = sprintf {|MyLs2000 is a revolutionary file listing tool

Usage:
  cli [-v] [-n] [-d <dir>] [-s {alpha|chrono|owner}] [--] [args...]

Options:|}

  let parse argv =
    let t = ref default in
    let specs = Arg.align Arg.[
      "-v", Unit (fun () -> t := {!t with verbose=true}),
        " Enable verbose mode";
      "-n", Int (fun n -> t := {!t with max_files=n}),
        sprintf "<n> Sets maximum number of files to list (default: %d)"
          default.max_files;
      "-d", String (fun s -> t := {!t with dir_to_list=s}),
        "<dir>  Names directory to list files";
      "-s", Symbol (["alpha"; "chrono"; "owner"],
                    fun s -> t := {!t with sort_order=sort_order_of_string s}),
        " Allows to sort files alphabetically, chronologically, or by owner";
      "--", Rest (fun arg -> t := {!t with args=(!t.args @ [arg])}),
        " Stop interpreting keywords and print the rest";
    ] in
    let f arg = t := {!t with args=(!t.args @ [arg])} in
    match Arg.parse_argv argv specs f usage with
    | () -> !t
    | exception Arg.Bad message -> eprintf "%s" message; exit 2
    | exception Arg.Help message -> printf "%s" message; exit 0
end


let main =
  let result = CLI.parse Sys.argv in
  match result with {
    verbose;
    max_files;
    dir_to_list;
    sort_order;
    args;
  } ->
    printf "-v %b\n-n %d\n-d %S\n" verbose max_files dir_to_list;
    List.iter print_endline args





(* Original from
   https://scylardor.fr/2013/10/14/ocaml-parsing-a-programs-arguments-with-the-arg-module/

let verbose = ref false
let max_files_to_list = ref 1
let dir_to_list = ref "."
let time_hours = ref 0
let time_minutes = ref 0

let sort_files = function
"alpha" -> print_endline "Alpha sort"
| "chrono" -> print_endline "Chrono sort"
| "owner" -> print_endline "Owner sort"
| _ -> raise (Arg.Bad("Shouldn't happen"))

let main =
begin
let speclist = [("-v", Arg.Set verbose, "Enables verbose mode");
("-n", Arg.Set_int max_files_to_list, "Sets maximum number of files to list");
("-d", Arg.Set_string dir_to_list, "Names directory to list files");
("-t", Arg.Tuple ([Arg.Set_int time_hours ; Arg.Set_int time_minutes]), "Sets creation hours and minutes listed files have to match");
("-s", Arg.Symbol (["alpha"; "chrono"; "owner"], sort_files), " Allows to sort listed files alphabetically, chronologically, or by owner");
("--", Arg.Rest (fun arg -> print_endline ("The rest contains: " ^ arg)), "Stop interpreting keywords and prints the rest");
]
in let usage_msg = "MyLs2000 is a revolutionary file listing tool. Options available:"
in Arg.parse speclist (fun anon -> print_endline ("Anonymous argument: " ^ anon)) usage_msg;
print_endline ("Verbose mode: " ^ string_of_bool !verbose);
print_endline ("Max files to list: " ^ string_of_int !max_files_to_list);
print_endline ("Directory to list files: " ^ !dir_to_list);
print_endline ("Time of files to list: " ^ string_of_int(!time_hours) ^ ":" ^ string_of_int(!time_minutes));
end

*)