#+begin_src elisp tangle: no :results none :exports none
(setq pwd (file-name-directory buffer-file-name))
(setq name (file-name-nondirectory (substring buffer-file-name 0 -4)))
(setq lib (concat pwd "lib/"))
(setq testdir (concat pwd "test/"))
(setq mli (concat lib name ".mli"))
(setq ml  (concat lib name ".ml"))
(setq test-ml  (concat testdir name ".ml"))
(org-babel-tangle)
#+end_src

* Command line
  :PROPERTIES:
  :header-args: :noweb yes :comments both
  :END:

  This module is a wrapper around the ~Getopt~ library and helps to
  define command-line arguments.

  Here is an example of how to use this module.
  First, define the specification:
  #+begin_src ocaml :tangle no
let open Command_line in
begin
  set_header_doc (Sys.argv.(0) ^ " - One-line description");
  set_description_doc "Long description of the command.";
  set_specs
    [ { short='c'; long="check"; opt=Optional;
        doc="Checks the input data";
        arg=Without_arg; };

      { short='b' ; long="basis" ; opt=Mandatory;
        arg=With_arg "<string>";
        doc="Name of the file containing the basis set"; } ;

      { short='m' ; long="multiplicity" ; opt=Optional;
        arg=With_arg "<int>";
        doc="Spin multiplicity (2S+1). Default is singlet"; } ;
    ]
end;
  #+end_src

  Then, define what to do with the arguments:
  #+begin_src ocaml :tangle no
let c =
  Command_line.get_bool "check"
in

let basis =
  match Command_line.get "basis" with
  | Some x -> x
  | None -> assert false
in

let multiplicity =
  match Command_line.get "multiplicity" with
  | None -> 1
  | Some n -> int_of_string n
in
  #+end_src

** Type

   #+NAME:type
   #+begin_src ocaml :tangle (eval mli)
type short_opt     = char
type long_opt      = string
type optional      = Mandatory | Optional
type documentation = string
type argument      = With_arg of string | Without_arg | With_opt_arg of string

type description = {
  short: short_opt ;
  long : long_opt  ;
  opt  : optional  ;
  doc  : documentation ;
  arg  : argument ;
}

   #+end_src

   - Short option: in the command line, a dash with a single character
     (ex: =ls -l=)
   - Long option: in the command line, two dashes with a word
     (ex: =ls --directory=)
   - Command-line options can be ~Mandatory~ or ~Optional~
   - Documentation of the option is used in the help function
   - Some options require an argument (~ls --ignore="*.ml"~ ), some
     don't (~ls -l~) and for some arguments the argument is optional
     (~git --log[=<n>]~)

   #+begin_src ocaml :tangle (eval ml) :exports none
<<type>>
   #+end_src

** Mutable attributes

   All the options are stored in the hash table ~dict~ where the key
   is the long option and the value is a value of type ~description~.

   #+begin_src ocaml :tangle (eval ml) :exports none
let header_doc      = ref ""
let description_doc = ref ""
let footer_doc      = ref ""
let anon_args_ref   = ref []
let specs           = ref []
let dict = Hashtbl.create 67
   #+end_src

   #+begin_src ocaml :tangle (eval mli)
val set_header_doc : string -> unit
val set_description_doc : string -> unit
val set_footer_doc : string -> unit
   #+end_src

   Functions to set the header, footer and main description of the
   documentation provided by the ~help~ function:

   #+begin_src ocaml :tangle (eval ml) :exports none
let set_header_doc s = header_doc := s
let set_description_doc s = description_doc := s
let set_footer_doc s = footer_doc := s
   #+end_src


   #+begin_src ocaml :tangle (eval mli)
val anonymous : long_opt -> optional -> documentation -> description
   #+end_src

   Function to create an anonymous argument.

   #+begin_src ocaml :tangle (eval ml) :exports none
let anonymous name opt doc =
  { short=' ' ; long=name; opt; doc; arg=Without_arg; }
   #+end_src

** Text formatting functions                                       :noexport:

   Function to print some text such that it fits on the screen

   #+begin_src ocaml :tangle (eval ml) :exports none
let output_text t =
  Format.printf "@[<v 0>";
  begin
    match Str.split (Str.regexp "\n") t with
    | x :: [] ->
        Format.printf "@[<hov 0>";
        Str.split (Str.regexp " ") x
        |> List.iter (fun y -> Format.printf "@[%s@]@ " y) ;
        Format.printf "@]"
    | t ->
        List.iter (fun x ->
          Format.printf "@[<hov 0>";
          Str.split (Str.regexp " ") x
          |> List.iter (fun y -> Format.printf "@[%s@]@ " y) ;
          Format.printf "@]@;"
        ) t
  end;
  Format.printf "@]"
   #+end_src


   Function to build the short description of the command-line
   arguments, such as

   #+begin_example
my_program -b <string> [-h] [-u <float>] -x <string> [--]
   #+end_example

   #+begin_src ocaml :tangle (eval ml) :exports none
let output_short x =
  match x.short, x.opt, x.arg  with
  | ' ', Mandatory, _ -> Format.printf "@[%s@]"   x.long
  | ' ', Optional , _ -> Format.printf "@[[%s]@]" x.long
  |  _ , Mandatory, Without_arg -> Format.printf "@[-%c@]"   x.short
  |  _ , Optional , Without_arg -> Format.printf "@[[-%c]@]" x.short
  |  _ , Mandatory, With_arg arg -> Format.printf "@[-%c %s@]"   x.short arg
  |  _ , Optional , With_arg arg -> Format.printf "@[[-%c %s]@]" x.short arg
  |  _ , Mandatory, With_opt_arg arg -> Format.printf "@[-%c [%s]@]"   x.short arg
  |  _ , Optional , With_opt_arg arg -> Format.printf "@[[-%c [%s]]@]" x.short arg
   #+end_src


   Function to build the long description of the command-line
   arguments, such as

   #+begin_example
  -x  --xyz=<string>              Name of the file containing the nuclear
                                  coordinates in xyz format
   #+end_example

   #+begin_src ocaml :tangle (eval ml) :exports none
let output_long max_width x =
  let arg =
    match x.short, x.arg with
    | ' ' , _                -> x.long
    |  _  , Without_arg      -> x.long
    |  _  , With_arg     arg -> Printf.sprintf "%s=%s" x.long arg
    |  _  , With_opt_arg arg -> Printf.sprintf "%s[=%s]" x.long arg
  in
  let long =
    let l = String.length arg in
    arg^(String.make (max_width-l) ' ')
  in
  Format.printf "@[<v 0>";
  begin
    match x.short with
    | ' '   -> Format.printf "@[%s       @]" long
    | short -> Format.printf "@[-%c  --%s @]" short long
  end;
  Format.printf "@]";
  output_text  x.doc
   #+end_src

** Query functions

   #+begin_src ocaml :tangle (eval mli)
val get       : long_opt -> string option
val get_bool  : long_opt -> bool
val anon_args : unit -> string list
   #+end_src

   | ~get~       | Returns the argument associated with a long option             |
   | ~get_bool~  | True if the ~Optional~ argument is present in the command-line |
   | ~anon_args~ | Returns the list of anonymous arguments                        |


   #+begin_src ocaml :tangle (eval ml) :exports none
let anon_args () = !anon_args_ref

let help () =

  (* Print the header *)
  output_text !header_doc;
  Format.printf "@.@.";

  (* Find the anonymous arguments *)
  let anon =
    List.filter (fun x -> x.short = ' ') !specs
  in

  (* Find the options *)
  let options =
    List.filter (fun x -> x.short <> ' ') !specs
    |> List.sort (fun x y -> Char.compare x.short y.short)
  in

  (* Find column lengths *)
  let max_width =
    List.map (fun x ->
      ( match x.arg with
        | Without_arg      -> String.length x.long
        | With_arg arg     -> String.length x.long + String.length arg
        | With_opt_arg arg -> String.length x.long + String.length arg + 2
      )
      + ( if x.opt = Optional then 2 else 0)
    ) !specs
    |> List.fold_left max 0
  in


  (* Print usage *)
  Format.printf "@[<v>@[<v 2>Usage:@,@,@[<hov 4>@[%s@]" Sys.argv.(0);
  List.iter (fun x -> Format.printf "@ "; output_short x) options;
  Format.printf "@ @[[--]@]";
  List.iter (fun x -> Format.printf "@ "; output_short x;) anon;
  Format.printf "@]@,@]@,";


  (* Print arguments and doc *)
  Format.printf "@[<v 2>Arguments:@,";
  Format.printf "@[<v 0>" ;
  List.iter (fun x -> Format.printf "@ "; output_long max_width x) anon;
  Format.printf "@]@,@]@,";


  (* Print options and doc *)
  Format.printf "@[<v 2>Options:@,";

  Format.printf "@[<v 0>" ;
  List.iter (fun x -> Format.printf "@ "; output_long max_width x) options;
  Format.printf "@]@,@]@,";


  (* Print footer *)
  if !description_doc <> "" then
    begin
      Format.printf "@[<v 2>Description:@,@,";
      output_text !description_doc;
      Format.printf "@,"
    end;

  (* Print footer *)
  output_text !footer_doc;
  Format.printf "@."


let get x =
  try Some (Hashtbl.find dict x)
  with Not_found -> None


let get_bool x = Hashtbl.mem dict x
   #+end_src

** Specification

   #+begin_src ocaml :tangle (eval mli)
val set_specs : description list -> unit
   #+end_src

   Sets the specifications of the current program from a list of
   ~descrption~ variables.

   #+begin_src ocaml :tangle (eval ml) :exports none
let set_specs specs_in =
  specs := { short = 'h' ;
             long  = "help" ;
             doc   = "Prints the help message." ;
             arg   = Without_arg ;
             opt   = Optional ;
           } :: specs_in;

  let cmd_specs =
    List.filter (fun x -> x.short != ' ') !specs
    |> List.map (fun { short ; long ; arg ; _ } ->
      match arg with
      |  With_arg _ ->
          (short, long, None, Some (fun x -> Hashtbl.replace dict long x) )
      |  Without_arg ->
          (short, long, Some (fun () -> Hashtbl.replace dict long ""), None)
      |  With_opt_arg _ ->
          (short, long, Some (fun () -> Hashtbl.replace dict long ""),
           Some (fun x -> Hashtbl.replace dict long x) )
    )
  in

  Getopt.parse_cmdline cmd_specs (fun x -> anon_args_ref := !anon_args_ref @ [x]);

  if (get_bool "help") then
    (help () ; exit 0);

  (* Check that all mandatory arguments are set *)
  List.filter (fun x -> x.short <> ' ' && x.opt = Mandatory) !specs
  |> List.iter (fun x ->
    match get x.long with
    | Some _ -> ()
    | None -> failwith ("Error: --"^x.long^" option is missing.")
  )
   #+end_src