type ctl =
  | Bold of bool
  | Fg of color option

and color = R | G | Y | U | C

type t = ctl list

let string_of_ctl = function
  | Bold true   -> "1"
  | Bold false  -> "22"
  (* | Fg (Some B) -> "30" *)
  | Fg (Some R) -> "31"
  | Fg (Some G) -> "32"
  | Fg (Some Y) -> "33"
  | Fg (Some U) -> "34"
  (* | Fg (Some M) -> "35" *)
  | Fg (Some C) -> "36"
  (* | Fg (Some W) -> "37" *)
  | Fg None     -> "39"

let rec pr_rec pb pre suf = function
  | [] ->
    Buffer.add_string pb suf
  | ctl :: ctls ->
    Buffer.add_string pb pre;
    Buffer.add_string pb (string_of_ctl ctl);
    pr_rec pb ";" "m" ctls
    
let pr pb ctls =
  pr_rec pb "\x1b[" "" ctls