open Types

type serialiser = { mutable buf : string; sz : int; mutable pos : int }

let write_ansi a =
  let rec intersperse sep ls =
    match ls with
    | [] | [ _ ] -> ls
    | hd :: tl -> hd :: sep :: intersperse sep tl
  and string_of_colour ?(bg = false) c =
    let prefix = if bg then "4" else "3" and si = string_of_int in
    c |> function
    | Intrinsic i -> prefix ^ si i
    | Simple i -> prefix ^ "8;5;" ^ si i
    | RGB (r, g, b) -> prefix ^ "8;2;" ^ si r ^ ";" ^ si g ^ ";" ^ si b
  in
  let ansi =
    a
    |> List.map (fun a ->
           match a with
           | Fg c -> string_of_colour c
           | Bg c -> string_of_colour ~bg:true c
           | Reset -> "0"
           | Other i -> string_of_int i)
    |> intersperse ";"
    |> List.fold_left (fun acc el -> acc ^ el) ""
  in
  "\x1b[" ^ ansi ^ "m"

let flush t =
  if t.pos > 0 then (
    print_string (String.sub t.buf 0 t.pos);
    t.pos <- 0)

let serialise t chunk =
  let input =
    match chunk with
    | Text s -> s
    | Separator s -> s
    | Delimiter s -> s
    | Ansi a -> write_ansi a
  in
  let input_sz = String.length input in
  if t.pos + input_sz > t.sz then flush t;
  if input_sz > t.sz then print_string input
  else t.buf <- (if t.pos > 0 then String.sub t.buf 0 t.pos else "") ^ input;
  t.pos <- t.pos + input_sz

let create = { buf = String.empty; sz = 4096; pos = 0 }

let print_debug t =
  print_endline
    ("pos is " ^ string_of_int t.pos ^ "\nsz is " ^ string_of_int t.sz
   ^ "\ncontents are: " ^ t.buf)