#include "share/atspre_staload.hats"

staload "kernel/writer.sats"

extern castfn i2u8 {n: nat} (i: int n): uint8 n

extern fun get_vram():<> [l: agz] (@[screenChar][N] @ l | ptr l) = "mac#"

extern prfun eat_writer (pf: writer): void

%{^
  #define get_vram() ((void *) 0xB8000 + 1988)
%}

fun color_value(c : color): uint8 = 
  case+ c of 
    | Black() => i2u8 0
    | Blue() => i2u8 1
    | Green() => i2u8 2
    | Cyan() => i2u8 3
    | Red() => i2u8 4
    | Magenta() => i2u8 5
    | Brown() => i2u8 6
    | LightGray() => i2u8 7
    | DarkGray() => i2u8 8
    | LightBlue() => i2u8 9
    | LightGreen() => i2u8 10
    | LightCyan() => i2u8 11
    | LightRed() => i2u8 12
    | Pink() => i2u8 13
    | Yellow() => i2u8 14
    | White() => i2u8 15

fun code_value(foreground: color, background:color): uint8 = 
  (color_value(background) << 4) lor color_value(foreground)

fun put_char (c : char, writer: &writer) : void = let
  val v = writer.buffer.1
  val pos = writer.position
in
    v->[writer.position] := @{ ascii_character = c, color_code = writer.color_code};

    if (pos < N - 1) then
      writer.position := succ(pos)
end

implement print_char(c : char) : void = let
  val (pf_vram | vram) = get_vram()
  var writer = @{position = 0, color_code = code_value(Black,Yellow), buffer = (pf_vram | vram)} : writer
in 
  put_char(c,writer);
  put_char(c,writer);
  put_char(c,writer);
  put_char(c,writer);
  put_char(c,writer);
  let prval () = eat_writer writer in () end
end