type t = [ `Px
         | `Zero
         | `Auto
         | `Rem of float
         | `Fraction of int * int
         | `Full
         | `Screen
         | `Min
         | `Max
         | `Fit
         | `Viewport of [`W | `H] * [`S | `L | `D] ]

let to_string = function
  | `Px -> "px"
  | `Zero -> "0"
  | `Auto -> "auto"
  | `Rem f ->
      let s = string_of_float f in
      if String.ends_with ~suffix:".0" s then
        String.sub s 0 (String.length s - 2)
      else if String.ends_with ~suffix:"." s then
        String.sub s 0 (String.length s - 1)
      else s
  | `Fraction (n, d) -> Printf.sprintf "%d/%d" n d
  | `Full -> "full"
  | `Screen -> "screen"
  | `Min -> "min"
  | `Max -> "max"
  | `Fit -> "fit"
  | `Viewport (dir, size) ->
      let d = match dir with `W -> "w" | `H -> "h" in
      let s = match size with `S -> "s" | `L -> "l" | `D -> "d" in
      Printf.sprintf "%sv%s" s d

let px = `Px
let zero = `Zero
let auto = `Auto
let full = `Full
let screen = `Screen

let rem f = `Rem f

let fraction n d = `Fraction (n, d)