open Fieldglass

let sample : (string * bool, string) lens' =
  lens ~view:fst ~set:(fun value (_, other) -> value, other)

let () = assert (view sample ("colour", true) = "colour")

let () =
  let source = "colour", true in
  assert (set sample "grey" source = ("grey", true));
  assert (set sample (view sample source) source = source);
  assert (set sample "blue" (set sample "grey" source) = set sample "blue" source);
  let calls = ref 0 in
  assert (over sample ~f:(fun text -> incr calls; text ^ "s") source = ("colours", true));
  assert (!calls = 1)

let () =
  let first = (fst, fun value (_, rest) -> value, rest) in
  let second = (snd, fun value (rest, _) -> rest, value) in
  let focus = compose first second in
  assert (view focus ((true, "grey"), false) = "grey");
  assert (set focus 9 ((true, "grey"), false) = ((true, 9), false))

let () =
  assert (set _1 "grey" (1, true) = ("grey", true));
  assert (over _2 ~f:string_of_int (false, 9) = (false, "9"));
  assert (view (compose _1 _2) ((true, "grey"), ()) = "grey")