module Colour = struct
  type t = { red : int; green : int; blue : int } [@@fieldglass generate]
end

module Legacy = struct
  type t = { value : string } [@@lens generate]
end

let () =
  let colour = Colour.{ red = 3; green = 4; blue = 5 } in
  assert (Colour.red colour = 3);
  assert (Colour.green colour = 4);
  assert (Legacy.value Legacy.{ value = "grey" } = "grey")

module Box = struct
  type 'a t = { contents : 'a } [@@fieldglass generate]
end

module Mutable = struct
  type t = { mutable count : int; label : string } [@@fieldglass generate]
end

let () =
  let original = Colour.{ red = 3; green = 4; blue = 5 } in
  assert (Colour.set_red 8 original = Colour.{ red = 8; green = 4; blue = 5 });
  assert (Colour.red original = 3);
  assert (Box.set_contents "grey" Box.{ contents = 9 } = Box.{ contents = "grey" });
  let original = Mutable.{ count = 1; label = "grey" } in
  let changed = Mutable.set_count 2 original in
  assert (original.Mutable.count = 1 && changed.Mutable.count = 2)

let () =
  let calls = ref 0 in
  let original = Colour.{ red = 3; green = 4; blue = 5 } in
  let changed = Colour.update_green ~f:(fun n -> incr calls; n + 1) original in
  assert (Colour.green changed = 5 && !calls = 1);
  assert (Box.update_contents ~f:string_of_int Box.{ contents = 9 } = Box.{ contents = "9" });
  (try ignore (Colour.update_red ~f:(fun _ -> failwith "callback") original); assert false
   with Failure message -> assert (message = "callback"));
  assert (Colour.red original = 3)

module Swatch = struct
  type t = { colour : Colour.t; label : string } [@@fieldglass generate]
end

let () =
  let open Fieldglass in
  let original = Swatch.{ colour = Colour.{ red = 3; green = 4; blue = 5 }; label = "grey" } in
  let focus = compose Swatch._colour Colour._red in
  assert (view focus original = 3);
  let changed = set focus 8 original in
  assert (view focus changed = 8 && Swatch.label changed = "grey");
  assert (set focus (view focus original) original = original);
  assert (set Box._contents "grey" Box.{ contents = 9 } = Box.{ contents = "grey" })