module Parameter = struct
  type 'a t = { value : 'a; label : string } [@@fieldglass generate]
end

module Private = struct
  type t = private { value : int }
    [@@fieldglass generate ~no_set ~no_update ~no_lens]
  let read : t -> int = value
end

module Universal = struct
  type t = { apply : 'a. 'a -> 'a }
    [@@fieldglass generate ~no_set ~no_update ~no_lens]
end

module Flags = struct
  type t = { count : int }
    [@@fieldglass generate ~no_get:false ~no_set:false ~no_update:false
       ~no_lens:false ~just_lens:false ~self_arg_first:false
       ~field_prefix_from_type:false ~func_no_named_arg:false]
end

module Group = struct
  type left = { count : int } [@@fieldglass generate ~get_prefix:read]
  and right = { size : int } [@@fieldglass generate ~field_prefix_from_type]
end

module Names = struct
  type t = { __fg_source : int; __fg_value : string; __fg_function : bool }
    [@@fieldglass generate ~field_prefix:local]
end

module Alias = struct
  type original = { number : int; label : string }
  type t = original = { number : int; label : string } [@@fieldglass generate]
end

module Unmarked = struct
  type t = { number : int }
  let number _ = 99
end

let () =
  let original = Parameter.{ value = 3; label = "grey" } in
  let changed = Parameter.set_value "three" original in
  assert (changed = Parameter.{ value = "three"; label = "grey" });
  assert (Parameter.update_value ~f:string_of_int original = Parameter.{ value = "3"; label = "grey" });
  assert (Fieldglass.set Parameter._value "three" original = changed);
  let identity = Universal.{ apply = fun value -> value } in
  assert (Universal.apply identity 3 = 3);
  assert (Universal.apply identity "grey" = "grey");
  let count = Flags.{ count = 3 } in
  assert (Flags.count (Flags.set_count 4 count) = 4);
  assert (Flags.count (Flags.update_count ~f:succ count) = 4);
  assert (Fieldglass.view Flags._count count = 3);
  assert (Group.read_left_count Group.{ count = 3 } = 3);
  assert (Group.read_right_size Group.{ size = 4 } = 4);
  let names = Names.{ __fg_source = 3; __fg_value = "grey"; __fg_function = true } in
  assert (Names.local_source names = 3);
  assert (Names.local_value (Names.set_local_value "blue" names) = "blue");
  assert (Alias.number (Alias.set_number 4 Alias.{ number = 3; label = "grey" }) = 4);
  assert (Unmarked.number Unmarked.{ number = 3 } = 99)