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open Data_encoding.Encoding

let test_too_big_fails i =
  let exception Failed in
  let encoder = int32 in
  let encodable = i in
  let encoded = Data_encoding.Binary.to_string_exn encoder encodable in
  let decoder = int31 in
  try
    let _decoded = Data_encoding.Binary.of_string_exn decoder encoded in
    raise Failed
  with
  | Failed as exc -> raise exc
  | _ -> ()

let test_32_is_not_31 () =
  test_too_big_fails Int32.max_int ;
  test_too_big_fails Int32.(sub max_int 1l) ;
  test_too_big_fails Int32.(sub max_int 3124l) ;
  test_too_big_fails Int32.min_int ;
  test_too_big_fails Int32.(add min_int 1l) ;
  test_too_big_fails Int32.(add min_int 3124l) ;
  ()

let test_small_enough_succeeds i =
  let encoder = int31 in
  let encodable = i in
  let encoded = Data_encoding.Binary.to_string_exn encoder encodable in
  let decoder = int31 in
  let decoded = Data_encoding.Binary.of_string_exn decoder encoded in
  assert (encodable = decoded)

let test_31_is_31 () =
  test_small_enough_succeeds 0 ;
  test_small_enough_succeeds 0x23f4 ;
  test_small_enough_succeeds Int32.(to_int (div max_int 2l)) ;
  test_small_enough_succeeds Int32.(to_int (div min_int 2l)) ;
  ()

let test_small_enough_is_compatible i =
  let encoder = int32 in
  let encodable = i in
  let encoded = Data_encoding.Binary.to_string_exn encoder encodable in
  let decoder = int31 in
  let decoded = Data_encoding.Binary.of_string_exn decoder encoded in
  assert (encodable = Int32.of_int decoded)

let test_small_32_is_31 () =
  test_small_enough_is_compatible 0l ;
  test_small_enough_is_compatible 0x23f4l ;
  test_small_enough_is_compatible Int32.(div max_int 2l) ;
  test_small_enough_is_compatible Int32.(div min_int 2l) ;
  ()

let tests =
  [
    ("int32-max-int-not-an-int31", `Quick, test_32_is_not_31);
    ("small-int32-is-int31", `Quick, test_small_32_is_31);
    ("int31-is-int31", `Quick, test_31_is_31);
  ]