#!/usr/bin/env escript
%%! -noshell

%% The expected argument for _LatestTravisOTP is the string returned
%% from `/.travis/get_latest_travis /.travis.yml` e.g. "20.2"
main([[LD,LU|_] = _LatestTravisOTP]) ->
  %% The major version in the master branch is the corresponding major
  %% version part of the latest version known to travis, plus one
  MasterMajor = list_to_integer([LD,LU]) + 1,
  CurrentOTPRelease =
    case erlang:system_info(otp_release) of
      "R" ++ _ -> 16; %% ... or earlier
      [D,U|_] -> list_to_integer([D,U])
    end,
  io:format("-define(OTP_VERSION, ~w).~n", [CurrentOTPRelease]),
  add_befores_for(CurrentOTPRelease + 1, MasterMajor).

add_befores_for(Release, MasterMajor) when Release =< MasterMajor ->
  add_before_for(Release),
  add_befores_for(Release + 1, MasterMajor);
add_befores_for(_, _MasterMajor) -> ok.

add_before_for(Release) ->
  io:format("-define(BEFORE_OTP_~p, true).~n", [Release]).