#!/usr/bin/env escript
%% -*- erlang -*-

-mode(compile).
main(Argv) ->
    {Opts, Args} = parse_opts(Argv, [], []),
    [InFile, OutFile] = if length(Args) == 2 -> Args;
                           true -> usage(), halt(1)
                        end,
    Vsn = case proplists:get_value(override_version, Opts) of
              undefined ->
                  get_version_from_git();
              Version ->
                  Version
          end,
    BaseStr = case file:read_file(InFile) of
                  {ok, S} ->
                      S;
                  {error, Reason} ->
                      file_err(read_file, InFile, Reason)
              end,
    SedList =
        [
            {<<"@vsn@">>, Vsn},
            {<<"is expected to be">>, <<"was">>},
            {<<"%% The version below">>, [<<"%% DO NOT EDIT -- generated ">>,
                <<"from gpb_version.hrl.in\n%% The version below">>]},
            {<<"%% NB: The build.mk_version_hrl depends.*">>, <<"">>}
        ],
    VersionStr = lists:foldl(fun({Patten, Replacement}, Acc) ->
        re:replace(Acc, Patten, Replacement, [{return, binary}])
                             end, BaseStr, SedList),
    case file:write_file(OutFile, VersionStr) of
        ok ->
            ok;
        {error, Reason2} ->
            file_err(write_file, OutFile, Reason2)
    end.

parse_opts(["--override-version="++Vsn | Rest], Opts, Args) ->
    parse_opts(Rest, [{override_version, Vsn} | Opts], Args);
parse_opts([Arg | Rest], Opts, Args) ->
    parse_opts(Rest, Opts, [Arg | Args]);
parse_opts([], Opts, Args) ->
    {lists:reverse(Opts), lists:reverse(Args)}.

usage() ->
    io:format("mk_version_hrl [Opts] InFile OutFile~n"
              "Opts: --override-version=VSN~n").

-define(NOT_IN_GIT_ERR_MSG,
    "ERROR: To build outside a git work tree, you must first create
           a versioned archive, and then unpack it and build that.
           This is for the version number to get correctly set.
           Use helpers/mk-versioned-archive to create such an archive.

           The helpers/mk-versioned-archive can be used from a git worktree
           or from eg Github's automatically generated tar/zip files
           or similar. If you use it from a (non-shallow) git work tree
           with tags intact, the version will get picked up automatically,
           otherwise you must know the proper version and specify it manually,
           see mk-versioned-archive --help for further assistance.

           For further info, see the README.md, the section section
           named Building outside of a git work tree.").


get_version_from_git() ->
    InGit = os:cmd("git rev-parse --is-inside-work-tree  2>&1"),
    case InGit of
        "true" ++ _ ->
            next;
        _ ->
            io:format(standard_error, "~s~n", [?NOT_IN_GIT_ERR_MSG]),
            halt(1)
    end,
    Vsn0 = os:cmd("git describe --always --tags --match [0-9]*.[0-9]*"),
    lists:sublist(Vsn0, length(Vsn0) - 1).

file_err(FunName, FileName, Reason) ->
    io:format(standard_error, "file:~p(~s) excute failed!, Reason :~s ~n",
              [FunName, FileName, file:format_error(Reason)]),
    halt(1).