#!/usr/bin/env escript
%% -*- mode: erlang;erlang-indent-level: 4;indent-tabs-mode: nil -*-
%% ex: ft=erlang ts=4 sw=4 et

main(Args) ->
    %% Get a string repr of build time
    Built = build_time(),

    %% Get a string repr of first matching VCS changeset
    VcsInfo = vcs_info([{hg, ".hg", "hg identify -i", "hg status"},
                        {git, ".git", "git describe --always --tags",
                         "git status -s"}]),

    %% Check for force=1 flag to force a rebuild
    case lists:member("force=1", Args) of
        true ->
            rm("ebin/*.beam");
        false ->
            rm("ebin/rebar.beam")
    end,

    %% Add check for debug flag
    DebugFlag = case lists:member("debug", Args) of
                    true -> debug_info;
                    false -> undefined
                end,

    %% Extract the system info of the version of OTP we use to compile rebar
    OtpInfo = string:strip(erlang:system_info(otp_release), both, $\n),

    %% Types dict:dict() and digraph:digraph() have been introduced in
    %% Erlang 17.
    %% At the same time, their counterparts dict() and digraph() are to be
    %% deprecated in Erlang 18. namespaced_types option is used to select
    %% proper type name depending of the OTP version used.
    NamespacedTypes = case is_otp(OtpInfo, "^[0-9]+") of
                          true -> {d, namespaced_types};
                          false -> undefined
                      end,

    %% Compile all src/*.erl to ebin
    case make:files(filelib:wildcard("src/*.erl"),
                    [{outdir, "ebin"}, {i, "include"},
                     DebugFlag,
                     NamespacedTypes,
                     {d, 'BUILD_TIME', Built},
                     {d, 'VCS_INFO', VcsInfo},
                     {d, 'OTP_INFO', OtpInfo}]) of
        up_to_date ->
            ok;
        error ->
            io:format("Failed to compile rebar files!\n"),
            halt(1)
    end,

    %% Make sure file:consult can parse the .app file
    case file:consult("ebin/rebar.app") of
        {ok, _} ->
            ok;
        {error, Reason} ->
            io:format("Invalid syntax in ebin/rebar.app: ~p\n", [Reason]),
            halt(1)
    end,

    %% Add ebin/ to our path
    true = code:add_path("ebin"),

    %% Run rebar compile to do proper .app validation etc.
    %% and rebar escriptize to create the rebar script
    RebarArgs = Args -- ["debug"], %% Avoid trying to run 'debug' command
    rebar:main(["compile", "escriptize"] ++ RebarArgs),

    %% Finally, update executable perms for our script on *nix,
    %%  or write out script files on win32.
    case os:type() of
        {unix,_} ->
            [] = os:cmd("chmod u+x rebar"),
            ok;
        {win32,_} ->
            write_windows_scripts(),
            ok;
        _ ->
            ok
    end,

    %% Add a helpful message
    io:format("Congratulations! You now have a self-contained script called"
              " \"rebar\" in\n"
              "your current working directory. "
              "Place this script anywhere in your path\n"
              "and you can use rebar to build OTP-compliant apps.\n").

is_otp(OtpInfo, Regex) ->
     case re:run(OtpInfo, Regex, [{capture, none}]) of
          match -> true;
          nomatch -> false
     end.

rm(Path) ->
    NativePath = filename:nativename(Path),
    Cmd = case os:type() of
              {unix,_} -> "rm -f ";
              {win32,_} -> "del /q "
          end,
    [] = os:cmd(Cmd ++ NativePath),
    ok.

build_time() ->
    {{Y, M, D}, {H, Min, S}} = calendar:now_to_universal_time(now()),
    lists:flatten(io_lib:format("~4..0w~2..0w~2..0w_~2..0w~2..0w~2..0w",
                                [Y, M, D, H, Min, S])).

vcs_info([]) ->
    "No VCS info available.";
vcs_info([{Id, Dir, VsnCmd, StatusCmd} | Rest]) ->
    case filelib:is_dir(Dir) of
        true ->
            Vsn = string:strip(os:cmd(VsnCmd), both, $\n),
            Status = case string:strip(os:cmd(StatusCmd), both, $\n) of
                         [] ->
                             "";
                         _ ->
                             "-dirty"
                     end,
            lists:concat([Id, " ", Vsn, Status]);
        false ->
            vcs_info(Rest)
    end.

write_windows_scripts() ->
    CmdScript=
        "@echo off\r\n"
        "setlocal\r\n"
        "set rebarscript=%~f0\r\n"
        "escript.exe \"%rebarscript:.cmd=%\" %*\r\n",
    ok = file:write_file("rebar.cmd", CmdScript).