#!/usr/bin/env escript
%% -*- mode:erlang;tab-width:4;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"},
                        {git, ".git", "git describe --always"}]),

    %% Check for force=1 flag to force a rebuild
    case lists:member("force=1", Args) of
        true ->
            [] = os:cmd("rm -rf ebin/*.beam"),
            ok;
        false ->
            os:cmd("rm -f ebin/rebar_core.beam"),
            ok
    end,

    %% Compile all src/*.erl to ebin
    case make:files(filelib:wildcard("src/*.erl"), [{outdir, "ebin"}, {i, "include"},
                                                    {d, 'BUILD_TIME', Built},
                                                    {d, 'VCS_INFO', VcsInfo}]) 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 to do proper .app validation and such
    rebar:main(["compile"] ++ Args),

    %% Read the contents of the files in ebin and templates; note that we place
    %% all the beam files at the top level of the code archive so that code loading
    %% works properly.
    Files = load_files("*", "ebin") ++ load_files("priv/templates/*", "."),

    case zip:create("mem", Files, [memory]) of
        {ok, {"mem", ZipBin}} ->
            %% Archive was successfully created. Prefix that binary with our
            %% header and write to "rebar" file
            Script = <<"#!/usr/bin/env escript\n%%! -noshell -noinput\n", ZipBin/binary>>,
            case file:write_file("rebar", Script) of
                ok ->
                    ok;
                {error, WriteError} ->
                    io:format("Failed to write rebar script: ~p\n", [WriteError]),
                    halt(1)
            end;
        {error, ZipError} ->
            io:format("Failed to construct rebar script archive: ~p\n", [ZipError]),
            halt(1)
    end,

    %% Finally, update executable perms for our script
    [] = os:cmd("chmod u+x rebar"),

    %% 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").


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])).


load_files(Wildcard, Dir) ->
    [read_file(Filename, Dir) || Filename <- filelib:wildcard(Wildcard, Dir)].

read_file(Filename, Dir) ->
    {ok, Bin} = file:read_file(filename:join(Dir, Filename)),
    {Filename, Bin}.

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