#!/usr/bin/env escript

%% -*- erlang -*-

-mode(compile).

%% We expect the list of Erlang source and header files to arrive on

%% stdin, with the entries colon-separated.

main([TargetFile, EbinDir]) ->

    ErlsAndHrls = [ string:strip(S,left) ||

                      S <- string:tokens(io:get_line(""), ":\n")],

    ErlFiles = [F || F <- ErlsAndHrls, lists:suffix(".erl", F)],

    Modules = sets:from_list(

                [list_to_atom(filename:basename(FileName, ".erl")) ||

                    FileName <- ErlFiles]),

    HrlFiles = [F || F <- ErlsAndHrls, lists:suffix(".hrl", F)],

    IncludeDirs = lists:usort([filename:dirname(Path) || Path <- HrlFiles]),

    Headers = sets:from_list(HrlFiles),

    Deps = lists:foldl(

             fun (Path, Deps1) ->

                     dict:store(Path, detect_deps(IncludeDirs, EbinDir,

                                                  Modules, Headers, Path),

                                Deps1)

             end, dict:new(), ErlFiles),

    {ok, Hdl} = file:open(TargetFile, [write, delayed_write]),

    dict:fold(

      fun (_Path, [], ok) ->

              ok;

          (Path, Dep, ok) ->

              Module = filename:basename(Path, ".erl"),

              ok = file:write(Hdl, [EbinDir, "/", Module, ".beam: ",

                                   Path]),

              ok = sets:fold(fun (E, ok) -> file:write(Hdl, [" ", E]) end,

                             ok, Dep),

              file:write(Hdl, ["\n"])

      end, ok, Deps),

    ok = file:write(Hdl, [TargetFile, ": ", escript:script_name(), "\n"]),

    ok = file:sync(Hdl),

    ok = file:close(Hdl).

detect_deps(IncludeDirs, EbinDir, Modules, Headers, Path) ->

    {ok, Forms} = epp:parse_file(Path, IncludeDirs, [{use_specs, true}]),

    lists:foldl(

      fun ({attribute, _LineNumber, Attribute, Behaviour}, Deps)

          when Attribute =:= behaviour orelse Attribute =:= behavior ->

              case sets:is_element(Behaviour, Modules) of

                  true  -> sets:add_element(

                             [EbinDir, "/", atom_to_list(Behaviour), ".beam"],

                             Deps);

                  false -> Deps

              end;

          ({attribute, _LineNumber, file, {FileName, _LineNumber1}}, Deps) ->

              case sets:is_element(FileName, Headers) of

                  true  -> sets:add_element(FileName, Deps);

                  false -> Deps

              end;

          (_Form, Deps) ->

              Deps

      end, sets:new(), Forms).