#!/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).