-module(id3_v1).
-import(lists, [filter/2, map/2, reverse/1]).
-export([test/0, dir/1, read_id3_tag/1]).

test() -> dir("/home/joe/music_keep").

dir(Dir) ->
    Files = lib_find:files(Dir, "*.mp3", true),
    L1 = map(fun(I) -> 
		     {I, (catch read_id3_tag(I))}
	    end,  Files),
  L1 = [ { File , Parse } ] where  = error | [ { Tag ,  } ]
    %% we now have to remove all the entries from L where
   = error . We can do this with a filter operation
    L2 = filter(fun({_,error}) -> false;
		   (_) -> true
		end, L1),
    lib_misc:dump("mp3data", L2).

read_id3_tag(File) ->
    case file:open(File, [read,binary,raw]) of
        {ok, S} ->
	    Size = filelib:file_size(File),
	    {ok, B2} = file:pread(S, Size-128, 128),
	    Result = parse_v1_tag(B2),
	    file:close(S),
	    Result;
        _Error ->
            error
    end.

parse_v1_tag(<<$T,$A,$G,
	      Title:30/binary, Artist:30/binary,
	      Album:30/binary, _Year:4/binary,
	      _Comment:28/binary, 0:8,Track:8,_Genre:8>>) ->
    {"ID3v1.1", 
     [{track,Track}, {title,trim(Title)},
      {artist,trim(Artist)}, {album, trim(Album)}]};
parse_v1_tag(<<$T,$A,$G,
	      Title:30/binary, Artist:30/binary,
	      Album:30/binary, _Year:4/binary,
	      _Comment:30/binary,_Genre:8>>) ->
    {"ID3v1", 
     [{title,trim(Title)}, 
      {artist,trim(Artist)}, {album, trim(Album)}]};
parse_v1_tag(_) ->
    error.

trim(Bin) -> 
    list_to_binary(trim_blanks(binary_to_list(Bin))).

trim_blanks(X) -> reverse(skip_blanks_and_zero(reverse(X))).

skip_blanks_and_zero([$\s|T]) -> skip_blanks_and_zero(T);
skip_blanks_and_zero([0|T])   -> skip_blanks_and_zero(T);
skip_blanks_and_zero(X)       -> X.

 we now have to remove all the entries from L where
-module(id3_v1).
-import(lists, [filter/2, map/2, reverse/1]).
-export([test/0, dir/1, read_id3_tag/1]).

test() -> dir("/home/joe/music_keep").

dir(Dir) ->
    Files = lib_find:files(Dir, "*.mp3", true),
    L1 = map(fun(I) -> 
		     {I, (catch read_id3_tag(I))}
	    end,  Files),
  L1 = [ { File , Parse } ] where  = error | [ { Tag ,  } ]
   = error . We can do this with a filter operation
    L2 = filter(fun({_,error}) -> false;
		   (_) -> true
		end, L1),
    lib_misc:dump("mp3data", L2).

read_id3_tag(File) ->
    case file:open(File, [read,binary,raw]) of
        {ok, S} ->
	    Size = filelib:file_size(File),
	    {ok, B2} = file:pread(S, Size-128, 128),
	    Result = parse_v1_tag(B2),
	    file:close(S),
	    Result;
        _Error ->
            error
    end.

parse_v1_tag(<<$T,$A,$G,
	      Title:30/binary, Artist:30/binary,
	      Album:30/binary, _Year:4/binary,
	      _Comment:28/binary, 0:8,Track:8,_Genre:8>>) ->
    {"ID3v1.1", 
     [{track,Track}, {title,trim(Title)},
      {artist,trim(Artist)}, {album, trim(Album)}]};
parse_v1_tag(<<$T,$A,$G,
	      Title:30/binary, Artist:30/binary,
	      Album:30/binary, _Year:4/binary,
	      _Comment:30/binary,_Genre:8>>) ->
    {"ID3v1", 
     [{title,trim(Title)}, 
      {artist,trim(Artist)}, {album, trim(Album)}]};
parse_v1_tag(_) ->
    error.

trim(Bin) -> 
    list_to_binary(trim_blanks(binary_to_list(Bin))).

trim_blanks(X) -> reverse(skip_blanks_and_zero(reverse(X))).

skip_blanks_and_zero([$\s|T]) -> skip_blanks_and_zero(T);
skip_blanks_and_zero([0|T])   -> skip_blanks_and_zero(T);
skip_blanks_and_zero(X)       -> X.
