ex310.erl

%% Erlang Programming Exercise 3-10
%% https://gist.github.com/yamasushi/69d6f5ab6cd7115ab525fe011ec67dfe
-module(ex310).
-export([test_data/0,fill/2,justify/2]).

fill(Words,Width) ->
    GW = gather_words_acc(Words,Width,0,0,[],[]),
    %% io:format("~p~n",[GW]),
    lists:foreach(fun(K)->io:format("~s~n",[K]) end , 
                  lists:map(fun({_,L}) -> fill_line(L) end, GW)).

justify(Words,Width) ->
    GW = gather_words_acc(Words,Width,0,0,[],[]),
    %% io:format("~p~n",[GW]),
    lists:foreach(fun(K)->io:format("~s~n",[K]) end , 
                  lists:map(fun({LW,L}) -> justify_line(L,LW,Width) end, GW)).


gather_words_acc([],   _Width, LenWords, _LenLine, AccLine, Acc) -> 
    lists:reverse([{LenWords, lists:reverse(AccLine) } |Acc]);
gather_words_acc([H|T], Width, LenWords, LenLine, AccLine, Acc) -> 
    LenWord=length(H),
    if
        (LenWord+LenLine+1) > Width ->
            gather_words_acc(T, Width, LenWord, LenWord,
                            [H], [{LenWords, lists:reverse(AccLine)} |Acc]);
        true ->
            gather_words_acc(T, Width , LenWords+LenWord, LenLine+LenWord+1,
                            [H|AccLine],Acc)
    end.


fill_line([H]) -> H;
fill_line([H|T]) -> H ++ " " ++ fill_line(T).

justify_line([H], _LenWords, _Width) -> H;
justify_line(L, LenWords, Width) ->
    N = length(L),
    Spc = Width-LenWords,
    SpcUnit = Spc div (N-1),
    justify_concat_acc(L, Spc, SpcUnit, []).

justify_concat_acc([H1,H2], Spc, _SpcUnit, Acc) ->
    %% io:format(">>>>> ~p,~p | ~p (~w)~n~n", [H1, H2, Acc, Spc]),
    lists:concat(lists:reverse([H2, lists:duplicate(Spc, $\s), H1 | Acc]));
justify_concat_acc([H|T], Spc, SpcUnit, Acc) ->
    io:format("~p,~p,~p,~p~n",[[H|T],Acc,Spc,SpcUnit]),
    justify_concat_acc(T, Spc-SpcUnit, SpcUnit, 
                       [lists:duplicate(SpcUnit,$\s),H|Acc]).

test_data() ->
    {ok,S} = file:read_file("test.dat"),
    string:lexemes(binary_to_list(S)," \n") .