text_processing exercise.

format.erl

-module(format).
-export([text_processing/3]).

% Used to read a file into a list of lines.
% Example files available in:
%   gettysburg-address.txt (short)
%   dickens-christmas.txt  (long)

% Get the contents of a text file into a list of lines.
% Each line has its trailing newline removed.

get_file_contents(Name) ->
    {ok,File} = file:open(Name,[read]),
    Rev = get_all_lines(File,[]),
lists:reverse(Rev).

% Auxiliary function for get_file_contents.
% Not exported.

get_all_lines(File,Partial) ->
    case io:get_line(File,"") of
        eof -> file:close(File),
               Partial;
        Line -> {Strip,_} = lists:split(length(Line)-1,Line),
                get_all_lines(File,[Strip|Partial])
    end.

% Show the contents of a list of strings.
% Can be used to check the results of calling get_file_contents.

show_file_contents([L|Ls]) ->
    io:format("~s~n",[L]),
    show_file_contents(Ls);
show_file_contents([]) ->
    ok.    


-spec text_processing(string(),string(),integer()) -> string().
text_processing(File,Format,MaxLen) -> 
	F = get_file_contents(File),
	T = get_tokens(F,[]),
	L = lists:concat(T),	
	case Format of
		vb -> F;
		cv -> io:fwrite(string:join(my_pad(fit_words(L,MaxLen,[],0,[]),MaxLen,both,[]),"\n"));
		lp -> io:fwrite(string:join(fit_words(L,MaxLen,[],0,[]),"\n"));
		rp -> io:fwrite(string:join(my_pad(fit_words(L,MaxLen,[],0,[]),MaxLen,leading,[]),"\n"));
		ju -> io:fwrite(string:join(justify(fit_words(L,MaxLen,[],0,[]),MaxLen,[]),"\n"))
	end.	

%Generates a list of words from our text.
-spec get_tokens([list()],[T]) -> [T].
get_tokens([],Acc) ->
	lists:reverse(Acc);
get_tokens([H|T],Acc) ->
	get_tokens(T,[string:tokens(H, " ")|Acc]).

%From a list of words it creates a list of string with lengh < MaxLengh
-spec fit_words(list(),integer(),list(),integer(),[T]) -> [T].
fit_words([],_MaxLen,[],0,Acc) -> 
	lists:reverse(Acc);
fit_words([],MaxLen,CurrentLine,_CumulatedLen,Acc) -> 
	fit_words([],MaxLen,[],0,[string:join(lists:reverse(CurrentLine)," ")|Acc]);
fit_words([H|T],MaxLen,CurrentLine,CumulatedLen,Acc) ->
	case length(H) + CumulatedLen =< MaxLen of
		true -> fit_words(T,MaxLen,[H|CurrentLine],CumulatedLen + length(H) + 1 ,Acc);
		false -> fit_words([H|T],MaxLen,[],0,[string:join(lists:reverse(CurrentLine)," ")|Acc])
	end.

%calls pad function for every line in our text.
%we have to say if we want it leadding or trailing.
-spec my_pad([T],integer(),atom(),[T]) -> [T].
my_pad([],_MaxLen,_PadMode,Acc) -> 
	lists:reverse(Acc);
my_pad([H|T],MaxLen,PadMode,Acc) -> 
	my_pad(T,MaxLen,PadMode,[string:pad(H,MaxLen,PadMode)|Acc]).

%calls expand function for every line in our text.
%this tells spand function how spaces has to insert.
-spec justify([T],integer(),[T]) -> [T].
justify([],_MaxLen,Acc) -> 
	lists:reverse(Acc);
justify([H|T],MaxLen,Acc) -> 
	justify(T,MaxLen,[expand(H,[],MaxLen - length(H),0)|Acc]).

%expands a string inserting spaces until the desired length is reached.
-spec expand(string(),integer(),string(),integer()) -> string().
expand([],Acc,0,_Previous) -> lists:reverse(Acc);
expand([H|T],Acc,0,_Previous) -> expand(T,[H|Acc],0,H);
expand([$\s|T],Acc,ExpandLength,$\s) -> expand(T,[$\s|Acc],ExpandLength,$\s);
expand([$\s|T],Acc,ExpandLength,_Previous) -> expand(T,[$\s,$\s|Acc],ExpandLength - 1,$\s);
expand([H|T],Acc,ExpandLength,_Previous) -> expand(T,[H|Acc],ExpandLength,H);
expand([],Acc,ExpandLength,_Previous) -> expand(lists:reverse(Acc),[],ExpandLength,0).

%sample_outputs:
%
%
%
%
%
%149> format:text_processing("text",cv,60).
% The heat bloomed in December as the carnival season kicked 
%  into gear. Nearly helpless with sun and glare, I avoided  
%Rio's brilliant sidewalks and glittering beaches, panting in
% dark corners and waiting out the inverted southern summer. ok
%
%
%
%
%150> format:text_processing("text",lp,40).
%The heat bloomed in December as the
%carnival season kicked into gear. Nearly
%helpless with sun and glare, I avoided
%Rio's brilliant sidewalks and glittering
%beaches, panting in dark corners and
%waiting out the inverted southern
%summer.ok
%
%151> format:text_processing("text",rp,40).
%     The heat bloomed in December as the
%carnival season kicked into gear. Nearly
%  helpless with sun and glare, I avoided
%Rio's brilliant sidewalks and glittering
%    beaches, panting in dark corners and
%       waiting out the inverted southern
%                                 summer.ok
%
%2> format:text_processing("text",ju,50).
%The  heat  bloomed  in  December  as  the carnival
%season  kicked into gear. Nearly helpless with sun
%and glare, I avoided Rio's brilliant sidewalks and
%glittering  beaches,  panting  in dark corners and
%waiting   out   the   inverted   southern  summer.ok
%
%
%
%
%3> format:text_processing("text",ju,30).
%The  heat  bloomed in December
%as  the carnival season kicked
%into   gear.  Nearly  helpless
%with  sun and glare, I avoided
%Rio's  brilliant sidewalks and
%glittering beaches, panting in
%dark  corners  and waiting out
%the  inverted southern summer.ok