-module(a2).
-export([punct/1,wsp/1,get_word/1,drop_word/1,drop_wsp/1,words/1,get_line/2,drop_line/2,lines/1,check/1]).
-export([text/0,show_line/1,print_line/1,show_doc/1,print_doc/1,test/0]).
-export([replicate/2,show_line_right/1,print_line_right/1,show_doc_right/1,print_doc_right/1,test_right/0]).

%% Dummy definition

dummy() -> dummy().

%% Is a character punctuation?

-spec punct(integer()) -> boolean().

punct(Ch) -> lists:member(Ch,"\'\"\.\,\ \;\:\!\?\`\(\)").

%% Is a character whitespace?

-spec wsp(integer()) -> boolean().

wsp(Ch) -> lists:member(Ch,"\ \t\n").

%% get a word from the front of the string
%% split at whitespace, as defined in wsp.
%% e.g.
%% a2:get_word("hello? there") = "hello?"

-spec get_word(string()) -> string().

get_word(Line) ->
  lists:nth(
    1,
    string:split(drop_wsp(Line), " ")
  ).


%% drop a word from the front of the string
%% split at whitespace, as defined in wsp.
%% e.g.
%% a2:drop_word("hello? there") = " there"

-spec drop_word(string()) -> string().


drop_word(Line) ->
   lists:join(" ", tl(string:split(drop_wsp(Line),  " "))).




%% drop whitespace from the front of the string
%% e.g.
%% a2:drop_wsp(" there") = "there"

-spec drop_wsp(string()) -> string().

drop_wsp(Line) -> string:strip(Line, left, $\s).



%% Break a string into words, using the functions above.
%%
%% Assumption: words is always called on a string
%% without white space at the start.
%% e.g. a2:words("hello? there") = ["hello?","there"]

-spec words(string()) -> list(string()).

words(Line) ->
    Clean = drop_wsp(Line),
    Word = get_word(Clean),
    Rest = drop_word(Clean),
    [Word | if Rest =/= "" -> words(Rest); true -> [] end].


%% Splitting a list of words into lines, each of
%% which is a list of words.

%% To build a line, take as many words as possible, keeping
%% the total length (including a single inter-word space
%% between adjacent words) below the specified length, which
%% is the second parameter of get_line and drop_line.

%% e.g.
%% 1> a2:get_line(["When", "riding", "at", "night,"],20).
%% ["When","riding","at"]
%% 2> a2:drop_line(["When", "riding", "at", "night,"],20).
%% ["night,"]

-define(LINELEN,40).

-spec get_line(list(),integer()) -> list(string()).

get_line(_, 0) -> [];
get_line(List, X) ->
  Word = get_word(List),
  Length = string:length(Word) + 1,
  [Word | get_line(drop_word(List), max(0, X - Length))].

 %%  [Word | get_line(lists:nth(2,drop_word(List)), max(0, X - Length))].

%% Partner function of get_line: drops a line word of words.

-spec drop_line(string(),integer()) -> list(string()).

drop_line(_,_) -> dummy().

%% Repeatedly apply get_line and drop_line to turn
%% a lost of words into a list of lines i.e.
%% a list of list of words.

-spec lines(list(string())) -> list(list(string())).

lines(_) -> dummy().

%% Checking that all words no longer than ?LINELEN.

-spec check(list(string())) -> boolean().

check(_) -> dummy().

%% Showing and printing lines and documents.

%% Join words, interspersed with spaces, and newline at the end.

-spec show_line(list(string())) -> string().

show_line([W]) -> W ++ "\n";
show_line([W|Ws]) -> W ++ " " ++ show_line(Ws).

%% As for show_line, but padded with spaces at the start to make
%% the length of the line equal to ?LISTLEN.
%% May use the replicate function.

-spec show_line_right(list(string())) -> string().

show_line_right(_) -> dummy().

%% Build a list out of replicated copies of an item.
%% e.g. replicate(5,3) = [3,3,3,3,3].

-spec replicate(integer(),T) -> list(T).

replicate(_,_) -> dummy().

%% Print out a line, i.e. resolve the layout.

-spec print_line(list(string())) -> ok.

print_line(X) -> io:format(show_line(X)).

%% As for print-line, but right-aligned.

-spec print_line_right(list(string())) -> ok.

print_line_right(_) -> dummy().

%% Show a whole doc, i.e. list of lines.

-spec show_doc(list(list(string()))) -> string().

show_doc(Ls) ->
    lists:concat(lists:map(fun show_line/1, Ls)).

%% Show a whole doc, i.e. list of lines, right aligned.

-spec show_doc_right(list(list(string()))) -> string().

show_doc_right(_) -> dummy().

%% Print a doc.

-spec print_doc(list(list(string()))) -> ok.

print_doc(X) -> io:format(show_doc(X)).

%% Print a doc, right-aligned.

-spec print_doc_right(list(list(string()))) -> ok.

print_doc_right(_) -> dummy().

%% Test cases

text() -> "When riding at night, make sure your headlight beam is aiming slightly " ++
          "downwards so oncoming traffic can " ++
          "see you without being dazzled. Be sure not to dip it too much, " ++
          "though, as you’ll still want to see the road around 20 metres ahead of you if riding at speed.".

test() -> print_doc(lines(words(text()))).

test_right() -> print_doc_right(lines(words(text()))).

%% Expected outputs

%% 1> a2:test().
%% When riding at night, make sure your
%% headlight beam is aiming slightly
%% downwards so oncoming traffic can see
%% you without being dazzled. Be sure not
%% to dip it too much, though, as you’ll
%% still want to see the road around 20
%% metres ahead of you if riding at speed.
%% ok

%% 2> a2:test_right().
%%     When riding at night, make sure your
%%        headlight beam is aiming slightly
%%    downwards so oncoming traffic can see
%%   you without being dazzled. Be sure not
%%    to dip it too much, though, as you’ll
%%     still want to see the road around 20
%%  metres ahead of you if riding at speed.
%% ok