elli_cookie

%%%===================================================================
%%% @author aj heller <aj@drfloob.com>
%%% @copyright (C) 2012, aj heller
%%% @copyright (C) 2016, Eric Bailey
%%% @doc A library application for reading and managing cookies in elli.
%%% @end
%%% Created :  3 Oct 2012 by aj heller <aj@drfloob.com>
%%%===================================================================
-module(elli_cookie).

%% Basic Cookie Management
-export([parse/1, get/2, get/3, new/2, new/3, delete/1, delete/2]).

%% Cookie Options
-export([expires/1, path/1, domain/1, secure/0, http_only/0, max_age/1]).

-include_lib("elli/include/elli.hrl").

-type stringy()       :: string() | binary().
-type cookie()        :: {binary(), binary()}.
-type cookie_list()   :: [cookie()].
-type cookie_option() :: {atom(), string()}.

%% returns a proplist made from the submitted cookies
-spec parse(Req :: #req{}) -> no_cookies | cookie_list().
parse(Req = #req{}) -> tokenize(elli_request:get_header(<<"Cookie">>, Req)).

%% gets a specific cookie value from the set of parsed cookie
-spec get(Key :: binary(), Cookies :: cookie_list()) -> undefined | binary().
get(_, no_cookies) ->
  undefined;
get(Key, Cookies) ->
  ok = valid_cookie_name(Key),
  proplists:get_value(to_bin(Key), Cookies).

-spec get(Key :: binary(), Cookies :: cookie_list(), Default) -> Default | binary().
get(_, no_cookies, Default) ->
  Default;
get(Key, Cookies, Default) ->
  ok = valid_cookie_name(Key),
  proplists:get_value(to_bin(Key), Cookies, Default).

%% creates a new cookie in a format appropriate for server response
-spec new(Name :: stringy(), Value :: stringy()) -> cookie().
new(Name, Value) ->
  ok = valid_cookie_name(Name),
  ok = valid_cookie_value(Value),
  BName = to_bin(Name),
  BVal = to_bin(Value),
  {<<"Set-Cookie">>, <<BName/binary, "=", BVal/binary>>}.

-spec new(Name :: stringy(), Value :: stringy(), Options :: [cookie_option()]) -> cookie().
new(Name, Value, Options) ->
  ok = valid_cookie_name(Name),
  ok = valid_cookie_value(Value),
  BName = to_bin(Name),
  BValue = to_bin(Value),
  Bin = <<BName/binary,"=",BValue/binary>>,
  FinalBin = lists:foldl(fun set_cookie_attribute/2, Bin, Options),
  {<<"Set-Cookie">>, FinalBin}.

%% Creates a header that will delete a specific cookie on the client
-spec delete(Name :: stringy()) -> cookie().
delete(Name) -> delete(Name, []).

-spec delete(Name :: stringy(), Options :: [cookie_option()]) -> cookie().
delete(Name, Options) ->
  ok = valid_cookie_name(Name),
  new(Name, "", [expires({{1970,1,1},{0,0,0}}) | Options]).


%%%===================================================================
%%% Cookie Option helpers
%%%===================================================================

%% set a path for a cookie
path(P) -> {path, P}.

%% set a domain for a cookie
domain(P) -> {domain, P}.

%% make the cookie secure (SSL)
secure() -> secure.

%% make an http-only cookie
http_only() -> http_only.

%% set cookie expiration
expires({S, seconds}) -> expires_plus(S);
expires({M, minutes}) -> expires_plus(M*60);
expires({H, hours})   -> expires_plus(H*60*60);
expires({D, days})    -> expires_plus(D*24*60*60);
expires({W, weeks})   -> expires_plus(W*7*24*60*60);
expires(Date)         -> {expires, httpd_util:rfc1123_date(Date)}.

max_age({S, seconds}) -> {max_age, (S)};
max_age({M, minutes}) -> {max_age, (M*60)};
max_age({H, hours})   -> {max_age, (H*60*60)};
max_age({D, days})    -> {max_age, (D*24*60*60)};
max_age({W, weeks})   -> {max_age, (W*7*24*60*60)};
max_age(Seconds)      -> {max_age, Seconds}.


%%%===================================================================
%%% Internal functions
%%%===================================================================

to_bin(B) when is_binary(B) -> B;
to_bin(L) when is_list(L)   -> list_to_binary(L);
to_bin(X)                   -> throw({error, {not_a_string, X}}).

tokenize(<<>>) ->
  [];
tokenize(CookieStr) when is_binary(CookieStr) ->
  Cookies = binary:split(CookieStr, <<";">>, [trim, global]),
  lists:map(fun tokenize2/1, Cookies);
tokenize(_) ->
  no_cookies.

tokenize2(NVP) ->
  case binary:split(NVP, <<"=">>, [trim]) of
    [N,V] -> {strip_bin(N), strip_bin(V)};
    [N]   -> {strip_bin(N), <<>>}
  end.

set_cookie_attribute({expires, Exp}, Bin) ->
  BExp = to_bin(Exp),
  <<Bin/binary, ";Expires=", BExp/binary>>;
set_cookie_attribute({max_age, Exp}, Bin) ->
  BExp = to_bin(integer_to_list(Exp)),
  <<Bin/binary, ";Max-Age=", BExp/binary>>;
set_cookie_attribute({path, Path}, Bin) ->
  BPath = to_bin(Path),
  <<Bin/binary, ";Path=", BPath/binary>>;
set_cookie_attribute({domain, Domain}, Bin) ->
  BDomain = to_bin(Domain),
  <<Bin/binary, ";Domain=", BDomain/binary>>;
set_cookie_attribute(secure, Bin) ->
  <<Bin/binary, ";Secure">>;
set_cookie_attribute(http_only, Bin) ->
  <<Bin/binary, ";HttpOnly">>;
set_cookie_attribute(X, _) ->
  throw({error, {invalid_cookie_attribute, X}}).

expires_plus(N) ->
  UT = calendar:datetime_to_gregorian_seconds(calendar:universal_time()),
  UTE = UT + N,
  Date = calendar:gregorian_seconds_to_datetime(UTE),
  {expires, httpd_util:rfc1123_date(Date)}.

strip_bin(B) ->
  list_to_binary(string:strip(binary_to_list(B))).


%%%===================================================================
%%% Predicates
%%%===================================================================

%% TODO: implement cookie spec checking: https://tools.ietf.org/html/rfc6265
valid_cookie_name(B) when is_binary(B) ->
  Str = binary_to_list(B),
  valid_cookie_name2(string:str(Str, "="), B);
valid_cookie_name(N) when is_list(N) ->
  valid_cookie_name2(string:str(N, "="), N);
valid_cookie_name(X) ->
  {invalid_cookie_name, X}.

valid_cookie_name2(0, _) -> ok;
valid_cookie_name2(_, N) -> {invalid_cookie_name, N}.

%% TODO: implement cookie spec checking: https://tools.ietf.org/html/rfc6265
valid_cookie_value(B) when is_binary(B); is_list(B) ->
  ok;
valid_cookie_value(X) ->
  {invalid_cookie_value, X}.