qdate/src/qdate.erl

-module(qdate).

-export([
	to_string/1,
	to_string/2,
	to_string/3,
	to_date/1,
	to_date/2,
	to_now/1,
	to_unixtime/1,
	unixtime/0
]).

%% -export([
%% 	register_parser/2,
%% 	register_parser/1
%% ]).
%%
%% -export([
%% 	register_format/2,
%% 	register_format/1
%% ]).
%% 
-export([
	set_timezone/1,
	set_timezone/2,
	get_timezone/0,
	get_timezone/1,
	clear_timezone/0,
	clear_timezone/1
]).


%% Exported for API compatibility with ec_date
-export([
	format/1,format/2,
	nparse/1,
	parse/1
]).

%% This the value in gregorian seconds for jan 1st 1970, 12am
%% It's used to convert to and from unixtime, since unixtime starts 
%% 1970-01-01 12:00am
-define(UNIXTIME_BASE,62167219200).

%% This is the timezone only if the qdate application variable 
%% "default_timezone" isn't set or is set to undefined.
%% It's recommended that your app sets the var in a config, or at least using
%%
%% 		application:set_env(qdate, default_timezone, "GMT").
%%
-define(DEFAULT_TZ, case application:get_env(qdate, default_timezone) of 
						undefined -> "GMT";
						TZ -> TZ 
					end).

-define(DETERMINE_TZ, determine_timezone()).


to_string(Format) ->
	to_string(Format, now()).

to_string(Format, Date) ->
	to_string(Format, ?DETERMINE_TZ, Date).

to_string(Format, ToTZ, Date) ->
	ec_date:format(Format,to_date(Date,ToTZ)).

format(Format) ->
	to_string(Format).

format(Format, Date) ->
	to_string(Format, Date).

parse(String) ->
	to_date(String).

nparse(String) ->
	to_now(String).

%% This converts dates without regard to timezone.
%% Unixtime just goes to UTC
raw_to_date(Unixtime) when is_integer(Unixtime) ->
	unixtime_to_date(Unixtime);
raw_to_date(DateString) when is_list(DateString) ->
	ec_date:parse(DateString);
raw_to_date(Now = {_,_,_}) ->
	calendar:now_to_datetime(Now);
raw_to_date(Date = {{_,_,_},{_,_,_}}) ->
	Date.

to_date(RawDate) ->
	to_date(RawDate, ?DETERMINE_TZ).

to_date(RawDate, ToTZKey) when is_atom(ToTZKey) orelse is_tuple(ToTZKey) ->
	case get_timezone(ToTZKey) of
		undefined -> throw({timezone_key_not_found,ToTZKey});
		ToTZ -> to_date(RawDate, ToTZ)
	end;
to_date(RawDate, ToTZ)  ->
	{RawDate2,FromTZ} = extract_timezone(RawDate),
	Date = raw_to_date(RawDate2),
	localtime:local_to_local(Date,FromTZ,ToTZ).

set_timezone(TZ) ->
	qdate_srv:set_timezone(TZ).

set_timezone(Key,TZ) ->
	qdate_srv:set_timezone(Key, TZ).

get_timezone() ->
	qdate_srv:get_timezone().

get_timezone(Key) ->
	qdate_srv:get_timezone(Key).

clear_timezone() ->
	qdate_srv:clear_timezone().

clear_timezone(Key) ->
	qdate_srv:clear_timezone(Key).

extract_timezone(Unixtime) when is_integer(Unixtime) ->
	{Unixtime, ?DETERMINE_TZ};
extract_timezone(DateString) when is_list(DateString) ->
	AllTimezones = localtime:list_timezones(),
	RevDate = lists:reverse(DateString),
	extract_timezone_helper(RevDate, AllTimezones);
extract_timezone(Date={{_,_,_},{_,_,_}}) ->
	{Date, ?DETERMINE_TZ};
extract_timezone(Now={_,_,_}) ->
	{Now, ?DETERMINE_TZ};
extract_timezone({MiscDate,TZ}) ->
	{MiscDate,TZ}.
	
extract_timezone_helper(RevDate, []) ->
	{lists:reverse(RevDate), ?DETERMINE_TZ};
extract_timezone_helper(RevDate, [TZ | TZs]) ->
	RevTZ = lists:reverse(TZ),
	case lists:split(length(TZ),RevDate) of
		{RevTZ," " ++ Remainder} ->
			{lists:reverse(Remainder), TZ};
		_ ->
			extract_timezone_helper(RevDate, TZs)
	end.

determine_timezone() ->
	case qdate_srv:get_timezone() of
		undefined -> ?DEFAULT_TZ;
		TZ -> TZ
	end.

to_unixtime(Unixtime) when is_integer(Unixtime) ->
	Unixtime;
to_unixtime({MegaSecs,Secs,_}) ->
	MegaSecs*1000000 + Secs;
to_unixtime(ToParse) ->
	Date = to_date(ToParse),
	calendar:datetime_to_gregorian_seconds(Date) - ?UNIXTIME_BASE.

unixtime() ->
	to_unixtime(now()).

to_now(Now = {_,_,_}) ->
	Now;
to_now(ToParse) ->
	Unixtime = to_unixtime(ToParse),
	unixtime_to_now(Unixtime).


unixtime_to_now(T) when is_integer(T) ->
	MegaSec = floor(T/1000000),
	Secs = T - MegaSec*1000000,
	{MegaSec,Secs,0}.

unixtime_to_date(T) ->
	Now = unixtime_to_now(T),
	calendar:now_to_datetime(Now).

floor(N) when N >= 0 ->
	trunc(N);
floor(N) when N < 0 ->
	Int = trunc(N),
	if
		Int==N -> Int;
		true -> Int-1
	end.
	

%% TESTS
-include_lib("eunit/include/eunit.hrl").

%% emulates as if a forum-type website has a Site tz, and a user-specified tz
-define(SITE_TZ,"PST").
-define(USER_TZ,"CST").
-define(SELF_TZ,"EST"). %% Self will be the pid of the current running process
-define(SITE_KEY,test_site_key).
-define(USER_KEY,test_user_key).



tz_test_() ->
	{
		setup,
		fun start_test/0,
		fun stop_test/1,
		fun(SetupData) ->
			{spawn,[
				simple_test(),
				tz_tests(SetupData)
			]}
		end
	}.

tz_tests(_) ->
	[
		?_assertEqual(?SELF_TZ,begin set_timezone(?SELF_TZ),get_timezone() end),
		?_assertEqual(?USER_TZ,get_timezone(?USER_KEY)),
		?_assertEqual(?SITE_TZ,get_timezone(?SITE_KEY))
	].

simple_test() ->
	[
		?_assertEqual(0,to_unixtime({0,0,0})),
		?_assertEqual({0,0,0},to_now(0)),
		?_assertEqual(0,to_unixtime("1970-01-01 12:00am GMT")),
		?_assertEqual(21600,to_unixtime("1970-01-01 12:00am CST")),
		?_assertEqual(0,to_unixtime({{1970,1,1},{0,0,0}})),
		?_assertEqual({{1970,1,1},{0,0,0}},to_date(0)),
		?_assertEqual({{2013,03,07},{0,0,0}},to_date(to_unixtime("2013-03-07 12am"))),
		?_assertEqual("2012-12-01 1:00pm", to_string("Y-m-d g:ia","EST","2012-12-01 12:00pm CST")),
		?_assertEqual(to_unixtime("2012-01-01 12:00pm CST"), to_unixtime("2012-01-01 10:00am PST")),
		?_assertEqual({{2012,12,31},{18,15,15}},to_date("Dec 31, 2012 6:15:15pm")),
		?_assertEqual({{2013,1,1},{0,15,15}},to_date("December 31, 2012 6:15:15pm CST","GMT"))
	].

%%tz_char_tests(_) ->
%%	qdate:set_timezone(?SELF_TZ),



	
		
		
start_test() ->
	application:start(qdate),
	qdate:set_timezone(?SITE_KEY,?SITE_TZ),
	qdate:set_timezone(?USER_KEY,?USER_TZ).

stop_test(_) ->
	ok.