require('strict')

local yesno = require('Module:Yesno')

local getArgs = require ('Module:Arguments').getArgs



local tz = {};																	-- holds local copy of the specified timezone table from tz_data{}

local cfg = {};																	-- for internationalization 





--[[--------------------------< I S _ S E T >------------------------------------------------------------------



Whether variable is set or not.  A variable is set when it is not nil and not empty.



]]



local function is_set( var )

	return not (nil == var or '' == var);

end





--[[--------------------------< S U B S T I T U T E >----------------------------------------------------------



Populates numbered arguments in a message string using an argument table.



]]



local function substitute (msg, args)

	return args and mw.message.newRawMessage (msg, args):plain() or msg;

end





--[[--------------------------< E R R O R _ M S G >------------------------------------------------------------



create an error message



]]



local function error_msg (msg, arg)

	return substitute (cfg.err_msg, substitute (cfg.err_textmsg], arg))

end





--[[--------------------------< D E C O D E _ D S T _ E V E N T >----------------------------------------------



extract ordinal, day-name, and month from daylight saving start/end definition string as digits:

	Second Sunday in March

returns

	2 0 3



Casing doesn't matter but the form of the string does:

	<ordinal> <day> <any single word> <month> – all are separated by spaces



]]



local function decode_dst_event (dst_event_string)

	local ord, day, month;

	

	dst_event_string = dst_event_string:lower();								-- force the string to lower case because that is how the tables above are indexed

	ord, day, month = dst_event_string:match ('([%a%d]+)%s+(%a+)%s+%a+%s+(%a+)');

	

	if not (is_set (ord) and is_set (day) and is_set (month)) then				-- if one or more of these not set, then pattern didn't match

		return nil;

	end

	

	return cfg.ordinalsord], cfg.daysday], cfg.monthsmonth];

end





--[[--------------------------< G E T _ D A Y S _ I N _ M O N T H >--------------------------------------------



Returns the number of days in the month where month is a number 1–12 and year is four-digit Gregorian calendar.

Accounts for leap year.



]]



local function get_days_in_month (year, month)

	local days_in_month = {31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};

	

	year = tonumber (year);														-- force these to be numbers just in case

	month = tonumber (month);



	if (2 == month) then														-- if February

		if (0 == (year%4) and (0 ~= (year%100) or 0 == (year%400))) then		-- is year a leap year?

			return 29;															-- if leap year then 29 days in February

		end

	end

	return days_in_month month];

end





--[[--------------------------< G E T _ D S T _ M O N T H _ D A Y >--------------------------------------------



Return the date (month and day of the month) for the day that is the ordinal (nth) day-name in month (second

Friday in June) of the current year



timestamp is today's date-time number from os.time(); used to supply year

timezone is the timezone parameter value from the template call



Equations used in this function taken from Template:Weekday_in_month



]]



local function get_dst_month_day (timestamp, start)

	local ord, weekday_num, month;

	local first_day_of_dst_month_num;

	local last_day_of_dst_month_num;

	local days_in_month;

	local year;



	if true == start then

		ord, weekday_num, month = decode_dst_event (tz.dst_begins);				-- get start string and convert to digits

	else

		ord, weekday_num, month = decode_dst_event (tz.dst_ends);				-- get end string and convert to digits

	end

	

	if not (is_set (ord) and is_set (weekday_num) and is_set (month)) then

		return nil;																-- could not decode event string

	end

	

	year = os.date ('%Y', timestamp);



	if -1 == ord then		-- j = t + 7×(n + 1) - (wt - w) mod 7				-- if event occurs on the last day-name of the month ('last Sunday of October')

		days_in_month = get_days_in_month (year, month);

		last_day_of_dst_month_num = os.date ('%w', os.time ({['year'=year, 'month'=month, 'day'=days_in_month}));

		return month, days_in_month + 7*(ord + 1) - ((last_day_of_dst_month_num - weekday_num) % 7);

	else	-- j = 7×n - 6 + (w - w1) mod 7

		first_day_of_dst_month_num = os.date ('%w', os.time ({['year'=year, 'month'=month, 'day'=1}))

		return month, 7 * ord - 6 + (weekday_num - first_day_of_dst_month_num) % 7;		-- return month and calculated date

	end

end





--[[--------------------------< G E T _ U T C _ O F F S E T >--------------------------------------------------



Get utc offset in hours and minutes, convert to seconds.  If the offset can't be converted return nil.

TODO: return error message?

TODO: limit check this? +/-n hours?

]]



local function get_utc_offset ()

	local sign;

	local hours;

	local minutes;

	

	sign, hours, minutes = mw.ustring.match (tz.utc_offset, '([%+%-±−]?)(%d%d):(%d%d)');



	if '-' == sign then sign = -1; else sign = 1; end

	if is_set (hours) and is_set (minutes) then

		return sign * ((hours * 3600) + (minutes * 60));

	else

		return nil;																-- we require that all timezone tables have what appears to be a valid offset

	end

end





--[[--------------------------< M A K E _ D S T _ T I M E S T A M P S >----------------------------------------



Return UTC timestamps for the date/time of daylight saving time events (beginning and ending).  These timestamps

will be compared to current UTC time.  A dst timestamp is the date/time in seconds UTC for the timezone at the

hour of the dst event.



For dst rules that specify local event times, the timestamp is the sum of:

	timestamp = current year + dst_month + dst_day + dst_time (all in seconds) local time

Adjust local time to UTC by subtracting utc_offset:

	timestamp = timestamp - utc_offset (in seconds)

For dst_end timestamp, subtract an hour for DST

	timestamp = timestamp - 3600 (in seconds)



For dst rules that specify utc event time the process is the same except that utc offset is not subtracted.



]]



local function make_dst_timestamps (timestamp)

	local dst_begin, dst_end;													-- dst begin and end time stamps 

	local year;																	-- current year

	local dst_b_month, dst_e_month, dst_day;									-- month and date of dst event

	local dst_hour, dst_minute;													-- hour and minute of dst event on year-dst_month-dst_day

	local invert = false;														-- flag to pass on when dst_begin month is numerically larger than dst_end month (southern hemisphere)

	local utc_offset;

	local utc_flag;



	year = os.date ('%Y', timestamp);											-- current year

	utc_offset = get_utc_offset ();												-- in seconds

	if not is_set (utc_offset) then												-- utc offset is a required timezone property

		return nil;

	end



	dst_b_month, dst_day = get_dst_month_day (timestamp, true);					-- month and day that dst begins

	if not is_set (dst_b_month) then

		return nil;

	end

	

	dst_hour, dst_minute = tz.dst_time:match ('(%d%d):(%d%d)');					-- get dst time

	utc_flag = tz.dst_time:find ('[Uu][Tt][Cc]%s*$');							-- set flag when dst events occur at a specified utc time



	dst_begin = os.time ({['year' = year, 'month' = dst_b_month, 'day' = dst_day, 'hour' = dst_hour, 'min' = dst_minute});	-- form start timestamp

	if not is_set (utc_flag) then												-- if dst events are specified to occur at local time

		dst_begin = dst_begin - utc_offset;										-- adjust local time to utc by subtracting utc offset

	end



	dst_e_month, dst_day = get_dst_month_day (timestamp, false);				-- month and day that dst ends

	if not is_set (dst_e_month) then

		return nil;

	end

	

	if is_set (tz.dst_e_time) then

		dst_hour, dst_minute = tz.dst_e_time:match ('(%d%d):(%d%d)');			-- get ending dst time; this one for those locales that use different start and end times

		utc_flag = tz.dst_e_time:find ('[Uu][Tt][Cc]%s*$');						-- set flag if dst is pegged to utc time

	end	



	dst_end = os.time ({['year' = year, 'month' = dst_e_month, 'day' = dst_day, 'hour' = dst_hour, 'min' = dst_minute});	-- form end timestamp

	if not is_set (utc_flag) then												-- if dst events are specified to occur at local time

		dst_end = dst_end - 3600;												-- assume that local end time is DST so adjust to local ST

		dst_end = dst_end - utc_offset;											-- adjust local time to utc by subtracting utc offset

	end





	if dst_b_month > dst_e_month then

		invert = true;															-- true for southern hemisphere eg: start September YYYY end April YYYY+1

	end



	return dst_begin, dst_end, invert;

end





--[[--------------------------< G E T _ T E S T _ T I M E >----------------------------------------------------



decode ISO formatted date/time into a table suitable for os.time().  Fallback to {{Timestamp}} format.

For testing, this time is UTC just as is returned by the os.time() function.



]]



local function get_test_time (iso_date)

	local year, month, day, hour, minute, second;



	year, month, day, hour, minute, second = iso_date:match ('(%d%d%d%d)%-(%d%d)%-(%d%d)T(%d%d):(%d%d):(%d%d)');

	if not year then

		year, month, day, hour, minute, second = iso_date:match ('^(%d%d%d%d)(%d%d)(%d%d)(%d%d)(%d%d)(%d%d)$');

		if not year then

			return nil;															-- test time did not match the specified patterns

		end

	end

	return {['year' = year, 'month' = month, 'day' = day, 'hour' = hour, 'min' = minute, 'sec' = second};

end



--[[----------------------< G E T _ F U L L _ U T C _ O F F S E T >-----------------------------------------------



Creates a standard UTC offset from numerical inputs, for function time to convert to a table.  Expected inputs shall have the form:

	<sign><hour><separator><portion>

where:

	<sign> – optional; one of the characters: '+', '-' (hyphen), '±', '−' (minus); defaults to '+'

	<hour> - one or two digits

	<separator> - one of the characters '.' or ':'; required when <portion> is included; ignored else

	<portion> - optional; one or two digits when <separator> is '.'; two digits else



returns correct utc offset string when input has a correct form; else returns the unmodified input



]]



local function get_full_utc_offset (utc_offset)

	local h, m, sep, sign;

	

	local patterns = {

		'^([%+%-±−]?)(%d%d?)(%.)(%d%d?)$',										-- one or two fractional hour digits

		'^([%+%-±−]?)(%d%d?)(:)(%d%d)$',										-- two minute digits

		'^([%+%-±−]?)(%d%d?)[%.:]?$',											-- hours only; ignore trailing separator

		}

	

	for _, pattern in ipairs(patterns) do										-- loop through the patterns

		sign, h, sep, m = mw.ustring.match (utc_offset, pattern);

		if h then

			break;																-- if h is set then pattern matched

		end

	end



	if not h then

		return utc_offset;														-- did not match a pattern

	end

	

	sign = ('' == sign) and '+' or sign;										-- sign character is required; set to '+' if not specified



	m = ('.' == sep) and ((sep .. m) * 60) or m or 0;							-- fractional h to m



	return string.format ('utc%s%02d:%02d', sign, h, m);

end





--[[--------------------------< T A B L E _ L E N >------------------------------------------------------------



return number of elements in table



]]



local function table_len (tbl)

	local count = 0;

	for _ in pairs (tbl) do

		count = count + 1;

	end

	return count;

end





--[[--------------------------< F I R S T _ S E T >------------------------------------------------------------



scans through a list of parameter names that are aliases of each other and returns the value assigned to the

first args[alias] that has a set value; nil else. scan direction is right-to-left (top-to-bottom)



]]



local function first_set (list, args)

	local i = 1;

	local count = table_len (list);												-- get count of items in list

	

	while i <= count do															-- loop through all items in list

		if is_set( argslisti]] ) then											-- if parameter name in list is set in args

			return argslisti]];												-- return the value assigned to the args parameter

		end

		i = i + 1;																-- point to next

	end

end





--[=[-------------------------< T I M E >----------------------------------------------------------------------



This template takes several parameters (some positonal, some not); none are required:

	1. the time zone abbreviation/UTC offset (positional, always the first unnamed parameter)

	2. a date format flag; second positional parameter or |df=; can have one of several values

	3. |dst= when set to 'no' disables dst calculations for locations that do not observe dst – Arizona in MST

	4. |timeonly= when set to 'yes' only display the time

	5. |dateonly= when set to 'yes' only display the date

	6. |hide-refresh = when set to 'yes' removes the refresh link

	7. |hide-tz = when set to 'yes' removes the timezone name

	8. |unlink-tz = when set to 'yes' unlinks the timzone name

	9. |_TEST_TIME_= a specific utc time in ISO date time format used for testing this code

	

TODO: convert _TEST_TIME_ to |time=?



Timezone abbreviations can be found here: [[List_of_time_zone_abbreviations]]



For custom date format parameters |df-cust=,  |df-cust-a=,  |df-cust-p= use codes 

described here: [[:mw:Help:Extension:ParserFunctions##time]]



]=]



local function time (frame)

	local args = getArgs (frame);

	local utc_timestamp, timestamp;												-- current or _TEST_TIME_ timestamps; timestamp is local ST or DST time used in output

	local dst_begin_ts, dst_end_ts;												-- DST begin and end timestamps in UTC

	local tz_abbr;																-- select ST or DST timezone abbreviaion used in output 

	local time_string;															-- holds output time/date in |df= format

	local utc_offset;

	local invert;																-- true when southern hemisphere

	local DF;																	-- date format flag; the |df= parameter

	local is_dst_tz;



	local data = table.concat ({'Module:Time/data', frame:getTitle():find('sandbox', 1, true) and '/sandbox' or ''}); -- make a data module name; sandbox or live

	data = mw.loadData (data);													-- load the data module

	cfg = data.cfg;																-- get the configuration table

	local tz_aliases = data.tz_aliases;											-- get the aliases table

	local tz_data = data.tz_data;												-- get the tz data table



	local Timeonly = yesno(first_set (cfg.aliases'timeonly'], args));			-- boolean

	local Dateonly = yesno(first_set (cfg.aliases'dateonly'], args));			-- boolean

	if Timeonly and Dateonly then												-- invalid condition when both are set

		Timeonly, Dateonly = false;

	end

	

	local Hide_refresh = yesno(first_set (cfg.aliases'hide-refresh'], args));	-- boolean

	local Hide_tz = yesno(first_set (cfg.aliases'hide-tz'], args));			-- boolean

	local Unlink_tz = yesno(first_set (cfg.aliases'unlink-tz'], args));		-- boolean

	local DST = first_set (cfg.aliases'dst'], args) or true;					-- string 'always' or boolean

	

	local Lang = first_set (cfg.aliases'lang'], args);							-- to render in a language other than the local wiki's language

	

	local DF_cust = first_set (cfg.aliases'df-cust'], args);					-- custom date/time formats

	

	local DF_cust_a = first_set (cfg.aliases'df-cust-a'], args);				-- for am/pm sensitive formats

	local DF_cust_p = first_set (cfg.aliases'df-cust-p'], args);



	if not ((DF_cust_a and DF_cust_p) or										-- DF_cust_a xor DF_cust_p

			(not DF_cust_a and not DF_cust_p))then

		return error_msg ('bad_df_pair');										-- both are required

	end



	if args1 then

		args1 = get_full_utc_offset (args1]):lower();						-- make lower case because tz table member indexes are lower case

	else

		args1 = 'utc';														-- default to utc

	end



	if mw.ustring.match (args1], 'utc[%+%-±−]%d%d:%d%d') then					-- if rendering time for a UTC offset timezone

		tz.abbr = args1]:upper():gsub('%-', '−');								-- set the link label to upper case and replace hyphen with a minus character (U+2212)

		tz.article = tz.abbr;													-- article title same as abbreviation

		tz.utc_offset = mw.ustring.match (args1], 'utc([%+%-±−]?%d%d:%d%d)'):gsub('−', '%-');	-- extract the offset value; replace minus character with hyphen

		local s, t = mw.ustring.match (tz.utc_offset, '(±)(%d%d:%d%d)');		-- ± only valid for offset 00:00

		if s and '00:00' ~= t then

			return error_msg ('bad_sign');

		end

		tz.df = 'iso';

		args1 = 'utc_offsets';												-- spoof to show that we recognize this timezone

	else

		tz = tz_aliasesargs1]] and tz_datatz_aliasesargs1]]] or tz_dataargs1]];	-- make a local copy of the timezone table from tz_data{}

		if not tz then

			return error_msg ('unknown_tz', args1]);							-- if the timezone given isn't in module:time/data(/sandbox)

		end

	end



	DF = first_set (cfg.aliases'df'], args) or args2 or tz.df or cfg.default_df;	-- template |df= overrides typical df from tz properties

	DF = DF:lower();															-- normalize to lower case

	if not cfg.df_valsDF then

		return error_msg ('bad_format', DF);

	end



	if is_set (args._TEST_TIME_) then											-- typically used to test the code at a specific utc time

		local test_time = get_test_time (args._TEST_TIME_);

		if not test_time then

			return error_msg ('test_time');

		end



		utc_timestamp = os.time(test_time);

	else

		utc_timestamp = os.time ();												-- get current server time (UTC)

	end

	utc_offset = get_utc_offset ();												-- utc offset for specified timezone in seconds

	timestamp = utc_timestamp + utc_offset;										-- make local time timestamp



	if 'always' == DST then														-- if needed to always display dst time

		timestamp = timestamp + 3600;											-- add a hour for dst

		tz_abbr = tz.dst_abbr;													-- dst abbreviation

	elseif not yesno(DST) then													-- for timezones that DO observe dst but for this location ...

		tz_abbr = tz.abbr;														-- ... dst is not observed (|dst=no) show time as standard time

	else

		if is_set (tz.dst_begins) and is_set (tz.dst_ends) and is_set (tz.dst_time) then	-- make sure we have all of the parts

			dst_begin_ts, dst_end_ts, invert = make_dst_timestamps (timestamp);	-- get begin and end dst timestamps and invert flag



			if nil == dst_begin_ts or nil == dst_end_ts then

				return error_msg ('bad_dst');

			end

	

			if invert then														-- southern hemisphere; use beginning and ending of standard time in the comparison

				if utc_timestamp >= dst_end_ts and utc_timestamp < dst_begin_ts then	-- is current date time standard time?

					tz_abbr = tz.abbr;											-- standard time abbreviation

				else		

					timestamp = timestamp + 3600;								-- add an hour

					tz_abbr = tz.dst_abbr;										-- dst abbreviation

				end

			else																-- northern hemisphere

				if utc_timestamp >= dst_begin_ts and utc_timestamp < dst_end_ts then	-- all timestamps are UTC

					timestamp = timestamp + 3600;								-- add an hour 

					tz_abbr = tz.dst_abbr;

				else

					tz_abbr = tz.abbr;

				end

			end

		elseif is_set (tz.dst_begins) or is_set (tz.dst_ends) or is_set (tz.dst_time) then	-- if some but not all not all parts then emit error message

			return error_msg ('bad_def', args1]:upper());

		else

			tz_abbr = tz.abbr;													-- dst not observed for this timezone

		end

	end

	

	if Dateonly then

		if 'iso' == DF then														-- |df=iso

			DF = 'iso_date';

		elseif DF:find ('^dmy') or 'y' == DF then								-- |df=dmy, |df=dmy12, |df=dmy24, |df=y

			DF = 'dmy_date';

		else

			DF = 'mdy_date';													-- default

		end



	elseif Timeonly or DF:match ('^%d+$') then									-- time only of |df= is just digits

		DF = table.concat ({'t', DF:match ('%l*(12)') or '24'});				-- |df=12, |df=24, |df=dmy12, |df=dmy24, |df=mdy12, |df=mdy24; default to t24

		

	elseif 'y' == DF or 'dmy24' == DF then

		DF = 'dmy';



	elseif 'mdy24' == DF then

		DF = 'mdy';

	end

	

	local dformat;

	if is_set (DF_cust) then

		dformat=DF_cust;

	elseif is_set (DF_cust_a) then												-- custom format is am/pm sensitive?

		if 'am' == os.date ('%P', timestamp) then								-- if current time is am

			dformat = DF_cust_a;												-- use custom am format

		else

			dformat = DF_cust_p;												-- use custom pm format

		end

	else

		dformat = cfg.formatDF];												-- use format from tables or from |df=

	end



	time_string = frame:callParserFunction ({name='#time', args={dformat, '@'..timestamp, Lang}});

	if Lang then

		time_string = table.concat ({											-- bidirectional isolation of non-local language; yeah, rather brute force but simple

			'<bdi lang="',														-- start of opening bdi tag

			Lang,																-- insert rendered language code

			'">',																-- end of opening tag

			time_string,														-- insert the time string

			'</bdi>'															-- and close the tag

			});

	end



	if not is_set (tz.article) then												-- if some but not all not all parts then emit error message

		return error_msg ('bad_def', args1]:upper());

	end

	

	local refresh_link = (Hide_refresh and '') or

		table.concat ({

			' <span class="plainlinks" style="font-size:85%;">[[',				-- open span

			mw.title.getCurrentTitle():fullUrl({action = 'purge'}),				-- add the a refresh link url

			' ',

			cfg'refresh-label'],												-- add the label

			']]</span>',														-- close the span

			});



	local tz_tag = (Hide_tz and '') or

		((Unlink_tz and table.concat ({' ', tz_abbr})) or						-- unlinked

			table.concat ({' [[', tz.article, '|', tz_abbr, ']]'}));			-- linked

	

	return table.concat ({time_string, tz_tag, refresh_link});



end





--[[--------------------------< E X P O R T E D   F U N C T I O N S >------------------------------------------

]]



return {time = time}