Module:Time
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 
 
 
 --[[--------------------------&lt; I S _ S E T &gt;------------------------------------------------------------------
 
 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
 
 
 --[[--------------------------&lt; S U B S T I T U T E &gt;----------------------------------------------------------
 
 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
 
 
 --[[--------------------------&lt; E R R O R _ M S G &gt;------------------------------------------------------------
 
 create an error message
 
 ]]
 
 local function error_msg (msg, arg)
 	return substitute (cfg.err_msg, substitute (cfg.err_text[msg], arg))
 end
 
 
 --[[--------------------------&lt; D E C O D E _ D S T _ E V E N T &gt;----------------------------------------------
 
 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:
 	&lt;ordinal&gt; &lt;day&gt; &lt;any single word&gt; &lt;month&gt; – 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.ordinals[ord], cfg.days[day], cfg.months[month];
 end
 
 
 --[[--------------------------&lt; G E T _ D A Y S _ I N _ M O N T H &gt;--------------------------------------------
 
 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
 
 
 --[[--------------------------&lt; G E T _ D S T _ M O N T H _ D A Y &gt;--------------------------------------------
 
 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
 
 
 --[[--------------------------&lt; G E T _ U T C _ O F F S E T &gt;--------------------------------------------------
 
 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
 
 
 --[[--------------------------&lt; M A K E _ D S T _ T I M E S T A M P S &gt;----------------------------------------
 
 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 &gt; 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
 
 
 --[[--------------------------&lt; G E T _ T E S T _ T I M E &gt;----------------------------------------------------
 
 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
 
 --[[----------------------&lt; G E T _ F U L L _ U T C _ O F F S E T &gt;-----------------------------------------------
 
 Creates a standard UTC offset from numerical inputs, for function time to convert to a table.  Expected inputs shall have the form:
 	&lt;sign&gt;&lt;hour&gt;&lt;separator&gt;&lt;portion&gt;
 where:
 	&lt;sign&gt; – optional; one of the characters: '+', '-' (hyphen), '±', '−' (minus); defaults to '+'
 	&lt;hour&gt; - one or two digits
 	&lt;separator&gt; - one of the characters '.' or ':'; required when &lt;portion&gt; is included; ignored else
 	&lt;portion&gt; - optional; one or two digits when &lt;separator&gt; 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
 
 
 --[[--------------------------&lt; T A B L E _ L E N &gt;------------------------------------------------------------
 
 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
 
 
 --[[--------------------------&lt; F I R S T _ S E T &gt;------------------------------------------------------------
 
 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 &lt;= count do															-- loop through all items in list
 		if is_set( args[list[i]] ) then											-- if parameter name in list is set in args
 			return args[list[i]];												-- return the value assigned to the args parameter
 		end
 		i = i + 1;																-- point to next
 	end
 end
 
 
 --[=[-------------------------&lt; T I M E &gt;----------------------------------------------------------------------
 
 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 args[1] then
 		args[1] = get_full_utc_offset (args[1]):lower();						-- make lower case because tz table member indexes are lower case
 	else
 		args[1] = 'utc';														-- default to utc
 	end
 
 	if mw.ustring.match (args[1], 'utc[%+%-±−]%d%d:%d%d') then					-- if rendering time for a UTC offset timezone
 		tz.abbr = args[1]: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 (args[1], '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';
 		args[1] = 'utc_offsets';												-- spoof to show that we recognize this timezone
 	else
 		tz = tz_aliases[args[1]] and tz_data[tz_aliases[args[1]]] or tz_data[args[1]];	-- make a local copy of the timezone table from tz_data{}
 		if not tz then
 			return error_msg ('unknown_tz', args[1]);							-- if the timezone given isn't in module:time/data(/sandbox)
 		end
 	end
 
 	DF = first_set (cfg.aliases['df'], args) or args[2] 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_vals[DF] 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 &gt;= dst_end_ts and utc_timestamp &lt; 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 &gt;= dst_begin_ts and utc_timestamp &lt; 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', args[1]: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.format[DF];												-- 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
 			'&lt;bdi lang=&quot;',														-- start of opening bdi tag
 			Lang,																-- insert rendered language code
 			'&quot;&gt;',																-- end of opening tag
 			time_string,														-- insert the time string
 			'&lt;/bdi&gt;'															-- 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', args[1]:upper());
 	end
 	
 	local refresh_link = (Hide_refresh and '') or
 		table.concat ({
 			' &lt;span class=&quot;plainlinks&quot; style=&quot;font-size:85%;&quot;&gt;[[',				-- open span
 			mw.title.getCurrentTitle():fullUrl({action = 'purge'}),				-- add the a refresh link url
 			' ',
 			cfg['refresh-label'],												-- add the label
 			']]&lt;/span&gt;',														-- 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
 
 
 --[[--------------------------&lt; E X P O R T E D   F U N C T I O N S &gt;------------------------------------------
 ]]