×
Create a new article
Write your page title here:
We currently have 223 articles on Farthest Frontier. Type your article name above or create one of the articles listed here!



    Farthest Frontier

    Module:Citation/CS1/Date validation/sandbox

    Documentation for this module may be created at Module:Citation/CS1/Date validation/sandbox/doc

    --[[
    History of changes since last sync: 2022-07-01
    
    ]]
    
    
    --[[--------------------------< F O R W A R D   D E C L A R A T I O N S >--------------------------------------
    ]]
    
    local add_prop_cat, is_set, in_array, set_message, substitute, wrap_style;		-- imported functions from selected Module:Citation/CS1/Utilities
    local cfg;																		-- table of tables imported from selected Module:Citation/CS1/Configuration
    
    
    --[[--------------------------< F I L E - S C O P E   D E C L A R A T I O N S >--------------------------------
    
    File-scope variables are declared here
    
    ]]
    
    local lang_object = mw.getContentLanguage();									-- used by is_valid_accessdate(), is_valid_year(), date_name_xlate(); TODO: move to ~/Configuration?
    local year_limit;																-- used by is_valid_year()
    
    
    --[=[-------------------------< I S _ V A L I D _ A C C E S S D A T E >----------------------------------------
    
    returns true if:
    	Wikipedia start date <= accessdate < today + 2 days
    
    Wikipedia start date is 2001-01-15T00:00:00 UTC which is 979516800 seconds after 1970-01-01T00:00:00 UTC (the start of Unix time)
    accessdate is the date provided in |access-date= at time 00:00:00 UTC
    today is the current date at time 00:00:00 UTC plus 48 hours
    	if today is 2015-01-01T00:00:00 then
    		adding 24 hours gives 2015-01-02T00:00:00 – one second more than today
    		adding 24 hours gives 2015-01-03T00:00:00 – one second more than tomorrow
    
    This function does not work if it is fed month names for languages other than English.  Wikimedia #time: parser
    apparently doesn't understand non-English date month names. This function will always return false when the date
    contains a non-English month name because good1 is false after the call to lang.formatDate().  To get around that
    call this function with YYYY-MM-DD format dates.
    
    ]=]
    
    local function is_valid_accessdate (accessdate)
    	local good1, good2;
    	local access_ts, tomorrow_ts;												-- to hold Unix time stamps representing the dates
    
    	good1, access_ts = pcall (lang_object.formatDate, lang_object, 'U', accessdate );			-- convert accessdate value to Unix timestamp 
    	good2, tomorrow_ts = pcall (lang_object.formatDate, lang_object, 'U', 'today + 2 days' );	-- today midnight + 2 days is one second more than all day tomorrow
    	
    	if good1 and good2 then														-- lang.formatDate() returns a timestamp in the local script which which tonumber() may not understand
    		access_ts = tonumber (access_ts) or lang_object:parseFormattedNumber (access_ts);		-- convert to numbers for the comparison;
    		tomorrow_ts = tonumber (tomorrow_ts) or lang_object:parseFormattedNumber (tomorrow_ts);
    	else
    		return false;															-- one or both failed to convert to Unix time stamp
    	end
    
    	if 979516800 <= access_ts and access_ts < tomorrow_ts then					-- Wikipedia start date <= accessdate < tomorrow's date
    		return true;
    	else
    		return false;															-- accessdate out of range
    	end
    end
    
    
    --[[--------------------------< G E T _ M O N T H _ N U M B E R >----------------------------------------------
    
    returns a number according to the month in a date: 1 for January, etc.  Capitalization and spelling must be correct.
    If not a valid month, returns 0
    
    ]]
    
    local function get_month_number (month)
    	return cfg.date_names['local'].long[month] or cfg.date_names['local'].short[month] or	-- look for local names first
    			cfg.date_names['en'].long[month] or	cfg.date_names['en'].short[month] or		-- failing that, look for English names
    			0;																				-- not a recognized month name
    end
    
    
    --[[--------------------------< G E T _ S E A S O N _ N U M B E R >--------------------------------------------
    
    returns a number according to the sequence of seasons in a year: 21 for Spring, etc.  Capitalization and spelling
    must be correct. If not a valid season, returns 0.
    	21-24 = Spring, Summer, Autumn, Winter, independent of “Hemisphere”
    
    returns 0 when <param> is not |date=
    
    Season numbering is defined by Extended Date/Time Format (EDTF) specification (https://www.loc.gov/standards/datetime/)
    which became part of ISO 8601 in 2019.  See '§Sub-year groupings'.  The standard defines various divisions using
    numbers 21-41.  cs1|2 only supports generic seasons.  EDTF does support the distinction between north and south
    hemisphere seasons but cs1|2 has no way to make that distinction.
    
    These additional divisions not currently supported:
    	25-28 = Spring - Northern Hemisphere, Summer- Northern Hemisphere, Autumn - Northern Hemisphere, Winter - Northern Hemisphere
    	29-32 = Spring – Southern Hemisphere, Summer– Southern Hemisphere, Autumn – Southern Hemisphere, Winter - Southern Hemisphere
    	33-36 = Quarter 1, Quarter 2, Quarter 3, Quarter 4 (3 months each)
    	37-39 = Quadrimester 1, Quadrimester 2, Quadrimester 3 (4 months each)
    	40-41 = Semestral 1, Semestral-2 (6 months each)
    
    ]]
    
    local function get_season_number (season, param)
    	if 'date' ~= param then
    		return 0;																-- season dates only supported by |date=
    	end
    	return cfg.date_names['local'].season[season] or							-- look for local names first
    			cfg.date_names['en'].season[season] or								-- failing that, look for English names
    			0;																	-- not a recognized season name
    end
    
    
    --[[--------------------------< G E T _ Q U A R T E R _ N U M B E R >------------------------------------------
    
    returns a number according to the sequence of quarters in a year: 33 for first quarter, etc.  Capitalization and spelling
    must be correct. If not a valid quarter, returns 0.
    	33-36 = Quarter 1, Quarter 2, Quarter 3, Quarter 4 (3 months each)
    
    returns 0 when <param> is not |date=
    
    Quarter numbering is defined by Extended Date/Time Format (EDTF) specification (https://www.loc.gov/standards/datetime/)
    which became part of ISO 8601 in 2019.  See '§Sub-year groupings'.  The standard defines various divisions using
    numbers 21-41.  cs1|2 only supports generic seasons and quarters.
    
    These additional divisions not currently supported:
    	37-39 = Quadrimester 1, Quadrimester 2, Quadrimester 3 (4 months each)
    	40-41 = Semestral 1, Semestral-2 (6 months each)
    
    ]]
    
    local function get_quarter_number (quarter, param)
    	if 'date' ~= param then
    		return 0;																-- quarter dates only supported by |date=
    	end
    	quarter = mw.ustring.gsub (quarter, ' +', ' ');								-- special case replace multiple space chars with a single space char
    	return cfg.date_names['local'].quarter[quarter] or							-- look for local names first
    			cfg.date_names['en'].quarter[quarter] or							-- failing that, look for English names
    			0;																	-- not a recognized quarter name
    end
    
    
    --[[--------------------------< G E T _ P R O P E R _ N A M E _ N U M B E R >----------------------------------
    
    returns a non-zero number if date contains a recognized proper-name.  Capitalization and spelling must be correct.
    
    returns 0 when <param> is not |date=
    
    ]]
    
    local function get_proper_name_number (name, param)
    	if 'date' ~= param then
    		return 0;																-- proper-name dates only supported by |date=
    	end
    	return cfg.date_names['local'].named[name] or								-- look for local names dates first
    			cfg.date_names['en'].named[name] or									-- failing that, look for English names
    			0;																	-- not a recognized named date
    end
    
    
    --[[--------------------------< G E T _ E L E M E N T _ N U M B E R <------------------------------------------
    
    returns true if month or season or quarter or proper name is valid (properly spelled, capitalized, abbreviated)
    
    ]]
    
    local function get_element_number (element, param)
    	local num;
    	
    	local funcs = {get_month_number, get_season_number, get_quarter_number, get_proper_name_number};	-- list of functions to execute in order
    	
    	for _, func in ipairs (funcs) do											-- spin through the function list
    		num = func (element, param);											-- call the function and get the returned number
    		if 0 ~= num then														-- non-zero when valid month season quarter 
    			return num;															-- return that number
    		end
    	end
    	return nil;																	-- not valid
    end
    
    
    --[[--------------------------< I S _ V A L I D _ Y E A R >----------------------------------------------------
    
    Function gets current year from the server and compares it to year from a citation parameter.  Years more than one
    year in the future are not acceptable.
    
    Special case for |pmc-embargo-date=: years more than two years in the future are not acceptable
    
    ]]
    
    local function is_valid_year (year, param)
    	if not is_set (year_limit) then
    		year_limit = tonumber(os.date("%Y"))+1;									-- global variable so we only have to fetch it once
    	end
    
    	year = tonumber (year) or lang_object:parseFormattedNumber (year);			-- convert to number for the comparison;
    	
    	if 'pmc-embargo-date' == param then											-- special case for |pmc-embargo-date=
    		return year and (year <= tonumber(os.date("%Y"))+2) or false;			-- years more than two years in the future are not accepted
    	end	
    	return year and (year <= year_limit) or false;
    end
    
    
    --[[--------------------------< I S _ V A L I D _ D A T E >----------------------------------------------------
    
    Returns true if day is less than or equal to the number of days in month and year is no farther into the future
    than next year; else returns false.
    
    Assumes Julian calendar prior to year 1582 and Gregorian calendar thereafter. Accounts for Julian calendar leap
    years before 1582 and Gregorian leap years after 1582. Where the two calendars overlap (1582 to approximately
    1923) dates are assumed to be Gregorian.
    
    ]]
    
    local function is_valid_date (year, month, day, param)
    local days_in_month = {31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};
    local month_length;
    	if not is_valid_year (year, param) then										-- no farther into the future than next year except |pmc-embargo-date= no more than two years in the future
    		return false;
    	end
    	
    	month = tonumber (month);													-- required for YYYY-MM-DD dates
    	
    	if (2 == month) then														-- if February
    		month_length = 28;														-- then 28 days unless
    		if 1582 > tonumber(year) then											-- Julian calendar
    			if 0 == (year%4) then												-- is a leap year?
    				month_length = 29;												-- if leap year then 29 days in February
    			end
    		else																	-- Gregorian calendar
    			if (0 == (year%4) and (0 ~= (year%100) or 0 == (year%400))) then	-- is a leap year?
    				month_length = 29;												-- if leap year then 29 days in February
    			end
    		end
    	else
    		month_length = days_in_month[month];
    	end
    
    	if tonumber (day) > month_length then
    		return false;
    	end
    	return true;
    end
    
    
    --[[--------------------------< I S _ V A L I D _ M O N T H _ R A N G E _ S T Y L E >--------------------------
    
    Months in a range are expected to have the same style: Jan–Mar or October–December but not February–Mar or Jul–August. 
    This function looks in cfg.date_names{} to see if both month names are listed in the long subtable or both are
    listed in the short subtable.  When both have the same style (both are listed in the same table), returns true; false else
    
    ]]
    
    local function is_valid_month_range_style (month1, month2)
    	if (cfg.date_names.en.long[month1] and cfg.date_names.en.long[month2]) or					-- are both English names listed in the long subtable?
    		(cfg.date_names.en.short[month1] and cfg.date_names.en.short[month2]) or				-- are both English names listed in the short subtable?
    		(cfg.date_names['local'].long[month1] and cfg.date_names['local'].long[month2]) or		-- are both local names listed in the long subtable?
    		(cfg.date_names['local'].short[month1] and cfg.date_names['local'].short[month2]) then	-- are both local names listed in the short subtable?
    			return true;
    	end
    	return false;																-- names are mixed
    end
    
    
    --[[--------------------------< I S _ V A L I D _ M O N T H _ S E A S O N _ R A N G E >------------------------
    
    Check a pair of months or seasons to see if both are valid members of a month or season pair.
    
    Month pairs are expected to be left to right, earliest to latest in time.
    
    All season ranges are accepted as valid because there are publishers out there who have published a Summer–Spring YYYY issue, hence treat as ok
    
    ]]
    
    local function is_valid_month_season_range(range_start, range_end, param)
    	local range_start_number = get_month_number (range_start);
    	local range_end_number;
    
    	if 0 == range_start_number then												-- is this a month range?
    		range_start_number = get_season_number (range_start, param);			-- not a month; is it a season? get start season number
    		range_end_number = get_season_number (range_end, param);				-- get end season number
    
    		if (0 ~= range_start_number) and (0 ~= range_end_number) and (range_start_number ~= range_end_number) then
    			return true;														-- any season pairing is accepted except when both are the same
    		end
    		return false;															-- range_start and/or range_end is not a season
    	end
    																				-- here when range_start is a month
    	range_end_number = get_month_number (range_end);							-- get end month number
    	if range_start_number < range_end_number and								-- range_start is a month; does range_start precede range_end?
    		is_valid_month_range_style (range_start, range_end) then				-- do months have the same style?
    			return true;														-- proper order and same style
    	end
    	return false;																-- range_start month number is greater than or equal to range end number; or range end isn't a month
    end
    
    
    --[[--------------------------< M A K E _ C O I N S _ D A T E >------------------------------------------------
    
    This function receives a table of date parts for one or two dates and an empty table reference declared in
    Module:Citation/CS1.  The function is called only for |date= parameters and only if the |date=<value> is 
    determined to be a valid date format.  The question of what to do with invalid date formats is not answered here.
    
    The date parts in the input table are converted to an ISO 8601 conforming date string:
    	single whole dates:		yyyy-mm-dd
    	month and year dates:	yyyy-mm
    	year dates:				yyyy
    	ranges:					yyyy-mm-dd/yyyy-mm-dd
    							yyyy-mm/yyyy-mm
    							yyyy/yyyy
    
    Dates in the Julian calendar are reduced to year or year/year so that we don't have to do calendar conversion from
    Julian to Proleptic Gregorian.
    
    The input table has:
    	year, year2 – always present; if before 1582, ignore months and days if present
    	month, month2 – 0 if not provided, 1-12 for months, 21-24 for seasons; 99 Christmas
    	day, day2 –  0 if not provided, 1-31 for days
    	
    the output table receives:
    	rftdate:	an ISO 8601 formatted date
    	rftchron:	a free-form version of the date, usually without year which is in rftdate (season ranges and proper-name dates)
    	rftssn:		one of four season keywords: winter, spring, summer, fall (lowercase)
    	rftquarter:	one of four values: 1, 2, 3, 4
    
    ]]
    
    local function make_COinS_date (input, tCOinS_date)
    	local date;																	-- one date or first date in a range
    	local date2 = '';															-- end of range date
    -- start temporary Julian / Gregorian calendar uncertainty detection
    	local year = tonumber(input.year);											-- this temporary code to determine the extent of sources dated to the Julian/Gregorian
    	local month = tonumber(input.month);										-- interstice 1 October 1582 – 1 January 1926
    	local day = tonumber (input.day);
    	if (0 ~= day) and															-- day must have a value for this to be a whole date
    		(((1582 == year) and (10 <= month) and (12 >= month)) or				-- any whole 1582 date from 1 October to 31 December or
    			((1926 == year) and (1 == month) and (1 == input.day)) or			-- 1 January 1926 or
    				((1582 < year) and (1925 >= year))) then						-- any date 1 January 1583 – 31 December 1925
    					tCOinS_date.inter_cal_cat = true;							-- set category flag true
    	end
    -- end temporary Julian / Gregorian calendar uncertainty detection
    	
    	if 1582 > tonumber(input.year) or 20 < tonumber(input.month) then			-- Julian calendar or season so &rft.date gets year only
    		date = input.year;
    		if 0 ~= input.year2 and input.year ~= input.year2 then					-- if a range, only the second year portion when not the same as range start year
    			date = string.format ('%.4d/%.4d', tonumber(input.year), tonumber(input.year2))		-- assemble the date range
    		end
    		if 20 < tonumber(input.month) then										-- if season or proper-name date
    			local season = {[24] = 'winter', [21] = 'spring', [22] = 'summer', [23] = 'fall', [33] = '1', [34] = '2', [35] = '3', [36] = '4', [98] = 'Easter', [99] = 'Christmas'};	-- seasons lowercase, no autumn; proper-names use title case
    			if 0 == input.month2 then											-- single season date
    				if 40 < tonumber(input.month) then
    					tCOinS_date.rftchron = season[input.month];					-- proper-name dates
    				elseif 30 < tonumber(input.month) then
    					tCOinS_date.rftquarter = season[input.month];				-- quarters
    				else
    					tCOinS_date.rftssn = season[input.month];					-- seasons
    				end
    			else																-- season range with a second season specified
    				if input.year ~= input.year2 then								-- season year – season year range or season year–year
    					tCOinS_date.rftssn = season[input.month];					-- start of range season; keep this?
    					if 0~= input.month2 then
    						tCOinS_date.rftchron = string.format ('%s %s – %s %s', season[input.month], input.year, season[input.month2], input.year2);
    					end
    				else															-- season–season year range
    					tCOinS_date.rftssn = season[input.month];					-- start of range season; keep this?
    					tCOinS_date.rftchron = season[input.month] .. '–' .. season[input.month2];	-- season–season year range
    				end
    			end
    		end
    		tCOinS_date.rftdate = date;
    		return;																	-- done
    	end
    	
    	if 0 ~= input.day then
    		date = string.format ('%s-%.2d-%.2d', input.year, tonumber(input.month), tonumber(input.day));	-- whole date
    	elseif 0 ~= input.month then
    		date = string.format ('%s-%.2d', input.year, tonumber(input.month));	-- year and month
    	else
    		date = string.format ('%s', input.year);								-- just year
    	end
    
    	if 0 ~= input.year2 then
    		if 0 ~= input.day2 then
    			date2 = string.format ('/%s-%.2d-%.2d', input.year2, tonumber(input.month2), tonumber(input.day2));		-- whole date
    		elseif 0 ~= input.month2 then
    			date2 = string.format ('/%s-%.2d', input.year2, tonumber(input.month2));	-- year and month
    		else
    			date2 = string.format ('/%s', input.year2);							-- just year
    		end
    	end
    	
    	tCOinS_date.rftdate = date .. date2;										-- date2 has the '/' separator
    	return;
    end
    
    
    --[[--------------------------< P A T T E R N S >--------------------------------------------------------------
    
    this is the list of patterns for date formats that this module recognizes.  Approximately the first half of these
    patterns represent formats that might be reformatted into another format.  Those that might be reformatted have
    'indicator' letters that identify the content of the matching capture: 'd' (day), 'm' (month), 'a' (anchor year),
    'y' (year); second day, month, year have a '2' suffix.
    
    These patterns are used for both date validation and for reformatting.  This table should not be moved to ~/Configuration
    because changes to this table require changes to check_date() and to reformatter() and reformat_date()
    
    ]]
    
    local patterns = {
    	 																			-- year-initial numerical year-month-day
    	['ymd'] = {'^(%d%d%d%d)%-(%d%d)%-(%d%d)$', 'y', 'm', 'd'},					
    																				-- month-initial: month day, year
    	['Mdy'] = {'^(%D-) +([1-9]%d?), +((%d%d%d%d?)%a?)$', 'm', 'd', 'a', 'y'},
    																				-- month-initial day range: month day–day, year; days are separated by endash
    	['Md-dy'] = {'^(%D-) +([1-9]%d?)[%-–]([1-9]%d?), +((%d%d%d%d)%a?)$', 'm', 'd', 'd2', 'a', 'y'},
    																				-- day-initial: day month year
    	['dMy'] = {'^([1-9]%d?) +(%D-) +((%d%d%d%d?)%a?)$', 'd', 'm', 'a', 'y'},
    																				-- year-initial: year month day; day: 1 or 2 two digits, leading zero allowed; not supported at en.wiki
    	--	['yMd'] = {'^((%d%d%d%d?)%a?) +(%D-) +(%d%d?)$', 'a', 'y', 'm', 'd'},
    																				-- day-range-initial: day–day month year; days are separated by endash
    	['d-dMy'] = {'^([1-9]%d?)[%-–]([1-9]%d?) +(%D-) +((%d%d%d%d)%a?)$', 'd', 'd2', 'm', 'a', 'y'},
    																				-- day initial month-day-range: day month - day month year; uses spaced endash
    	['dM-dMy'] = {'^([1-9]%d?) +(%D-) +[%-–] +([1-9]%d?) +(%D-) +((%d%d%d%d)%a?)$', 'd', 'm', 'd2', 'm2', 'a', 'y'},
    																				-- month initial month-day-range: month day – month day, year;  uses spaced endash
    	['Md-Mdy'] = {'^(%D-) +([1-9]%d?) +[%-–] +(%D-) +([1-9]%d?), +((%d%d%d%d)%a?)$','m', 'd', 'm2', 'd2', 'a', 'y'},
    																				-- day initial month-day-year-range: day month year - day month year; uses spaced endash
    	['dMy-dMy'] = {'^([1-9]%d?) +(%D-) +(%d%d%d%d) +[%-–] +([1-9]%d?) +(%D-) +((%d%d%d%d)%a?)$', 'd', 'm', 'y', 'd2', 'm2', 'a', 'y2'},
    																				-- month initial month-day-year-range: month day, year – month day, year;  uses spaced endash
    	['Mdy-Mdy'] = {'^(%D-) +([1-9]%d?), +(%d%d%d%d) +[%-–] +(%D-) +([1-9]%d?), +((%d%d%d%d)%a?)$', 'm', 'd', 'y', 'm2', 'd2', 'a', 'y2'},
    
    																				-- these date formats cannot be converted, per se, but month name can be rendered short or long
    																				-- month/season year - month/season year; separated by spaced endash
    	['My-My'] = {'^(%D-) +(%d%d%d%d) +[%-–] +(%D-) +((%d%d%d%d)%a?)$', 'm', 'y', 'm2', 'a', 'y2'},
    																				-- month/season range year; months separated by endash
    	['M-My'] = {'^(%D-)[%-–](%D-) +((%d%d%d%d)%a?)$', 'm', 'm2', 'a', 'y'},
    																				-- month/season year or proper-name year; quarter year when First Quarter YYYY etc.
    	['My'] = {'^([^%d–]-) +((%d%d%d%d)%a?)$', 'm', 'a', 'y'},					-- this way because endash is a member of %D; %D- will match January–March 2019 when it shouldn't
    
    																				-- these date formats cannot be converted
    	['Sy4-y2'] = {'^(%D-) +((%d%d)%d%d)[%-–]((%d%d)%a?)$'},						-- special case Winter/Summer year-year (YYYY-YY); year separated with unspaced endash
    	['Sy-y'] = {'^(%D-) +(%d%d%d%d)[%-–]((%d%d%d%d)%a?)$'},						-- special case Winter/Summer year-year; year separated with unspaced endash
    	['y-y'] = {'^(%d%d%d%d?)[%-–]((%d%d%d%d?)%a?)$'},							-- year range: YYY-YYY or YYY-YYYY or YYYY–YYYY; separated by unspaced endash; 100-9999
    	['y4-y2'] = {'^((%d%d)%d%d)[%-–]((%d%d)%a?)$'},								-- year range: YYYY–YY; separated by unspaced endash
    	['y'] = {'^((%d%d%d%d?)%a?)$'},												-- year; here accept either YYY or YYYY
    	}
    
    
    --[[--------------------------< I S _ V A L I D _ E M B A R G O _ D A T E >------------------------------------
    
    returns true and date value if that value has proper dmy, mdy, ymd format.
    
    returns false and 9999 (embargoed forever) when date value is not proper format; assumes that when |pmc-embargo-date= is
    set, the editor intended to embargo a PMC but |pmc-embargo-date= does not hold a single date.
    
    ]]
    
    local function is_valid_embargo_date (v)
    	if v:match (patterns['ymd'][1]) or											-- ymd
    		v:match (patterns['Mdy'][1]) or											-- dmy
    		v:match (patterns['dMy'][1]) then										-- mdy
    			return true, v;
    	end
    	return false, '9999';														-- if here not good date so return false and set embargo date to long time in future
    end
    
    
    --[[--------------------------< C H E C K _ D A T E >----------------------------------------------------------
    
    Check date format to see that it is one of the formats approved by WP:DATESNO or WP:DATERANGE. Exception: only
    allowed range separator is endash.  Additionally, check the date to see that it is a real date: no 31 in 30-day
    months; no 29 February when not a leap year.  Months, both long-form and three character abbreviations, and seasons
    must be spelled correctly.  Future years beyond next year are not allowed.
    
    If the date fails the format tests, this function returns false and does not return values for anchor_year and
    COinS_date.  When this happens, the date parameter is (DEBUG: not?) used in the COinS metadata and the CITEREF identifier gets
    its year from the year parameter if present otherwise CITEREF does not get a date value.
    
    Inputs:
    	date_string - date string from date-holding parameters (date, year, publication-date, access-date, pmc-embargo-date, archive-date, lay-date)
    
    Returns:
    	false if date string is not a real date; else
    	true, anchor_year, COinS_date
    		anchor_year can be used in CITEREF anchors
    		COinS_date is ISO 8601 format date; see make_COInS_date()
    
    ]]
    
    local function check_date (date_string, param, tCOinS_date)
    	local year;																	-- assume that year2, months, and days are not used;
    	local year2 = 0;															-- second year in a year range
    	local month = 0;
    	local month2 = 0;															-- second month in a month range
    	local day = 0;
    	local day2 = 0;																-- second day in a day range
    	local anchor_year;
    	local coins_date;
    
    	if date_string:match (patterns['ymd'][1]) then								-- year-initial numerical year month day format
    		year, month, day = date_string:match (patterns['ymd'][1]);
    		if 12 < tonumber(month) or 1 > tonumber(month) or 1582 > tonumber(year) or 0 == tonumber(day) then return false; end	-- month or day number not valid or not Gregorian calendar
    		anchor_year = year;
    	
    	elseif mw.ustring.match(date_string, patterns['Mdy'][1]) then				-- month-initial: month day, year
    		month, day, anchor_year, year = mw.ustring.match(date_string, patterns['Mdy'][1]);
    		month = get_month_number (month);
    		if 0 == month then return false; end									-- return false if month text isn't one of the twelve months
    				
    	elseif mw.ustring.match(date_string, patterns['Md-dy'][1]) then				-- month-initial day range: month day–day, year; days are separated by endash
    		month, day, day2, anchor_year, year = mw.ustring.match(date_string, patterns['Md-dy'][1]);
    		if tonumber(day) >= tonumber(day2) then return false; end				-- date range order is left to right: earlier to later; dates may not be the same;
    		month = get_month_number (month);
    		if 0 == month then return false; end									-- return false if month text isn't one of the twelve months
    		month2=month;															-- for metadata
    		year2 = year;
    
    	elseif mw.ustring.match(date_string, patterns['dMy'][1]) then				-- day-initial: day month year
    		day, month, anchor_year, year = mw.ustring.match(date_string, patterns['dMy'][1]);
    		month = get_month_number (month);
    		if 0 == month then return false; end									-- return false if month text isn't one of the twelve months
    
    --[[ NOT supported at en.wiki
    	elseif mw.ustring.match(date_string, patterns['yMd'][1]) then				-- year-initial: year month day; day: 1 or 2 two digits, leading zero allowed
    		anchor_year, year, month, day = mw.ustring.match(date_string, patterns['yMd'][1]);
    		month = get_month_number (month);
    		if 0 == month then return false; end									-- return false if month text isn't one of the twelve months
    -- end NOT supported at en.wiki ]]
    
    	elseif mw.ustring.match(date_string, patterns['d-dMy'][1]) then				-- day-range-initial: day–day month year; days are separated by endash
    		day, day2, month, anchor_year, year = mw.ustring.match(date_string, patterns['d-dMy'][1]);
    		if tonumber(day) >= tonumber(day2) then return false; end				-- date range order is left to right: earlier to later; dates may not be the same;
    		month = get_month_number (month);
    		if 0 == month then return false; end									-- return false if month text isn't one of the twelve months
    		month2 = month;															-- for metadata
    		year2 = year;
    
    	elseif mw.ustring.match(date_string, patterns['dM-dMy'][1]) then			-- day initial month-day-range: day month - day month year; uses spaced endash
    		day, month, day2, month2, anchor_year, year = mw.ustring.match(date_string, patterns['dM-dMy'][1]);
    		if (not is_valid_month_season_range(month, month2)) or not is_valid_year(year) then return false; end	-- date range order is left to right: earlier to later;
    		month = get_month_number (month);										-- for metadata
    		month2 = get_month_number (month2);
    		year2 = year;
    
    	elseif mw.ustring.match(date_string, patterns['Md-Mdy'][1]) then			-- month initial month-day-range: month day – month day, year; uses spaced endash
    		month, day, month2, day2, anchor_year, year = mw.ustring.match(date_string, patterns['Md-Mdy'][1]);
    		if (not is_valid_month_season_range(month, month2, param)) or not is_valid_year(year) then return false; end
    		month = get_month_number (month);										-- for metadata
    		month2 = get_month_number (month2);
    		year2 = year;
    
    	elseif mw.ustring.match(date_string, patterns['dMy-dMy'][1]) then			-- day initial month-day-year-range: day month year - day month year; uses spaced endash
    		day, month, year, day2, month2, anchor_year, year2 = mw.ustring.match(date_string, patterns['dMy-dMy'][1]);
    		if tonumber(year2) <= tonumber(year) then return false; end				-- must be sequential years, left to right, earlier to later
    		if not is_valid_year(year2) or not is_valid_month_range_style(month, month2) then return false; end		-- year2 no more than one year in the future; months same style
    		month = get_month_number (month);										-- for metadata
    		month2 = get_month_number (month2);
    		if 0 == month or 0 == month2 then return false; end						-- both must be valid
    
    	elseif mw.ustring.match(date_string, patterns['Mdy-Mdy'][1]) then			-- month initial month-day-year-range: month day, year – month day, year; uses spaced endash
    		month, day, year, month2, day2, anchor_year, year2 = mw.ustring.match(date_string, patterns['Mdy-Mdy'][1]);
    		if tonumber(year2) <= tonumber(year) then return false; end				-- must be sequential years, left to right, earlier to later
    		if not is_valid_year(year2) or not is_valid_month_range_style(month, month2) then return false; end		-- year2 no more than one year in the future; months same style
    		month = get_month_number (month);										-- for metadata
    		month2 = get_month_number(month2);
    		if 0 == month or 0 == month2 then return false; end						-- both must be valid
    
    	elseif mw.ustring.match(date_string, patterns['Sy4-y2'][1]) then			-- special case Winter/Summer year-year (YYYY-YY); year separated with unspaced endash
    		local century;
    		month, year, century, anchor_year, year2 = mw.ustring.match(date_string, patterns['Sy4-y2'][1]);
    		if 'Winter' ~= month and 'Summer' ~= month then return false end;		-- 'month' can only be Winter or Summer
    		anchor_year = year .. '–' .. anchor_year;								-- assemble anchor_year from both years
    		year2 = century..year2;													-- add the century to year2 for comparisons
    		if 1 ~= tonumber(year2) - tonumber(year) then return false; end			-- must be sequential years, left to right, earlier to later
    		if not is_valid_year(year2) then return false; end						-- no year farther in the future than next year
    		month = get_season_number(month, param);
    
    	elseif mw.ustring.match(date_string, patterns['Sy-y'][1]) then				-- special case Winter/Summer year-year; year separated with unspaced endash
    		month, year, anchor_year, year2 = mw.ustring.match(date_string, patterns['Sy-y'][1]);
    		month = get_season_number (month, param);								-- <month> can only be winter or summer; also for metadata
    		if (month ~= cfg.date_names['en'].season['Winter']) and (month ~= cfg.date_names['en'].season['Summer']) then
    			return false;														-- not Summer or Winter; abandon
    		end
    		anchor_year = year .. '–' .. anchor_year;								-- assemble anchor_year from both years
    		if 1 ~= tonumber(year2) - tonumber(year) then return false; end			-- must be sequential years, left to right, earlier to later
    		if not is_valid_year(year2) then return false; end						-- no year farther in the future than next year
    
    	elseif mw.ustring.match(date_string, patterns['My-My'][1]) then				-- month/season year - month/season year; separated by spaced endash
    		month, year, month2, anchor_year, year2 = mw.ustring.match(date_string, patterns['My-My'][1]);
    		anchor_year = year .. '–' .. anchor_year;								-- assemble anchor_year from both years
    		if tonumber(year) >= tonumber(year2) then return false; end				-- left to right, earlier to later, not the same
    		if not is_valid_year(year2) then return false; end						-- no year farther in the future than next year
    		if 0 ~= get_month_number(month) and 0 ~= get_month_number(month2) and is_valid_month_range_style(month, month2) then 	-- both must be month year, same month style
    			month = get_month_number(month);
    			month2 = get_month_number(month2);
    		elseif 0 ~= get_season_number(month, param) and 0 ~= get_season_number(month2, param) then	-- both must be season year, not mixed
    			month = get_season_number(month, param);
    			month2 = get_season_number(month2, param);
    		else
    			 return false;
    		end
    
    	elseif mw.ustring.match(date_string, patterns['M-My'][1]) then				-- month/season range year; months separated by endash 
    		month, month2, anchor_year, year = mw.ustring.match(date_string, patterns['M-My'][1]);
    		if (not is_valid_month_season_range(month, month2, param)) or (not is_valid_year(year)) then return false; end
    		if 0 ~= get_month_number(month) then									-- determined to be a valid range so just check this one to know if month or season
    			month = get_month_number(month);
    			month2 = get_month_number(month2);
    			if 0 == month or 0 == month2 then return false; end
    		else
    			month = get_season_number(month, param);
    			month2 = get_season_number(month2, param);
    		end
    		year2 = year;
    		
    	elseif mw.ustring.match(date_string, patterns['My'][1]) then				-- month/season/quarter/proper-name year
    		month, anchor_year, year = mw.ustring.match(date_string, patterns['My'][1]);
    		if not is_valid_year(year) then return false; end
    		month = get_element_number(month, param);								-- get month season quarter proper-name number or nil
    		if not month then return false; end										-- not valid whatever it is
    
    	elseif mw.ustring.match(date_string, patterns['y-y'][1]) then				-- Year range: YYY-YYY or YYY-YYYY or YYYY–YYYY; separated by unspaced endash; 100-9999
    		year, anchor_year, year2 = mw.ustring.match(date_string, patterns['y-y'][1]);
    		anchor_year = year .. '–' .. anchor_year;								-- assemble anchor year from both years
    		if tonumber(year) >= tonumber(year2) then return false; end				-- left to right, earlier to later, not the same
    		if not is_valid_year(year2) then return false; end						-- no year farther in the future than next year
    
    	elseif mw.ustring.match(date_string, patterns['y4-y2'][1]) then				-- Year range: YYYY–YY; separated by unspaced endash
    		local century;
    		year, century, anchor_year, year2 = mw.ustring.match(date_string, patterns['y4-y2'][1]);
    		anchor_year = year .. '–' .. anchor_year;								-- assemble anchor year from both years
    
    		if in_array (param, {'date', 'publication-date', 'year'}) then
    			add_prop_cat ('year-range-abbreviated');
    		end
    
    		if 13 > tonumber(year2) then return false; end							-- don't allow 2003-05 which might be May 2003
    		year2 = century .. year2;												-- add the century to year2 for comparisons
    		if tonumber(year) >= tonumber(year2) then return false; end				-- left to right, earlier to later, not the same
    		if not is_valid_year(year2) then return false; end						-- no year farther in the future than next year
    
    	elseif mw.ustring.match(date_string, patterns['y'][1]) then					-- year; here accept either YYY or YYYY
    		anchor_year, year = mw.ustring.match(date_string, patterns['y'][1]);
    		if false == is_valid_year(year) then
    			return false;
    		end
    
    	else
    		return false;															-- date format not one of the MOS:DATE approved formats
    	end
    
    	if param ~= 'date' then														-- CITEREF disambiguation only allowed in |date=; |year= & |publication-date= promote to date
    		if anchor_year:match ('%l$') then
    			return false;
    		end
    	end
    
    	if 'access-date' == param then												-- test accessdate here because we have numerical date parts
    		if 0 ~= year and 0 ~= month and 0 ~= day and 							-- all parts of a single date required
    			0 == year2 and 0 == month2 and 0 == day2 then						-- none of these; accessdate must not be a range
    				if not is_valid_accessdate(year .. '-' .. month .. '-' .. day) then	
    					return false;												-- return false when accessdate out of bounds
    				end
    		else
    			return false;														-- return false when accessdate is a range of two dates
    		end
    	end
    
    	local result=true;															-- check whole dates for validity; assume true because not all dates will go through this test
    	if 0 ~= year and 0 ~= month and 0 ~= day and 0 == year2 and 0 == month2 and 0 == day2 then		-- YMD (simple whole date)
    		result = is_valid_date (year, month, day, param);						-- <param> for |pmc-embargo-date=
    
    	elseif 0 ~= year and 0 ~= month and 0 ~= day and 0 == year2 and 0 == month2 and 0 ~= day2 then	-- YMD-d (day range)
    		result = is_valid_date (year, month, day);
    		result = result and is_valid_date (year, month, day2);
    
    	elseif 0 ~= year and 0 ~= month and 0 ~= day and 0 == year2 and 0 ~= month2 and 0 ~= day2 then	-- YMD-md (day month range)
    		result = is_valid_date (year, month, day);
    		result = result and is_valid_date (year, month2, day2);
    
    	elseif 0 ~= year and 0 ~= month and 0 ~= day and 0 ~= year2 and 0 ~= month2 and 0 ~= day2 then	-- YMD-ymd (day month year range)
    		result = is_valid_date(year, month, day);
    		result = result and is_valid_date(year2, month2, day2);
    	end
    	
    	if false == result then return false; end
    
    	if nil ~= tCOinS_date then													-- this table only passed into this function when testing |date= parameter values
    		make_COinS_date ({year = year, month = month, day = day, year2 = year2, month2 = month2, day2 = day2}, tCOinS_date);	-- make an ISO 8601 date string for COinS
    	end
    	
    	return true, anchor_year;													-- format is good and date string represents a real date
    end	
    
    
    --[[--------------------------< D A T E S >--------------------------------------------------------------------
    
    Cycle the date-holding parameters in passed table date_parameters_list through check_date() to check compliance with MOS:DATE. For all valid dates, check_date() returns
    true. The |date= parameter test is unique, it is the only date holding parameter from which values for anchor_year (used in CITEREF identifiers) and COinS_date (used in
    the COinS metadata) are derived.  The |date= parameter is the only date-holding parameter that is allowed to contain the no-date keywords "n.d." or "nd" (without quotes).
    
    Unlike most error messages created in this module, only one error message is created by this function. Because all of the date holding parameters are processed serially,
    parameters with errors are added to the <error_list> sequence table as the dates are tested.
    
    ]]
    
    local function dates(date_parameters_list, tCOinS_date, error_list)
    	local anchor_year;															-- will return as nil if the date being tested is not |date=
    	local COinS_date;															-- will return as nil if the date being tested is not |date=
    	local embargo_date;															-- if embargo date is a good dmy, mdy, ymd date then holds original value else reset to 9999
    	local good_date = false;
    
    	for k, v in pairs(date_parameters_list) do									-- for each date-holding parameter in the list
    		if is_set(v.val) then													-- if the parameter has a value
    			v.val = mw.ustring.gsub(v.val, '%d', cfg.date_names.local_digits);	-- translate 'local' digits to Western 0-9
    			if v.val:match("^c%. [1-9]%d%d%d?%a?$") then						-- special case for c. year or with or without CITEREF disambiguator - only |date= and |year=
    				local year = v.val:match("c%. ([1-9]%d%d%d?)%a?");				-- get the year portion so it can be tested
    				if 'date' == k then
    					anchor_year, COinS_date = v.val:match("((c%. [1-9]%d%d%d?)%a?)");	-- anchor year and COinS_date only from |date= parameter
    					good_date = is_valid_year(year);
    				elseif 'year' == k then
    					good_date = is_valid_year(year);
    				end
    			elseif 'date' == k then												-- if the parameter is |date=
    				if v.val:match("^n%.d%.%a?$") then -- ToDo: I18N								-- if |date=n.d. with or without a CITEREF disambiguator
    					good_date, anchor_year, COinS_date = true, v.val:match("((n%.d%.)%a?)"); -- ToDo: I18N	-- "n.d."; no error when date parameter is set to no date
    				elseif v.val:match("^nd%a?$") then -- ToDo: I18N								-- if |date=nd with or without a CITEREF disambiguator
    					good_date, anchor_year, COinS_date = true, v.val:match("((nd)%a?)"); -- ToDo: I18N	-- "nd";	no error when date parameter is set to no date
    				else
    					good_date, anchor_year, COinS_date = check_date (v.val, k, tCOinS_date);	-- go test the date
    				end
    			elseif 'year' == k then												-- if the parameter is |year= it should hold only a year value
    				if v.val:match("^[1-9]%d%d%d?%a?$") then						-- if |year = 3 or 4 digits only with or without a CITEREF disambiguator
    					good_date, anchor_year, COinS_date = true, v.val:match("((%d+)%a?)");
    				end
    			elseif 'pmc-embargo-date' == k then									-- if the parameter is |pmc-embargo-date=
    				good_date = check_date (v.val, k);								-- go test the date
    				if true == good_date then										-- if the date is a valid date
    					good_date, embargo_date = is_valid_embargo_date (v.val);	-- is |pmc-embargo-date= date a single dmy, mdy, or ymd formatted date? yes: returns embargo date; no: returns 9999
    				end
    			else																-- any other date-holding parameter
    				good_date = check_date (v.val, k);								-- go test the date
    			end
    			if false == good_date then											-- assemble one error message so we don't add the tracking category multiple times
    				table.insert (error_list, wrap_style ('parameter', v.name));	-- make parameter name suitable for error message list
    			end
    		end
    	end
    	return anchor_year, embargo_date;											-- and done
    end
    
    
    --[[--------------------------< Y E A R _ D A T E _ C H E C K >------------------------------------------------
    
    Compare the value provided in |year= with the year value(s) provided in |date=.  This function sets a local numeric value:
    	0 - year value does not match the year value in date
    	1 - (default) year value matches the year value in date or one of the year values when date contains two years
    	2 - year value matches the year value in date when date is in the form YYYY-MM-DD and year is disambiguated (|year=YYYYx)
    
    the numeric value in <result> determines the 'output' if any from this function:
    	0 – adds error message to error_list sequence table
    	1 – adds maint cat
    	2 – does nothing
    
    ]]
    
    local function year_date_check (year_string, year_origin, date_string, date_origin, error_list)
    	local year;
    	local date1;
    	local date2;
    	local result = 1;															-- result of the test; assume that the test passes
    
    	year = year_string:match ('(%d%d%d%d?)');
    
    	if date_string:match ('%d%d%d%d%-%d%d%-%d%d') and year_string:match ('%d%d%d%d%a') then	--special case where both date and year are required YYYY-MM-DD and YYYYx
    		date1 = date_string:match ('(%d%d%d%d)');
    		year = year_string:match ('(%d%d%d%d)');
    		if year ~= date1 then
    			result = 0;															-- years don't match
    		else
    			result = 2;															-- years match; but because disambiguated, don't add to maint cat
    		end
    		
    	elseif date_string:match ("%d%d%d%d?.-%d%d%d%d?") then						-- any of the standard range formats of date with two three- or four-digit years
    		date1, date2 = date_string:match ("(%d%d%d%d?).-(%d%d%d%d?)");
    		if year ~= date1 and year ~= date2 then
    			result = 0;
    		end
    
    	elseif mw.ustring.match(date_string, "%d%d%d%d[%-–]%d%d") then				-- YYYY-YY date ranges
    		local century;
    		date1, century, date2 = mw.ustring.match(date_string, "((%d%d)%d%d)[%-–]+(%d%d)");
    		date2 = century..date2;													-- convert YY to YYYY
    		if year ~= date1 and year ~= date2 then
    			result = 0;
    		end
    
    	elseif date_string:match ("%d%d%d%d?") then									-- any of the standard formats of date with one year
    		date1 = date_string:match ("(%d%d%d%d?)");
    		if year ~= date1 then
    			result = 0;
    		end
    	else																		-- should never get here; this function called only when no other date errors
    		result = 0;																-- no recognizable year in date
    	end
    
    	if 0 == result then															-- year / date mismatch
    		table.insert (error_list, substitute (cfg.messages['mismatch'], {year_origin, date_origin}));	-- add error message to error_list sequence table
    	elseif 1 == result then														-- redundant year / date
    		set_message ('maint_date_year');										-- add a maint cat
    	end
    end
    
    
    --[[--------------------------< R E F O R M A T T E R >--------------------------------------------------------
    
    reformat 'date' into new format specified by format_param if pattern_idx (the current format of 'date') can be
    reformatted.  Does the grunt work for reformat_dates().
    
    The table re_formats maps pattern_idx (current format) and format_param (desired format) to a table that holds:
    	format string used by string.format()
    	identifier letters ('d', 'm', 'y', 'd2', 'm2', 'y2') that serve as indexes into a table t{} that holds captures
    		from mw.ustring.match() for the various date parts specified by  patterns[pattern_idx][1]
    
    Items in patterns{} have the general form:
    	['ymd'] = {'^(%d%d%d%d)%-(%d%d)%-(%d%d)$', 'y', 'm', 'd'}, where:
    		['ymd'] is pattern_idx
    		patterns['ymd'][1] is the match pattern with captures for mw.ustring.match()
    		patterns['ymd'][2] is an indicator letter identifying the content of the first capture
    		patterns['ymd'][3] ... the second capture etc.
    
    when a pattern matches a date, the captures are loaded into table t{} in capture order using the idemtifier
    characters as indexes into t{}  For the above, a ymd date is in t{} as:
    	t.y = first capture (year), t.m = second capture (month), t.d = third capture (day)
    
    To reformat, this function is called with the pattern_idx that matches the current format of the date and with
    format_param set to the desired format.  This function loads table t{} as described and then calls string.format()
    with the format string specified by re_format[pattern_idx][format_param][1] using values taken from t{} according
    to the capture identifier letters specified by patterns[pattern_idx][format_param][n] where n is 2..
    
    ]]
    
    local re_formats = {
    	['ymd'] = {																	-- date format is ymd; reformat to:
    		['mdy'] = {'%s %s, %s', 'm', 'd', 'y'},									-- |df=mdy
    		['dmy'] = {'%s %s %s', 'd', 'm', 'y'},									-- |df=dmy
    	--		['yMd'] = {'%s %s %s', 'y', 'm', 'd'},								-- |df=yMd; not supported at en.wiki
    		},
    	['Mdy'] = {																	-- date format is Mdy; reformat to:
    		['mdy'] = {'%s %s, %s', 'm', 'd', 'y'},									-- for long/short reformatting
    		['dmy'] = {'%s %s %s', 'd', 'm', 'y'},									-- |df=dmy
    		['ymd'] = {'%s-%s-%s', 'y', 'm', 'd'},									-- |df=ymd
    	--		['yMd'] = {'%s %s %s', 'y', 'm', 'd'},								-- |df=yMd; not supported at en.wiki
    		},
    	['dMy'] = {																	-- date format is dMy; reformat to:
    		['dmy'] = {'%s %s %s', 'd', 'm', 'y'},									-- for long/short reformatting
    		['mdy'] = {'%s %s, %s', 'm', 'd', 'y'},									-- |df=mdy
    		['ymd'] = {'%s-%s-%s', 'y', 'm', 'd'},									-- |df=ymd
    	--		['yMd'] = {'%s %s %s', 'y', 'm', 'd'},								-- |df=yMd; not supported at en.wiki
    		},
    	['Md-dy'] = {																-- date format is Md-dy; reformat to:
    		['mdy'] = {'%s %s–%s, %s', 'm', 'd', 'd2', 'y'},						-- for long/short reformatting
    		['dmy'] = {'%s–%s %s %s', 'd', 'd2', 'm', 'y'},							-- |df=dmy -> d-dMy 
    		},
    	['d-dMy'] = {																-- date format is d-d>y; reformat to:
    		['dmy'] = {'%s–%s %s %s', 'd', 'd2', 'm', 'y'},							-- for long/short reformatting
    		['mdy'] = {'%s %s–%s, %s', 'm', 'd', 'd2', 'y'},						-- |df=mdy -> Md-dy 
    		},
    	['dM-dMy'] = {																-- date format is dM-dMy; reformat to:
    		['dmy'] = {'%s %s – %s %s %s', 'd', 'm', 'd2', 'm2', 'y'},				-- for long/short reformatting
    		['mdy'] = {'%s %s – %s %s, %s', 'm', 'd', 'm2', 'd2', 'y'},				-- |df=mdy -> Md-Mdy 
    		},
    	['Md-Mdy'] = {																-- date format is Md-Mdy; reformat to:
    		['mdy'] = {'%s %s – %s %s, %s', 'm', 'd',  'm2', 'd2', 'y'},			-- for long/short reformatting
    		['dmy'] = {'%s %s – %s %s %s', 'd', 'm', 'd2', 'm2', 'y'},				-- |df=dmy -> dM-dMy 
    		},
    	['dMy-dMy'] = {																-- date format is dMy-dMy; reformat to:
    		['dmy'] = {'%s %s %s – %s %s %s', 'd', 'm', 'y', 'd2', 'm2', 'y2'},		-- for long/short reformatting
    		['mdy'] = {'%s %s, %s – %s %s, %s', 'm', 'd', 'y', 'm2', 'd2', 'y2'},	-- |df=mdy -> Mdy-Mdy 
    		},
    	['Mdy-Mdy'] = {																-- date format is Mdy-Mdy; reformat to:
    		['mdy'] = {'%s %s, %s – %s %s, %s', 'm', 'd', 'y', 'm2', 'd2', 'y2'},	-- for long/short reformatting
    		['dmy'] = {'%s %s %s – %s %s %s', 'd', 'm', 'y', 'd2', 'm2', 'y2'},		-- |df=dmy -> dMy-dMy 
    		},
    	['My-My'] = {																-- these for long/short reformatting
    		['any'] = {'%s %s – %s %s', 'm', 'y', 'm2', 'y2'},						-- dmy/mdy agnostic
    		},
    	['M-My'] = {																-- these for long/short reformatting
    		['any'] = {'%s–%s %s', 'm', 'm2', 'y'},									-- dmy/mdy agnostic
    		},
    	['My'] = {																	-- these for long/short reformatting
    		['any'] = {'%s %s', 'm', 'y'},											-- dmy/mdy agnostic
    		},
    	--	['yMd'] = {																-- not supported at en.wiki
    	--		['mdy'] = {'%s %s, %s', 'm', 'd', 'y'},								-- |df=mdy
    	--		['dmy'] = {'%s %s %s', 'd', 'm', 'y'},								-- |df=dmy
    	--		['ymd'] = {'%s-%s-%s', 'y', 'm', 'd'},								-- |df=ymd
    	--		},
    	}
    
    
    local function reformatter (date, pattern_idx, format_param, mon_len)
    	if not in_array (pattern_idx, {'ymd', 'Mdy', 'Md-dy', 'dMy', 'yMd', 'd-dMy', 'dM-dMy', 'Md-Mdy', 'dMy-dMy', 'Mdy-Mdy', 'My-My', 'M-My', 'My'}) then
    		return;																	-- not in this set of date format patterns then not a reformattable date
    	end
    	
    	if 'ymd' == format_param and in_array (pattern_idx, {'ymd', 'Md-dy', 'd-dMy', 'dM-dMy', 'Md-Mdy', 'dMy-dMy', 'Mdy-Mdy', 'My-My', 'M-My', 'My'}) then
    		return;																	-- ymd date ranges not supported at en.wiki; no point in reformatting ymd to ymd
    	end
    
    	if in_array (pattern_idx, {'My', 'M-My', 'My-My'}) then						-- these are not dmy/mdy so can't be 'reformatted' into either
    		format_param = 'any';													-- so format-agnostic 
    	end
    
    																				-- yMd is not supported at en.wiki; when yMd is supported at your wiki, uncomment the next line
    	--	if 'yMd' == format_param and in_array (pattern_idx, {'yMd', 'Md-dy', 'd-dMy', 'dM-dMy', 'Md-Mdy', 'dMy-dMy', 'Mdy-Mdy'}) then	-- these formats not convertable; yMd not supported at en.wiki
    	if 'yMd' == format_param then												-- yMd not supported at en.wiki; when yMd is supported at your wiki, remove or comment-out this line
    		return;																	-- not a reformattable date
    	end
    	
    	local c1, c2, c3, c4, c5, c6, c7;											-- these hold the captures specified in patterns[pattern_idx][1]
    	c1, c2, c3, c4, c5, c6, c7 = mw.ustring.match (date, patterns[pattern_idx][1]);	-- get the captures
    
    	local t = {																	-- table that holds k/v pairs of date parts from the captures and patterns[pattern_idx][2..]
    		[patterns[pattern_idx][2]] = c1;										-- at minimum there is always one capture with a matching indicator letter
    		[patterns[pattern_idx][3] or 'x'] = c2;									-- patterns can have a variable number of captures; each capture requires an indicator letter;
    		[patterns[pattern_idx][4] or 'x'] = c3;									-- where there is no capture, there is no indicator letter so n in patterns[pattern_idx][n] will be nil;
    		[patterns[pattern_idx][5] or 'x'] = c4;									-- the 'x' here spoofs an indicator letter to prevent 'table index is nil' error
    		[patterns[pattern_idx][6] or 'x'] = c5;
    		[patterns[pattern_idx][7] or 'x'] = c6;
    		[patterns[pattern_idx][8] or 'x'] = c7;
    		};
    
    	if t.a then																	-- if this date has an anchor year capture (all convertable date formats except ymd)
    		if t.y2 then															-- for year range date formats														
    			t.y2 = t.a;															-- use the anchor year capture when reassembling the date
    		else																	-- here for single date formats (except ymd)
    			t.y = t.a;															-- use the anchor year capture when reassembling the date
    		end
    	end
    
    	if tonumber(t.m) then														-- if raw month is a number (converting from ymd)
    		if 's' == mon_len then													-- if we are to use abbreviated month names
    			t.m = cfg.date_names['inv_local_short'][tonumber(t.m)];					-- convert it to a month name
    		else
    			t.m = cfg.date_names['inv_local_long'][tonumber(t.m)];					-- convert it to a month name
    		end
    		t.d = t.d:gsub ('0(%d)', '%1');											-- strip leading '0' from day if present
    	elseif 'ymd' == format_param then											-- when converting to ymd
    		t.y = t.y:gsub ('%a', '');												-- strip CITREF disambiguator if present; anchor year already known so process can proceed; TODO: maint message?
    		if 1582 > tonumber (t.y) then											-- ymd format dates not allowed before 1582
    			return;
    		end
    		t.m = string.format ('%02d', get_month_number (t.m));					-- make sure that month and day are two digits
    		t.d = string.format ('%02d', t.d);
    	elseif mon_len then															-- if mon_len is set to either 'short' or 'long'
    		for _, mon in ipairs ({'m', 'm2'}) do									-- because there can be two month names, check both 
    			if t[mon] then
    				t[mon] = get_month_number (t[mon]);								-- get the month number for this month (is length agnostic)
    				if 0 == t[mon] then return; end									-- seasons and named dates can't be converted
    				t[mon] = (('s' == mon_len) and cfg.date_names['inv_local_short'][t[mon]]) or cfg.date_names['inv_local_long'][t[mon]];	-- fetch month name according to length
    			end
    		end
    	end
    
    	local new_date = string.format (re_formats[pattern_idx][format_param][1],	-- format string
    		t[re_formats[pattern_idx][format_param][2]],							-- named captures from t{}
    		t[re_formats[pattern_idx][format_param][3]],
    		t[re_formats[pattern_idx][format_param][4]],
    		t[re_formats[pattern_idx][format_param][5]],
    		t[re_formats[pattern_idx][format_param][6]],
    		t[re_formats[pattern_idx][format_param][7]],
    		t[re_formats[pattern_idx][format_param][8]]
    		);
    
    	return new_date;
    end
    
    
    --[[-------------------------< R E F O R M A T _ D A T E S >--------------------------------------------------
    
    Reformats existing dates into the format specified by format.
    
    format is one of several manual keywords: dmy, dmy-all, mdy, mdy-all, ymd, ymd-all.  The -all version includes
    access- and archive-dates; otherwise these dates are not reformatted.
    
    This function allows automatic date formatting.  In ~/Configuration, the article source is searched for one of
    the {{use xxx dates}} templates.  If found, xxx becomes the global date format as xxx-all.  If |cs1-dates= in
    {{use xxx dates}} has legitimate value then that value determines how cs1|2 dates will be rendered.  Legitimate
    values for |cs1-dates= are:
    	l - all dates are rendered with long month names
    	ls - publication dates use long month names; access-/archive-dates use abbreviated month names
    	ly - publication dates use long month names; access-/archive-dates rendered in ymd format
    	s - all dates are rendered with abbreviated (short) month names
    	sy - publication dates use abbreviated month names; access-/archive-dates rendered in ymd format
    	y - all dates are rendered in ymd format
    
    the format argument for automatic date formatting will be the format specified by {{use xxx dates}} with the
    value supplied by |cs1-dates so one of: xxx-l, xxx-ls, xxx-ly, xxx-s, xxx-sy, xxx-y, or simply xxx (|cs1-dates=
    empty, omitted, or invalid) where xxx shall be either of dmy or mdy.
    
    dates are extracted from date_parameters_list, reformatted (if appropriate), and then written back into the
    list in the new format.  Dates in date_parameters_list are presumed here to be valid (no errors).  This function
    returns true when a date has been reformatted, false else.  Actual reformatting is done by reformatter().
    
    ]]
    
    local function reformat_dates (date_parameters_list, format)
    	local all = false;															-- set to false to skip access- and archive-dates
    	local len_p = 'l';															-- default publication date length shall be long
    	local len_a = 'l';															-- default access-/archive-date length shall be long
    	local result = false;
    	local new_date;																
    	
    	if format:match('%a+%-all') then											-- manual df keyword; auto df keyword when length not specified in {{use xxx dates}}; 
    		format = format:match('(%a+)%-all');									-- extract the format
    		all = true;																-- all dates are long format dates because this keyword doesn't specify length
    	elseif format:match('%a+%-[lsy][sy]?') then									-- auto df keywords; internal only
    		all = true;																-- auto df applies to all dates; use length specified by capture len_p for all dates
    		format, len_p, len_a = format:match('(%a+)%-([lsy])([sy]?)');			-- extract the format and length keywords
    		if 'y' == len_p then													-- because allowed by MOS:DATEUNIFY (sort of) range dates and My dates not reformatted
    			format = 'ymd';														-- override {{use xxx dates}}
    		elseif (not is_set(len_a)) or (len_p == len_a) then						-- no access-/archive-date length specified or same length as publication dates then
    			len_a = len_p;														-- in case len_a not set
    		end
    	end																			-- else only publication dates and they are long
    
    	for param_name, param_val in pairs (date_parameters_list) do				-- for each date-holding parameter in the list
    		if is_set (param_val.val) then											-- if the parameter has a value
    			if not (not all and in_array (param_name, {'access-date', 'archive-date'})) then	-- skip access- or archive-date unless format is xxx-all; yeah, ugly; TODO: find a better way
    				for pattern_idx, pattern in pairs (patterns) do
    					if mw.ustring.match (param_val.val, pattern[1]) then
    						if all and in_array (param_name, {'access-date', 'archive-date'}) then	-- if this date is an access- or archive-date
    							new_date = reformatter (param_val.val, pattern_idx, (('y' == len_a) and 'ymd') or format, len_a);	-- choose ymd or dmy/mdy according to len_a setting
    						else													-- all other dates
    							new_date = reformatter (param_val.val, pattern_idx, format, len_p);
    						end
    						
    						if new_date then										-- set when date was reformatted
    							date_parameters_list[param_name].val = new_date;	-- update date in date list
    							result = true;										-- and announce that changes have been made
    						end
    					end	-- if
    				end		-- for
    			end			-- if
    		end				-- if
    	end					-- for
    	return result;																-- declare boolean result and done
    end
    
    
    --[[--------------------------< D A T E _ H Y P H E N _ T O _ D A S H >----------------------------------------
    
    Loops through the list of date-holding parameters and converts any hyphen to an ndash.  Not called if the cs1|2
    template has any date errors.
    
    Modifies the date_parameters_list and returns true if hyphens are replaced, else returns false.
    
    ]]
    
    local function date_hyphen_to_dash (date_parameters_list)
    	local result = false;
    	local n;
    	for param_name, param_val in pairs(date_parameters_list) do					-- for each date-holding parameter in the list
    		if is_set (param_val.val) and
    			not mw.ustring.match (param_val.val, patterns.ymd[1]) then			-- for those that are not ymd dates (ustring because here digits may not be Western)
    				param_val.val, n = param_val.val:gsub ('%-', '–');				-- replace any hyphen with ndash
    				if 0 ~= n then
    					date_parameters_list[param_name].val = param_val.val;		-- update the list
    					result = true;
    				end
    		end
    	end
    	return result;																-- so we know if any hyphens were replaced
    end
    
    
    --[[-------------------------< D A T E _ N A M E _ X L A T E >------------------------------------------------
    
    Attempts to translate English date names to local-language date names using names supplied by MediaWiki's
    date parser function.  This is simple name-for-name replacement and may not work for all languages.
    
    if xlat_dig is true, this function will also translate Western (English) digits to the local language's digits.
    This will also translate ymd dates.
    
    ]]
    
    local function date_name_xlate (date_parameters_list, xlt_dig)
    	local xlate;
    	local mode;																	-- long or short month names
    	local modified = false;
    	local date;
    	
    	local sources_t = {
    		{cfg.date_names.en.long, cfg.date_names.inv_local_long},				-- for translating long English month names to long local month names
    		{cfg.date_names.en.short, cfg.date_names.inv_local_short},				-- short month names
    		{cfg.date_names.en.quarter, cfg.date_names.inv_local_quarter},			-- quarter date names
    		{cfg.date_names.en.season, cfg.date_names.inv_local_season},			-- season date nam
    		{cfg.date_names.en.named, cfg.date_names.inv_local_named},				-- named dates
    		}
    
    	local function is_xlateable (month)											-- local function to get local date name that replaces existing English-language date name
    		for _, date_names_t in ipairs (sources_t) do							-- for each sequence table in date_names_t
    			if date_names_t[1][month] then										-- if date name is English month (long or short), quarter, season or named and
    				if date_names_t[2][date_names_t[1][month]] then					-- if there is a matching local date name
    					return date_names_t[2][date_names_t[1][month]];				-- return the local date name
    				end
    			end
    		end
    	end
    
    	for param_name, param_val in pairs(date_parameters_list) do					-- for each date-holding parameter in the list
    		if is_set(param_val.val) then											-- if the parameter has a value
    			date = param_val.val;
    			for month in mw.ustring.gmatch (date, '[%a ]+') do					-- iterate through all date names in the date (single date or date range)
    				month = mw.text.trim (month);									-- this because quarterly dates contain whitespace
    				xlate = is_xlateable (month);									-- get translate <month>; returns translation or nil
    				
    --				if cfg.date_names.en.long[month] then							-- long month dates
    --					if cfg.date_names.inv_local_long[cfg.date_names.en.long[month]] then
    --						xlate = cfg.date_names.inv_local_long[cfg.date_names.en.long[month]];
    --					end
    ----					mode = 'F';													-- English name is long so use long local name
    --				elseif cfg.date_names.en.short[month] then						-- short month dates
    --					if cfg.date_names.inv_local_short[cfg.date_names.en.short[month]] then
    --						xlate = cfg.date_names.inv_local_short[cfg.date_names.en.short[month]];
    --					end
    ----					mode = 'M';													-- English name is short so use short local name
    --				elseif cfg.date_names.en.quarter[month] then					-- quarter dates
    --					if cfg.date_names.inv_local_quarter[cfg.date_names.en.quarter[month]] then
    --						xlate = cfg.date_names.inv_local_quarter[cfg.date_names.en.quarter[month]];
    --					end
    --				elseif cfg.date_names.en.season[month] then						-- season dates
    --					if cfg.date_names.inv_local_season[cfg.date_names.en.season[month]] then
    --						xlate = cfg.date_names.inv_local_season[cfg.date_names.en.season[month]];
    --					end
    --				elseif cfg.date_names.en.named[month] then						-- named dates
    --					if cfg.date_names.inv_local_named[cfg.date_names.en.named[month]] then
    --						xlate = cfg.date_names.inv_local_named[cfg.date_names.en.named[month]];
    --					end
    --				else
    --					xlate=nil;													-- not an English month name; could be local language month name
    ----					mode = nil;													-- not an English month name; could be local language month name or an English season name
    --				end
    
    				if xlate then		
    --				if mode then													-- might be a season
    --					xlate = lang_object:formatDate(mode, '1' .. month);			-- translate the month name to this local language
    					date = mw.ustring.gsub (date, month, xlate);				-- replace the English with the translation
    					date_parameters_list[param_name].val = date;				-- save the translated date
    					modified = true;
    				end
    			end
    
    			if xlt_dig then														-- shall we also translate digits?
    				date = date:gsub ('%d', cfg.date_names.xlate_digits);			-- translate digits from Western to 'local digits'
    				date_parameters_list[param_name].val = date;					-- save the translated date
    				modified = true;
    			end
    		end
    	end
    	
    	return modified;
    end
    
    
    --[[--------------------------< S E T _ S E L E C T E D _ M O D U L E S >--------------------------------------
    
    Sets local imported functions table to same (live or sandbox) as that used by the other modules.
    
    ]]
    
    local function set_selected_modules (cfg_table_ptr, utilities_page_ptr)
    	add_prop_cat = utilities_page_ptr.add_prop_cat ;							-- import functions from selected Module:Citation/CS1/Utilities module
    	is_set = utilities_page_ptr.is_set;
    	in_array = utilities_page_ptr.in_array;
    	set_message = utilities_page_ptr.set_message;
    	substitute = utilities_page_ptr.substitute;
    	wrap_style = utilities_page_ptr.wrap_style;
    
    	cfg = cfg_table_ptr;														-- import tables from selected Module:Citation/CS1/Configuration
    end
    
    
    --[[--------------------------< E X P O R T E D   F U N C T I O N S >------------------------------------------
    ]]
    
    return {																		-- return exported functions
    	dates = dates,
    	year_date_check = year_date_check,
    	reformat_dates = reformat_dates,
    	date_hyphen_to_dash = date_hyphen_to_dash,
    	date_name_xlate = date_name_xlate,
    	set_selected_modules = set_selected_modules
    	}
    
    Cookies help us deliver our services. By using our services, you agree to our use of cookies.
    Cookies help us deliver our services. By using our services, you agree to our use of cookies.