# Module:Citation/CS1/Date validation

----------------------------< 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  

--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  

--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  

--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  

--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 year and (100 > year) then -- years less than 100 not supported  
return false;  
end  

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 to , 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  

--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  
input.year = tonumber (input.year) or lang_object:parseFormattedNumber (input.year); -- language-aware tonumber  
input.year2 = tonumber (input.year2) or lang_object:parseFormattedNumber (input.year2); -- COinS dates are pseudo-ISO 8601 so convert to Arabic numerals  

if ((1582 == input.year) and (10 > tonumber(input.month))) or (1582 > input.year) then -- if a Julian calendar date  
tCOinS_date.rftdate = tostring (input.year); -- &rft.date gets year only  
return; -- done  
end  
-- here for all forms of Gregorian dates  
if 20 < tonumber (input.month) then -- if season, quarter, or proper-name date  
date = input.year; -- &rft.date gets year only  
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', input.year, input.year2) -- assemble the date range  
end  

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, quarter, or proper-name date  
if 40 < tonumber(input.month) then  
tCOinS_date.rftchron = season[input.month]; -- proper-name date; used in journal metadata only  
elseif 30 < tonumber(input.month) then  
tCOinS_date.rftquarter = season[input.month]; -- quarter date; used in journal metadata only  
else  
tCOinS_date.rftssn = season[input.month]; -- season date; used in journal metadata only  
end  
else -- season ranges are lumped into &rft.chron; &rft.ssn and &rft.quarter are blank  
if input.year ~= input.year2 then -- season year – season year range or season year–year  
if 0 ~= input.month2 then  
tCOinS_date.rftchron = string.format ('%s %s – %s %s', season[input.month], input.year, season[input.month2], input.year2); -- used in journal metadata only  
end  
else -- season–season year range  
tCOinS_date.rftchron = season[input.month] .. '–' .. season[input.month2]; -- season–season year range; used in journal metadata only  
end  
end  

tCOinS_date.rftdate = tostring (date);  
return; -- done  
end  
-- here for gregorian calendar dates  
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 _ T >----------------------------------------------------------  

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_t = {  
-- 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  
}  

--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_t['ymd'][1]) or -- ymd  
v:match (patterns_t['Mdy'][1]) or -- dmy  
v:match (patterns_t['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_t['ymd'][1]) then -- year-initial numerical year month day format  
year, month, day = date_string:match (patterns_t['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_t['Mdy'][1]) then -- month-initial: month day, year  
month, day, anchor_year, year = mw.ustring.match(date_string, patterns_t['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_t['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_t['Md-dy'][1]);  
if tonumber(day) >= tonumber(day2) then return false; end -- date range order is to : 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_t['dMy'][1]) then -- day-initial: day month year  
day, month, anchor_year, year = mw.ustring.match(date_string, patterns_t['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_t['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_t['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_t['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_t['d-dMy'][1]);  
if tonumber(day) >= tonumber(day2) then return false; end -- date range order is to : 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_t['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_t['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 to : earlier to later;  
month = get_month_number (month); -- for metadata  
month2 = get_month_number (month2);  
year2 = year;  

elseif mw.ustring.match(date_string, patterns_t['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_t['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_t['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_t['dMy-dMy'][1]);  
if tonumber(year2) <= tonumber(year) then return false; end -- must be sequential years, to , 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_t['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_t['Mdy-Mdy'][1]);  
if tonumber(year2) <= tonumber(year) then return false; end -- must be sequential years, to , 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_t['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_t['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, to , 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_t['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_t['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, to , 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_t['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_t['My-My'][1]);  
anchor_year = year .. '–' .. anchor_year; -- assemble anchor_year from both years  
if tonumber(year) >= tonumber(year2) then return false; end -- to , 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_t['M-My'][1]) then -- month/season range year; months separated by endash  
month, month2, anchor_year, year = mw.ustring.match(date_string, patterns_t['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_t['My'][1]) then -- month/season/quarter/proper-name year  
month, anchor_year, year = mw.ustring.match(date_string, patterns_t['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_t['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_t['y-y'][1]);  
anchor_year = year .. '–' .. anchor_year; -- assemble anchor year from both years  
if tonumber(year) >= tonumber(year2) then return false; end -- to , 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_t['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_t['y4-y2'][1]);  
anchor_year = year .. '–' .. anchor_year; -- assemble anchor year from both years  

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 -- to , 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 in_array (param, {'date', 'publication-date', 'year'}) then -- here when 'valid' abbreviated year range; if one of these parameters  
add_prop_cat ('year-range-abbreviated'); -- add properties cat  
end  

elseif mw.ustring.match(date_string, patterns_t['y'][1]) then -- year; here accept either YYY or YYYY  
anchor_year, year = mw.ustring.match(date_string, patterns_t['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 access-date 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 -- of these; access-date must not be a range  
if not is_valid_accessdate(year .. '-' .. month .. '-' .. day) then  
return false; -- return false when access-date out of bounds  
end  
else  
return false; -- return false when access-date is a range of two dates  
end  
end  

if 'archive-date' == param then -- test archive-date here because we have numerical date parts  
if not (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 -- of these; archive-date must not be a range  
return false; -- return false when archive-date 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  

--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  

--year= for acceptable values:  
YYY, YYYY, year-only ranges, their circa forms, with or without CITEREF disambiguators.  

When |year= holds some form of date that is not one of these year-only dates, emit a maintenance message.  

This function necessary because many non-cs1|2 templates have a |year= parameter so cirrus searches are more-or-  
less useless  

local function year_check (year)  
year = year:gsub ('c%. *', ''); -- remove circa annotation (if present) before testing <year>  

for _, index in ipairs ({'y-y', 'y4-y2', 'y'}) do -- spin through these indexes into patterns_t  
if mw.ustring.match (year, patterns_t[index][1]) then  
return; -- if a match then |year= holds a valid 'year'  
end  
end  

set_message ('maint_year'); -- if here, |year= value is not an accepted value; add a maint cat  
end  

--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_t[pattern_idx][1]  

Items in patterns_t{} have the general form:  
['ymd'] = {'^(%d%d%d%d)%-(%d%d)%-(%d%d)$', 'y', 'm', 'd'}, where:  
['ymd'] is pattern_idx  
patterns_t['ymd'][1] is the match pattern with captures for mw.ustring.match  
patterns_t['ymd'][2] is an indicator letter identifying the content of the first capture  
patterns_t['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_t[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_t 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_t[pattern_idx][1]  
c1, c2, c3, c4, c5, c6, c7 = mw.ustring.match (date, patterns_t[pattern_idx][1]); -- get the captures  

local t = { -- table that holds k/v pairs of date parts from the captures and patterns_t[pattern_idx][2..]  
[patterns_t[pattern_idx][2]] = c1; -- at minimum there is always one capture with a matching indicator letter  
[patterns_t[pattern_idx][3] or 'x'] = c2; -- patterns_t can have a variable number of captures; each capture requires an indicator letter;  
[patterns_t[pattern_idx][4] or 'x'] = c3; -- where there is no capture, there is no indicator letter so n in patterns_t[pattern_idx][n] will be nil;  
[patterns_t[pattern_idx][5] or 'x'] = c4; -- the 'x' here spoofs an indicator letter to prevent 'table index is nil' error  
[patterns_t[pattern_idx][6] or 'x'] = c5;  
[patterns_t[pattern_idx][7] or 'x'] = c6;  
[patterns_t[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  

--cs1-dates= in  
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 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 ;  
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  
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_t) 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  
break;  
end  
end -- if  
end -- for  
end -- if  
end -- if  
end -- for  
return result; -- declare boolean result and done  
end  

--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_t.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 xlate then  
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  

--archive-date= with the timestamp in Wayback machine urls. Emits an error message with suggested  
date from the |archive-url= timestamp in an appropriate format when the value in |archive-date= does not match  
the timestamp.  

this function never called when any date in a cs1|2 template has errors  

error message suggests new |archive-date= value in an appropriate format specified by <df>. <df> is either  
|df= or cfg.global_df in that order. If <df> is nil, suggested date has format from |archive-date=. There is  
a caveat: when |df=dmy or |df=mdy, the reformatter leaves |access-date= and |archive-date= formats as they are.  
The error message suggested date is passed to the formatter as YYYY-MM-DD so when |df=dmy or |df=mdy, the format  
is not changed.  

local function archive_date_check (archive_date, archive_url_timestamp, df)  
local archive_date_format = 'dmy-y'; -- holds the date format of date in |archive-date; default to ymd; 'dmy' used here to spoof reformat_dates  

for _, v_t in ipairs do -- is |archive-date= format dmy or mdy?  
if archive_date:match (patterns_t[v_t[1]][1]) then -- does the pattern match?  
archive_date_format = cfg.keywords_xlate[v_t[2]]; -- get appropriate |df= supported keyword from the i18n translator table  
break;  
end  
end  

local dates_t = {};  
dates_t['archive-date'] = {val=archive_date, name=''}; -- setup to call reformat_dates; never called when errors so <name> unset as not needed  
reformat_dates (dates_t, 'dmy-y'); -- reformat |archive-date= to ymd; 'dmy' used here to spoof reformat_dates  
local archive_url_date = archive_url_timestamp:gsub ('(%d%d%d%d)(%d%d)(%d%d)%d*', '%1-%2-%3'); -- make ymd format date from timestamp  

if dates_t['archive-date'].val == archive_url_date then -- are the two dates the same  
return; -- yes, done  
else  
dates_t['archive-date'] = {val=archive_url_date, name=''}; -- setup to call reformat_dates with the timestamp date  
reformat_dates (dates_t, df or archive_date_format); -- reformat timestamp to format specified by <df> or format used in |archive-date=  
archive_url_date = dates_t['archive-date'].val;  
set_message ('err_archive_date_url_ts_mismatch', archive_url_date); -- emit an error message  
end  
end  

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

return { -- return exported functions  
archive_date_check = archive_date_check,  
date_hyphen_to_dash = date_hyphen_to_dash,  
date_name_xlate = date_name_xlate,  
dates = dates,  
reformat_dates = reformat_dates,  
set_selected_modules = set_selected_modules,  
year_check = year_check,  
year_date_check = year_date_check,  
}