Module:Auto date formatter

 require('strict');

 locallang_obj=mw.language.getContentLanguage();-- needed for the function to reformat dates

 localglobal_df=mw.loadData('Module:Citation/CS1/Configuration').global_df;-- fetch global date format specified by {{use xxx dates}} template
 localbase_format=global_dfandglobal_df:match('^(%a%a%a)');-- get {{use xxx dates}} base date format: 'dmy' or 'mdy'
 localdate_style=global_dfandglobal_df:match('^%a%a%a%-(.+)');-- get |cs1-dates= style modifiers


 --[[--------------------------< F O R M A T T E R >------------------------------------------------------------

 local function to format <date> according to <format> (dmy or mdy) and <style> (long, short, year initial) as
 specified by the |cs1-dates= parameter of the {{use xxx dates}} template.

 valid |cs1-dates= format character strings are:
 	l, ll, all	– default; long-form publication and access- / archive-dates; 'all' when |cs1-dates= omitted or empty
 	ls			– long-form publication dates; abbreviated access- / archive-dates
 	ly			– long-form publication dates; year-initial numeric access- / archive-dates (ymd)
 	s, ss		– abbreviated publication and access- / archive-dates
 	sy			– abbreviated publication dates; year-initial numeric access- / archive-dates (ymd)
 	y, yy		– year-initial numeric publication, access- and archive-dates (ymd); overrides base format

 note: 'all' is added by get_date_format() in Module:Citation/CS1/Configuration when |cs1-dates= is omitted or empty;
 cs1|2 and this module then assume long-form date style for all dates

 ]]

 localfunctionformatter(date,format,style)
 --[[
 First check for year-only in the date field.
 Next check for a year and month only.
 In either case, just return the date as provided.
 ]]
 ifdate:match('^%d%d%d%d$')then-- YYYY
 returndate
 end

 ifdate:match('^%a+%s+%d%d%d%d$')or-- "Month YYYY"
 date:match('^%d%d%d%d%-%d%d$')then-- "YYYY-MM"
 returndate
 end

 localformat_strings_t={-- map <style> to formatDate() format strings (same as #time parser function)
 ['dmy']={
 ['l']='j F Y',-- long month name
 ['s']='j M Y',-- abbreviated month name
 ['y']='Y-m-d'-- year initial numeric; overrides <format> (dmy/mdy)
 },
 ['mdy']={
 ['l']='F j, Y',-- long month name
 ['s']='M j, Y',-- abbreviated month name
 ['y']='Y-m-d'-- year initial numeric; overrides <format> (dmy/mdy)
 }
 }

 localgood,new_date=pcall(lang_obj.formatDate,lang_obj,format_strings_t[format][style],date);-- attempt to reformat; on success, <good> is boolean true
 return(goodandnew_date)ordate;-- returns <new_date> when <good> is boolean true; <date> else
 end


 --[[--------------------------< _ P U B _ D A T E _ F O R M A T >----------------------------------------------

 Module entry point

 For publication dates |date=, |publication-date=, etc

 ]]

 localfunction_pub_date_format(date)
 ifnotglobal_dfthen
 returndate;-- when article does not have {{use xxx dates}}, abandon
 end

 localstyles_t={all='l',ll='l',l='l',ls='l',ly='l',s='s',ss='s',sy='s',yy='y',y='y'};-- map known styles for publication dates
 returnformatter(date,base_format,styles_t[date_style]or'l');-- not a known style default to 'l' (long form)
 end


 --[[--------------------------< P U B _ D A T E _ F O R M A T >------------------------------------------------

 #invoke entry point

 For publication dates |date=, |publication-date=, etc

 	{{#invoke:auto date formatter|pub_date_format|16 March 2025}}

 ]]

 localfunctionpub_date_format(frame)
 return_pub_date_format(frame.args[1]);-- <args[1]> is date to be formatted
 end


 --[[--------------------------< _ A C C E S S _ A R C H I V E _ F O R M A T >----------------------------------

 module entry point

 For access and archive dates |access-date=, |accessdate=, archive-date=, archivedate=

 ]]

 localfunction_access_archive_format(date)
 ifnotglobal_dfthen
 returndate;-- when article does not have {{use xxx dates}}, abandon
 end

 localstyles_t={all='l',ll='l',l='l',ls='s',ly='y',s='s',ss='s',sy='y',yy='y',y='y'};-- map known styles for access/archive dates
 returnformatter(date,base_format,styles_t[date_style]or'l');-- not a known style default to 'l' (long form)
 end


 --[[--------------------------< A C C E S S _ A R C H I V E _ F O R M A T >------------------------------------

 #invoke entry point

 For access and archive dates |access-date=, |accessdate=, archive-date=, archivedate=

 	{{#invoke:auto date formatter|access_archive_format|16 March 2025}}

 ]]

 localfunctionaccess_archive_format(frame)
 return_access_archive_format(frame.args[1]);-- <args[1]> is date to be formatted
 end


 --[[--------------------------< E X P O R T S >----------------------------------------------------------------
 ]]

 return{
 pub_date_format=pub_date_format,-- #invoke entry points
 access_archive_format=access_archive_format,

 _pub_date_format=_pub_date_format,-- module entry points
 _access_archive_format=_access_archive_format,
 }