This module is intended for processing of date strings.
 
Please do not modify this code without applying the changes first at Module:ISOdate/sandbox and testing 
at Module:ISOdate/sandbox/testcases and Module talk:ISOdate/sandbox/testcases.
 
Authors and maintainers:
 
]]
 
 
local p = {}
 
-- =======================================
-- === Dependencies ======================
-- =======================================
local D = require('Module:Date2')
 
--
ISOyear
 
This function returns year part of date string.
 
Usage:
 
Parameters
 1: The date string 
 
Error Handling:
 If the string does not look like it contain the year than the function will not return anything.
 That is the preferred treatment for the template:Creator which is the main (only?) template calling it.

function p.ISOyear( frame )
	local input = frame.args[1]
	if not input then
		input = frame.args["s"]
	end
	input = mw.text.trim( input )
 
	-- if empty string then return it
	if input == "" then
		return input
	end
 
	-- if number then return it
	if tonumber( input ) then
		return mw.ustring.format
	end
 
	-- otherwise use regular expression match
	input = mw.ustring.match( input, '^(-?%d%d?%d?%d?)-' )
	if input then
		return mw.ustring.format
	else
		return ''
	end
end
 
--
ISOdate
 
This function is the core part of the ISOdate template. 
 
Usage:
 
Parameters:
 1: The date string 
 lang: The language to display it in
 form: Language format  for some languages
 class: CSS class for the  node
 
 Error Handling:
 If the string does not look like it contain the proper ISO date than the function will return the original string.
 
 That is the preferred treatment for the template:Information (and similar templates) which calling it.

function p.ISOdate(frame)
	local datestr, succeded
	datestr, succeded = p._ISOdate(
		mw.text.trim(frame.args[1]),
		frame.args["lang"], -- language
		frame.args["trim_year"] or '100-999' -- by default pad one and 2 digit years to be 4 digit long, while keeping 3 digit years as is	
	)
	return datestr
end
 
function p._ISOdate
 
	-- pattern: regexp - regular expresion to test; dlen - number of date elements; tail = which element is a "tail" if any
	-- regexp hints:
	-- 1) Strings starting with "^" and ending with "$" indicate whole string match
	-- 2) optional tail part copied as-is and following the main parsed part of the date have to be separated from the date by a whitespace, so "(\s.+)?"
	local patterns = {
		-- strings starting with YYYY-MM-DD. Year 1-4 digits, the rest 1-2
		-- strings starting with YYYY-MM. Year 3-4 digits, month 2 digits
		-- (want to avoit converting to dates strings like 10-5 = 5
		-- if whole string is in YYYY-MM form: If Year 1-4 digits, month 1-2 digits
		-- string starts with a number -> it has to be 3 or 4 digit long to be a year
		 -- if whole string is a number (1-4 digit long) than it will be interpreted as a year
 
	-- create datevec based on which variables are provided
	local datevec, tail, formatNum
	datevec, tail, formatNum = p.test_date_formats
	if datevec[1]=='' or datevec[1]==nil then
		-- quickly return if datestr does not look like date (it could be a template)
		return datestr, false
	end
 
	-- call p._Date function to format date string
	local succeded, datestr2
	succeded, datestr2 = pcall
	if succeded and datestr2~='' then
		return mw.text.trim( datestr2 .. tail), true
	else -- in case of errors return the original string
		return datestr, false
	end	
end
 
function p.ISOdate_extended(frame)
	-- pattern: regexp - regular expresion to test; dlen - number of date elements; tail = which element is a "tail" if any
	-- regexp hints:
	-- 1) Strings starting with "^" and ending with "$" indicate whole string match
	-- 2) optional tail part copied as-is and following the main parsed part of the date have to be separated from the date by a whitespace, so "(\s.+)?"
 
	local datestr, succeded
	datestr, succeded = p._ISOdate(
		mw.text.trim(frame.args[1]),
		frame.args["lang"], -- language
		frame.args["trim_year"] or '100-999' -- by default pad one and 2 digit years to be 4 digit long, while keeping 3 digit years as is	
	)
	if succeded then
		return datestr
	end
 
	local datevec, tail, formatNum, category = ''
	datevec, tail, formatNum = p.test_date_formats
	if formatNum==1 or formatNum==2 then
		vec = datevec;
		if tonumber(datevec[1])>12 then
			frame.args[1] = string.format
			category = 'Category:Date in DD/MM/YYYY format'
			return mw.text.trim( p.ISOdate(frame) .. tail);
		elseif tonumber(datevec[2])>12 then
			frame.args[1] = string.format
			category = 'Category:Date in MM/DD/YYYY format'
			return mw.text.trim( p.ISOdate(frame) .. tail);
		end
	elseif (formatNum==3 or formatNum==4) and (datevec[3]=='' or datevec[3]~=nil) then
		local str = mw.getCurrentFrame:callParserFunction
		local vec = {str:match( "^(%d%d?%d?%d?)-(%d%d?)-(%d%d?)$" )}
		if vec and vec[1]~=nil then
			frame.args[1] = string.format
			category = 'Category:Date in word format'
			return p.ISOdate(frame);
		end
	end	
	return datestr
end
 
function p.test_date_formats
	-- pattern: regexp - regular expresion to test; dlen - number of date elements; tail = which element is a "tail" if any
 
	local datevec = {'','','','','',''}
	local tail = ''
	local vec, pat
	local formatNum = 0
	for i, pat in ipairs( patterns ) do
		vec = {datestr:match( pat.regexp )}
		if vec and vec[1]~=nil then
			for j=1,pat.dlen do
				datevec[j] = vec[j]
			end
			if pat.tail>0 and vec[pat.tail]~=nil then
				tail = mw.ustring.gsub
			end
			formatNum = i
			break
		end
	end
	return datevec, tail, formatNum
end