-- Implement various "age of" and other date-related templates.



local mtext = {

	-- Message and other text that should be localized.

	-- Also need to localize text in table names in function dateDifference.

	'mt-bad-param1' =             'Invalid parameter $1',

	'mt-bad-param2' =             'Parameter $1=$2 is invalid',

	'mt-bad-show' =               'Parameter show=$1 is not supported here',

	'mt-cannot-add' =             'Cannot add "$1"',

	'mt-conflicting-show' =       'Parameter show=$1 conflicts with round=$2',

	'mt-date-wrong-order' =       'The second date must be later in time than the first date',

	'mt-dd-future' =              'Death date (first date) must not be in the future',

	'mt-dd-wrong-order' =         'Death date (first date) must be later in time than the birth date (second date)',

	'mt-invalid-bd-age' =         'Invalid birth date for calculating age',

	'mt-invalid-dates-age' =      'Invalid dates for calculating age',

	'mt-invalid-end' =            'Invalid end date in second parameter',

	'mt-invalid-start' =          'Invalid start date in first parameter',

	'mt-need-jdn' =               'Need valid Julian date number',

	'mt-need-valid-bd' =          'Need valid birth date: year, month, day',

	'mt-need-valid-bd2' =         'Need valid birth date (second date): year, month, day',

	'mt-need-valid-date' =        'Need valid date',

	'mt-need-valid-dd' =          'Need valid death date (first date): year, month, day',

	'mt-need-valid-ymd' =         'Need valid year, month, day',

	'mt-need-valid-ymd-current' = 'Need valid year|month|day or "currentdate"',

	'mt-need-valid-ymd2' =        'Second date should be year, month, day',

	'mt-template-bad-name' =      'The specified template name is not valid',

	'mt-template-x' =             'The template invoking this must have "|template=x" where x is the wanted operation',

	'txt-and' =                   ' and ',

	'txt-or' =                    ' or ',

	'txt-category' =              'Category:Age error',

	'txt-comma-and' =             ', and ',

	'txt-error' =                 'Error: ',

	'txt-format-default' =        'mf',  -- 'df' (day first = dmy) or 'mf' (month first = mdy)

	'txt-module-convertnumeric' = 'Module:ConvertNumeric',

	'txt-module-date' =           'Module:Date',

	'txt-sandbox' =               'sandbox',

	'txt-bda' = '<span style="display:none"> (<span class="bday">$1</span>) </span>$2<span class="noprint ForceAgeToShow"> (age&nbsp;$3)</span>',

	'txt-dda' = '$2<span style="display:none">($1)</span> (aged&nbsp;$3)',

	'txt-bda-disp' = 'disp_raw',  -- disp_raw → age is a number only; disp_age → age is a number and unit (normally years but months or days if very young)

	'txt-dda-disp' = 'disp_raw',

	'txt-dmy' = '%-d %B %-Y',

	'txt-mdy' = '%B %-d, %-Y',

}



local isWarning = {

	'mt-bad-param1' = true,

}



local translate, from_en, to_en, isZero

if translate then

	-- Functions to translate from en to local language and reverse go here.

	-- See example at [[:bn:Module:বয়স]].

else

	from_en = function (text)

		return text

	end

	isZero = function (text)

		return tonumber(text) == 0

	end

end



local _Date, _currentDate

local function getExports(frame)

	-- Return objects exported from the date module or its sandbox.

	if not _Date then

		local sandbox = frame:getTitle():find(mtext'txt-sandbox'], 1, true) and ('/' .. mtext'txt-sandbox']) or ''

		local datemod = require(mtext'txt-module-date' .. sandbox)

		local realDate = datemod._Date

		_currentDate = datemod._current

		if to_en then

			_Date = function (...)

				local args = {}

				for i, v in ipairs({...}) do

					argsi = to_en(v)

				end

				return realDate(unpack(args))

			end

		else

			_Date = realDate

		end

	end

	return _Date, _currentDate

end



local Collection  -- a table to hold items

Collection = {

	add = function (self, item)

		if item ~= nil then

			self.n = self.n + 1

			selfself.n = item

		end

	end,

	join = function (self, sep)

		return table.concat(self, sep)

	end,

	remove = function (self, pos)

		if self.n > 0 and (pos == nil or (0 < pos and pos <= self.n)) then

			self.n = self.n - 1

			return table.remove(self, pos)

		end

	end,

	sort = function (self, comp)

		table.sort(self, comp)

	end,

	new = function ()

		return setmetatable({n = 0}, Collection)

	end

}

Collection.__index = Collection



local function stripToNil(text)

	-- If text is a string, return its trimmed content, or nil if empty.

	-- Otherwise return text (which may, for example, be nil).

	if type(text) == 'string' then

		text = text:match('(%S.-)%s*$')

	end

	return text

end



local function dateFormat(args)

	-- Return string for wanted date format.

	local default = mtext'txt-format-default'

	local other = default == 'df' and 'mf' or 'df'

	local wanted = stripToNil(argsother]) and other or default

	return wanted == 'df' and mtext'txt-dmy' or mtext'txt-mdy'

end



local function substituteParameters(text, ...)

	-- Return text after substituting any given parameters for $1, $2, etc.

	return mw.message.newRawMessage(text, ...):plain()

end



local function yes(parameter)

	-- Return true if parameter should be interpreted as "yes".

	-- Do not want to accept mixed upper/lowercase unless done by current templates.

	-- Need to accept "on" because "round=on" is wanted.

	return ({ y = true, yes = true, on = true })[parameter

end



local function message(msg, ...)

	-- Return formatted message text for an error or warning.

	local function getText(msg)

		return mtextmsg or error('Bug: message "' .. tostring(msg) .. '" not defined')

	end

	local categories = {

		error = mtext'txt-category'],

		warning = mtext'txt-category'],

	}

	local a, b, k, category

	local text = substituteParameters(getText(msg), ...)

	if isWarningmsg then

		a = '<sup>[<i>'

		b = '</i>]</sup>'

		k = 'warning'

	else

		a = '<strong class="error">' .. getText('txt-error')

		b = '</strong>'

		k = 'error'

	end

	if mw.title.getCurrentTitle():inNamespaces(0) then

		-- Category only in namespaces: 0=article.

		category = '[[' .. categoriesk .. ']]'

	end

	return

		a ..

		mw.text.nowiki(text) ..

		b ..

		(category or '')

end



local function formatNumber(number)

	-- Return the given number formatted with commas as group separators,

	-- given that the number is an integer.

	local numstr = tostring(number)

	local length = #numstr

	local places = Collection.new()

	local pos = 0

	repeat

		places:add(pos)

		pos = pos + 3

	until pos >= length

	places:add(length)

	local groups = Collection.new()

	for i = places.n, 2, -1 do

		local p1 = length - placesi + 1

		local p2 = length - placesi - 1

		groups:add(numstr:sub(p1, p2))

	end

	return groups:join(',')

end



local function spellNumber(number, options, i)

	-- Return result of spelling number, or

	-- return number (as a string) if cannot spell it.

	-- i == 1 for the first number which can optionally start with an uppercase letter.

	number = tostring(number)

	return require(mtext'txt-module-convertnumeric']).spell_number(

		number,

		nil,                       -- fraction numerator

		nil,                       -- fraction denominator

		i == 1 and options.upper,  -- true: 'One' instead of 'one'

		not options.us,            -- true: use 'and' between tens/ones etc

		options.adj,               -- true: hyphenated

		options.ordinal            -- true: 'first' instead of 'one'

	) or number

end



local function makeExtra(args, flagCurrent)

	-- Return extra text that will be inserted before the visible result

	-- but after any sort key.

	local extra = args.prefix or ''

	if mw.ustring.len(extra) > 1 then

		-- Parameter "~" gives "~3" whereas "over" gives "over 3".

		if extra:sub(-6, -1) ~= '&nbsp;' then

			extra = extra .. ' '

		end

	end

	if flagCurrent then

		extra = '<span class="currentage"></span>' .. extra

	end

	return extra

end



local function makeSort(value, sortable)

	-- Return a sort key if requested.

	-- Assume value is a valid number which has not overflowed.

	if sortable == 'sortable_table' or sortable == 'sortable_on' or sortable == 'sortable_debug' then

		local sortKey

		if value == 0 then

			sortKey = '5000000000000000000'

		else

			local mag = math.floor(math.log10(math.abs(value)) + 1e-14)

			if value > 0 then

				sortKey = 7000 + mag

			else

				sortKey = 2999 - mag

				value = value + 10^(mag+1)

			end

			sortKey = string.format('%d', sortKey) .. string.format('%015.0f', math.floor(value * 10^(14-mag)))

		end

		local result

		if sortable == 'sortable_table' then

			result = 'data-sort-value="_SORTKEY_"|'

		elseif sortable == 'sortable_debug' then

			result = '<span data-sort-value="_SORTKEY_♠"><span style="border:1px solid">_SORTKEY_♠</span></span>'

		else

			result = '<span data-sort-value="_SORTKEY_♠"></span>'

		end

		return (result:gsub('_SORTKEY_', sortKey))

	end

end



local translateParameters = {

	abbr = {

		off = 'abbr_off',

		on = 'abbr_on',

	},

	disp = {

		age = 'disp_age',

		raw = 'disp_raw',

	},

	format = {

		raw = 'format_raw',

		commas = 'format_commas',

	},

	round = {

		on = 'on',

		yes = 'on',

		months = 'ym',

		weeks = 'ymw',

		days = 'ymd',

		hours = 'ymdh',

	},

	sep = {

		comma = 'sep_comma',

		',' = 'sep_comma',

		serialcomma = 'sep_serialcomma',

		space = 'sep_space',

	},

	show = {

		hide = { id = 'hide' },

		y = { 'y', id = 'y' },

		ym = { 'y', 'm', id = 'ym' },

		ymd = { 'y', 'm', 'd', id = 'ymd' },

		ymw = { 'y', 'm', 'w', id = 'ymw' },

		ymwd = { 'y', 'm', 'w', 'd', id = 'ymwd' },

		yd = { 'y', 'd', id = 'yd', keepZero = true },

		m = { 'm', id = 'm' },

		md = { 'm', 'd', id = 'md' },

		w = { 'w', id = 'w' },

		wd = { 'w', 'd', id = 'wd' },

		h = { 'H', id = 'h' },

		hm = { 'H', 'M', id = 'hm' },

		hms = { 'H', 'M', 'S', id = 'hms' },

		M = { 'M', id = 'M' },

		s = { 'S', id = 's' },

		d = { 'd', id = 'd' },

		dh = { 'd', 'H', id = 'dh' },

		dhm = { 'd', 'H', 'M', id = 'dhm' },

		dhms = { 'd', 'H', 'M', 'S', id = 'dhms' },

		ymdh = { 'y', 'm', 'd', 'H', id = 'ymdh' },

		ymdhm = { 'y', 'm', 'd', 'H', 'M', id = 'ymdhm' },

		ymwdh = { 'y', 'm', 'w', 'd', 'H', id = 'ymwdh' },

		ymwdhm = { 'y', 'm', 'w', 'd', 'H', 'M', id = 'ymwdhm' },

	},

	sortable = {

		off = false,

		on = 'sortable_on',

		table = 'sortable_table',

		debug = 'sortable_debug',

	},

}



local spellOptions = {

	cardinal = {},

	Cardinal = { upper = true },

	cardinal_us = { us = true },

	Cardinal_us = { us = true, upper = true },

	ordinal = { ordinal = true },

	Ordinal = { ordinal = true, upper = true },

	ordinal_us = { ordinal = true, us = true },

	Ordinal_us = { ordinal = true, us = true, upper = true },

}



local function dateExtract(frame)

	-- Return part of a date after performing an optional operation.

	local Date = getExports(frame)

	local args = frame:getParent().args

	local parms = {}

	for i, v in ipairs(args) do

		parmsi = v

	end

	if yes(args.fix) then

		table.insert(parms, 'fix')

	end

	if yes(args.partial) then

		table.insert(parms, 'partial')

	end

	local show = stripToNil(args.show) or 'dmy'

	local date = Date(unpack(parms))

	if not date then

		if show == 'format' then

			return 'error'

		end

		return message('mt-need-valid-date')

	end

	local add = stripToNil(args.add)

	if add then

		for item in add:gmatch('%S+') do

			date = date + item

			if not date then

				return message('mt-cannot-add', item)

			end

		end

	end

	local sortKey, result

	local sortable = translateParameters.sortableargs.sortable

	if sortable then

		local value = (date.partial and date.partial.first or date).jdz

		sortKey = makeSort(value, sortable)

	end

	if show ~= 'hide' then

		result = dateshow

		if result == nil then

			result = from_en(date:text(show))

		elseif type(result) == 'boolean' then

			result = result and '1' or '0'

		else

			result = from_en(tostring(result))

		end

	end

	return (sortKey or '') .. makeExtra(args) .. (result or '')

end



local function rangeJoin(range)

	-- Return text to be used between a range of ages.

	return range == 'dash' and '–' or mtext'txt-or'

end



local function makeText(values, components, names, options, noUpper)

	-- Return wikitext representing an age or duration.

	local text = Collection.new()

	local count = #values

	local sep = names.sep or ''

	for i, v in ipairs(values) do

		-- v is a number (say 4 for 4 years), or a table ({4,5} for 4 or 5 years).

		local islist = type(v) == 'table'

		if (islist or v > 0) or (text.n == 0 and i == count) or (text.n > 0 and components.keepZero) then

			local fmt, vstr

			if options.spell then

				fmt = function(number)

					return spellNumber(number, options.spell, noUpper or i)

				end

			elseif i == 1 and options.format == 'format_commas' then

				-- Numbers after the first should be small and not need formatting.

				fmt = formatNumber

			else

				fmt = tostring

			end

			if islist then

				vstr = fmt(v1]) .. rangeJoin(options.range)

				noUpper = true

				vstr = vstr .. fmt(v2])

			else

				vstr = fmt(v)

			end

			local name = namescomponentsi]]

			if name then

				if type(name) == 'table' then

					name = mw.getContentLanguage():plural(islist and v2 or v, name)

				end

				text:add(vstr .. sep .. name)

			else

				text:add(vstr)

			end

		end

	end

	local first, last

	if options.join == 'sep_space' then

		first = ' '

		last = ' '

	elseif options.join == 'sep_comma' then

		first = ', '

		last = ', '

	elseif options.join == 'sep_serialcomma' and text.n > 2 then

		first = ', '

		last = mtext'txt-comma-and'

	else

		first = ', '

		last = mtext'txt-and'

	end

	for i, v in ipairs(text) do

		if i < text.n then

			texti = v .. (i + 1 < text.n and first or last)

		end

	end

	local sign = ''

	if options.isnegative then

		-- Do not display negative zero.

		if text.n > 1 or (text.n == 1 and text1]:sub(1, 1) ~= '0' ) then

			if options.format == 'format_raw' then

				sign = '-'  -- plain hyphen so result can be used in a calculation

			else

				sign = '−'  -- Unicode U+2212 MINUS SIGN

			end

		end

	end

	return

		(options.sortKey or '') ..

		(options.extra or '') ..

		sign ..

		text:join() ..

		(options.suffix or '')

end



local function dateDifference(parms)

	-- Return a formatted date difference using the given parameters

	-- which have been validated.

	local names = {

		-- Each name is:

		-- * a string if no plural form of the name is used; or

		-- * a table of strings, one of which is selected using the rules at

		--   https://translatewiki.net/wiki/Plural/Mediawiki_plural_rules

		abbr_off = {

			sep = '&nbsp;',

			y = {'year', 'years'},

			m = {'month', 'months'},

			w = {'week', 'weeks'},

			d = {'day', 'days'},

			H = {'hour', 'hours'},

			M = {'minute', 'minutes'},

			S = {'second', 'seconds'},

		},

		abbr_on = {

			y = 'y',

			m = 'm',

			w = 'w',

			d = 'd',

			H = 'h',

			M = 'm',

			S = 's',

		},

		abbr_infant = {      -- for {{age for infant}}

			sep = '&nbsp;',

			y = {'yr', 'yrs'},

			m = {'mo', 'mos'},

			w = {'wk', 'wks'},

			d = {'day', 'days'},

			H = {'hr', 'hrs'},

			M = {'min', 'mins'},

			S = {'sec', 'secs'},

		},

		abbr_raw = {},

	}

	local diff = parms.diff  -- must be a valid date difference

	local show = parms.show  -- may be nil; default is set below

	local abbr = parms.abbr or 'abbr_off'

	local defaultJoin

	if abbr ~= 'abbr_off' then

		defaultJoin = 'sep_space'

	end

	if not show then

		show = 'ymd'

		if parms.disp == 'disp_age' then

			if diff.years < 3 then

				defaultJoin = 'sep_space'

				if diff.years >= 1 then

					show = 'ym'

				else

					show = 'md'

				end

			else

				show = 'y'

			end

		end

	end

	if type(show) ~= 'table' then

		show = translateParameters.showshow

	end

	if parms.disp == 'disp_raw' then

		defaultJoin = 'sep_space'

		abbr = 'abbr_raw'

	elseif parms.wantSc then

		defaultJoin = 'sep_serialcomma'

	end

	local diffOptions = {

		round = parms.round,

		duration = parms.wantDuration,

		range = parms.range and true or nil,

	}

	local sortKey

	if parms.sortable then

		local value = diff.age_days + (parms.wantDuration and 1 or 0)  -- days and fraction of a day

		if diff.isnegative then

			value = -value

		end

		sortKey = makeSort(value, parms.sortable)

	end

	local textOptions = {

		extra = parms.extra,

		format = parms.format,

		join = parms.sep or defaultJoin,

		isnegative = diff.isnegative,

		range = parms.range,

		sortKey = sortKey,

		spell = parms.spell,

		suffix = parms.suffix,  -- not currently used

	}

	if show.id == 'hide' then

		return sortKey or ''

	end

	local values = { diff:age(show.id, diffOptions) }

	if values1 then

		return makeText(values, show, namesabbr], textOptions)

	end

	if diff.partial then

		-- Handle a more complex range such as

		-- {{age_yd|20 Dec 2001|2003|range=yes}} → 1 year, 12 days or 2 years, 11 days

		local opt = {

			format = textOptions.format,

			join = textOptions.join,

			isnegative = textOptions.isnegative,

			spell = textOptions.spell,

		}

		return

			(textOptions.sortKey or '') ..

			makeText({ diff.partial.mindiff:age(show.id, diffOptions) }, show, namesabbr], opt) ..

			rangeJoin(textOptions.range) ..

			makeText({ diff.partial.maxdiff:age(show.id, diffOptions) }, show, namesabbr], opt, true) ..

			(textOptions.suffix or '')

	end

	return message('mt-bad-show', show.id)

end



local function getDates(frame, getopt)

	-- Parse template parameters and return one of:

	-- * date         (a date table, if single)

	-- * date1, date2 (two date tables, if not single)

	-- * text         (a string error message)

	-- A missing date is optionally replaced with the current date.

	-- If wantMixture is true, a missing date component is replaced

	-- from the current date, so can get a bizarre mixture of

	-- specified/current y/m/d as has been done by some "age" templates.

	-- Some results may be placed in table getopt.

	local Date, currentDate = getExports(frame)

	getopt = getopt or {}

	local function flagCurrent(text)

		-- This allows the calling template to detect if the current date has been used,

		-- that is, whether both dates have been entered in a template expecting two.

		-- For example, an infobox may want the age when an event occurred, not the current age.

		-- Don't bother detecting if wantMixture is used because not needed and it is a poor option.

		if not text then

			if getopt.noMissing then

				return nil  -- this gives a nil date which gives an error

			end

			text = 'currentdate'

			if getopt.flag == 'usesCurrent' then

				getopt.usesCurrent = true

			end

		end

		return text

	end

	local args = frame:getParent().args

	local fields = {}

	local isNamed = args.year or args.year1 or args.year2 or

		args.month or args.month1 or args.month2 or

		args.day or args.day1 or args.day2

	if isNamed then

		fields1 = args.year1 or args.year

		fields2 = args.month1 or args.month

		fields3 = args.day1 or args.day

		fields4 = args.year2

		fields5 = args.month2

		fields6 = args.day2

	else

		fields1 = args3

		fields2 = args1

		fields3 = args2

		fields4 = args6

		fields5 = args4

		fields6 = args5

	end

	local imax = 0

	for i = 1, 6 do

		fieldsi = stripToNil(fieldsi])

		if fieldsi then

			imax = i

		end

		if getopt.omitZero and i % 3 ~= 1 then  -- omit zero months and days as unknown values but keep year 0 which is 1 BCE

			if isZero(fieldsi]) then

				fieldsi = nil

				getopt.partial = true

			end

		end

	end

	local fix = getopt.fix and 'fix' or ''

	local partialText = getopt.partial and 'partial' or ''

	local dates = {}

	if isNamed or imax >= 3 then

		local nrDates = getopt.single and 1 or 2

		if getopt.wantMixture then

			-- Cannot be partial since empty fields are set from current.

			local components = { 'year', 'month', 'day' }

			for i = 1, nrDates * 3 do

				fieldsi = fieldsi or currentDatecomponentsi > 3 and i - 3 or i]]

			end

			for i = 1, nrDates do

				local index = i == 1 and 1 or 4

				local y, m, d = fieldsindex], fieldsindex+1], fieldsindex+2

				if (m == 2 or m == '2') and (d == 29 or d == '29') then

					-- Workaround error with following which attempt to use invalid date 2001-02-29.

					-- {{age_ymwd|year1=2001|year2=2004|month2=2|day2=29}}

					-- {{age_ymwd|year1=2001|month1=2|year2=2004|month2=1|day2=29}}

					-- TODO Get rid of wantMixture because even this ugly code does not handle

					-- 'Feb' or 'February' or 'feb' or 'february'.

					if not ((y % 4 == 0 and y % 100 ~= 0) or y % 400 == 0) then

						d = 28

					end

				end

				datesi = Date(y, m, d)

			end

		else

			-- If partial dates are allowed, accept

			--     year only, or

			--     year and month only

			-- Do not accept year and day without a month because that makes no sense

			-- (and because, for example, Date('partial', 2001, nil, 12) sets day = nil, not 12).

			for i = 1, nrDates do

				local index = i == 1 and 1 or 4

				local y, m, d = fieldsindex], fieldsindex+1], fieldsindex+2

				if (getopt.partial and y and (m or not d)) or (y and m and d) then

					datesi = Date(fix, partialText, y, m, d)

				elseif not y and not m and not d then

					datesi = Date(flagCurrent())

				end

			end

		end

	else

		getopt.textdates = true  -- have parsed each date from a single text field

		dates1 = Date(fix, partialText, flagCurrent(fields1]))

		if not getopt.single then

			dates2 = Date(fix, partialText, flagCurrent(fields2]))

		end

	end

	if not dates1 then

		return message(getopt.missing1 or 'mt-need-valid-ymd')

	end

	if getopt.single then

		return dates1

	end

	if not dates2 then

		return message(getopt.missing2 or 'mt-need-valid-ymd2')

	end

	return dates1], dates2

end



local function ageGeneric(frame)

	-- Return the result required by the specified template.

	-- Can use sortable=x where x = on/table/off/debug in any supported template.

	-- Some templates default to sortable=on but can be overridden.

	local name = frame.args.template

	if not name then

		return message('mt-template-x')

	end

	local args = frame:getParent().args

	local specs = {

		age_days = {                -- {{age in days}}

			show = 'd',

			disp = 'disp_raw',

		},

		age_days_nts = {            -- {{age in days nts}}

			show = 'd',

			disp = 'disp_raw',

			format = 'format_commas',

			sortable = 'on',

		},

		duration_days = {           -- {{duration in days}}

			show = 'd',

			disp = 'disp_raw',

			duration = true,

		},

		duration_days_nts = {       -- {{duration in days nts}}

			show = 'd',

			disp = 'disp_raw',

			format = 'format_commas',

			sortable = 'on',

			duration = true,

		},

		age_full_years = {          -- {{age}}

			show = 'y',

			abbr = 'abbr_raw',

			flag = 'usesCurrent',

			omitZero = true,

			range = 'dash',

		},

		age_full_years_nts = {      -- {{age nts}}

			show = 'y',

			abbr = 'abbr_raw',

			format = 'format_commas',

			sortable = 'on',

		},

		age_in_years = {            -- {{age in years}}

			show = 'y',

			abbr = 'abbr_raw',

			negative = 'error',

			range = 'dash',

		},

		age_in_years_nts = {        -- {{age in years nts}}

			show = 'y',

			abbr = 'abbr_raw',

			negative = 'error',

			range = 'dash',

			format = 'format_commas',

			sortable = 'on',

		},

		age_infant = {              -- {{age for infant}}

			-- Do not set show because special processing is done later.

			abbr = yes(args.abbr) and 'abbr_infant' or 'abbr_off',

			disp = 'disp_age',

			sep = 'sep_space',

			sortable = 'on',

		},

		age_m = {                   -- {{age in months}}

			show = 'm',

			disp = 'disp_raw',

		},

		age_w = {                   -- {{age in weeks}}

			show = 'w',

			disp = 'disp_raw',

		},

		age_wd = {                  -- {{age in weeks and days}}

			show = 'wd',

		},

		age_yd = {                  -- {{age in years and days}}

			show = 'yd',

			format = 'format_commas',

			sep = args.sep ~= 'and' and 'sep_comma' or nil,

		},

		age_yd_nts = {              -- {{age in years and days nts}}

			show = 'yd',

			format = 'format_commas',

			sep = args.sep ~= 'and' and 'sep_comma' or nil,

			sortable = 'on',

		},

		age_ym = {                  -- {{age in years and months}}

			show = 'ym',

			sep = 'sep_comma',

		},

		age_ymd = {                 -- {{age in years, months and days}}

			show = 'ymd',

			range = true,

		},

		age_ymwd = {                -- {{age in years, months, weeks and days}}

			show = 'ymwd',

			wantMixture = true,

		},

	}

	local spec = specsname

	if not spec then

		return message('mt-template-bad-name')

	end

	if name == 'age_days' then

		local su = stripToNil(args'show unit'])

		if su then

			if su == 'abbr' or su == 'full' then

				spec.disp = nil

				spec.abbr = su == 'abbr' and 'abbr_on' or nil

			end

		end

	end

	local partial, autofill

	local range = stripToNil(args.range) or spec.range

	if range then

		-- Suppose partial dates are used and age could be 11 or 12 years.

		-- "|range=" (empty value) has no effect (spec is used).

		-- "|range=yes" or spec.range == true sets range = true (gives "11 or 12")

		-- "|range=dash" or spec.range == 'dash' sets range = 'dash' (gives "11–12").

		-- "|range=no" or spec.range == 'no' sets range = nil and fills each date in the diff (gives "12").

		--     ("on" is equivalent to "yes", and "off" is equivalent to "no").

		-- "|range=OTHER" sets range = nil and rejects partial dates.

		range = ({ dash = 'dash', off = 'no', no = 'no', true = true })[range or yes(range)

		if range then

			partial = true  -- accept partial dates with a possible age range for the result

			if range == 'no' then

				autofill = true  -- missing month/day in first or second date are filled from other date or 1

				range = nil

			end

		end

	end

	local getopt = {

		fix = yes(args.fix),

		flag = stripToNil(args.flag) or spec.flag,

		omitZero = spec.omitZero,

		partial = partial,

		wantMixture = spec.wantMixture,

	}

	local date1, date2 = getDates(frame, getopt)

	if type(date1) == 'string' then

		return date1

	end

	local format = stripToNil(args.format)

	local spell = spellOptionsformat

	if format then

		format = 'format_' .. format

	elseif name == 'age_days' and getopt.textdates then

		format = 'format_commas'

	end

	local parms = {

		diff = date2:subtract(date1, { fill = autofill }),

		wantDuration = spec.duration or yes(args.duration),

		range = range,

		wantSc = yes(args.sc),

		show = args.show == 'hide' and 'hide' or spec.show,

		abbr = spec.abbr,

		disp = spec.disp,

		extra = makeExtra(args, getopt.usesCurrent and format ~= 'format_raw'),

		format = format or spec.format,

		round = yes(args.round),

		sep = spec.sep,

		sortable = translateParameters.sortableargs.sortable or spec.sortable],

		spell = spell,

	}

	if (spec.negative or frame.args.negative) == 'error' and parms.diff.isnegative then

		return message('mt-date-wrong-order')

	end

	return from_en(dateDifference(parms))

end



local function isFake(args)

	-- Some templates have TemplateData with an auto value like "{{Birth date and age|YYYY|MM|DD}}".

	-- Return true if that appears to be the case so the caller can output nothing rather than an error.

	return args1 == 'YYYY'

end



local function bda(frame)

	-- Implement [[Template:Birth date and age]].

	local args = frame:getParent().args

	if isFake(args) then

		return ''

	end

	local options = {

		missing1 = 'mt-need-valid-bd',

		noMissing = true,

		single = true,

	}

	local date = getDates(frame, options)

	if type(date) == 'string' then

		return date  -- error text

	end

	local Date = getExports(frame)

	local diff = Date('currentdate') - date

	if diff.isnegative or diff.years > 150 then

		return message('mt-invalid-bd-age')

	end

	local disp = mtext'txt-bda-disp'

	local show = 'y'

	if diff.years < 2 then

		disp = 'disp_age'

		if diff.years == 0 and diff.months == 0 then

			show = 'd'

		else

			show = 'm'

		end

	end

	local result = substituteParameters(

		mtext'txt-bda'],

		date:text('%-Y-%m-%d'),

		from_en(date:text(dateFormat(args))),

		from_en(dateDifference({

			diff = diff,

			show = show,

			abbr = 'abbr_off',

			disp = disp,

			sep = 'sep_space',

		}))

	)

	local warnings = tonumber(frame.args.warnings)

	if warnings and warnings > 0 then

		local good = {

			df = true,

			mf = true,

			day = true,

			day1 = true,

			month = true,

			month1 = true,

			year = true,

			year1 = true,

		}

		local invalid

		local imax = options.textdates and 1 or 3

		for k, _ in pairs(args) do

			if type(k) == 'number' then

				if k > imax then

					invalid = tostring(k)

					break

				end

			else

				if not goodk then

					invalid = k

					break

				end

			end

		end

		if invalid then

			result = result .. message('mt-bad-param1', invalid)

		end

	end

	return result

end



local function dda(frame)

	-- Implement [[Template:Death date and age]].

	local args = frame:getParent().args

	if isFake(args) then

		return ''

	end

	local options = {

		missing1 = 'mt-need-valid-dd',

		missing2 = 'mt-need-valid-bd2',

		noMissing = true,

		partial = true,

	}

	local date1, date2 = getDates(frame, options)

	if type(date1) == 'string' then

		return date1

	end

	local diff = date1 - date2

	if diff.isnegative then

		return message('mt-dd-wrong-order')

	end

	local Date = getExports(frame)

	local today = Date('currentdate') + 1  -- one day in future allows for timezones

	if date1 > today then

		return message('mt-dd-future')

	end

	local years

	if diff.partial then

		years = diff.partial.years

		years = type(years) == 'table' and years2 or years

	else

		years = diff.years

	end

	if years > 150 then

		return message('mt-invalid-dates-age')

	end

	local fmt_date, fmt_ymd

	if date1.day then  -- y, m, d known

		fmt_date = dateFormat(args)

		fmt_ymd = '%-Y-%m-%d'

	elseif date1.month then  -- y, m known; d unknown

		fmt_date = '%B %-Y'

		fmt_ymd = '%-Y-%m-00'

	else  -- y known; m, d unknown

		fmt_date = '%-Y'

		fmt_ymd = '%-Y-00-00'

	end

	local sortKey

	local sortable = translateParameters.sortableargs.sortable

	if sortable then

		local value = (date1.partial and date1.partial.first or date1).jdz

		sortKey = makeSort(value, sortable)

	end

	local result = (sortKey or '') .. substituteParameters(

		mtext'txt-dda'],

		date1:text(fmt_ymd),

		from_en(date1:text(fmt_date)),

		from_en(dateDifference({

			diff = diff,

			show = 'y',

			abbr = 'abbr_off',

			disp = mtext'txt-dda-disp'],

			range = 'dash',

			sep = 'sep_space',

		}))

	)

	local warnings = tonumber(frame.args.warnings)

	if warnings and warnings > 0 then

		local good = {

			df = true,

			mf = true,

		}

		local invalid

		local imax = options.textdates and 2 or 6

		for k, _ in pairs(args) do

			if type(k) == 'number' then

				if k > imax then

					invalid = tostring(k)

					break

				end

			else

				if not goodk then

					invalid = k

					break

				end

			end

		end

		if invalid then

			result = result .. message('mt-bad-param1', invalid)

		end

	end

	return result

end



local function dateToGsd(frame)

	-- Implement [[Template:Gregorian serial date]].

	-- Return Gregorian serial date of the given date, or the current date.

	-- The returned value is negative for dates before 1 January 1 AD

	-- despite the fact that GSD is not defined for such dates.

	local date = getDates(frame, { wantMixture=true, single=true })

	if type(date) == 'string' then

		return date

	end

	return tostring(date.gsd)

end



local function jdToDate(frame)

	-- Return formatted date from a Julian date.

	-- The result includes a time if the input includes a fraction.

	-- The word 'Julian' is accepted for the Julian calendar.

	local Date = getExports(frame)

	local args = frame:getParent().args

	local date = Date('juliandate', args1], args2])

	if date then

		return from_en(date:text())

	end

	return message('mt-need-jdn')

end



local function dateToJd(frame)

	-- Return Julian date (a number) from a date which may include a time,

	-- or the current date ('currentdate') or current date and time ('currentdatetime').

	-- The word 'Julian' is accepted for the Julian calendar.

	local Date = getExports(frame)

	local args = frame:getParent().args

	local date = Date(args1], args2], args3], args4], args5], args6], args7])

	if date then

		return tostring(date.jd)

	end

	return message('mt-need-valid-ymd-current')

end



local function timeInterval(frame)

	-- Implement [[Template:Time interval]].

	-- There are two positional arguments: date1, date2.

	-- The default for each is the current date and time.

	-- Result is date2 - date1 formatted.

	local Date = getExports(frame)

	local args = frame:getParent().args

	local parms = {

		extra = makeExtra(args),

		wantDuration = yes(args.duration),

		range = yes(args.range) or (args.range == 'dash' and 'dash' or nil),

		wantSc = yes(args.sc),

	}

	local fix = yes(args.fix) and 'fix' or ''

	local date1 = Date(fix, 'partial', stripToNil(args1]) or 'currentdatetime')

	if not date1 then

		return message('mt-invalid-start')

	end

	local date2 = Date(fix, 'partial', stripToNil(args2]) or 'currentdatetime')

	if not date2 then

		return message('mt-invalid-end')

	end

	parms.diff = date2 - date1

	for argname, translate in pairs(translateParameters) do

		local parm = stripToNil(argsargname])

		if parm then

			parm = translateparm

			if parm == nil then  -- test for nil because false is a valid setting

				return message('mt-bad-param2', argname, argsargname])

			end

			parmsargname = parm

		end

	end

	if parms.round then

		local round = parms.round

		local show = parms.show

		if round ~= 'on' then

			if show then

				if show.id ~= round then

					return message('mt-conflicting-show', args.show, args.round)

				end

			else

				parms.show = translateParameters.showround

			end

		end

		parms.round = true

	end

	return from_en(dateDifference(parms))

end



return {

	age_generic = ageGeneric,           -- can emulate several age templates

	birth_date_and_age = bda,           -- Template:Birth_date_and_age

	death_date_and_age = dda,           -- Template:Death_date_and_age

	gsd = dateToGsd,                    -- Template:Gregorian_serial_date

	extract = dateExtract,              -- Template:Extract

	jd_to_date = jdToDate,              -- Template:?

	JULIANDAY = dateToJd,               -- Template:JULIANDAY

	time_interval = timeInterval,       -- Template:Time_interval

}