-- 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
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 = :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
fields[1] = args.year1 or args.year
fields[2] = args.month1 or args.month
fields[3] = args.day1 or args.day
fields[4] = args.year2
fields[5] = args.month2
fields[6] = args.day2
else
for i = 1, 6 do
fields[i] = args[i]
end
end
local imax = 0
for i = 1, 6 do
fields[i] = stripToNil(fields[i])
if fields[i] 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(fields[i]) then
fields[i] = 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
fields[i] = fields[i] or currentDate[components[i > 3 and i - 3 or i]]
end
for i = 1, nrDates do
local index = i == 1 and 1 or 4
local y, m, d = fields[index], fields[index+1], fields[index+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.
---
---
-- 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
dates[i] = 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 = fields[index], fields[index+1], fields[index+2]
if (getopt.partial and y and (m or not d)) or (y and m and d) then
dates[i] = Date(fix, partialText, y, m, d)
elseif not y and not m and not d then
dates[i] = Date(flagCurrent)
end
end
end
else
getopt.textdates = true -- have parsed each date from a single text field
dates[1] = Date(fix, partialText, flagCurrent(fields[1]))
if not getopt.single then
dates[2] = Date(fix, partialText, flagCurrent(fields[2]))
end
end
if not dates[1] then
return message(getopt.missing1 or 'mt-need-valid-ymd')
end
if getopt.single then
return dates[1]
end
if not dates[2] then
return message(getopt.missing2 or 'mt-need-valid-ymd2')
end
return dates[1], dates[2]
end  
local function ageGeneric
-- 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 = .args.template
if not name then
return message('mt-template-x')
end
local args = :getParent.args
local specs = {
age_days = { --
show = 'd',
disp = 'disp_raw',
},
age_days_nts = { --
show = 'd',
disp = 'disp_raw',
format = 'format_commas',
sortable = 'on',
},
duration_days = { --
show = 'd',
disp = 'disp_raw',
duration = true,
},
duration_days_nts = { --
show = 'd',
disp = 'disp_raw',
format = 'format_commas',
sortable = 'on',
duration = true,
},
age_full_years = { --
show = 'y',
abbr = 'abbr_raw',
flag = 'usesCurrent',
omitZero = true,
range = 'dash',
},
age_full_years_nts = { --
show = 'y',
abbr = 'abbr_raw',
format = 'format_commas',
sortable = 'on',
},
age_in_years = { --
show = 'y',
abbr = 'abbr_raw',
negative = 'error',
range = 'dash',
},
age_in_years_nts = { --
show = 'y',
abbr = 'abbr_raw',
negative = 'error',
range = 'dash',
format = 'format_commas',
sortable = 'on',
},
age_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 = { --
show = 'm',
disp = 'disp_raw',
},
age_w = { --
show = 'w',
disp = 'disp_raw',
},
age_wd = { --
show = 'wd',
},
age_yd = { --
show = 'yd',
format = 'format_commas',
sep = args.sep ~= 'and' and 'sep_comma' or nil,
},
age_yd_nts = { --
show = 'yd',
format = 'format_commas',
sep = args.sep ~= 'and' and 'sep_comma' or nil,
sortable = 'on',
},
age_ym = { --
show = 'ym',
sep = 'sep_comma',
},
age_ymd = { --
show = 'ymd',
range = true,
},
age_ymwd = { --
show = 'ymwd',
wantMixture = true,
},
}
local spec = specs[name]
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(, getopt)
if type(date1) == 'string' then
return date1
end
local format = stripToNil(args.format)
local spell = spellOptions[format]
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.sortable[args.sortable or spec.sortable],
spell = spell,
}
if (spec.negative or .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 "".