Module:Age

-- Code to implement 24 years, 7 months. -- This could be extended to handle the many other 24 templates. -- However, calendar functions will be needed in many areas, so this may be -- superseded by some other system, perhaps using functions from the PHP host.

local MINUS = '−' -- Unicode U+2212 MINUS SIGN (UTF-8: e2 88 92)

local function number_name(number, singular, plural, sep) plural = plural or (singular .. 's') sep = sep or ' ' return tostring(number) .. sep .. ((number == 1) and singular or plural) end

local function strip(text) -- If text is a string, return its content with no leading/trailing -- whitespace. Otherwise return nil (a nil argument gives a nil result). if type(text) == 'string' then return text:match("^%s*(.-)%s*$") end end

local function is_leap_year(year) -- Return true if year is a leap year, assuming Gregorian calendar. return (year % 4 == 0 and year % 100 ~= 0) or year % 400 == 0 end

local function days_in_month(year, month) -- Return number of days (1..31) in given month (1..12). local month_days = { 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 } if month == 2 and is_leap_year(year) then return 29 end return month_days[month] end

local Date = { -- A naive date that assumes the Gregorian calendar always applied. year = 0,  -- 1 to 9999 (0 if never set) month = 1, -- 1 to 12 day = 1,   -- 1 to 31 isvalid = false, new = function (self, o)       o = o or {} setmetatable(o, self) self.__index = self return o   end }

function Date:set_current -- Set date from current time (UTC) and return self. local d = os.date('!*t') self.year = d.year self.month = d.month self.day = d.day self.isvalid = true return self end

function Date:set_ymd(y, m, d)   -- Set date from year, month, day (strings or numbers) and return self. -- LATER: If m is a name like "March" or "mar", translate it to a month. y = tonumber(y) m = tonumber(m) d = tonumber(d) if type(y) == 'number' and type(m) == 'number' and type(d) == 'number' then self.year = y       self.month = m        self.day = d        self.isvalid = (1 <= y and y <= 9999 and 1 <= m and m <= 12 and                        1 <= d and d <= days_in_month(y, m)) end return self end

function Date:less_than(rhs) -- Set true if self < rhs. if self.year < rhs.year then return true end if self.year == rhs.year then if self.month < rhs.month then return true end if self.month == rhs.month then return self.day < rhs.day end end return false end

local DateDiff = { -- Simple difference between two dates, assuming Gregorian calendar. isnegative = false, -- true if second date is before first years = 0, months = 0, days = 0, new = function (self, o)       o = o or {} setmetatable(o, self) self.__index = self return o   end }

function DateDiff:set(date1, date2) -- Set difference between the two dates, and return self. -- Difference is negative if the second date is older than the first. local isnegative if date2:less_than(date1) then isnegative = true date1, date2 = date2, date1 else isnegative = false end -- It is known that date1 <= date2. local y1, m1, d1 = date1.year, date1.month, date1.day local y2, m2, d2 = date2.year, date2.month, date2.day local years, months, days = y2 - y1, m2 - m1, d2 - d1   if days < 0 then days = days + days_in_month(y1, m1) months = months - 1 end if months < 0 then months = months + 12 years = years - 1 end self.years, self.months, self.days, self.isnegative = years, months, days, isnegative return self end

function DateDiff:age_ym -- Return text specifying difference in years, months. local sign = self.isnegative and MINUS or '' local mtext = number_name(self.months, 'month') local result if self.years > 0 then local ytext = number_name(self.years, 'year') if self.months == 0 then result = ytext else result = ytext .. ', ' .. mtext end else if self.months == 0 then sign = '' end result = mtext end return sign .. result end

local function error_wikitext(text) -- Return message for display when template parameters are invalid. -- TODO Get opinions on whether the prefix and category are suitable. local prefix = 'Module error:' local cat = '' return ' ' .. prefix .. ' ' .. text .. cat .. ' ' end

local function get_parms(pframe) -- Return date1, date2 from parameters to template. -- If date1 is missing or invalid, the returned date1 is nil. -- If date2 is missing, the returned date2 is the current date. -- If date2 is invalid, the returned date2 is nil. local args = {} -- arguments passed to template for i = 1, 6 do       args[i] = strip(pframe.args[i]) end local date1, date2 if args[1] and args[2] and args[3] then date1 = Date:new:set_ymd(args[1], args[2], args[3]) if not date1.isvalid then date1 = nil end end if args[4] and args[5] and args[6] then date2 = Date:new:set_ymd(args[4], args[5], args[6]) if not date2.isvalid then date2 = nil end else date2 = Date:new:set_current end return date1, date2 end

local function age_ym(frame) local date1, date2 = get_parms(frame:getParent) if date1 then if not date2 then return error_wikitext('Second date should be year, month, day') end local diff = DateDiff:new:set(date1, date2) return diff:age_ym end return error_wikitext('Need date: year, month, day') end

return { age_ym = age_ym }