Module:FindYDCportal/sandbox explained

--

local p =

-- This table of existing decade portals is the first check of whether a portal-- exists for a given decade.-- If the decade is listed in this table, then a system call is made to verify its existence-- This approach has two advantages:-- 1/ It reduces server load by reducing the number of expensive system calls-- 2/ It avoids creating backlinks to non-existing portals, because a each .exists check-- generates a backlinklocal existingDecadePortals =

-- check for the existence of a portal with the given name-- if it exists, returns the name-- otherwise returns nilfunction doesPortalExist(portalName) local portalPage = mw.title.new(portalName, "Portal") if (portalPage.exists) then return portalName end return nilend

-- check for the existence of a portal with the name of that year-- if it exists, returns the year-- otherwise calls decadeCheck, and returns that result-- otherwise returns nilfunction checkYear(yearParam)--the year portals have all been deleted, so comment out this section if doesPortalExist(yearParam) then return yearParam end---- myDecade = the year, with the last digit stripped -- e.g. "1694" → "1690" -- Note that a decade is written as usul=ally written "YYY0s" local myDecade = mw.ustring.gsub(yearParam, "%d$", "") return checkDecade(myDecade)end

-- check for the existence of a portal with the name of that decade-- if it exists, returns the year-- otherwise calls decadeCheck, and returns that result-- otherwise returns nilfunction checkDecade(decadeParam) local mydecade = decadeParam .. "0s" if (existingDecadePortals[mydecade]

true) then if doesPortalExist(mydecade) then return mydecade end end -- We don't have a portal for the decade, so now try the century.--the century portals have all been deleted, so comment out this section

local myCenturyString = mw.ustring.gsub(decadeParam, "%d$", "") local myCenturyNum = tonumber(myCenturyString) local myCenturyNum = tonumber(myCenturyString) -- increment by one, because we have now conveted e.g. "1870s" to "18" -- but that's the 19th century myCenturyNum = myCenturyNum + 1 -- the century portals have all been deleted, so disable the centeury checking -- return checkCentury(tostring(myCenturyNum))

-- return ""end

-- check for the existence of a portal with the name of that century-- if it exists, returns the century-- otherwise returns an empty stringfunction checkCentury(centuryParam) local myCenturyString = ordinal_numbers(centuryParam) .. " century" if doesPortalExist(myCenturyString) then return myCenturyString end return ""end

-- converts a string number to an string ordinal-- e.g. 21 → 21st-- 17 → 17th-- code copied from https://stackoverflow.com/questions/20694133/how-to-to-add-th-or-rd-to-the-date (license:CC BY-SA 3.0)function ordinal_numbers(n) local ordinal, digit =, string.sub(n, -1) if tonumber(digit) > 0 and tonumber(digit) <= 3 and string.sub(n,-2) ~= 11 and string.sub(n,-2) ~= 12 and string.sub(n,-2) ~= 13 then return n .. ordinal[tonumber(digit)] else return n .. "th" endend

function trim(s) return s:match "^%s*(.-)%s*$"end

function p.findydcportal(frame) -- Expects one parameter -- = a 3- or 4-digit year or deacde -- e.g. 1916 -- 1504 -- 1630s -- 920s local arg1 = frame.args[1] if arg1

nil then return "" end arg1 = trim(arg1) -- strip leading and trailing spaces if (mw.ustring.match(arg1, "^%d%d%d%d?$")) then -- it's a 3- or 4-digit-year return checkYear(arg1) elseif (mw.ustring.match(arg1, "^%d%d%d?0s$")) then -- it's a 3- or 4-digit decade -- so strip the trailing "0s" local decadeArg = mw.ustring.gsub(arg1, "0s$", "") return checkDecade(decadeArg) end -- If we get here, then arg1 was neither a year nor a decade -- This is going to be a helper template, and diagnostics woud be intrusive -- So just return an empty string return ""end

return p