Module:FindYDCportal

A helper module to find the most specific chronology portal which actually exists for a given year or decade. Used to simplify linking to a chronology portal.

October 2019 update

All by-year and by-century portals have been deleted. There are now only 8 decade portals, listed in Category:Decades portals.

So all checking for century and year portals has been disabled.

If any of the decade portals are deleted, then this module should be edited to remove that decade from the table existingDecadePortals

Parameters

Takes one parameter, which must be either a year (e.g. "1879", "1123") or a decade (e.g. "1940s", "730s").

If the parameter is missing, empty, or does not fit the required format, an empty string is returned.

Output

If a portal is found, returns its name without the namespace prefix, e.g.

• for "Portal:1980s" return 1980s
• for "Portal:19th century" return 19th century

If no portal is found, it returns an empty string.

Usage

Year parameter

{{#invoke: FindYDCportal | findydcportal |YYYY}} ... where YYYY is a 3- or 4-digit year

Decade parameter

{{#invoke: FindYDCportal | findydcportal |YYY0s}} ... where YYY0s is a 3- or 4-digit decade

Examples

Years

• {{#invoke: FindYDCportal | findydcportal |2018}} →
• {{#invoke: FindYDCportal | findydcportal |1935}} →
• {{#invoke: FindYDCportal | findydcportal |1857}} →
• {{#invoke: FindYDCportal | findydcportal |736}} →
• {{#invoke: FindYDCportal | findydcportal |1800}} →

Decades

• {{#invoke: FindYDCportal | findydcportal |2000s}} →
• {{#invoke: FindYDCportal | findydcportal |1940s}} →
• {{#invoke: FindYDCportal | findydcportal |560s}} →

Missing parameter

• {{#invoke: FindYDCportal | findydcportal}} →

Empty parameter

• {{#invoke: FindYDCportal | findydcportal | }} →

Invalid parameter

• {{#invoke: FindYDCportal | findydcportal | 1927-related}} →
• {{#invoke: FindYDCportal | findydcportal | Swedish chef}} →

Logic

If the parameter is a year:

1. If the year portal exists, return its name.
   Otherwise try the decade.
2. If the decade portal exists, return its name.
   Otherwise try the century
3. If the century portal exists, return its name.
   Otherwise return an empty string

If the parameter is a decade:

1. If the decade portal exists, return its name.
   Otherwise try the century
2. If the century portal exists, return its name.
   Otherwise return an empty string

See also

• Template:Portal
• Template:Portalbar
• Wikipedia:Portals

---

--[[
   For a given 3- or 4-digit year or decade, find the most specific portal
   which actually exists.
   Takes one parameter, which must be either a year (e.g. "1879", "1123")
   or a decade (e.g. "1940s", "790s").
   If a portal is found, return its name without the namespace prefix
   (e.g. for "Portal:1980s" return "1980s"); otherwise return an empty string.
   If the parameter is missing, empty, or does not fit the required format,
   an empty string is returned"
]]

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 backlink
local existingDecadePortals = {
	["1920s"] = true,
	["1950s"] = true,
	["1960s"] = true,
	["1980s"] = true,
	["1990s"] = true,
	["2010s"] = true
}

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


-- 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 nil
function 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 nil
function 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 string
function 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 = {"st", "nd", "rd"}, 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"
  end
end

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

function p.findydcportal(frame)
	-- Expects one parameter
	-- {{{1}}} = 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