local p = {}



function make_cat_link(catname, disp)

	local displaytext

	if (disp ~= "") then

		displaytext = disp

	else

		displaytext = catname

	end

	local link = "[[:Category:" .. catname .. "|" .. displaytext .. "]]"

	local fmtlink

	local linktitle = mw.title.new( catname, "Category" )

	if (linktitle.exists) then

		fmtlink = link

	else

		fmtlink = "<span style=\"color:#888\">" .. displaytext .. "</span>"

	end



	return fmtlink

end



function make_cat_link4(catname, disp)

	local link = "{{LinkCatIfExists2|" .. catname

	if (disp ~= "") then

		link = link .. "|" .. disp

	end

	link = link .. "}}"

	return link

end



function make_decade_cat_link(prefix, start, rest, decadenum)

	local decadestart = (prefix * 100) + (decadenum * 10)

	local decadename = decadestart .. "s"

	return make_cat_link(start .. decadename .. rest, decadename)

end



function ordinal_numbers(n)

  local ordinal, digit = {"st", "nd", "rd"}, string.sub(n, -1)

  if tonumber(digit) > 0 and tonumber(digit) <= 3 and mw.ustring.sub(n,-2) ~= 11 and mw.ustring.sub(n,-2) ~= 12 and mw.ustring.sub(n,-2) ~= 13 then

    return n .. ordinaltonumber(digit)]

  else

    return n .. "th"

  end

end



function make_century_name(n)

	local centuryordinal = ordinal_numbers(n)

	return centuryordinal ..  " century"

end



function p.main(frame)

	local pagename

	local nilly

	if (frame.args1 ~= "") then -- a parameter was supplied, so use it as page title

		nilly = "no nil.   value='" .. frame.args1 .. "'"

		if (string.match(frame.args1], "^Category *: *")) then

			pagename = mw.ustring.gsub(frame.args1], "^Category *: *", "");

		else

			pagename = frame.args1

		end

	else -- use the page title

		nilly = "nil"

		pagename = mw.title.getCurrentTitle().text

	end

	if (false) then

		return nilly

	end

	local dddo = mw.ustring.match(pagename, "%d%d*0s")

	if (dddo == nil) then

		return "Error: no 'YYOs' in '" .. pagename .. "'"

	end

	local dd = mw.ustring.match(dddo, "^%d*")

	local yy = (dd - (dd % 100))/ 100

	local startoftitle = mw.ustring.gsub(pagename, dddo .. ".*$", "")

	local restoftitle = mw.ustring.gsub(pagename, "^.*" .. dddo, "")

	local diagnotics = "; pagename\n* " .. pagename .. "\n;dddo\n*" .. dddo .. "\n;dd\n*" .. dd

	diagnotics = diagnotics .. "\n;yy\n*" .. yy .. "\n;startoftitle\n*<code>'" .. startoftitle	.. "'</code>"

	diagnotics = diagnotics .. "\n;restoftitle\n*<code>'" .. restoftitle .. "'</code>"

	local retval

	retval = "{| class=\"toccolours\" style=\"border:1px solid black; padding:5px\"\n|-\n|style=\"text-align:center\"| '''" .. startoftitle

	if (startoftitle == "") then

		retval = retval .. "Decades "

	else

		retval = retval .. " decades "

	end

	retval = retval .. " of the " .. make_century_name(yy+1) .. restoftitle .. "'''\n|-\n| "

	retval = retval .. "<small>''" .. make_decade_cat_link(yy, startoftitle, restoftitle, -1) .. "&nbsp;&bull; " .. "''</small>"

	local i;

	for i = 0, 9 do

		retval = retval .. make_decade_cat_link(yy, startoftitle, restoftitle, i)

		if i < 9 then

			retval = retval .. "&nbsp;&bull; "

		end

	end

	retval = retval .. "<small>''" .. "&nbsp;&bull; " .. make_decade_cat_link(yy, startoftitle, restoftitle, 10) .. "''</small>"

	retval = retval .. "\n|}"

	

	return retval

end



return p