Module:Category series navigation/navyear

local p = {}

local greyLinkColor = "#888"

-- Make a piped link to a category, if it exists
-- If it doesn't exist, just display the greyed the link title without linking
function makeCatLink(catname, disp)
	local displaytext
	if (disp ~= "") and (disp ~= nil) then
		-- use 'disp' parameter, but strip any trailing disambiguator
		displaytext = mw.ustring.gsub(disp, "%s+%(.+$", "");
	else
		displaytext = catname
	end
	local fmtlink
	local catPage = mw.title.new( catname, "Category" )
	if (catPage.exists) then
		fmtlink = "[[:Category:" .. catname .. "|" .. displaytext .. "]]"
	else
		fmtlink = '<span style="color:' .. greyLinkColor .. '">' .. displaytext .. "</span>"
	end

	return fmtlink
end

function p.navyear(frame)
	--Expects a PAGENAME of the form "Some sequential 2015 example cat", where 
	--	{{{1}}}=Some sequential
	--	{{{2}}}=2015
	--	{{{3}}}=example cat
	--	{{{4}}}=1758 ('min' year parameter; optional)
	--	{{{5}}}=1800 ('max' year parameter; optional)
	local arg1 = frame.args[1]
	local arg2 = tonumber(frame.args[2])
	local arg3 = frame.args[3]
	local arg4 = tonumber(frame.args[4])
	local arg5 = tonumber(frame.args[5])
	if arg4 == nil then arg4 = -9999 end
	if arg5 == nil then arg5 = 9999 end
	
	local navyear = '{| class="toccolours hlist" style="text-align: center; margin: auto;"\n'..'|\n'
	
	local i = -5
	while i <= 5 do
		local year = arg2 + i
		if i ~= 0 then
			if ((year >= arg4) and (year <= arg5)) then
				navyear = navyear .. '*' .. makeCatLink(arg1 .. ' ' .. year.. ' '.. arg3, year) .. '\n'
			else
				navyear = navyear..'*<span style="visibility:hidden">'..year..'</span>\n'
			end
		else
			navyear = navyear..'*<b>'..arg2..'</b>\n'
		end
		i = i + 1
	end
	return navyear..'|}'
end

return p