local p = {}
function p.main(frame)
	local args = frame:getParent().args
	if args.nocat == "1" or args.nocat == "yes" then
		return ""
	end
	return p._main(frame.args[1])
end
function p._main(title)
	title = mw.text.unstripNoWiki(title)
	-- Decode HTML entities unless the title itself is demonstrating one
	if title:sub(1, 1) ~= "&" then
		title = mw.text.decode(title)
	end
	title = title:gsub("'","")
	-- Add a trailing "a" to distinguish empty from no fragment
	local titleObj = mw.title.new(title.."a")
	if not titleObj or title == "/." then
		if title:find("%[") or title:find("%]") or title:find("<") or title:find(">") or title:find("{") or title:find("}") then
			return "[[Category:Restricted titles (brackets)]]"
		elseif title:find("|") then
			return "[[Category:Restricted titles (vertical bar)]]"
		else
			return "[[Category:Restricted titles (other)]]"
		end
	elseif #titleObj.fragment > 0 then
		if #titleObj.text > 0 then
			return "[[Category:Restricted titles (non-leading number sign)]]"
		else
			return "[[Category:Restricted titles (leading number sign)]]"
		end
	elseif #titleObj.interwiki > 0 then
		return "[[Category:Restricted titles (interwiki prefix)]]"
	elseif not titleObj.isContentPage then
		return "[[Category:Restricted titles (namespace)]]"
	else
		return "[[Category:Pages using technically valid titles in correct title hatnotes]]"
	end
end
return p