Module:Vital article

local p = {}

local getLink = function(page)
	local subpage = mw.ustring.upper(mw.ustring.sub(page, 1, 1)) -- get first letter of article name
	local codepoint = mw.ustring.codepoint(page, 1, 1)
	if codepoint<65 or codepoint>90 then --first letter is not between A-Z
		subpage = 'others'
	end
	local data_page = 'Wikipedia:Vital articles/data/' .. subpage .. '.json'
	local data = mw.loadJsonData(data_page)[page]
	if data then
		local level = tostring(data.level)
		if level then
			local trimmed_link = data.trimmed_link
			local link
			if trimmed_link then
				link = 'Wikipedia:Vital articles' .. trimmed_link
			else
				link = 'Wikipedia:Vital articles/Level/' .. level
				if (level=='4' or level=='5') and data.topic then
					link = link .. '/' .. data.topic
				end
				if data.sublist then
					link = link .. '/' .. data.sublist
				end
				--if data.section then -- not used until we have stable section anchors to link to
				--	link = link .. '#' .. data.section
				--end
			end
			return link, level
		end
	end
end

p.link = function(frame)
	local page = frame.args.page~='' and frame.args.page or mw.title.getCurrentTitle().subjectPageTitle.text
	local link, level = getLink(page)
	return '[[' .. page .. ']]' .. (link and '&nbsp;[[File:Círculos Concéntricos.svg|11px]]&nbsp;[[' .. link .. '|' .. level .. ']]' or '')
end

local top = function(container, frame)
	return frame:expandTemplate{title = 'Possibly empty category'}
		.. frame:expandTemplate{title = 'Wikipedia category', args = {container = container}}
		.. frame:expandTemplate{title = 'CatAutoTOC'}
end

p.header = function(frame)
	local cat = frame.args.category~='' and frame.args.category or mw.title.getCurrentTitle().subjectPageTitle.text
	local class, topic = cat:match('^([%a-]+) vital articles in ([%a ]+)$')
	if class and topic then
		class = class:match('(%a+)-Class') or 'Unassessed'
		return top(false, frame)
			.. '[[Category:Wikipedia vital articles in ' .. topic .. ' by class|' .. class .. ']]'
			.. '[[Category:' .. class .. (class=='Unassessed' and '' or '-Class') .. ' vital articles by topic|' .. (topic=='an unknown topic' and 'Unknown' or topic) .. ']]'
	end
	topic = cat:match('^Wikipedia vital articles in ([%a ]+) by class$')
	if topic then
		return top(true, frame)
			.. '[[Category:Wikipedia vital articles in ' .. topic .. '|Class]]'
			..	'[[Category:Wikipedia vital articles by topic by class|' .. topic .. ']]'
	end
	class = cat:match('^([%a-]+) vital articles by topic$')
	if class then
		class = class:match('(%a+)-Class') or 'Unassessed'
		return top(true, frame)
			.. '[[Category:' .. class .. (class=='Unassessed' and '' or '-Class') .. '-Class vital articles|Topic]]'
			.. '[[Category:Wikipedia vital articles by class by topic|' .. class .. ']]'
	end
end

return p
Usage
