local p = {}

-- Copy from [[Module:Section link]]
local function normalizeTitle(title)
	title = mw.ustring.gsub(mw.ustring.gsub(title, "'", ""), '"', '')
	title = mw.ustring.gsub(title, "%b<>", "")
	return mw.title.new(title).prefixedText
end

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 page2 = tostring(tonumber(page))==page and tonumber(page) or page --convert to number if page is numerical, otherwise loadJsonData does not work
	local data = mw.loadJsonData(data_page)[page2]
	if data then
		local level = tostring(data.level)
		if level then
			local 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
				link = link .. '#' .. data.section
			end
			return link, level
		end
	end
end

p.link = function(frame)
	local pargs = frame:getParent().args
	local page
	if frame.args.page and frame.args.page~='' then
		page = mw.title.new(frame.args.page)
	else
		page = mw.title.getCurrentTitle()
	end
	page = page.subjectPageTitle.text
	local link, level = getLink(page)
	lcfg = {
		'pv', -- page views
		'edit', -- edit
		't', -- talk
		'h', -- history
	}
	local args = {page = page}
	if pargs.links=='yes' then
		for i, l in ipairs(lcfg) do
			args[i] = l
		end
	end
	local class = pargs.class and (' ' .. frame:expandTemplate{title = 'icon', args = {[1] = pargs.class}}) or ''
	local icon = '<span style="color:#2b1c72">'
		.. frame:expandTemplate{
			title = 'Tooltip',
			args = {
				[1] = '◎',
				[2] = 'Vital article',
				dotted = 'no'
			}
		} .. '</span>'
	return require('Module:PageLinks').main(args)
		.. (link and (icon .. ' [[' .. link .. '|' .. level .. ']]') or '[[File:Escape suspect.svg|11px|Non-vital article]]')
		.. class
end

p.isVital = function(frame)
	local page = frame.args.page~='' and frame.args.page or mw.title.getCurrentTitle().subjectPageTitle.text
	local _, level = getLink(page)
	return level or ''
end

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

p.header = function(frame)
	local pargs = frame:getParent().args
	local cat = pargs.category~='' and pargs.category or mw.title.getCurrentTitle().subjectPageTitle.text
	local topic, class, level
	topic = cat:match('^Vital articles in ([%a ]+) by quality$')
	if topic then -- Category:Vital articles in TOPIC by quality
		return top(true, frame)
			.. '[[Category:Wikipedia vital articles in ' .. topic .. '|Quality]]'
			..	'[[Category:Vital articles by topic and quality|' .. (topic=='an unknown topic' and 'Unknown' or topic) .. ']]'
	end
	class = cat:match('^([%a-]+) vital articles by topic$')
	if class then -- Category:CLASS vital articles by topic
		return top(true, frame)
			.. '[[Category:' .. class .. ' vital articles|Topic]]'
			.. '[[Category:Vital articles by quality by topic|' .. class .. ']]'
	end
	topic = cat:match('^Wikipedia vital articles in ([%a ]+) by level$')
	if topic then -- Category:Wikipedia vital articles in TOPIC by level
		return top(true, frame)
			.. '[[Category:Wikipedia vital articles in ' .. topic .. '|Level]]'
			.. '[[Category:Wikipedia vital articles by topic by level|' .. (topic=='an unknown topic' and 'Unknown' or topic) .. ']]'
	end
	level = cat:match('^Wikipedia level%-(%w+) vital articles by topic$')
	if level then -- Category:Wikipedia level-LEVEL vital articles by topic
		return top(true, frame)
			.. '[[Category:Wikipedia level-' .. level .. ' vital articles|Topic]]'
			.. '[[Category:Wikipedia vital articles by level and topic|' .. level .. ']]'
	end
	class = cat:match('^([%a-]+) vital articles by level$')
	if class then -- Category:CLASS vital articles by level
		return top(true, frame)
			.. '[[Category:' .. class .. ' vital articles|Level]]'
			.. '[[Category:Vital articles by quality and level|' .. class .. ']]'
	end
	level = cat:match('^Level%-(%w+) vital articles by quality$')
	if level then -- Category:Level-LEVEL vital articles by quality
		return top(true, frame)
			.. '[[Category:Wikipedia level-' .. level .. ' vital articles|Quality]]'
			.. '[[Category:Vital articles by level and quality|' .. level .. ']]'
	end
	topic = cat:match('^Wikipedia vital articles in ([%a ]+)$')
	if topic then -- Category:Wikipedia vital articles in TOPIC
		return top(false, frame)
			.. '[[Category:Wikipedia vital articles by topic|' .. (topic=='an unknown topic' and 'Unknown' or topic) .. ']]'
	end
	level = cat:match('^Wikipedia level%-(%w+) vital articles$')
	if level then -- Category:Wikipedia level-LEVEL vital articles
		return top(true, frame)
			.. '[[Category:Wikipedia vital articles by level|' .. level .. ']]'
	end
	class, level = cat:match('^([%a%-]+) level%-(%w+) vital articles$')
	if class and level then -- Category:CLASS level-LEVEL vital articles
		return top(false, frame)
			.. '[[Category:' .. class .. ' vital articles by level|' .. level .. ']]'
			.. '[[Category:Level-' .. string.lower(level) .. ' vital articles by quality|' ..class .. ']]'
	end
	class = cat:match('^([%a-]+) vital articles$')
	if class then -- Category:CLASS vital articles
		class = class:match('(%a+)-Class') or class
		return top(true, frame)
			.. '[[Category:Vital articles by quality|' .. class .. ']]'
	end
	level, topic = cat:match('^Wikipedia level%-(%w+) vital articles in ([%a ]+)$')
	if level and topic then -- Category:Wikipedia level-LEVEL vital articles in TOPIC
		return top(false, frame)
			.. '[[Category:Wikipedia vital articles in ' .. topic .. ' by level|' .. level .. ']]'
			.. '[[Category:Wikipedia level-' .. level .. ' vital articles by topic|' .. (topic=='an unknown topic' and 'Unknown' or topic) .. ']]'
	end
	class, topic = cat:match('^([%a-]+) vital articles in ([%a ]+)$')
	if class and topic then -- Category:CLASS vital articles in TOPIC
		return top(false, frame)
			.. '[[Category:Vital articles in ' .. topic .. ' by quality|' .. class .. ']]'
			.. '[[Category:' .. class .. ' vital articles by topic|' .. (topic=='an unknown topic' and 'Unknown' or topic) .. ']]'
	end
end

return p