local aliases = {
	commons = 'commons.wikimedia',
	donate = 'donate.wikimedia',
	foundation = 'foundation.wikimedia',
	incubator = 'incubator.wikimedia',
	meta = 'meta.wikimedia',
	species = 'species.wikimedia',
	wikidata = 'www.wikidata',
	wikifunctions = 'www.wikifunctions',
	wikimania = 'wikimania.wikimedia',
	wikitech = 'wikitech.wikimedia',
}

local function trimArg(arg, i)
	arg = mw.text.trim(arg or '')
	if arg == '' then
		if i then
			error('Parameter ' .. i .. ' is missing. See template documentation')
		end
		return nil
	end
	return mw.ustring.lower(arg)
end

local function getValue(stats, action, map)
	if action == 'depth' then
		-- https://meta.wikimedia.org/wiki/Wikipedia_article_depth
		-- This gives silly results if, for example, the number of articles is small.
		local n = { 'articles', 'edits', 'pages' }
		if map then
			for i, v in ipairs(n) do
				n[i] = map[v]
			end
		end
		for i, v in ipairs(n) do
			n[i] = stats[v] or 0
		end
		local articles, edits, pages = n[1], n[2], n[3]
		if pages == 0 or articles == 0 then
			return 0
		end
		return math.floor((edits/pages) * ((pages - articles)/articles)^2)
	end
	if map then
		action = map[action]
	end
	return stats[action]
end

local function getIfLocal(site, action)
	-- If wanted site is the local site where module is running,
	-- return numberof result for given action, or nil.
	-- This is faster than reading the cached table, and gives the current value.
	local localSite = string.match(mw.site.server, '.*//(.*)%.org$')  -- examples: 'af.wikipedia', 'commons.wikimedia'
	if site == localSite then
		if action == 'activeusers' then
			action = 'activeUsers'
		end
		return getValue(mw.site.stats, action)
	end
end

local function main(frame)
	local metaWords = { active = true, closed = true, languages = true, }
	local args = frame:getParent().args
	local action = trimArg(args[1], 1)  -- activeusers, admins, articles, edits, files, pages, users, depth, active, closed, languages
	if action:sub(1, 8) == 'numberof' then  -- numberofX is an alias for X
		action = trimArg(action:sub(9), 1)
	end
	local wantMeta = metaWords[action]
	local site = trimArg(args[2], 2)
	site = aliases[site] or site
	if not wantMeta and not site:find('.', 1, true) then
		-- site is like "af" or "af.wikipedia" or "af.wikiquote" etc., including "total"
		site = site .. '.wikipedia'
	end
	local wantComma = trimArg(args[3])  -- nil for no commas in output; "N" or anything nonblank inserts commas
	local result
	if wantMeta then
		local data = mw.loadData('Module:NUMBEROF/meta')
		local nrActive = data.nrActive[site]
		local nrClosed = data.nrClosed[site]
		if nrActive or nrClosed then
			-- If either is set, site is valid but there may not be an entry for both active and closed.
			nrActive = nrActive or 0
			nrClosed = nrClosed or 0
			if action == 'active' then
				result = nrActive
			elseif action == 'closed' then
				result = nrClosed
			elseif action == 'languages' then
				result = nrActive + nrClosed
			end
		end
	else
		result = getIfLocal(site, action)
		if not result then
			local data = mw.loadData('Module:NUMBEROF/data')
			local map = data.map
			data = data.data
			result = data[site]
			if result then
				result = getValue(result, action, map)
			end
		end
	end
	if result then
		if wantComma then
			result = mw.language.getContentLanguage():formatNum(result)
		end
		return result  -- number or formatted string
	end
	return -1
end

local function rank(frame)
	-- Rank sites in a specified sister project by their number of articles.
	local args = frame:getParent().args
	local parm = trimArg(args[1], 1)  -- a number like 12 or a site name like "af" (not "af.wikipedia")
	local base = trimArg(args[2]) or 'wikipedia'  -- base of full site name like "wikipedia" or "wikiquote"
	local wantComma = trimArg(args[3])
	local data = mw.loadData('Module:NUMBEROF/' .. (base == 'wikipedia' and 'rank' or 'other'))
	data = data[base]
	if data then
		local result
		parm = tonumber(parm) or parm
		if type(parm) == 'number' then
			result = data.rankByIndex[parm]
		else
			result = data.rankBySite[parm]
			if result and wantComma then
				result = mw.language.getContentLanguage():formatNum(result)
			end
		end
		if result then
			return result  -- number or string
		end
	end
	return -1
end

return {
	main = main,
	rank = rank,
}