local p = {}

local getArgs = require('Module:Arguments').getArgs



-- prefix of all World Factbook pages

local factbookPrefix = 'https://www.cia.gov/the-world-factbook/'



--  Format of archive link. Both %d represent the year of the archive

local archiveFormat = ' [https://www.cia.gov/the-world-factbook/about/archives/download/factbook-%d.zip (Archived %d edition.)]'



-- Function to turn a string into a URL fragment appropriate for CIA website

local function parseFragment(s)

	if not s then

		return ''

	end

	s = mw.ustring.lower(s)

	s = mw.ustring.gsub(s,' ','-')

	s = mw.ustring.gsub(s,',','')

	return s

end



-- Function to fill in factbook link:

-- Arguments:

--    args.country: topic of page (optional)

--    args.section: section of page (optional)

-- Returns:

--    link to World Factbook page about country, with section anchor

function p._country(args)

	if not args.country then

		return factbookPrefix

	end

	local result = factbookPrefix..'countries/'..parseFragment(args.country)

	if args.section then

		return result..'/#'..parseFragment(args.section)

	end

	return result

end



-- Function to fill in archive link:

-- Arguments:

--    args.archive: if non-empty, return nil

--    args.year: else if this is non-empty, use it for year

--    args.date: else if this is non-empty, parse it for a year

-- Returns:

--    the link, above, filled in with the year, or nil

function p._archive(args)

	if args.archive then

		return nil

	end

	local year = nil

	if args.year then

		year = tonumber(args.year)

	elseif args.date then

		i, j = mw.ustring.find(args.date,'20%d%d')

		if i and j then

			year = tonumber(mw.ustring.sub(args.date,i,j))

		end

	end

	if not year then

		return year

	end

	if year >= tonumber(os.date('%Y'))-1 then

		return false

	end

	return mw.ustring.format(archiveFormat, year, year)

end



function p.country(frame)

	local args = getArgs(frame)

	return p._country(args)

end



function p.archive(frame)

	local args = getArgs(frame)

	return p._archive(args) or ''

end



return p