Editing Module:Births and deaths by year for decade

local p = {}
local uc = {births="Births", deaths="Deaths"}

local page_content = {}
local function get_section(frame, page_name, section_name)
	if page_content[page_name] == nil then
		local title = mw.title.new(page_name)
		if title then
			if title.redirectTarget then title = title.redirectTarget end
			page_content[page_name] = title:getContent()
		end
	end
	if page_content[page_name] then
		if mw.ustring.find(page_content[page_name], "=%s*" .. section_name .. "%s*=", 1, false) then
			return frame:preprocess("{{#section-h::" .. page_name .. "|".. section_name .. "}}")
		end
	end
	return ""
end

local function transclude(frame, entry, year, article)
	local s = "'''{{dr|y|y|" .. year .. "|0|{{#ifexpr: " .. year ..
		" <= 100|na|n}}}}''' "
	s = frame:preprocess(s) .. get_section(frame, article, uc[entry])
	s = mw.ustring.gsub(s, '==+[^=]-==+%s*%c*', '')
	return mw.ustring.match(s, '.*%*.*%a.+')
end

function p.main(frame)
	local decade = mw.text.trim(frame.args[1] or frame:getParent().args[1] or '0')
	local result = {}
	local article_list = {}
	local year_list = {}

	if decade:sub(1, 1) == '-' then
		for i = -9, (decade == '-0' and -1 or 0)  do
			table.insert(article_list, frame:expandTemplate {
				title = "Year article",
				args = { decade .. '0', tostring(i) }
			})
			table.insert(year_list, decade .. math.abs(i))
		end
	else
		for i = (decade == '0' and 1 or 0), 9 do
			table.insert(article_list, frame:expandTemplate {
				title = "Year article",
				args = { decade .. '0', tostring(i) }
			})
			table.insert(year_list, decade .. tostring(i))
		end
	end
			
	for i, entry in ipairs({"births", "deaths"}) do
		table.insert(result, '== ' .. uc[entry] .. '==')
		table.insert(result, frame:expandTemplate { title = "transcluding article", args = article_list})

		for i, article in ipairs(article_list) do
			table.insert(result, transclude(frame, entry, year_list[i], article))
		end
	end
	
	return table.concat(result, "\n")
end

return p