add_lang_to_code_blocks.lua

local langs = {
	cpp = 'C++'
}

local function extract_lang(tag)
	local info_string = tag:as_info_string()
	if info_string == nil or info_string == "" then
		return nil
	end

	local lang = langs[info_string]
	if lang ~= nil then
		return lang
	end

	local first = info_string:sub(1, 1)
	local rest = info_string:sub(2)
	return first:upper() .. rest:lower()
end

return function(event)
	local tag = event:as_start_tag()
	if tag ~= nil then
		local lang = extract_lang(tag)
		if lang ~= nil then
			return {
				Event:html(
					'<figure class="code-wrapper"><figcaption class="code-lang">'
					.. lang
					.. '</figcaption>'
				),
				event
			}
		end
	end

	local tag = event:as_end_tag()
	if tag ~= nil then
		if extract_lang(tag) ~= nil then
			return {
				event,
				Event:html('</figure>')
			}
		end
	end

	return { event }
end

linkify_headers.lua

local target = ""
local last_events = {}

return function(event)
	-- On heading start, initialize last_events and consume input event
	local tag = event:as_start_tag()
	if tag ~= nil and tag:is_heading() then
		table.insert(last_events, event)
		return { }
	end

	-- On heading end, produce linkified header and return all consumed events
	tag = event:as_end_tag()
	if tag ~= nil and tag:is_heading() then
		local link_start = Event:html('<a href="' .. target .. '" class="header-link">')
		local link_end = Event:html('</a>')
		local events = last_events
		table.insert(events, 1, link_start)
		table.insert(events, event)
		table.insert(events, link_end)

		target = ""
		last_events = {}

		return events
	end

	-- If there is `{#target}` in text, extract `#target
	local text = event:as_text()
	if text ~= nil then
		local new_target = text:match('{(#[^"]-)}')
		if new_target ~= nil then
			target = new_target
		end
	end

	-- If we're consuming events, keep doing it
	if #last_events ~= 0 then
		table.insert(last_events, event)
		return { }
	end

	return { event }
end

remove_comments.lua

return function(event)
	local html = event:as_html()
	if html ~= nil
	   and html:find("^%s*<!%-%-[^-].-%-%->%s*$") == 1
	   and html:find("<!%-%- more %-%->") == nil
	then
		return { }
	end

	return { event }
end