require 'rack'
require './postfix_exporter'
require 'socket'

class Settings
	def initialize environment
		@environment = environment.to_s.to_sym
	end
	attr_reader :environment
	alias :env :environment
	def development?() :development == environment end
	def production?()   :production == environment end
	def test?()               :test == environment end
end

settings = Settings.new ENV['RACK_ENV']
collector = Collector.new settings: settings
collector.start
showqpath = '/var/spool/postfix/public/showq'
prometheus = collector.prometheus
metrics = OpenStruct.new(
	queued: prometheus.gauge( :postfix_queued, docstring: "Queued mails per queue and sender/recipient", labels: %i[queue sender recipient]),
)

def determine_domain str
	case str
	when /@([^.]+\.(?:(?:co|ac)\.)?[^.]+)\.?\z/
		$1
	when /\.([^.]+\.(?:(?:co|ac)\.)?[^.]+)\?.\z/
		"any.#$1"
	when 'MAILER-DAEMON'
		'MAILER-DAEMON'
	else
		'any'
	end
end

run lambda {|env|
	req = Rack::Request.new env
	case req.path
	when "/metrics"
		showq = ''
		UNIXSocket.open showqpath do |s|
			while '' != (r = s.read)
				showq += r
			end
		end
		showq =
			showq.split( "\x00\x00").map do |x|
				y = x.split "\x00"
				y.push ''  if y.length.odd?
				Hash[*y]
			end
		showq.group_by do |e|
			{queue: e['queue_name'], sender: determine_domain( e['sender']), recipient: determine_domain( e['recipient'])}
		end.each do |labels, entries|
			metrics.queued.set entries.length, labels: labels  if labels and labels[:queue]
		end
		[200, {"Content-Type" => "text/plain"}, [Prometheus::Client::Formats::Text.marshal( prometheus)]]
	else
		[404, {"Content-Type" => "text/plain"}, ["Not found\nYou want to try /metrics?\n"]]
	end
}