#!/usr/bin/ruby

require "net/http"

domain = ARGV.first

begin
  connection = Net::HTTP.start(domain, :use_ssl => true)
  certificate = connection.peer_cert

  if Time.now < certificate.not_before
    puts "Certificate #{domain} not valid until #{certificate.not_before}"
  elsif certificate.not_after - Time.now < 14 * 86400
    puts "Certificate #{domain} expires at #{certificate.not_after}"
  else
    subject_alt_name = certificate.extensions.find { |e| e.oid == "subjectAltName" }

    if subject_alt_name.nil?
      puts "Certificate #{domain} has no subjectAltName"
    else
      alt_names = subject_alt_name.value.split(/\s*,\s*/).sort

      ARGV.sort.each do |expected|
        puts "Certificate #{domain} is missing subjectAltName #{expected}" unless alt_names.shift == "DNS:#{expected}"
      end

      alt_names.each do |name|
        puts "Certificate #{domain} has unexpected subjectAltName #{name}"
      end
    end
  end

  connection.finish
rescue StandardError => error
  puts "Error connecting to #{domain}: #{error.message}"
end