#!/usr/bin/ruby

# frozen_string_literal: true

require 'yaml'
require 'openssl'
require 'acme-client'
require 'dnsruby'
require 'time'
require 'English'


def read_config(path = 'config.yaml')
  p "Reading config from #{path}"
  YAML.load_file(path)
rescue Psych::SyntaxError => e
  warn "Parsing configfile failed: #{e}"
  raise
rescue Errno::ENOENT => e
  warn "IO failed: #{e}"
  raise
end

def ensure_cert_dir(path = './certs')
  unless File.exist?(path)
    puts 'Certificate directory does not exist. Creating with secure permissions.'
    Dir.mkdir(path, 0o0700)
  end
  File.world_writable?(path) && warn('WARNING! Certificate directory is world writable! This could be a serious security issue!')
  File.world_readable?(path) && warn('WARNING! Certificate directory is world readable! This could be a serious security issue!')
  File.file?(path) && raise('Certificate directory is not a directory but a file. Aborting.')
  File.writable?(path) || raise('Certificate directory is not writable. Aborting.')
end

def read_account_key(path = 'pkey.pem')
  p "Reading account key from #{path}"
  if File.readable?(path)
    p "File #{path} is readable, trying to parse"
    privatekey_string = File.read(path)
    private_key = OpenSSL::PKey::EC.new(privatekey_string)
  elsif File.exist?(path)
    raise("The file #{path} exists but is not readable. Make it readable or specify different path")
  else
    p "File #{path} does not exist, trying to create"
    private_key = OpenSSL::PKey::EC.generate('prime256v1')
    File.write(path, private_key.private_to_pem)
  end
  return private_key
end

def read_cert_key(cert_name)
  folder = "./certs/#{cert_name}/"
  path = "#{folder}/current.key"
  p "cert_name #{cert_name}: Reading cert key from #{path}"
  if File.readable?(path)
    p "cert_name #{cert_name}: File #{path} is readable, trying to parse"
    privatekey_string = File.read(path)
    private_key = OpenSSL::PKey::EC.new(privatekey_string)
  elsif File.exist?(path)
    raise("cert_name #{cert_name}: The file #{path} exists but is not readable. Make it readable or specify different path")
  else
    p "cert_name #{cert_name}: File #{path} does not exist, trying to create"
    private_key = OpenSSL::PKey::EC.generate('prime256v1')
    pkey_file = File.new("#{folder}#{Time.now.to_i}.key", 'w')
    pkey_file.write(private_key.private_to_pem)
    File.symlink(File.basename(pkey_file), "#{File.dirname(pkey_file)}/current.key")
  end
  return private_key
end

def lookup_soa(domain)
  rec = Dnsruby::Recursor.new
  p "Domain #{domain}: Getting SOA records for #{domain}"
  rec.query_no_validation_or_recursion(domain, 'SOA')
rescue StandardError => e
  warn "Domain #{domain}: SOA lookup during deploy failed: #{e}"
  raise
end

def find_apex_domain(domain)
  domain_soa_resp = lookup_soa(domain)
  if domain_soa_resp.answer.empty?
    domain_soa_resp.authority[0].name
  else
    domain_soa_resp.answer[0].name
  end
end

def deploy_dns01_challenge_token(domain, challenge, nameserver, config)
  p "Domain #{domain}: Creating DNS UPDATE packet"

  apex_domain = find_apex_domain(domain)

  update = Dnsruby::Update.new(apex_domain)
  # TODO: delete challenge token record after validation
  update.delete("#{challenge.record_name}.#{domain}", challenge.record_type)
  update.add("#{challenge.record_name}.#{domain}", challenge.record_type, 10, challenge.record_content)

  p "Domain #{domain}: Creating object for contacting nameserver"
  res = Dnsruby::Resolver.new(nameserver)
  res.dnssec = false

  p "Domain #{domain}: Looking up TSIG parameters"
  tsig_name = config.dig('domains', domain, 'tsig_key') || config.dig('defaults', 'domains', 'tsig_key')
  tsig_key = config.dig('tsig_keys', tsig_name, 'key')
  tsig_alg = config.dig('tsig_keys', tsig_name, 'algorithm')

  p "Domain #{domain}: Creating TSIG object"
  tsig = Dnsruby::RR.create(
    {
      name: tsig_name,
      type: 'TSIG',
      key: tsig_key,
      algorithm: tsig_alg,
    }
  )

  p "Domain #{domain}: Signing DNS UPDATE packet with TSIG object"
  tsig.apply(update)

  p "Domain #{domain}: Sending UPDATE to nameserver"
  res.send_message(update)
rescue StandardError => e
  warn "Domain #{domain}: DNS Update failed: #{e}"
  raise
end

def wait_for_challenge_propagation(domain, challenge)
  rec = Dnsruby::Recursor.new
  p "Domain #{domain}: Getting SOA records for #{domain}"
  begin
    domain_soa_resp = rec.query_no_validation_or_recursion(domain, 'SOA')
  rescue StandardError => e
    warn "Domain #{domain}: SOA lookup during propagation wait failed: #{e}"
    raise
  end
  apex_domain = if domain_soa_resp.answer.empty?
                  domain_soa_resp.authority[0].name
                else
                  domain_soa_resp.answer[0].name
                end

  p "Domain #{domain}: Creating recursor object for checking challenge propagation"
  rec = Dnsruby::Recursor.new
  p "Domain #{domain}: Getting NS records for #{apex_domain}"
  begin
    domain_auth_ns = rec.query_no_validation_or_recursion(apex_domain, 'NS')
  rescue StandardError => e
    warn "Domain #{domain}: NS lookup failed: #{e}"
    raise
  end

  p "Domain #{domain}: Checking challenge status on all NS"

  threads = []

  domain_auth_ns.answer.each do |ns|
    threads << Thread.new(ns) do |my_ns|
      nameserver = my_ns.rdata.to_s
      p "Domain #{domain}: Creating resolver object for checking propagation on #{nameserver}"
      res = Dnsruby::Resolver.new(nameserver)
      res.dnssec = false
      res.do_caching = false
      loop do
        p "Domain #{domain}: Querying ACME challenge record"
        result = res.query_no_validation_or_recursion("_acme-challenge.#{domain}", 'TXT')
        propagated = result.answer.any? do |answer|
          answer.rdata[0] == challenge.record_content
        end
        break if propagated

        p "Domain #{domain}: Not yet propagated, still old value, sleeping before checking again"
        sleep(0.5)
      rescue Dnsruby::NXDomain
        p "Domain #{domain}: Not yet propagated, NXdomain, sleeping before checking again"
        sleep(0.5)
        retry
      rescue StandardError => e
        warn "Domain #{domain}: ACME challenge lookup failed: #{e}"
        raise
      end
    end
  end

  threads.each(&:join)
end

def acme_request_with_retries(retries: 5, &block)
  p "Retries: #{retries}"
  block.call(self)
rescue Acme::Client::Error::BadNonce
  raise unless retries.positive?

  p 'Retrying because of invalid nonce.'
  acme_request_with_retries(retries: retries - 1, &block)
end

def wait_for_challenge_validation(challenge, cert_name)
  p 'Requesting validation of challenge'
  acme_request_with_retries { challenge.request_validation }

  while challenge.status == 'pending'
    p "Cert #{cert_name}: Sleeping because challenge validation is pending"
    sleep(0.1)
    p 'Checking again'
    acme_request_with_retries { challenge.reload }
  end
end

def get_cert(order, cert_name, domains, domain_key)
  path = "./certs/#{cert_name}/"
  crt_file = "#{path}/cert.pem"
  p "Cert #{cert_name}: Creating CSR object"
  csr = Acme::Client::CertificateRequest.new(
    private_key: domain_key,
    names: domains,
    subject: { common_name: domains[0] }
  )
  p "Cert #{cert_name}: Finalize cert order"
  acme_request_with_retries { order.reload }
  acme_request_with_retries { order.finalize(csr: csr) }
  while order.status == 'processing'
    p "Cert #{cert_name}: Sleep while order is processing"
    sleep(0.1)
    p "Cert #{cert_name}: Rechecking order status"
    acme_request_with_retries { order.reload }
  end
  # p "order status: #{order.status}"
  # pp order
  cert = acme_request_with_retries { order.certificate }

  p "Cert #{cert_name}: Writing cert"
  cert_file = File.new("#{path}#{Time.now.to_i}.crt", 'w')
  cert_file.write(cert)
  if File.symlink?("#{File.dirname(cert_file)}/current.crt")
    File.unlink("#{File.dirname(cert_file)}/current.crt")
    File.symlink(File.basename(cert_file), "#{File.dirname(cert_file)}/current.crt")
  elsif File.file?("#{File.dirname(cert_file)}/current.crt")
    raise 'Could not place symlink for "current.crt" because that is already a normal file.'
  end
  return cert
end


config = read_config

cert_dir = config.dig('global', 'cert_dir') || './certs/'

ensure_cert_dir(cert_dir)

acme_threads = []
# iterate over configured certs
# TODO: make this one thread per cert
# TODO: check all domains for apex domain, deploy challenges for one apex_domain all at once
config['certs'].each_pair do |cert_name, cert_opts|
  acme_threads << Thread.new(cert_name, cert_opts) do |cert_name, cert_opts|
    ensure_cert_dir(cert_dir + cert_name)

    p "Cert #{cert_name}: Finding CA to use for cert"
    cert_ca = cert_opts['ca'] || config.dig('defaults', 'certs', 'ca')
    cert_ca_name = cert_ca['name']
    cert_ca_account = cert_ca['account']

    p "Cert #{cert_name}: Finding directory URL for CA"
    acme_directory_url = config.dig('CAs', cert_ca_name, 'directory_url')

    p "Cert #{cert_name}: Finding account to use for cert #{cert_name} from CA #{cert_ca_name}"
    account = config.dig('ca_accounts', cert_ca_account)
    email = account['email']

    private_key = read_account_key(account['keyfile'])

    p "Cert #{cert_name}: Creating client object for communication with CA"
    client = Acme::Client.new(private_key: private_key, directory: acme_directory_url)

    acme_request_with_retries { client.new_account(contact: "mailto:#{email}", terms_of_service_agreed: true) }

    p "Cert #{cert_name}: Creating order object for cert #{cert_name}"
    order = acme_request_with_retries { client.new_order(identifiers: cert_opts['domain_names']) }

    p "Cert #{cert_name}: order status"
    p order.status

    if order.status != 'ready'
      p "Cert #{cert_name}: Order is not ready, we need to authorize first"

      # TODO: collect dns modifications per primary NS, update all at once
      p "Cert #{cert_name}: Iterating over required authorizations"
      auths = acme_request_with_retries { order.authorizations }
      auths.each do |auth|
        p "Cert #{cert_name}: Processing authorization for #{auth.domain}"
        p "Cert #{cert_name}: Finding challenge type for #{auth.domain}"
        # p "Cert #{cert_name}: auth is:"
        # pp auth
        if auth.status == 'valid'
          p "Cert #{cert_name}: Authorization for #{auth.domain} is still valid, skipping"
          next
        end

        challenge = auth.dns01
        primary_ns = config.dig('domains', auth.domain, 'primary_ns') || config.dig('defaults', 'domains', 'primary_ns')
        deploy_dns01_challenge_token(auth.domain, challenge, primary_ns, config)
        wait_for_challenge_propagation(auth.domain, challenge)
        wait_for_challenge_validation(challenge, cert_name)
      end
    else
      p "Cert #{cert_name}: Order is ready, we don’t need to authorize"
    end
    domain_key = read_cert_key(cert_name)

    get_cert(order, cert_name, cert_opts['domain_names'], domain_key)
  end
end

acme_threads.each(&:join)