{
  me,
  lib,
  pkgs,
  ...
}:

let
  oneWeekInSeconds = 7 * 24 * 60 * 60;

  tailscaleRenewScript = pkgs.writeShellScript "tailscale-cert-renew" ''
    set -euxo pipefail

    check_validity() {
      pem=$1
      ${pkgs.openssl}/bin/openssl x509 \
    -checkend ${toString oneWeekInSeconds} \
    -noout <$pem
    }

    try_renew() {
      ${pkgs.tailscale}/bin/tailscale cert \
    --cert-file certificates/fullchain.pem \
    --key-file certificates/key.pem \
    ${me.tailscale.domain}
    }

    cut_out_certificate_authority() {
      fullchain=$1
      buf=""
      while read LINE; do
    if [[ $LINE == *"BEGIN CERTIFICATE"* ]]; then
      buf=""
    fi
    buf="$buf$LINE"$'\n'
      done < $fullchain
      echo "$buf"
    }

    install_certificates() {
      touch out/renewed
      cp -vp 'certificates/fullchain.pem' out/fullchain.pem
      cp -vp 'certificates/key.pem' out/key.pem
      ln -sf fullchain.pem out/cert.pem
      cat out/key.pem out/fullchain.pem > out/full.pem
      cut_out_certificate_authority out/fullchain.pem > out/chain.pem
      chown 'acme:nginx' out/*
      chmod 640 out/*
    }

    if [[ ! -e 'out/fullchain.pem' ]] || ! check_validity out/fullchain.pem; then
      echo 1>&2 "attempting tailscale certificate renewal..."
      if ! try_renew; then
    echo 1>&2 "renewal failed :("
    exit 1
      fi
      install_certificates
      echo 1>&2 "successfully renewed certificate :)"
    else
      echo 1>&2 "renewal not yet necessary."
    fi
  '';

in
{
  # overwrite default acme behaviour with tailscale
  systemd.services."acme-${me.tailscale.domain}" = {
    after = [ "tailscaled.service" ];
    requires = [ "tailscaled.service" ];
    serviceConfig = {
      ExecStart = lib.mkForce "+${tailscaleRenewScript}";
    };
  };

  # tailnet internal vhost
  services.nginx.virtualHosts.tailnet = {
    forceSSL = true;
    enableACME = true;
    serverName = me.tailscale.domain;
    listenAddresses = [ me.tailscale.ip ];
    # point to the default page, for now!
    locations."/" = {
      alias = "/var/www/html/";
    };
    extraConfig = ''
      access_log /var/log/nginx/tailnet.access.log json_combined;
    '';
  };
}