{ config, pkgs, lib, ... }:

with lib;
let
  cfg = config.fudo.backplane.dns;

  dns = import ../../../lib/dns.nix { inherit lib; };

  backup-directory = "/var/lib/fudo/backplane/dns";

  powerdns-home = "/var/lib/powerdns";

  powerdns-conf-dir = "${powerdns-home}/conf.d";

  backplaneOpts = { ... }: {
    options = {
      host = mkOption {
        type = types.str;
        description = "Hostname of the backplane jabber server.";
      };

      role = mkOption {
        type = types.str;
        description = "Backplane XMPP role name for the DNS server.";
        default = "service-dns";
      };

      password-file = mkOption {
        type = types.str;
        description = "File containing XMPP password for backplane role.";
      };

      database = mkOption {
        type = with types; submodule databaseOpts;
        description = "Database settings for backplane server.";
      };
    };
  };

  databaseOpts = { ... }: {
    options = {
      host = mkOption {
        type = types.str;
        description = "Hostname or IP of the PostgreSQL server.";
      };

      database = mkOption {
        type = types.str;
        description = "Database to use for DNS backplane.";
        default = "backplane_dns";
      };

      username = mkOption {
        type = types.str;
        description = "Database user for DNS backplane.";
        default = "backplane_dns";
      };

      password-file = mkOption {
        type = types.str;
        description = "File containing password for database user.";
      };
    };
  };

  lisp-libs = [];

  launchScript = pkgs.writeText "launch-backplane-dns.lisp" ''
    (load (merge-pathnames "quicklisp/setup.lisp" (user-homedir-pathname)))
    (ql:quickload :backplane-dns)
    (backplane-dns:start-listener-with-env)
    (loop (sleep 600))
  '';

in {
  options.fudo.backplane.dns = {
    enable = mkEnableOption "Enable backplane dynamic DNS server.";

    port = mkOption {
      type = types.port;
      description = "Port on which to serve authoritative DNS requests.";
      default = 53;
    };

    listen-addresses = mkOption {
      type = with types; listOf str;
      description = "IP addresses on which to listen for dns requests.";
      default = [ "0.0.0.0" ];
    };

    required-services = mkOption {
      type = with types; listOf str;
      description = "A list of services required before the DNS server can start.";
    };

    user = mkOption {
      type = types.str;
      description = "User as which to run DNS backplane listener service.";
      default = "backplane-dns";
    };

    group = mkOption {
      type = types.str;
      description = "Group as which to run DNS backplane listener service.";
      default = "backplane-dns";
    };

    database = mkOption {
      type = with types; submodule databaseOpts;
      description = "Database settings for the DNS server.";
    };

    backplane = mkOption {
      type = with types; submodule backplaneOpts;
      description = "Backplane Jabber settings for the DNS server.";
    };
  };

  config = mkIf cfg.enable {
    users = {
      users = {
        "${cfg.user}" = {
          isSystemUser = true;
          group = cfg.group;
          createHome = true;
          home = "/var/home/${cfg.user}";
        };
        backplane-powerdns = {
          isSystemUser = true;
        };
      };

      groups = {
        "${cfg.group}" = {
          members = [cfg.user];
        };
        backplane-powerdns = {
          members = [ "backplane-powerdns" ];
        };
      };
    };

    systemd = {
      targets = {
        backplane-dns = {
          description = "Fudo DNS backplane services.";
          wantedBy = [ "multi-user.target" ];
        };
      };

      services = {

        backplane-powerdns = let
          configDir = pkgs.writeTextDir "pdns.conf" ''
            local-address=${lib.concatStringsSep ", " cfg.listen-addresses}
            local-port=${toString cfg.port}
            launch=
            include-dir=${powerdns-conf-dir}/
          '';

          psql-user = config.services.postgresql.superUser;

        in {
          unitConfig.Documentation = "man:pdns_server(1) man:pdns_control(1)";
          description = "Backplane PowerDNS name server";
          requires = [
            "postgresql.service"
            "backplane-dns-config-generator.service"
            "backplane-dns.target"
          ];
          after = [
            "network.target"
            "postgresql.service"
          ];
          wantedBy = [ "multi-user.target" ];

          path = with pkgs; [ postgresql ];

          serviceConfig = {
            Restart="on-failure";
            RestartSec="10";
            StartLimitInterval="0";
            PrivateDevices=true;
            # CapabilityBoundingSet="CAP_CHOWN CAP_NET_BIND_SERVICE CAP_SETGID CAP_SETUID CAP_SYS_CHROOT";
            # NoNewPrivileges=true;
            ExecStartPre = "${pkgs.coreutils}/bin/mkdir -p ${powerdns-home}";
            ExecStart = "${pkgs.powerdns}/bin/pdns_server --setuid=backplane-powerdns --setgid=backplane-powerdns --chroot=${powerdns-home} --socket-dir=/ --daemon=no --guardian=no --disable-syslog --write-pid=no --config-dir=${configDir}";
            ProtectSystem="full";
            # ProtectHome=true;
            RestrictAddressFamilies="AF_UNIX AF_INET AF_INET6";
          };
        };

          backplane-dns-config-generator = {
            description = "Generate postgres configuration for backplane DNS server.";
            requiredBy = [ "backplane-powerdns.service" ];
            requires = cfg.required-services;
            serviceConfig.Type = "oneshot";
            restartIfChanged = true;
            partOf = [ "backplane-dns.target" ];

            # This builds the config in a bash script, to avoid storing the password
            # in the nix store at any point
            script = ''
              if [ ! -d ${powerdns-conf-dir} ]; then
              mkdir ${powerdns-conf-dir}
              fi

              TMPDIR=$(${pkgs.coreutils}/bin/mktemp -d -t pdns-XXXXXXXXXX)
              TMPCONF=$TMPDIR/pdns.local.gpgsql.conf

              if [ ! -f ${cfg.database.password-file} ]; then
              echo "${cfg.database.password-file} does not exist!"
              exit 1
              fi

              touch $TMPCONF
              chown backplane-powerdns:backplane-powerdns $TMPCONF
              chmod go-rwx $TMPCONF
              PASSWORD=$(cat ${cfg.database.password-file})
              echo "launch+=gpgsql" >> $TMPCONF
              echo "gpgsql-host=${cfg.database.host}" >> $TMPCONF
              echo "gpgsql-dbname=${cfg.database.database}" >> $TMPCONF
              echo "gpgsql-user=${cfg.database.username}" >> $TMPCONF
              echo "gpgsql-password=$PASSWORD" >> $TMPCONF
              echo "gpgsql-dnssec=yes" >> $TMPCONF

              mv $TMPCONF ${powerdns-conf-dir}/pdns.local.gpgsql.conf

              rm -rf $TMPDIR

              exit 0
            '';
          };

          backplane-dns = {
            description = "Fudo DNS Backplane Server";
            restartIfChanged = true;

            serviceConfig = {
              ExecStartPre = "${pkgs.lispPackages.quicklisp}/bin/quicklisp init";
              ExecStart = "${pkgs.sbcl}/bin/sbcl --load ${launchScript}";
              Restart = "on-failure";
              PIDFile = "/run/backplane-dns.$USERNAME.pid";
              User = cfg.user;
              Group = cfg.group;
            };

            environment = {
              LD_LIBRARY_PATH = "${pkgs.openssl_1_1.out}/lib";

              FUDO_DNS_BACKPLANE_XMPP_HOSTNAME = cfg.backplane.host;
              FUDO_DNS_BACKPLANE_XMPP_USERNAME = cfg.backplane.role;
              FUDO_DNS_BACKPLANE_XMPP_PASSWORD_FILE = cfg.backplane.password-file;
              FUDO_DNS_BACKPLANE_DATABASE_HOSTNAME = cfg.backplane.database.host;
              FUDO_DNS_BACKPLANE_DATABASE_NAME = cfg.backplane.database.database;
              FUDO_DNS_BACKPLANE_DATABASE_USERNAME = cfg.backplane.database.username;
              FUDO_DNS_BACKPLANE_DATABASE_PASSWORD_FILE = cfg.backplane.database.password-file;

              CL_SOURCE_REGISTRY = lib.concatStringsSep ":" (map (pkg: "${pkg}//")
                (lisp-libs ++ [pkgs.backplane-dns]));
            };

            requires = cfg.required-services;
            partOf = [ "backplane-dns.target" ];
            wantedBy = [ "multi-user.target" ];
          };
      };
    };
  };
}