nixos/duckdns: init module

{

  config,

  pkgs,

  lib,

  ...

}:

let

  cfg = config.services.duckdns;

  duckdns = pkgs.writeShellScriptBin "duckdns" ''

    DRESPONSE=$(curl -sS --max-time 60 --no-progress-meter -k -K- <<< "url = \"https://www.duckdns.org/update?verbose=true&domains=$DUCKDNS_DOMAINS&token=$DUCKDNS_TOKEN&ip=\"")

    IPV4=$(echo "$DRESPONSE" | awk 'NR==2')

    IPV6=$(echo "$DRESPONSE" | awk 'NR==3')

    RESPONSE=$(echo "$DRESPONSE" | awk 'NR==1')

    IPCHANGE=$(echo "$DRESPONSE" | awk 'NR==4')

    if [[ "$RESPONSE" = "OK" ]] && [[ "$IPCHANGE" = "UPDATED" ]]; then

        if [[ "$IPV4" != "" ]] && [[ "$IPV6" == "" ]]; then

            echo "Your IP was updated at $(date) to IPv4: $IPV4"

        elif [[ "$IPV4" == "" ]] && [[ "$IPV6" != "" ]]; then

            echo "Your IP was updated at $(date) to IPv6: $IPV6"

        else

            echo "Your IP was updated at $(date) to IPv4: $IPV4 & IPv6 to: $IPV6"

        fi

    elif [[ "$RESPONSE" = "OK" ]] && [[ "$IPCHANGE" = "NOCHANGE" ]]; then

        echo "DuckDNS request at $(date) successful. IP(s) unchanged."

    else

        echo -e "Something went wrong, please check your settings\nThe response returned was:\n$DRESPONSE\n"

        exit 1

    fi

  '';

in

{

  options.services.duckdns = {

    enable = lib.mkEnableOption "DuckDNS Dynamic DNS Client";

    tokenFile = lib.mkOption {

      default = null;

      type = lib.types.path;

      description = ''

        The path to a file containing the token

        used to authenticate with DuckDNS.

      '';

    };

    domains = lib.mkOption {

      default = null;

      type = lib.types.nullOr (lib.types.listOf lib.types.str);

      example = [ "examplehost" ];

      description = ''

        The domain(s) to update in DuckDNS

        (without the .duckdns.org suffix)

      '';

    };

    domainsFile = lib.mkOption {

      default = null;

      type = lib.types.nullOr lib.types.path;

      example = lib.literalExpression ''

        pkgs.writeText "duckdns-domains.txt" '''

          examplehost

          examplehost2

          examplehost3

        '''

      '';

      description = ''

        The path to a file containing a

        newline-separated list of DuckDNS

        domain(s) to be updated

        (without the .duckdns.org suffix)

      '';

    };

  };

  config = lib.mkIf cfg.enable {

    assertions = [

      {

        assertion = cfg.domains != null || cfg.domainsFile != null;

        message = "Either services.duckdns.domains or services.duckdns.domainsFile has to be defined";

      }

      {

        assertion = !(cfg.domains != null && cfg.domainsFile != null);

        message = "services.duckdns.domains and services.duckdns.domainsFile can't both be defined at the same time";

      }

      {

        assertion = (cfg.tokenFile != null);

        message = "services.duckdns.tokenFile has to be defined";

      }

    ];

    environment.systemPackages = [ duckdns ];

    systemd.services.duckdns = {

      description = "DuckDNS Dynamic DNS Client";

      after = [ "network.target" ];

      wantedBy = [ "multi-user.target" ];

      startAt = "*:0/5";

      path = [

        pkgs.gnused

        pkgs.systemd

        pkgs.curl

        pkgs.gawk

        duckdns

      ];

      serviceConfig = {

        Type = "simple";

        LoadCredential = [

          "DUCKDNS_TOKEN_FILE:${cfg.tokenFile}"

        ] ++ lib.optionals (cfg.domainsFile != null) [ "DUCKDNS_DOMAINS_FILE:${cfg.domainsFile}" ];

        DynamicUser = true;

      };

      script = ''

        export DUCKDNS_TOKEN=$(systemd-creds cat DUCKDNS_TOKEN_FILE)

        ${lib.optionalString (cfg.domains != null) ''

          export DUCKDNS_DOMAINS='${lib.strings.concatStringsSep "," cfg.domains}'

        ''}

        ${lib.optionalString (cfg.domainsFile != null) ''

          export DUCKDNS_DOMAINS=$(systemd-creds cat DUCKDNS_DOMAINS_FILE | sed -z 's/\n/,/g')

        ''}

        exec ${lib.getExe duckdns}

      '';

    };

  };

  meta.maintainers = with lib.maintainers; [ notthebee ];

}