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

with lib;

let

  inInitrd = any (fs: fs == "nfs") config.boot.initrd.supportedFilesystems;

  nfsStateDir = "/var/lib/nfs";

  rpcMountpoint = "${nfsStateDir}/rpc_pipefs";

  idmapdConfFile = pkgs.writeText "idmapd.conf" ''
    [General]
    Pipefs-Directory = ${rpcMountpoint}
    ${optionalString (config.networking.domain != null)
      "Domain = ${config.networking.domain}"}

    [Mapping]
    Nobody-User = nobody
    Nobody-Group = nogroup

    [Translation]
    Method = nsswitch
  '';

  nfsConfFile = pkgs.writeText "nfs.conf" cfg.extraConfig;

  cfg = config.services.nfs;

in

{
  ###### interface

  options = {
    services.nfs = {
      extraConfig = mkOption {
        type = types.lines;
        default = "";
        description = ''
          Extra nfs-utils configuration.
        '';
      };
    };
  };

  ###### implementation

  config = mkIf (any (fs: fs == "nfs" || fs == "nfs4") config.boot.supportedFilesystems) {

    services.rpcbind.enable = true;

    system.fsPackages = [ pkgs.nfs-utils ];

    boot.initrd.kernelModules = mkIf inInitrd [ "nfs" ];

    systemd.packages = [ pkgs.nfs-utils ];
    systemd.generator-packages = [ pkgs.nfs-utils ];

    environment.etc = {
      "idmapd.conf".source = idmapdConfFile;
      "nfs.conf".source = nfsConfFile;
    };

    systemd.services.nfs-blkmap =
      { restartTriggers = [ nfsConfFile ];
      };

    systemd.targets.nfs-client =
      { wantedBy = [ "multi-user.target" "remote-fs.target" ];
      };

    systemd.services.nfs-idmapd =
      { restartTriggers = [ idmapdConfFile ];
      };

    systemd.services.nfs-mountd =
      { restartTriggers = [ nfsConfFile ];
        enable = mkDefault false;
      };

    systemd.services.nfs-server =
      { restartTriggers = [ nfsConfFile ];
        enable = mkDefault false;
      };

    systemd.services.auth-rpcgss-module =
      {
        unitConfig.ConditionPathExists = [ "" "/etc/krb5.keytab" ];
      };

    systemd.services.rpc-gssd =
      { restartTriggers = [ nfsConfFile ];
        unitConfig.ConditionPathExists = [ "" "/etc/krb5.keytab" ];
      };

    systemd.services.rpc-statd =
      { restartTriggers = [ nfsConfFile ];

        preStart =
          ''
            mkdir -p /var/lib/nfs/{sm,sm.bak}
          '';
      };

  };
}