{
  inputs,
  pkgs,
  ...
}:
inputs.nixpkgs.lib.extend (
  final: prev:
  let
    lib = prev;
  in
  {
    ensureZfsMounts =
      dirs:
      pkgs.writeShellApplication {
        name = "zfslistmounted";
        runtimeInputs = with pkgs; [
          zfs
          gnugrep
          gawk
          coreutils
        ];

        text = ''
          #!/bin/sh

          TARGETS=$(echo "${lib.strings.concatStringsSep "\n" dirs}" | sort | uniq)
          MOUNTED=$(zfs list -o mountpoint,mounted -H | awk '$2 == "yes" {print $1}' | sort | uniq)
          NUM_MATCHED=$(echo "$MOUNTED" | grep -Ec '${lib.strings.concatStringsSep "\|" dirs}')
          if [[ "$NUM_MATCHED" -eq "${toString (lib.length dirs)}" ]]; then
             exit 0
          fi

          FOUND=$(printf "%s\n%s" "$TARGETS" "$MOUNTED" | sort | uniq -c | awk '$1 == "2" {print $2}' | sort)
          MISSING=$(printf "%s\n%s" "$FOUND" "$TARGETS" | sort | uniq -u | sort)

          echo "FAILURE, missing: $MISSING" 1>&2
          exit 1
        '';
      };

    serviceMountDeps = serviceName: dirs: {
      systemd.services."${serviceName}_mounts" = {
        wants = [ "zfs.target" ];
        before = [ "${serviceName}.service" ];

        serviceConfig = {
          Type = "oneshot";
          RemainAfterExit = true;
          ExecStart = lib.getExe (final.ensureZfsMounts dirs);
        };
      };

      systemd.services.${serviceName} = {
        wants = [ "${serviceName}_mounts.service" ];
        after = [ "${serviceName}_mounts.service" ];
        requires = [ "${serviceName}_mounts.service" ];
      };
    };

    # stolen from: https://stackoverflow.com/a/42398526
    optimizeWithFlags =
      pkg: flags:
      lib.overrideDerivation pkg (
        old:
        let
          newflags = lib.foldl' (acc: x: "${acc} ${x}") "" flags;
          oldflags = if (lib.hasAttr "NIX_CFLAGS_COMPILE" old) then "${old.NIX_CFLAGS_COMPILE}" else "";
        in
        {
          NIX_CFLAGS_COMPILE = "${oldflags} ${newflags}";
          # stdenv = pkgs.clang19Stdenv;
        }
      );

    optimizePackage =
      pkg:
      final.optimizeWithFlags pkg [
        "-O3"
        "-march=znver3"
        "-mtune=znver3"
      ];
  }
)