{
  config,
  pkgs,
  lib,
  ...
}:
let
  textfileDir = "/var/lib/prometheus-node-exporter-textfiles";

  diskUsageCollector = pkgs.writeShellApplication {
    name = "disk-usage-collector";
    runtimeInputs = with pkgs; [
      coreutils
      gawk
      config.boot.zfs.package
      util-linux # for mountpoint
    ];
    text = builtins.readFile ./disk-usage-collector.sh;
  };
in
lib.mkIf config.services.grafana.enable {
  systemd.services.disk-usage-collector = {
    description = "Collect ZFS pool and partition usage metrics for Prometheus";
    serviceConfig = {
      Type = "oneshot";
      ExecStart = lib.getExe diskUsageCollector;
    };
    environment.TEXTFILE = "${textfileDir}/disk-usage.prom";
  };

  systemd.timers.disk-usage-collector = {
    wantedBy = [ "timers.target" ];
    timerConfig = {
      OnCalendar = "minutely";
      RandomizedDelaySec = "10s";
    };
  };
}