{ lib,... }:
let
  disk_free_threshold = "10"; # at least this much free disk percentage
in {
  services.prometheus.rules = [(builtins.toJSON
    {
      groups = [
        { name = "shack-env";
          rules = [
            {
              alert = "RootPartitionFull";
              for = "30m";
              expr = ''(node_filesystem_avail_bytes{alias="wolf.shack",mountpoint="/"} * 100) / node_filesystem_size_bytes{alias="wolf.shack",mountpoint="/"} < ${disk_free_threshold}'';
              labels.severity = "warning";
              annotations.summary = "{{ $labels.alias }} root disk full";
              annotations.url = "http://grafana.shack/d/hb7fSE0Zz/shack-system-dashboard?orgId=1&var-job=node&var-hostname=All&var-node=wolf.shack:9100&var-device=All&var-maxmount=%2F&var-show_hostname=wolf";
              annotations.description = ''The root disk of {{ $labels.alias }} has {{ $value | printf "%.2f" }}% free disk space (Threshold at ${disk_free_threshold}%).A vast number of shackspace services will stop working. CI for deploying new configuration will also seize working. Log in to the system and run `nix-collect-garbage -d` and clean up the shack share folder in `/home/share` .If this does not help you can check `du -hs /var/ | sort -h`, run `docker system prune` or if you are really desperate run `du -hs / | sort -h` and go through the folders recursively until you've found something to delete'';
            }
            {
              alert = "RootPartitionFull";
              for = "30m";
              expr = ''(node_filesystem_avail_bytes{alias="puyak.shack",mountpoint="/"} * 100) / node_filesystem_size_bytes{alias="puyak.shack",mountpoint="/"} < ${disk_free_threshold}'';
              labels.severity = "warning";
              annotations.summary = "{{ $labels.alias }} root disk full";
              annotations.url = "http://grafana.shack/d/hb7fSE0Zz/shack-system-dashboard?orgId=1&var-job=node&var-hostname=All&var-node=wolf.shack:9100&var-device=All&var-maxmount=%2F&var-show_hostname=puyak";
              annotations.description = ''The root disk of {{ $labels.alias }} has {{ $value | printf "%.2f" }}% free disk space (Threshold at ${disk_free_threshold}%).Prometheus will not be able to create new alerts and CI for deploying new configuration will also seize working. Log in to the system and run `nix-collect-garbage -d` and if this does not help you can check `du -hs /var/ | sort -h`, run `docker system prune` or if you are really desperate run `du -hs / | sort -h` and go through the folders recursively until you've found something to delete'';
            }
            {
              alert = "HostDown";
              expr = ''up{alias="wolf.shack"} == 0'';
              for = "5m";
              labels.severity = "page";
              annotations.summary = "Instance {{ $labels.alias }} down for 5 minutes";
              annotations.url = "http://grafana.shack/d/hb7fSE0Zz/shack-system-dashboard?orgId=1&var-job=node&var-hostname=All&var-node=wolf.shack:9100&var-device=All&var-maxmount=%2F&var-show_hostname=wolf";
              annotations.description = ''Host {{ $labels.alias }} went down and has not been reconnected after 5 minutes. This is probably bad news, try to restart the host via naproxen ( http://naproxen.shack:8006 ). Wolf being down means that CI,glados automation, light management and a couple of other services will not work anymore.'';
            }
          ];
        }
      ];
    }
  )];
}