{
  config,
  lib,
  pkgs,
  ...
}: let
  inherit (lib.modules) mkIf;
  inherit (lib.options) mkEnableOption;

  cfg = config.modules.system.services.grafana;
  port = 4022;
in {
  options.modules.system.services.prometheus.enable = mkEnableOption "Grafana, a graphing service";

  config = mkIf cfg.enable {
    networking.firewall.allowedTCPPorts = [config.services.grafana.settings.server.http_port];

    modules.system.services.database.postgresql.enable = true;

    services.prometheus = {
      enable = true;
      package = pkgs.prometheus;
      inherit port;

      exporters = {
        node = {
          enable = true;
          port = 4023;
          enabledCollectors = ["systemd" "processes"];
        };

        postgres = {
          enable = true;
          port = 4024;
          user = "postgres";
        };
      };
      scrapeConfigs = [
        {
          job_name = "prometheus";
          scrape_interval = "30s";
          static_configs = [{targets = ["localhost:${toString port}"];}];
        }
        {
          job_name = "node";
          scrape_interval = "30s";
          static_configs = [{targets = ["localhost:${toString config.services.prometheus.exporters.node.port}"];}];
        }
        {
          job_name = "postgres";
          scrape_interval = "30s";
          static_configs = [{targets = ["localhost:${toString config.services.prometheus.exporters.postgres.port}"];}];
        }
      ];
    };
  };
}