{ config, lib, pkgs, ... }:
with lib;
let
  cfg = config.services.telegraf-magic;

  settingsFormat = pkgs.formats.toml {};
  configFile = settingsFormat.generate "config.toml" cfg.extraConfig;
in {
  options = {
    services.telegraf-magic = {
      enable = mkEnableOption (lib.mdDoc "telegraf server");

      package = mkOption {
        default = pkgs.telegraf;
        defaultText = literalExpression "pkgs.telegraf";
        description = lib.mdDoc "Which telegraf derivation to use";
        type = types.package;
      };

      settings = mkOption {
        default = {};
        description = lib.mdDoc "Extra configuration options for telegraf";
        type = settingsFormat.type;
        example = {
          outputs.influxdb = {
            urls = ["http://localhost:8086"];
            database = "telegraf";
          };
          inputs.statsd = {
            service_address = ":8125";
            delete_timings = true;
          };
        };
      };

      systemd = mkOption {
        default = {};
        description = lib.mdDoc "Applied to `systemd.services.telegraf`.";
        type = type.unspecified;
      };
    };
  };

  config = mkIf cfg.enable {
    systemd.services.telegraf = mkMerge [
      {
         description = "Telegraf Agent";
         wantedBy = [ "multi-user.target" ];
         after = [ "network-online.target" ];
         serviceConfig = {
           ExecStart="${cfg.package}/bin/telegraf -config ${configFile}";
           ExecReload="${pkgs.coreutils}/bin/kill -HUP $MAINPID";
           RuntimeDirectory = "telegraf";
           User = "telegraf";
           Group = "telegraf";
           Restart = "on-failure";
           # for ping probes
           AmbientCapabilities = [ "CAP_NET_RAW" ];
         };
       }
      (config.services.telegraf.systemd)
    ];

    users.users.telegraf = {
      uid = config.ids.uids.telegraf;
      group = "telegraf";
      description = "telegraf daemon user";
    };

    users.groups.telegraf = {};
  };
}