{ config, lib, pkgs, ... }:

with lib;

let

  cfg = config.services.zigbee2mqtt;

  device = "/dev/ttyACM0";
  dataFolder = "/srv/zigbee/data";
  zigbeeConfiguration = {

    # Home Assistant integration (MQTT discovery)
    homeassistant = false;
    # homeassistant = true;

    # allow new devices to join
    permit_join = cfg.discover;

    # MQTT settings
    mqtt = {
      # MQTT base topic for zigbee2mqtt MQTT messages
      base_topic = "zigbee2mqtt";
      # MQTT server URL
      server = "mqtt://127.0.0.1:1883";
      # MQTT server authentication, uncomment if required:
      user = "zigbee";
      password = cfg.mqttPassword;
    };

    # Serial settings
    serial = {
      port = device;
      # disable LED of CC2531 USB sniffer
      disable_led = true;
    };

    devices = cfg.devices;
  } // (lib.optionalAttrs (cfg.networkKey != null) {
    advanced.network_key = cfg.networkKey;
  });
  configurationYaml =
    pkgs.writeText "configuration.yml" (builtins.toJSON zigbeeConfiguration);

in {

  options.services.zigbee2mqtt = {
    enable = mkEnableOption "enable services.zigbee2mqtt";
    discover = mkEnableOption "discover new devices";
    mqttPassword = mkOption {
      type = with types; str;
      description = ''
        password of the mqtt server.
      '';
    };
    networkKey = mkOption {
      type = with types; nullOr (listOf int);
      description = ''
        you own network key,
        16 numbers between 0 and 255
        see https://www.zigbee2mqtt.io/how_tos/how_to_secure_network.html
      '';
      example = [7 3 5 7 9 11 13 15 0 2 4 6 8 11 12 13];
    };
    devices = mkOption {
      type = with types; attrs;
      description = ''
        device definitions.
      '';
    };
  };

  config = mkIf cfg.enable {

    # todo : einen eigenen container bauen mit dockerTool : https://nixos.wiki/wiki/Docker
    virtualisation.docker.enable = true;

    systemd.services."zigbee2mqtt" = {
      enable = true;
      description =
        "Allows you to use your Zigbee devices without the vendors bridge/gateway.";
      after = [ "docker.service" ];
      requires = [ "docker.service" ];
      # todo : udev rule erstellen, die diesen service erst startet, dieses wanted by ist labil
      wantedBy = [ "home-assistant.service" ];

      preStart = ''
        if [ -f ${dataFolder}/configuration.yaml ]
        then
            rm ${dataFolder}/configuration.yaml
        fi
        mkdir -p ${dataFolder}
        cat ${configurationYaml} | ${pkgs.yq}/bin/yq --yaml-output '.' > ${dataFolder}/configuration.yaml
      '';

      restartTriggers = [ configurationYaml ];

      script = ''
        # delete old instance to ensure update
        ${pkgs.docker}/bin/docker stop zigbee2mqtt || true && ${pkgs.docker}/bin/docker rm -f zigbee2mqtt || true
        # start instance
        ${pkgs.docker}/bin/docker run \
                       --network="host" \
                       --name zigbee2mqtt \
                       -v ${dataFolder}:/app/data \
                       --device=${device} \
                       koenkk/zigbee2mqtt
      '';
    };

  };
}