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

  # allow new devices to join
  enablePairing = false;

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

  sensors = {
    buttons = {
      "button_1".id = "0x00158d0002b04f65";
      "button_2".id = "0x00158d0002b04f09";
      "button_3".id = "0x00158d0002b00e04";
    };
    temperature = {
      "temperature_sensor_1".id = "0x00158d0002d79220";
      "temperature_sensor_2".id = "0x00158d0002d7913d";
    };
    motion = {
      "motion_sensor_1".id = "0x00158d0002fbd451";
      "motion_sensor_2".id = "0x00158d0002f9a6b8";
      "motion_sensor_3".id = "0x00158d0002f04522";
      "motion_sensor_4".id = "0x00158d0002f9a558";
      "motion_sensor_5".id = "0x00158d0002f9a56f";
      "motion_sensor_6".id = "0x00158d0002f9a5cb";
      "motion_sensor_7".id = "0x00158d0002f9a6aa";
      "motion_sensor_8".id = "0x00158d0002f04637";
    };
    door = {
      "door_sensor_1".id = "0x00158d000312dc52";
      "door_sensor_2".id = "0x00158d000316d5bf";
      "door_sensor_3".id = "0x00158d0002f9516f";
      "door_sensor_4".id = "0x00158d00031383b9";
      "door_sensor_5".id = "0x00158d0003120d3e";
    };
  };

  # todo : generate automatically
  allSensors = with sensors; buttons // temperature // motion // door;

  zigBee2MqttConfig = {

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

    # allow new devices to join
    permit_join = enablePairing;

    # 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 = lib.fileContents <secrets/zigbee/password>;
    };

    # Serial settings
    serial = {
      port = "/dev/ttyACM0";
      # Optional: disable LED of CC2531 USB sniffer
      disable_led = true;
    };

    devices = lib.mapAttrs' (name:
      { id, ... }: {
        name = id;
        value = {
          retain = false;
          friendly_name = name;
        };
      }) allSensors;
  };

  configurationYaml =
    pkgs.writeText "configuration.yml" (builtins.toJSON zigBee2MqttConfig);
in {
  imports = [ ./mqtt.nix ];

  services.homeAssistantConfig = {

    # define sensors
    # --------------
    sensor = let

      # define button sensors
      buttons = with lib;
        mapAttrsToList (name:
          { ... }: [{
            platform = "mqtt";
            name = name;
            icon = "mdi:toggle-switch";
            state_topic = "zigbee2mqtt/${name}";
            availability_topic = "zigbee2mqtt/bridge/state";
            value_template = "{{ value_json.click }}";
          }]) sensors.buttons;

      # define temperature sensors
      temperature = with lib;
        mapAttrsToList (name:
          { ... }: [
            {
              platform = "mqtt";
              name = name;
              state_topic = "zigbee2mqtt/${name}";
              availability_topic = "zigbee2mqtt/bridge/state";
              unit_of_measurement = "°C";
              device_class = "temperature";
              value_template = "{{ value_json.temperature }}";
            }
            {
              platform = "mqtt";
              name = "humidity_${name}";
              state_topic = "zigbee2mqtt/${name}";
              availability_topic = "zigbee2mqtt/bridge/state";
              unit_of_measurement = "%";
              device_class = "humidity";
              value_template = "{{ value_json.humidity }}";
            }
            {
              platform = "mqtt";
              name = "pressure_${name}";
              state_topic = "zigbee2mqtt/${name}";
              availability_topic = "zigbee2mqtt/bridge/state";
              unit_of_measurement = "hPa";
              device_class = "pressure";
              value_template = "{{ value_json.pressure }}";
            }
          ]) sensors.temperature;

      # define meta information sensors
      informations = lib.mapAttrsToList (name:
        { ... }: [
          {
            name = "battery_${name}";
            platform = "mqtt";
            state_topic = "zigbee2mqtt/${name}";
            availability_topic = "zigbee2mqtt/bridge/state";
            unit_of_measurement = "%";
            icon = "mdi:battery-10";
            value_template = "{{ value_json.battery }}";
          }
          {
            name = "link_${name}";
            platform = "mqtt";
            state_topic = "zigbee2mqtt/${name}";
            availability_topic = "zigbee2mqtt/bridge/state";
            icon = "mdi:signal";
            unit_of_measurement = "lqi";
            value_template = "{{ value_json.linkquality }}";
          }
        ]) allSensors;

    in lib.flatten (buttons ++ temperature ++ informations);

    # define binary sensors
    # ---------------------
    binary_sensor = let

      # define motion sensors
      # ---------------------
      motion = lib.mapAttrsToList (name:
        { ... }: {
          name = name;
          platform = "mqtt";
          device_class = "motion";
          state_topic = "zigbee2mqtt/${name}";
          availability_topic = "zigbee2mqtt/bridge/state";
          payload_on = true;
          payload_off = false;
          value_template = "{{ value_json.occupancy }}";
        }) sensors.motion;

      # define door sensors
      # -------------------
      door = lib.mapAttrsToList (name:
        { ... }: {
          name = name;
          platform = "mqtt";
          device_class = "door";
          state_topic = "zigbee2mqtt/${name}";
          availability_topic = "zigbee2mqtt/bridge/state";
          payload_on = false;
          payload_off = true;
          value_template = "{{ value_json.contact}}";
        }) sensors.door;

    in lib.flatten (motion ++ door);

    # create groups
    # -------------
    # to have nice panels for every device
    group = let

      information = name: [ "sensor.battery_${name}" "sensor.link_${name}" ];

      sensorButtons = lib.mapAttrs' (name:
        { ... }: {
          name = name;
          value = {
            control = "hidden";
            entities = [ "sensor.${name}" ] ++ (information name);
          };
        }) (sensors.buttons);

      sensorTemperature = lib.mapAttrs' (name:
        { ... }: {
          name = name;
          value = {
            control = "hidden";
            entities = [
              "sensor.${name}"
              "sensor.humidity_${name}"
              "sensor.pressure_${name}"
            ] ++ (information name);
          };
        }) (sensors.temperature);

      sensorMotions = lib.mapAttrs' (name:
        { ... }: {
          name = name;
          value = {
            control = "hidden";
            entities = [ "binary_sensor.${name}" ] ++ (information name);
          };
        }) (sensors.motion);

      sensorDoors = lib.mapAttrs' (name:
        { ... }: {
          name = name;
          value = {
            control = "hidden";
            entities = [ "binary_sensor.${name}" ] ++ (information name);
          };
        }) (sensors.door);

      views = {
        view_sensors = {
          name = "Sensoren";
          control = "hidden";
          view = true;
          entities =
            lib.mapAttrsToList (name: { ... }: "group.${name}") allSensors;
        };
      };

    in views // sensorButtons // sensorMotions // sensorTemperature
    // sensorDoors // {
      all_sensors.entities =
        (lib.mapAttrsToList (name: { ... }: "sensor.${name}")
          (sensors.buttons // sensors.temperature))
        ++ (lib.mapAttrsToList (name: { ... }: "binary_sensor.${name}")
          (sensors.motion // sensors.door));
    };

    # create automation
    # -----------------
    # todo : this belongs in the home-assistant.nix
    automation = let

      # hold, turn off the lights everywhere
      all_lights_off = map (button: {
        alias = "turn all lights off on holding a button";
        trigger = {
          platform = "mqtt";
          topic = "zigbee2mqtt/${button}";
        };
        condition = {
          condition = "template";
          value_template = ''{{ "hold" == trigger.payload_json.action }}'';
        };
        action = { service = "script.turn_all_off"; };
      }) [ "button_1" "button_2" "button_3" ];

      # one click, turn on the light in the room
      room_lights_on = map ({ button, room }: {
        alias = "turn on lights in ${room}, on ${button} click";
        trigger = {
          platform = "mqtt";
          topic = "zigbee2mqtt/${button}";
        };
        condition = {
          condition = "template";
          value_template = ''{{ "single" == trigger.payload_json.click }}'';
        };
        action = {
          service = "switch.turn_on";
          entity_id = "group.${room}";
        };
      }) [
        {
          button = "button_1";
          room = "living_room";
        }
        {
          button = "button_2";
          room = "bed_room";
        }
        {
          button = "button_3";
          room = "bed_room";
        }
      ];

      # double click, turn off the light in the room
      room_lights_off = map ({ button, room }: {
        alias = "turn on lights in ${room}, on ${button} click";
        trigger = {
          platform = "mqtt";
          topic = "zigbee2mqtt/${button}";
        };
        condition = {
          condition = "template";
          value_template = ''{{ "double" == trigger.payload_json.click }}'';
        };
        action = {
          service = "switch.turn_off";
          entity_id = "group.${room}";
        };
      }) [
        {
          button = "button_1";
          room = "living_room";
        }
        {
          button = "button_2";
          room = "bed_room";
        }
        {
          button = "button_3";
          room = "bed_room";
        }
      ];

      # kitchen light automation
      # ------------------------
      # https://www.home-assistant.io/integrations/binary_sensor.template/
      kitchen_lights = map (motion: [
        {
          alias = "turn on kitchen lights, on motion detected";
          trigger = {
            platform = "state";
            entity_id = "binary_sensor.${motion}";
            from = "off";
            to = "on";
          };
          action = {
            service = "switch.turn_on";
            entity_id = "group.kitchen_room";
          };
        }
        {
          alias = "turn off kitchen lights, on motion clear";
          trigger = {
            platform = "state";
            entity_id = "binary_sensor.${motion}";
            from = "on";
            to = "off";
          };
          action = {
            service = "switch.turn_off";
            entity_id = "group.kitchen_room";
          };
        }
      ]) [ "motion_sensor_1" ];

    in lib.flatten
    (kitchen_lights ++ all_lights_off ++ room_lights_on ++ room_lights_off);

    # click = double => music an aus

    # click = hold => film an aus

  };

  # manage zigbee2mqtt
  # ------------------

  # 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
    '';
  };

}