{ self, cfg, pkgs, lib, ... }:
let
  createMlatService =
    (name: feedConfig:
      let
        uuidFile = pkgs.writeTextFile {
          name = "${name}-uuid";
          text = "${feedConfig.uuid}";
        };
        options = [
          "--input-type"
          feedConfig.mlat.input.type
          "--no-udp"
          "--input-connect"
          "${feedConfig.mlat.input.host}:${toString feedConfig.mlat.input.port}"
          "--server"
          feedConfig.mlat.server
          "--user"
          feedConfig.username
          "--lat"
          cfg.latitude
          "--lon"
          cfg.longitude
          "--alt"
          (toString cfg.altitude)
          "--uuid-file"
          "${uuidFile}"
        ] ++ (
          if feedConfig.mlat.privacy
          then
            [
              "--privacy"
            ]
          else
            [ ]
        ) ++ (
          map (result: "--result ${result}") feedConfig.mlat.results
        );
      in
      {
        enable = feedConfig.mlat.enable;
        description = "${name} MLAT client.";
        wants = [ "network.target" ];
        after = [ "network.target" ];
        unitConfig = {
          Documentation = "https://github.com/makrsmark/mlat-client/";
        };
        serviceConfig = {
          Type = "simple";
          User = "${name}";
          RuntimeDirectory = "${name}-mlat";
          RuntimeDirectoryMode = "0755";
          ExecStart = "${self.packages.${pkgs.system}.adsbfi-mlat-client}/bin/mlat-client ${lib.concatStringsSep " " options}";
          SyslogIdentifier = "${name}-mlat";
          Restart = "on-failure";
          RestartSec = 30;
          Nice = -1;
        };
        wantedBy = [ "multi-user.target" ];
      }

    );
  createFeedService = (name: feedConfig:
    let
      uuidFile = pkgs.writeTextFile {
        name = "${name}-uuid";
        text = "${feedConfig.uuid}";
      };
      connectors = map
        (
          connector: "--net-connector ${connector}"
        )
        (
          map
            (
              connector: (
                lib.concatStringsSep "," (
                  [
                    connector.primary.host
                    (toString connector.primary.port)
                    connector.protocol
                  ] ++ (
                    if connector.silentFail
                    then
                      [
                        "silent_fail"
                      ]
                    else
                      [ ]
                  ) ++ (
                    if connector.secondary != null
                    then
                      [
                        connector.secondary.host
                        (toString connector.secondary.port)
                      ]
                    else
                      [ ]
                  )
                )
              )
            )
            feedConfig.feed.connectors
        );
      options = [
        "--quiet"
        "--net"
        "--net-only"
        "--write-json"
        "%t/${name}-feed"
        "--net-beast-reduce-interval 0.5"
        "--net-heartbeat 60"
        "--net-ro-size 1280"
        "--net-ro-interval 0.2"
        "--net-ro-port 0"
        "--net-sbs-port 0"
        "--net-bi-port ${toString feedConfig.feed.beastInputPort}"
        "--net-bo-port 0"
        "--net-ri-port 0"
        "--write-json-every 1"
        "--lat"
        cfg.latitude
        "--lon"
        cfg.longitude
        "--max-range 450"
        "--json-location-accuracy 2"
        "--range-outline-hours 24"
        "--uuid-file"
        "${uuidFile}"
      ] ++ connectors;
    in
    {
      enable = feedConfig.feed.enable;
      description = "ADSB.fi feeder.";
      wants = [ "network.target" ];
      after = [ "network.target" ];
      unitConfig = {
        Documentation = "https://github.com/widehopf/readsb/";
        StartLimitIntervalSec = 1;
      };
      serviceConfig = {
        Type = "simple";
        User = "${name}";
        RuntimeDirectory = "${name}-feed";
        RuntimeDirectoryMode = "0755";
        ExecStart = "${self.packages.${pkgs.system}.adsbfi-readsb}/bin/readsb ${lib.concatStringsSep " " options}";
        SyslogIdentifier = "${name}-feed";
        Restart = "on-failure";
        RestartSec = 30;
        StartLimitBurst = 100;
        Nice = -1;
      };
      wantedBy = [ "multi-user.target" ];
    }
  );
in
lib.mkIf cfg.enable {

  assertions = [
    {
      assertion = cfg.dump1090.device.type == "rtlsdr";
      message = "not set up for anything but rtlsdr yet";
    }
    {
      assertion = !(cfg.dump1090.device.type == "rtlsdr" && cfg.dump1090.device.rtlsdr.serial != null && cfg.dump1090.device.rtlsdr.index != null);
      message = "rtlsdr device cannot be selected by both serial and index";
    }
    {
      assertion = !(!cfg.dump978.enable && cfg.skyaware978.enable);
      message = "The skyaware978 service cannot be enabled if the dump978 service is disabled.";
    }
  ];

  boot.blacklistedKernelModules = [
    "dvb_usb_rtl28xxu"
  ];

  services.udev.packages = [
    pkgs.rtl-sdr
  ];

  users.groups.plugdev = { };

  users.groups.dump1090 = { };
  users.users.dump1090 = {
    isSystemUser = true;
    group = "dump1090";
    extraGroups = [ "plugdev" ];
  };

  users.groups.piaware = { };
  users.users.piaware = {
    isSystemUser = true;
    group = "piaware";
  };

  systemd.services."dump1090-fa" =
    let
      rtlsdrOptions =
        if cfg.dump1090.device.type == "rtlsdr"
        then
          (
            if cfg.dump1090.device.rtlsdr.serial != null
            then
              [
                "--device-index"
                cfg.dump1090.device.rtlsdr.serial
              ]
            else
              [ ]
          ) ++
          (
            if cfg.dump1090.device.rtlsdr.index != null
            then
              [
                "--device-index"
                (toString cfg.dump1090.device.rtlsdr.index)
              ]
            else
              [ ]
          ) ++ (
            if cfg.dump1090.device.rtlsdr.enableAgc
            then
              [
                "--enable-agc"
              ]
            else
              [ ]
          ) ++ (
            if cfg.dump1090.device.rtlsdr.frequencyCorrection != null
            then
              [
                "--ppm"
                (toString cfg.dump1090.device.rtlsdr.frequencyCorrection)
              ]
            else
              [ ]
          ) ++ (
            if cfg.dump1090.device.rtlsdr.directSamplingMode != null
            then
              [
                "--direct"
                (toString cfg.dump1090.device.rtlsdr.directSamplingMode)
              ]
            else
              [ ]
          )
        else
          [ ];
      adaptiveDynamicRangeOptions =
        if cfg.dump1090.adaptiveDynamicRange.enable
        then
          [
            "--adaptive-range"
          ] ++
          (
            if cfg.dump1090.adaptiveDynamicRange.target != null
            then
              [ "--adaptive-range-target" (toString cfg.dump1090.adaptiveDynamicRange.target) ]
            else
              [ ]
          ) ++
          (
            if cfg.dump1090.adaptiveDynamicRange.alpha != null
            then
              [ "--adaptive-range-alpha" (toString cfg.dump1090.adaptiveDynamicRange.alpha) ]
            else
              [ ]
          ) ++
          (
            if cfg.dump1090.adaptiveDynamicRange.percentile != null
            then
              [ "--adaptive-range-percentile" (toString cfg.dump1090.adaptiveDynamicRange.percentile) ]
            else
              [ ]
          ) ++
          (
            if cfg.dump1090.adaptiveDynamicRange.changeDelay != null
            then
              [ "--adaptive-range-change-delay" (toString cfg.dump1090.adaptiveDynamicRange.changeDelay) ]
            else
              [ ]
          ) ++
          (
            if cfg.dump1090.adaptiveDynamicRange.scanDelay != null
            then
              [ "--adaptive-range-scan-delay" (toString cfg.dump1090.adaptiveDynamicRange.scanDelay) ]
            else
              [ ]
          ) ++
          (
            if cfg.dump1090.adaptiveDynamicRange.rescanDelay != null
            then
              [ "--adaptive-range-rescan-delay" (toString cfg.dump1090.adaptiveDynamicRange.rescanDelay) ]
            else
              [ ]
          )
        else
          [ ];
      options = [
        "--quiet"
        "--device-type"
        cfg.dump1090.device.type
      ] ++ rtlsdrOptions ++ adaptiveDynamicRangeOptions ++ (
        if cfg.dump1090.device.gain != null
        then
          [
            "--gain"
            (toString cfg.dump1090.device.gain)
          ]
        else
          [ ]
      ) ++ (
        if cfg.dump1090.errorCorrection
        then
          [ "--fix" ]
        else
          [ ]
      ) ++ [
        "--lat"
        cfg.latitude
        "--lon"
        cfg.longitude
      ] ++
      (
        if cfg.dump1090.maxRange != null
        then
          [
            "--max-range"
            (toString cfg.dump1090.maxRange)
          ]
        else
          [ ]
      ) ++ (
        if cfg.dump1090.network.raw.input.enable
        then
          [
            "--net-ri-port"
            (lib.concatStringsSep "," (map toString cfg.dump1090.network.raw.input.ports))
          ]
        else
          [ ]
      ) ++ (
        if cfg.dump1090.network.raw.output.enable
        then
          [
            "--net-ro-port"
            (lib.concatStringsSep "," (map toString cfg.dump1090.network.raw.output.ports))
          ]
        else
          [ ]
      ) ++ (
        if cfg.dump1090.network.raw.output.size != null
        then
          [
            "--net-ro-size"
            (toString cfg.dump1090.network.raw.output.size)
          ]
        else
          [ ]
      ) ++ (
        if cfg.dump1090.network.raw.output.interval != null
        then
          [
            "--net-ro-interval"
            (toString cfg.dump1090.network.raw.output.interval)
          ]
        else
          [ ]
      ) ++
      (
        if cfg.dump1090.network.baseStation.enable
        then
          [
            "--net-sbs-port"
            (lib.concatStringsSep "," (map toString cfg.dump1090.network.baseStation.ports))
          ]
        else
          [ ]
      ) ++
      (
        if cfg.dump1090.network.beast.input.enable
        then
          [
            "--net-bi-port"
            (lib.concatStringsSep "," (map toString cfg.dump1090.network.beast.input.ports))
          ]
        else [ ]
      ) ++
      (
        if cfg.dump1090.network.beast.output.enable
        then
          [
            "--net-bo-port"
            (lib.concatStringsSep "," (map toString cfg.dump1090.network.beast.output.ports))
          ]
        else [ ]
      ) ++ [
        "--json-location-accuracy"
        (toString cfg.dump1090.jsonLocationAccuracy)
        "--write-json"
        "%t/dump1090-fa"
      ] ++ cfg.dump1090.extraOptions;
    in
    {
      enable = cfg.dump1090.enable;
      description = "dump1090 ADS-B receiver (FlightAware customization)";
      wants = [ "network.target" ];
      after = [ "network.target" ];
      unitConfig = {
        Documentation = "https://flightaware.com/adsb/piaware/";
      };
      serviceConfig = {
        Type = "simple";
        User = "dump1090";
        RuntimeDirectory = "dump1090-fa";
        RuntimeDirectoryMode = "0755";
        ExecStart = "${self.packages.${pkgs.system}.dump1090-fa}/bin/dump1090 ${lib.concatStringsSep " " options}";
        SyslogIdentifier = "dump1090-fa";
        Restart = "on-failure";
        RestartSec = 30;
        RestartPreventExitStatus = "64";
        Nice = -5;
      };
      wantedBy = [ "multi-user.target" ];
    };

  users.groups.skyaware = { };
  users.users.skyaware = {
    isSystemUser = true;
    group = "skyaware";
  };

  systemd.services."skyaware978" = {
    enable = cfg.skyaware978.enable;
    description = "skyaware978 ADS-B UAT web display";
    wants = [ "network.target" ];
    after = [ "network.target" "dump978-fa.service" ];
    unitConfig = {
      Documentation = "https://flightaware.com/adsb/piaware/";
    };
    serviceConfig = {
      Type = "simple";
      User = "skyaware";
      RuntimeDirectory = "skyaware978";
      RuntimeDirectoryMode = "0755";
      ExecStart = "${self.packages.${pkgs.system}.dump978-fa}/bin/skyaware978 --lat ${cfg.latitude} --lon ${cfg.longitude} --json-dir %t/skyaware978";
      SyslogIdentifier = "skyaware978";
      Restart = "on-failure";
      RestartSec = 30;
      RestartPreventExitStatus = "64";
    };
    wantedBy = [ "dump978-fa.service" ];
  };

  users.groups.adsbexchange = { };
  users.users.adsbexchange = {
    isSystemUser = true;
    group = "adsbexchange";
  };

  systemd.services."adsbexchange-mlat" =
    let
      uuidFile = pkgs.writeTextFile {
        name = "adsbx-uuid";
        text = "${cfg.adsbexchange.uuid}";
      };
      options = [
        "--input-type"
        cfg.adsbexchange.mlat.input.type
        "--no-udp"
        "--input-connect"
        "${cfg.adsbexchange.mlat.input.host}:${toString cfg.adsbexchange.mlat.input.port}"
        "--server"
        cfg.adsbexchange.mlat.server
        "--user"
        cfg.adsbexchange.username
        "--lat"
        cfg.latitude
        "--lon"
        cfg.longitude
        "--alt"
        (toString cfg.altitude)
        "--uuid-file"
        "${uuidFile}"
      ] ++ (
        if cfg.adsbexchange.mlat.privacy
        then
          [
            "--privacy"
          ]
        else
          [ ]
      ) ++ (
        map (result: "--result ${result}") cfg.adsbexchange.mlat.results
      );
    in
    {
      enable = cfg.adsbexchange.mlat.enable;
      description = "ADS-B Exchange MLAT client.";
      wants = [ "network.target" ];
      after = [ "network.target" ];
      unitConfig = {
        Documentation = "https://github.com/makrsmark/mlat-client/";
      };
      serviceConfig = {
        Type = "simple";
        User = "adsbexchange";
        RuntimeDirectory = "adsbexchange-mlat";
        RuntimeDirectoryMode = "0755";
        ExecStart = "${self.packages.${pkgs.system}.adsbfi-mlat-client}/bin/mlat-client ${lib.concatStringsSep " " options}";
        SyslogIdentifier = "adsbexchange-mlat";
        Restart = "on-failure";
        RestartSec = 30;
        Nice = -1;
      };
      wantedBy = [ "multi-user.target" ];
    };

  systemd.services."adsbexchange-feed" =
    let
      uuidFile = pkgs.writeTextFile {
        name = "adsbx-uuid";
        text = "${cfg.adsbexchange.uuid}";
      };
      options = [
        "--quiet"
        "--net"
        "--net-only"
        "--write-json"
        "%t/adsbexchange-feed"
        "--net-beast-reduce-interval 0.5"
        "--net-connector feed1.adsbexchange.com,30004,beast_reduce_out,feed2.adsbexchange.com,64004"
        "--net-heartbeat 60"
        "--net-ro-size 1280"
        "--net-ro-interval 0.2"
        "--net-ro-port 0"
        "--net-sbs-port 0"
        "--net-bi-port ${toString cfg.adsbexchange.feed.beastInputPort}"
        "--net-bo-port 0"
        "--net-ri-port 0"
        "--write-json-every 1"
        "--lat"
        cfg.latitude
        "--lon"
        cfg.longitude
        "--max-range 450"
        "--json-location-accuracy 2"
        "--range-outline-hours 24"
        "--uuid-file"
        "${uuidFile}"
        "--net-connector 127.0.0.1,30978,uat_in,silent_fail"
        "--net-connector 127.0.0.1,30005,beast_in,silent_fail"
      ];
    in
    {
      enable = cfg.adsbexchange.feed.enable;
      description = "ADS-B Exchange feeder.";
      wants = [ "network.target" ];
      after = [ "network.target" ];
      unitConfig = {
        Documentation = "https://github.com/wiedehopf/readsb/";
        StartLimitIntervalSec = 1;
      };
      serviceConfig = {
        Type = "simple";
        User = "adsbexchange";
        RuntimeDirectory = "adsbexchange-feed";
        RuntimeDirectoryMode = "0755";
        ExecStart = "${self.packages.${pkgs.system}.adsbfi-readsb}/bin/readsb ${lib.concatStringsSep " " options}";
        SyslogIdentifier = "adsbexchange-feed";
        Restart = "on-failure";
        RestartSec = 30;
        StartLimitBurst = 100;
        Nice = -1;
      };
      wantedBy = [ "multi-user.target" ];
    };

  ##
  ## ADSB.fi
  ##

  users.groups.adsbfi = { };
  users.users.adsbfi = {
    isSystemUser = true;
    group = "adsbexchange";
  };

  systemd.services."adsbfi-mlat" =
    let
      uuidFile = pkgs.writeTextFile {
        name = "adsbfi-uuid";
        text = "${cfg.adsbfi.uuid}";
      };
      options = [
        "--input-type"
        cfg.adsbfi.mlat.input.type
        "--no-udp"
        "--input-connect"
        "${cfg.adsbfi.mlat.input.host}:${toString cfg.adsbfi.mlat.input.port}"
        "--server"
        cfg.adsbfi.mlat.server
        "--user"
        cfg.adsbfi.username
        "--lat"
        cfg.latitude
        "--lon"
        cfg.longitude
        "--alt"
        (toString cfg.altitude)
        "--uuid-file"
        "${uuidFile}"
      ] ++ (
        if cfg.adsbfi.mlat.privacy
        then
          [
            "--privacy"
          ]
        else
          [ ]
      ) ++ (
        map (result: "--result ${result}") cfg.adsbfi.mlat.results
      );
    in
    {
      enable = cfg.adsbfi.mlat.enable;
      description = "ADSB.fi MLAT client.";
      wants = [ "network.target" ];
      after = [ "network.target" ];
      unitConfig = {
        Documentation = "https://github.com/makrsmark/mlat-client/";
      };
      serviceConfig = {
        Type = "simple";
        User = "adsbfi";
        RuntimeDirectory = "adsbfi-mlat";
        RuntimeDirectoryMode = "0755";
        ExecStart = "${self.packages.${pkgs.system}.adsbfi-mlat-client}/bin/mlat-client ${lib.concatStringsSep " " options}";
        SyslogIdentifier = "adsbfi-mlat";
        Restart = "on-failure";
        RestartSec = 30;
        Nice = -1;
      };
      wantedBy = [ "multi-user.target" ];
    };

  systemd.services."adsbfi-feed" =
    let
      uuidFile = pkgs.writeTextFile {
        name = "adsbfi-uuid";
        text = "${cfg.adsbfi.uuid}";
      };
      connectors = map
        (
          connector: "--net-connector ${connector}"
        )
        (
          map
            (
              connector: (
                lib.concatStringsSep "," (
                  [
                    connector.primary.host
                    (toString connector.primary.port)
                    connector.protocol
                  ] ++ (
                    if connector.silentFail
                    then
                      [
                        "silent_fail"
                      ]
                    else
                      [ ]
                  ) ++ (
                    if connector.secondary != null
                    then
                      [
                        connector.secondary.host
                        (toString connector.secondary.port)
                      ]
                    else
                      [ ]
                  )
                )
              )
            )
            cfg.adsbfi.feed.connectors
        );
      options = [
        "--quiet"
        "--net"
        "--net-only"
        "--write-json"
        "%t/adsbfi-feed"
        "--net-beast-reduce-interval 0.5"
        "--net-heartbeat 60"
        "--net-ro-size 1280"
        "--net-ro-interval 0.2"
        "--net-ro-port 0"
        "--net-sbs-port 0"
        "--net-bi-port ${toString cfg.adsbfi.feed.beastInputPort}"
        "--net-bo-port 0"
        "--net-ri-port 0"
        "--write-json-every 1"
        "--lat"
        cfg.latitude
        "--lon"
        cfg.longitude
        "--max-range 450"
        "--json-location-accuracy 2"
        "--range-outline-hours 24"
        "--uuid-file"
        "${uuidFile}"
      ] ++ connectors;
    in
    {
      enable = cfg.adsbfi.feed.enable;
      description = "ADSB.fi feeder.";
      wants = [ "network.target" ];
      after = [ "network.target" ];
      unitConfig = {
        Documentation = "https://github.com/widehopf/readsb/";
        StartLimitIntervalSec = 1;
      };
      serviceConfig = {
        Type = "simple";
        User = "adsbfi";
        RuntimeDirectory = "adsbfi-feed";
        RuntimeDirectoryMode = "0755";
        ExecStart = "${self.packages.${pkgs.system}.adsbfi-readsb}/bin/readsb ${lib.concatStringsSep " " options}";
        SyslogIdentifier = "adsbfi-feed";
        Restart = "on-failure";
        RestartSec = 30;
        StartLimitBurst = 100;
        Nice = -1;
      };
      wantedBy = [ "multi-user.target" ];
    };

  ##
  ## theairtraffic.com
  ##

  users.groups.theairtraffic = { };
  users.users.theairtraffic = {
    isSystemUser = true;
    group = "theairtraffic";
  };

  systemd.services."theairtraffic-mlat" = createMlatService "theairtraffic" cfg.theairtraffic;
  systemd.services."theairtraffic-feed" = createFeedService "theairtraffic" cfg.theairtraffic;

  systemd.tmpfiles.rules = [
    "d /var/cache/piaware 0755 piaware piaware - -"
  ];

  systemd.services."piaware" =
    let
      config = pkgs.writeTextFile {
        name = "piaware.conf";
        text = ''
          # https://flightaware.com/adsb/piaware/advanced_configuration
          allow-auto-updates no
          allow-manual-updates no
          allow-mlat ${if cfg.piaware.allowMLAT then "yes" else "no"}
          allow-modeac ${if cfg.piaware.allowModeAC then "yes" else "no"}
          feeder-id ${cfg.piaware.feederId}
        '';
      };
    in
    {
      enable = cfg.piaware.enable;
      description = "FlightAware ADS-B uploader";
      wants = [ "network-online.target" ];
      after = [ "dump1090-fa.service" "network-online.target" "time-sync.target" ];
      unitConfig = {
        Documentation = "https://flightaware.com/adsb/piaware/";
      };
      serviceConfig = {
        Type = "simple";
        User = "piaware";
        RuntimeDirectory = "piaware";
        ExecStart = "${self.packages.${pkgs.system}.piaware}/bin/piaware -p %t/piaware/piaware.pid -plainlog -configfile ${config} -statusfile %t/piaware/status.json";
        ExecReload = "${pkgs.coreutils}/bin/kill -HUP $MAINPID";
        Restart = "on-failure";
        RestartPreventExitStatus = "4 6";
      };
      wantedBy = [ "multi-user.target" ];
      reloadTriggers = [
        "/etc/piaware.conf"
      ];
    };

  services.nginx = {
    enable = true;
    virtualHosts = {
      "_" = {
        root = self.packages.${pkgs.system}.dump1090-fa.html;
        locations = {
          "=/status.json" = {
            alias = "/run/piaware/status.json";
            extraConfig = ''
              add_header Access-Control-Allow-Origin *;
            '';
          };
          "/data/" = {
            alias = "/run/dump1090-fa/";
            extraConfig = ''
              add_header Access-Control-Allow-Origin *;
            '';
          };
          "/data-978/" = {
            root = "/run/skyaware978/";
            extraConfig = ''
              add_header Access-Control-Allow-Origin *;
            '';
          };
        };
      };
    };
  };
}