{ host, rpi4 }:

{ config, pkgs, ... }:
{
  deployment.targetHost = host;
  deployment.hasFastConnection = true;
  nix.nixPath = [ "nixpkgs=${pkgs.path}" ];
  programs.command-not-found.dbPath = "${pkgs.path}/programs.sqlite";
  nixpkgs.system = "aarch64-linux";

  boot.loader.grub.enable = false;
  boot.loader.generic-extlinux-compatible.enable = true;
  boot.kernelParams = ["cma=64M"]; # work around https://github.com/raspberrypi/linux/issues/3208
  boot.kernelPackages = pkgs.linuxPackages_rpi4;
  boot.initrd.includeDefaultModules = false;

  fileSystems = {
    "/" = {
      device = "/dev/disk/by-label/NIXOS_SD";
      fsType = "ext4";
    };
  };

  services.openssh.enable = true;
  services.openssh.passwordAuthentication = false;
  services.openssh.extraConfig =
    ''
    StreamLocalBindUnlink yes
    '';
  programs.mosh.enable = true;

  networking.hostName = host;
  time.timeZone = "Asia/Hong_Kong";

  hardware.enableRedistributableFirmware = true;
  services.hostapd = {
    enable        = true;
    interface     = "wlan0";
    hwMode        = "g";
    ssid          = "M-Labs-ext";
    wpaPassphrase = (import /etc/nixos/secret/wifi_ext_password.nix);
    extraConfig   = ''
      ieee80211d=1
      country_code=HK
      ieee80211n=1
      wmm_enabled=1
      auth_algs=1
      wpa_key_mgmt=WPA-PSK
      rsn_pairwise=CCMP
    '';
  };
  networking.interfaces.eth0 = {
    ipv4.addresses = [{
      address = "192.168.1.30";
      prefixLength = 24;
    }];
    ipv6.addresses = [{
      address = "2001:470:f821:1:dea6:32ff:fe95:2fcf";
      prefixLength = 64;
    }];
    ipv4.routes = [{
      address = "0.0.0.0";
      prefixLength = 0;
      via = "192.168.1.1";
    }];
    ipv6.routes = [{
      address = "::";
      prefixLength = 0;
      via = "fe80::523e:aaff:fe0c:e49d";
    }];
  };
  networking.interfaces.wlan0 = {
    ipv4.addresses = [{
      address = "192.168.13.1";
      prefixLength = 24;
    }];
    ipv6.addresses = [{
      address = "2001:470:f821:3::";
      prefixLength = 64;
    }];
  };
  services.dnsmasq = {
    enable = true;
    servers = ["192.168.1.1#53"];
    extraConfig = ''
      interface=wlan0
      bind-interfaces
      dhcp-range=192.168.13.10,192.168.13.254,24h
      enable-ra
      dhcp-range=::,constructor:wlan0,ra-only
      no-resolv
    '';
  };
  boot.kernel.sysctl."net.ipv4.ip_forward" = 1;
  boot.kernel.sysctl."net.ipv6.conf.all.forwarding" = "1";
  boot.kernel.sysctl."net.ipv6.conf.default.forwarding" = "1";

  users.extraGroups.plugdev = { };
  users.mutableUsers = false;
  users.defaultUserShell = pkgs.fish;
  users.extraUsers = import ./common-users.nix { inherit pkgs; };
  security.sudo.wheelNeedsPassword = false;
  services.udev.extraRules = (import ./extra-udev.nix);

  documentation.enable = false;
  environment.systemPackages = with pkgs; [
    psmisc wget vim git sshfs usbutils lm_sensors file mosh tmux
    imagemagick
  ];
  programs.fish.enable = true;

  networking.firewall.allowedTCPPorts = [ 631 ];
  networking.firewall.interfaces.wlan0.allowedUDPPorts = [ 53 67 ];

  nix.settings.trusted-public-keys = ["nixbld.m-labs.hk-1:5aSRVA5b320xbNvu30tqxVPXpld73bhtOeH6uAjRyHc="];
  nix.settings.substituters = ["https://nixbld.m-labs.hk" "https://cache.nixos.org"];
  nix.settings.trusted-users = ["root" "sb"];

  nix.extraOptions = ''
    experimental-features = nix-command flakes impure-derivations
  '';
}