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

{
  # Options that affect multiple modules
  options.sbruder = {
    full = lib.mkOption {
      type = lib.types.bool;
      description = ''
        Whether to build the full system. If disabled, the system closure will
        be smaller, but some features will not be available.
      '';
      default = true;
    };
    trusted = (lib.mkEnableOption "the trusted status of this machine (i.e. encrypted root)") // { default = true; };
    gui.enable = lib.mkEnableOption "gui";
  };

  # All modules are imported but non-essential modules are activated by
  # configuration options
  imports = [
    ../pkgs/modules.nix
    ./ausweisapp.nix
    ./authoritative-dns.nix
    ./cups.nix
    ./docker.nix
    ./fancontrol.nix
    ./fonts.nix
    ./games.nix
    ./grub.nix
    ./gui.nix
    ./initrd-ssh.nix
    ./locales.nix
    ./logitech.nix
    ./mailserver
    ./media-mount.nix
    ./media-proxy.nix
    ./mullvad
    ./network-manager.nix
    ./nginx-interactive-index
    ./nginx.nix
    ./nix.nix
    ./office.nix
    ./pipewire.nix
    ./prometheus/node_exporter.nix
    ./pubkeys.nix
    ./qbittorrent
    ./restic
    ./secrets.nix
    ./ssh.nix
    ./static-webserver.nix
    ./syncthing.nix
    ./tmux.nix
    ./tools.nix
    ./udev.nix
    ./unfree.nix
    ./wireguard
  ];

  config = lib.mkMerge [
    {
      # Essential system tools
      environment.systemPackages = with pkgs; [
        git
        git-crypt # used to store secrets in configuration
        git-lfs # not so essential, but required to clone config
        htop
        tmux
        vim
      ];

      # Clean temporary files on boot
      boot.tmp.cleanOnBoot = true;

      # Set zsh as default shell with reasonable default config for all users
      programs.zsh = {
        enable = true;
        loginShellInit = ''
          # do not glob # (conflicts with nix flakes)
          disable -p '#'
        '';
        histSize = 100000;
      };
      users.defaultUserShell = pkgs.zsh;
      environment.etc."zshrc.local".source = "${pkgs.grml-zsh-config}/etc/zsh/zshrc";

      # command-not-found does not work without channels
      programs.command-not-found.enable = false;

      # Hard drive monitoring
      services.smartd.enable = lib.mkDefault true;
      # Network monitoring
      services.vnstat.enable = true;
      environment.etc."vnstat.conf".text = ''
        UseUTC=1
      '';

      # Support for exotic file systems
      boot.supportedFilesystems = lib.optional config.sbruder.full "ntfs";

      # Authentication/Encryption agents
      programs.gnupg.agent.enable = true;
      programs.ssh.startAgent = true;

      # When this is set to true (default), routing everything through a
      # wireguard tunnel does not work.
      networking.firewall.checkReversePath = false;

      # Open ports for quick tests
      networking.firewall = {
        allowedTCPPortRanges = lib.singleton { from = 9990; to = 9999; };
        allowedUDPPortRanges = lib.singleton { from = 9990; to = 9999; };
      };

      # Use nftables by default,
      # but allow it to be easily disabled on by-machine basis.
      networking.nftables.enable = lib.mkDefault true;

      # Globally set Let’s Encrypt requirements
      security.acme = {
        acceptTerms = true;
        defaults = {
          email = "security@sbruder.de";
        };
      };

      system.activationScripts.diff = ''
        [ -L /run/current-system ] && ${config.nix.package}/bin/nix \
            --experimental-features 'nix-command' \
            store \
            diff-closures /run/current-system "$systemConfig"
      '';

      # Allow users to set allow_other for fuse mounts
      programs.fuse.userAllowOther = true;

      i18n.supportedLocales = (options.i18n.supportedLocales.default) ++ (lib.optionals config.sbruder.full [
        "de_DE.UTF-8/UTF-8"
      ]);

      services.resolved = {
        # Set systemd-resolved’s fallback to Quad9 (instead of cloudflare/google)
        fallbackDns = [ "9.9.9.9" "149.112.112.112" "2620:fe::fe" "2620:fe::9" ];
        # Allow resolving single lable hostnames (e.g., hostnames on the local network)
        llmnr = "false";
        # resolved does not automatically append the search domain (for whatever reason)
        extraConfig = ''
          ResolveUnicastSingleLabel=yes
          Cache=no-negative
        '';
      };
    }
    (lib.mkIf config.sbruder.full {
      services.fwupd.enable = true;
    })
    (lib.mkIf (!config.sbruder.full) {
      documentation.enable = lib.mkDefault false;
    })
  ];
}