os/lib/modules.nix

{ lib }:
{
  modOverrides = { overrides }:
    { config, overrideModulesPath, ... }:
    let
      inherit (overrides) modules disabledModules;
    in
    {
      disabledModules = modules ++ disabledModules;
      imports = map
        (path: "${overrideModulesPath}/${path}")
        modules;
    };

  hmDefaults = { userSuites, extern, homeModules }: {
    home-manager = {
      useGlobalPkgs = true;
      useUserPackages = true;

      extraSpecialArgs = extern.userSpecialArgs // { suites = userSuites; };
      sharedModules = extern.userModules ++ (builtins.attrValues homeModules);
    };
  };

  globalDefaults = { self, nixos, inputs, multiPkgs }:
    let
      experimentalFeatures = [
        "flakes"
        "nix-command"
        "ca-references"
        "ca-derivations"
      ];
    in
    { config, pkgs, ... }: {
      users.mutableUsers = lib.mkDefault false;

      hardware.enableRedistributableFirmware = lib.mkDefault true;

      nix.nixPath = [
        "nixpkgs=${nixos}"
        "nixos-config=${self}/lib/compat/nixos"
        "home-manager=${inputs.home}"
      ];

      nixpkgs.pkgs = lib.mkDefault multiPkgs.${config.nixpkgs.system};

      nix.registry = {
        devos.flake = self;
        nixos.flake = nixos;
        override.flake = inputs.override;
      };

      nix.package = pkgs.nixFlakes;

      nix.extraOptions = ''
        experimental-features = ${lib.concatStringsSep " "
          experimentalFeatures
        }
      '';

      system.configurationRevision = lib.mkIf (self ? rev) self.rev;
    };

  cachix = { self }:
    let rootCachix = "${self}/cachix.nix"; in
    if builtins.pathExists rootCachix
    then rootCachix
    else { };

  flakeModules = { self, extern }: { imports = builtins.attrValues self.nixosModules ++ extern.modules; };

  isoConfig = { self, nixos, inputs, fullHostConfig }:
    { config, suites, ... }: {

      imports = let modpath = "nixos/modules"; in
        [ "${nixos}/${modpath}/installer/cd-dvd/installation-cd-minimal-new-kernel.nix" ];
      # avoid unwanted systemd service startups
      # all strings in disabledModules get appended to modulesPath
      # so convert each to list which can be coerced to string
      disabledModules = map lib.singleton suites.allProfiles;

      nix.registry = lib.mapAttrs (n: v: { flake = v; }) inputs;

      isoImage.isoBaseName = "nixos-" + config.networking.hostName;
      isoImage.contents = [{
        source = self;
        target = "/devos/";
      }];
      isoImage.storeContents = [
        self.devShell.${config.nixpkgs.system}
        # include also closures that are "switched off" by the
        # above profile filter on the local config attribute
        fullHostConfig.system.build.toplevel
      ];
      # still pull in tools of deactivated profiles
      environment.systemPackages = fullHostConfig.environment.systemPackages;

      # confilcts with networking.wireless which might be slightly
      # more useful on a stick
      networking.networkmanager.enable = lib.mkForce false;
      # confilcts with networking.wireless
      networking.wireless.iwd.enable = lib.mkForce false;

      # Set up a link-local boostrap network
      # See also: https://github.com/NixOS/nixpkgs/issues/75515#issuecomment-571661659
      networking.usePredictableInterfaceNames = lib.mkForce true; # so prefix matching works
      networking.useNetworkd = lib.mkForce true;
      networking.useDHCP = lib.mkForce false;
      networking.dhcpcd.enable = lib.mkForce false;
      systemd.network = {
        # https://www.freedesktop.org/software/systemd/man/systemd.network.html
        networks."boostrap-link-local" = {
          matchConfig = {
            Name = "en* wl* ww*";
          };
          networkConfig = {
            Description = "Link-local host bootstrap network";
            MulticastDNS = true;
            LinkLocalAddressing = "ipv6";
            DHCP = "yes";
          };
          address = [
            # fall back well-known link-local for situations where MulticastDNS is not available
            "fe80::47" # 47: n=14 i=9 x=24; n+i+x
          ];
          extraConfig = ''
            # Unique, yet stable. Based off the MAC address.
            IPv6LinkLocalAddressGenerationMode = "eui64"
          '';
        };
      };
    };

  hmConfig =
    { config, ... }: {
      home-manager.useUserPackages = lib.mkForce false;
      home-manager.sharedModules = [
        {
          home.sessionVariables = {
            inherit (config.environment.sessionVariables) NIX_PATH;
          };
          xdg.configFile."nix/registry.json".text =
            config.environment.etc."nix/registry.json".text;
        }
      ];
    };
}