nixos/modules/nix-conf.nix

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

let
  builderHosts = lib.filterAttrs (_n: v: (builtins.hasAttr "builder" v) && v.builder) metadata.hosts;
  cfg = config.greg.nix;
in
{
  options.greg.nix = {
    cache = lib.mkOption {
      type = lib.types.bool;
      default = true;
    };
  };

  config = {
    programs.ssh.extraConfig = builtins.concatStringsSep "\n" (
      lib.map (x: ''
        Host ${x}-builder
          Hostname ${x}.shire-zebra.ts.net
          User remote-builder-user
      '') (lib.attrNames builderHosts)
    );

    nix = {
      buildMachines = lib.mapAttrsToList (k: v: {
        inherit (v) systems;
        hostName = "${k}-builder";
        protocol = "ssh-ng";
      }) builderHosts;
      distributedBuilds = true;
      gc = {
        automatic = true;
        # Scheduling of them is different in nixos vs nix-darwin, so check for
        # the extra details there
        options = "--delete-older-than 30d";
      };

      package = pkgs.nixVersions.stable;

      settings = {
        cores = 0; # Use all cores for builds
        download-buffer-size = 500 * 1024 * 1024;
        experimental-features = "nix-command flakes";
        keep-outputs = true;
        keep-derivations = true;
        min-free = (toString (1024 * 1024 * 1024));
        max-free = (toString (5 * 1024 * 1024 * 1024));
        trusted-users = [
          "greg"
          "gregory.hellings"
        ]; # For home and for work machines
        substituters =
          (lib.optionals cfg.cache [
            "http://chronicles.shire-zebra.ts.net:9000/binary-cache/"
            "http://nas1.shire-zebra.ts.net:8080/default"
          ])
          ++ [
            "https://ai.cachix.org"
            "https://nixpkgs-python.cachix.org"
            "https://greg-hellings.cachix.org"
            "https://nix-community.cachix.org"
            "https://cache.nixos.org"
            "https://nixhelm.cachix.org"
          ];
        trusted-public-keys = [
          "chronicles.shire-zebra.ts.net:0qWYHn3gGllXChhAaaxKlNZtRy6yG/XJs1RFSqV3nW8="
          "default:DTGxNijw2D8FrZJPT1pFTWcLqbt60tovL+9Z+VW0HRY="
          "ai.cachix.org-1:N9dzRK+alWwoKXQlnn0H6aUx0lU/mspIoz8hMvGvbbc="
          "nixpkgs-python.cachix.org-1:hxjI7pFxTyuTHn2NkvWCrAUcNZLNS3ZAvfYNuYifcEU="
          "greg-hellings.cachix.org-1:y01Jl/L5evlhxdnUW6n56AiI1k8g1wxWhTxJCe7XSco="
          "nix-community.cachix.org-1:mB9FSh9qf2dCimDSUo8Zy7bkq5CX+/rkCWyvRCYg3Fs="
          "cache.nixos.org-1:6NCHdD59X431o0gWypbMrAURkbJ16ZPMQFGspcDShjY="
          "nixhelm.cachix.org-1:esqauAsR4opRF0UsGrA6H3gD21OrzMnBBYvJXeddjtY="
        ];
      };
    };
  };
}