{
  description = "Nix for Poby's MacOS";

  # TODO: is this necessary?
  # nixConfig = {
  #   substituters = [
  #     "https://nix-community.cachix.org"
  #     "https://cache.nixos.org"
  #   ];
  # };

  inputs = {
    # nixpkgs-darwin.url = "github:nixos/nixpkgs/nixpkgs-unstable"; # comment out for unstable version
    nixpkgs-darwin.url = "github:nixos/nixpkgs/nixpkgs-25.11-darwin";

    home-manager = {
      url = "github:nix-community/home-manager/release-25.11";
      inputs.nixpkgs.follows = "nixpkgs-darwin";
    };

    darwin = {
      url = "github:nix-darwin/nix-darwin/nix-darwin-25.11";
      inputs.nixpkgs.follows = "nixpkgs-darwin";
    };

    # Homebrew
    nix-homebrew.url = "github:zhaofengli/nix-homebrew";

    # Optional: Declarative tap management
    homebrew-core = {
      url = "github:homebrew/homebrew-core";
      flake = false;
    };
    homebrew-cask = {
      url = "github:homebrew/homebrew-cask";
      flake = false;
    };

    # NVF for neovim
    nvf = {
      url = "github:notashelf/nvf";
      inputs.nixpkgs.follows = "nixpkgs";
    };

    # sops-nix for secrets
    sops-nix = {
      url = "github:Mic92/sops-nix";
      inputs.nixpkgs.follows = "nixpkgs-darwin";
    };
  };

  outputs = inputs @ {
    self,
    nixpkgs,
    darwin,
    home-manager,
    nvf,
    sops-nix,
    nix-homebrew,
    ...
  }: let
    system = "aarch64-darwin";
    username = "poby";
    useremail = "smg981024@gmail.com";
    hostname = "fenrir"; # TODO break down to multiple hosts

    specialArgs =
      inputs
      // {
        inherit username useremail hostname;
      };
  in {
    darwinConfigurations."${hostname}" = darwin.lib.darwinSystem {
      inherit system specialArgs;
      modules = [
        ./hosts
        nix-homebrew.darwinModules.nix-homebrew
        home-manager.darwinModules.home-manager
        {
          home-manager = {
            useGlobalPkgs = true;
            useUserPackages = true;
            backupFileExtension = "backup";
            extraSpecialArgs = specialArgs;
            sharedModules = [
              nvf.homeManagerModules.nvf
              sops-nix.homeManagerModules.sops
            ];
            users.${username} = import ./home;
          };
        }
      ];
    };
    formatter.${system} = nixpkgs.legacyPackages.${system}.alejandra;
  };
}