{
  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,
      homebrew-core,
      homebrew-cask,
      ...
    }:
    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."${hostname}" = darwin.lib.darwinSystem {
        inherit system specialArgs;
        modules = [
          ./modules/nix-core.nix
          ./modules/system.nix
          ./modules/apps.nix
          ./modules/host-users.nix
          nix-homebrew.darwinModules.nix-homebrew
          {
            nix-homebrew = {
              enable = true;
              enableRosetta = true;
              user = username;
              taps = {
                "homebrew/homebrew-core" = homebrew-core;
                "homebrew/homebrew-cask" = homebrew-cask;
              };
              mutableTaps = false;
            };
          }
          (
            { config, ... }:
            {
              homebrew.taps = builtins.attrNames config.nix-homebrew.taps;
            }
          )
          home-manager.darwinModules.home-manager
          {
            home-manager = {
              useGlobalPkgs = true;
              useUserPackages = true;
              backupFileExtension = "backup";
              extraSpecialArgs = specialArgs;
              sharedModules = [
                nvf.homeManagerModules.nvf
                sops-nix.homeManagerModules.sops
              ];
              users.${username} = import ./home;
            };
          }
        ];
      };
      formatter.${system} = nixpkgs.legacyPackages.${system}.alejandra;
    };
}