{
  inputs = {
    nixpkgs.url = "github:NixOS/nixpkgs/nixpkgs-unstable";

    flake-utils = {
      url = "github:numtide/flake-utils";
      inputs.systems.follows = "systems";
    };
    treefmt-nix = {
      url = "github:numtide/treefmt-nix";
      inputs.nixpkgs.follows = "nixpkgs";
    };

    ### De-dupe flake dependencies
    systems.url = "github:nix-systems/default";
  };

  outputs =
    inputs:
    inputs.flake-utils.lib.eachDefaultSystem (
      system:
      let
        inherit (pkgs) lib;
        pkgs = inputs.nixpkgs.legacyPackages.${system};
        treefmtEval = inputs.treefmt-nix.lib.evalModule pkgs ./treefmt.nix;
      in
      {
        ### nix {run,shell,build}
        packages = rec {
          default = lib.warn "the 'default' package is now deprecated, please use the 'api' package instead." api;
          inherit ((pkgs.callPackage ./package.nix { })) api ui;
        };

        ### nix fmt
        formatter = treefmtEval.config.build.wrapper;

        ### nix flake check
        checks.formatting = treefmtEval.config.build.check inputs.self;

        ### nix develop
        devShells.default = pkgs.mkShellNoCC {
          nativeBuildInputs = with pkgs; [
            go
            nodePackages.prettier
            nodejs
            pnpm
            typescript-language-server
          ];
          shellHook = ''
            export IP_CHECKER_CITY_DB=${pkgs.dbip-city-lite.mmdb}
            export IP_CHECKER_ASN_DB=${pkgs.dbip-asn-lite.mmdb}
            export IP_CHECKER_MODE=dev
          '';
        };
      }
    );
}