{
  description = "A flake to deploy and configure Clicks' NixOS server";

  # input URLs
  inputs.nixpkgs.url = "github:nixos/nixpkgs/nixos-23.11";
  inputs.nixpkgs-unstable.url = "github:nixos/nixpkgs/nixos-unstable";
  inputs.nixpkgs-clicksforms.url = "github:nixos/nixpkgs/nixos-22.05";
  inputs.flake-utils.url = "github:numtide/flake-utils";
  inputs.deploy-rs.url = "github:serokell/deploy-rs";
  inputs.home-manager.url = "github:nix-community/home-manager/release-23.11";
  inputs.sops-nix.url = "github:Mic92/sops-nix";
  inputs.scalpel.url = "github:polygon/scalpel";

  inputs.nixpkgs-privatebin.url = "github:e1mo/nixpkgs/privatebin";
  inputs.nixpkgs-mongodb.url = "github:nixos/nixpkgs?rev=8dfad603247387df1df4826b8bea58efc5d012d8";

  inputs.helpers.url = "git+https://git.clicks.codes/Infra/NixHelpers";

  inputs.frappix.url = "github:ClicksCodes/frappix";

  # follow settings
  inputs.home-manager.inputs.nixpkgs.follows = "nixpkgs";

  inputs.sops-nix.inputs.nixpkgs.follows = "nixpkgs";

  inputs.scalpel.inputs.nixpkgs.follows = "nixpkgs";
  inputs.scalpel.inputs.sops-nix.follows = "sops-nix";

  inputs.gerrit-oauth = {
    url = "https://gerrit-ci.gerritforge.com/job/plugin-oauth-bazel-master-master/lastBuild/artifact/bazel-bin/plugins/oauth/oauth.jar";
    flake = false;
  };

  outputs = { self, nixpkgs, nixpkgs-unstable, deploy-rs, home-manager, sops-nix, scalpel
    , nixpkgs-privatebin, frappix, ... }@inputs:
    let
      system = "x86_64-linux";
      pkgs = import nixpkgs {
        inherit system;
        config.allowUnfree = true;

        # frappix -> wkhtmltopdf
        config.permittedInsecurePackages = ["openssl-1.1.1w"];

        overlays = [
          (final: prev: {
            inherit (nixpkgs-unstable.legacyPackages.${system})
              vaultwarden vaultwarden-postgresql # vaultwarden updates often fix compatibility with the extension
              matrix-sliding-sync; # matrix-sliding-sync updates very fast and being on an old version breaks app compatibility
          }) # pin-unstable
          (final: prev: {
            inherit (nixpkgs-privatebin.legacyPackages.${system})
              privatebin pbcli;
          })
          (functorBuster: frappix.toolsOverlay.${system} functorBuster)
          (functorBuster: frappix.pythonOverlay.${system} functorBuster)
          (functorBuster: frappix.frappeOverlay.${system} functorBuster)
          (final: prev: {
            python311 = prev.python311.override {
              packageOverrides = pyFinal: pyPrev: {
                elasticsearch = (
                  pyPrev.elasticsearch.overrideAttrs (prevAttrs: {
                    propagatedBuildInputs = prevAttrs.propagatedBuildInputs ++ [
                      final.python311Packages.elastic-transport
                    ];
                  })
                );
              };
            };
          })
        ];
      };
      helpers = inputs.helpers.helpers { inherit pkgs nixpkgs; };
      drive_paths = import ./variables/drive_paths.nix;

      a1d1 = import ./modules/a1d1 { inherit self pkgs system inputs drive_paths; };
      a1d2 = import ./modules/a1d2 { inherit self pkgs system inputs; drive_paths = null; };
    in rec {
      nixosConfigurations.clicks = let
        base = nixpkgs.lib.nixosSystem {
          inherit system pkgs;
          modules = [
            {
              system.stateVersion = "22.11";
              nix.settings.experimental-features = [ "nix-command" "flakes" ];
              nix.settings.trusted-users = [ "minion" "coded" ];
              time.timeZone = "Etc/UTC";
              users.mutableUsers = false;

              fileSystems."/" = {};
            }
          ]
          ++ (helpers.nixFilesIn ./modules/common)
          ++ [
            sops-nix.nixosModules.sops
            "${nixpkgs-privatebin}/nixos/modules/services/web-apps/privatebin.nix"
            frappix.nixosModules.${system}.frappix
          ];
          specialArgs = inputs // {
            base = null;
            inherit system;
            inherit helpers;
            drive_paths = null;
          };
        };
      in base.extendModules {
        modules = [ scalpel.nixosModules.scalpel ];
        specialArgs = { inherit base; };
      };

      nixosConfigurations.clicks-without-mongodb =
        nixosConfigurations.clicks.extendModules {
          modules = [{ services.mongodb.enable = nixpkgs.lib.mkForce false; }];
        };

      nixosConfigurations.a1d1 = a1d1.config;
      nixosConfigurations.a1d2 = a1d2.config;

      deploy.nodes.a1d1 = a1d1.deploy;
      deploy.nodes.a1d2 = a1d2.deploy;

      devShells.x86_64-linux.default =
        pkgs.mkShell { packages = [ pkgs.deploy-rs ]; };

      formatter.x86_64-linux = nixpkgs.legacyPackages.x86_64-linux.nixfmt;
    };
}