#+title: Useful Nix bits

This pages houses a few configuration snippets that might be useful if you are new to the nix ecosystem. It will be infrequently updated as I come across things that I deem to be interesting to such a reader.

* Importing a NixOS module that is not in nixpkgs

This requires changes in multiple locations. As an example we will use an early version of the mautrix-signal module by Niklas Korz.

1) Add the module source to flake.nix:

   #+begin_src nix flake.nix
     {
       inputs = {
         [...]
           # provides expressions for mautrix-signal
           nixpkgs-mautrix-signal ={
           url = github:niklaskorz/nixpkgs/nixos-23.11-mautrix-signal;
         };
         [...]
       };

       outputs = inputs@{
         self,
           [...]
             nixpkgs-mautrix-signal,
           [...]
       }: let
         [...]
           pkgsmautrix = import nixpkgs-mautrix-signal { inherit system;
                                                         config.allowUnfree = true;
                                                       };
         [...]
       in {
         nixosConfigurations = {
           matrix = nixpkgs.lib.nixosSystem {
             pkgs = pkgsmautrix;
             # this is to import a service module that is not on nixpkgs
             # this way avoids infinite recursion errors
             specialArgs.unstable = nixpkgs-mautrix-signal;
             modules = [
               [...]
             ];
           };
         };
       }
     }

   #+end_src

2) Import the module in the configuration:

   #+begin_src nix configuration.nix

     [...]
       imports = [
       [...]
       (unstable + "/nixos/modules/services/matrix/mautrix-signal.nix")
     ];

     [...]
   #+end_src

* Build a firefox addon

1) app id can be found in the manifest.json file of the .xpi (.xpi is just a normal archive)
2) url can be found by copy url of the "add extension" button on the addon page
3) the rest of the information is also found in the manifest.json, but might not be needed

#+begin_src nix configuration.nix
  programs.firefox = {
    [...]
     profiles.default = {
       [...]
       extensions = with pkgs.nur.repos.rycee.firefox-addons; [
         [...]
         (buildFirefoxXpiAddon {
           pname = ":emoji:";
           version = "0.1.3";
           addonId = "gonelf@gmail.com";
           url = "https://addons.mozilla.org/firefox/downloads/file/3365324/emojidots-0.1.3.xpi";
           sha256 = "4f7cc25c478fe52eb82f37c9ff4978dcaa3f95020398c5b184e517f6efa2c201";
           meta = with lib;
             {
               description = "emoji autocomplete anywhere on the internet";
               mozPermissions = [ "https://gist.githubusercontent.com/gonelf/d8ae3ccb7902b501c4a5dd625d4089da/raw/5eeda197ba92f8c8139e846a1225d5640077e06f/emoji_pretty.json" "tabs" "storage"];
               platforms = platforms.all;
             };
         })
   [...]
#+end_src

* Define shell utility as package

#+begin_src nix configuration.nix

  home.packages = with pkgs; [ # or for NixOS environment.systemPackages = with pkgs; [
    [...]
    (pkgs.writeShellApplication {
        name = "pass-fuzzel";
        runtimeInputs = [ pkgs.pass pkgs.fuzzel ];
        text = ''
         shopt -s nullglob globstar

         typeit=0
         if [[ $# -ge 1 && $1 == "--type" ]]; then
           typeit=1
           shift
         fi

         export PASSWORD_STORE_DIR=~/.local/share/password-store
         prefix=''${PASSWORD_STORE_DIR-~/.local/share/password-store}
         password_files=( "$prefix"/**/*.gpg )
         password_files=( "''${password_files[@]#"$prefix"/}" )
         password_files=( "''${password_files[@]%.gpg}" )

         password=$(printf '%s\n' "''${password_files[@]}" | fuzzel --dmenu "$@")

         [[ -n $password ]] || exit

         if [[ $typeit -eq 0 ]]; then
           pass show -c "$password" &>/tmp/pass-fuzzel
         else
           pass show "$password" | { IFS= read -r pass; printf %s "$pass"; } | wtype -
         fi
         notify-send -u critical -a pass -t 1000 "Copied/Typed Password"
       '';
      })

    [...]

#+end_src

* Add program with prebuild binaries to nix store

#+begin_src nix configuration.nix

  home.packages = with pkgs; [ # or for NixOS environment.systemPackages = with pkgs; [
    [...]
     (stdenv.mkDerivation {
      name = "oama";

      src = pkgs.fetchurl {
          name = "oama";
          url = "https://github.com/pdobsan/oama/releases/download/0.13.1/oama-0.13.1-Linux-x86_64-static.tgz";
          sha256 = "sha256-OTdCObVfnMPhgZxVtZqehgUXtKT1iyqozdkPIV+i3Gc=";
      };

      phases = [
        "unpackPhase"
      ];

      unpackPhase = ''
      mkdir -p $out/bin
      tar xvf $src -C $out/
      mv $out/oama-0.13.1-Linux-x86_64-static/oama $out/bin/
      '';

  })

    [...]
  #+end_src

* Patch a utilty for nix paths:
See https://drakerossman.com/blog/how-to-patch-a-package-source-on-nixos
* let-block for overriding a package in nixpkgs (here: replacing airsonic with airsonic-advanced)

This can be useful if a module does not let you use your own package yourself.

#+begin_src nix :tangle no

  pkgs = import nixpkgs { inherit system;
                          overlays = [ emacs-overlay.overlay
                                       nur.overlay
                                       nixgl.overlay
                                       (self: super: {
                                         airsonic = super.airsonic.overrideAttrs (_: rec {
                                           version = "11.0.2-kagemomiji";
                                           name = "airsonic-advanced-${version}";
                                           src = super.fetchurl {
                                             url = "https://github.com/kagemomiji/airsonic-advanced/releases/download/11.0.2/airsonic.war";
                                             sha256 = "PgErtEizHraZgoWHs5jYJJ5NsliDd9VulQfS64ackFo=";
                                           };
                                         });
                                       })
                                     ];
                          config.allowUnfree = true;
                        };

#+end_src