feat(nixos): select derivations via configuration

This doesn't require the user to specify the cumbersome `_module.args`.

2 files changed, 43 insertions, 19 deletions

diff --git a/README.adoc b/README.adoc
index 6ce53ad..639ddd3 100644
--- a/README.adoc
+++ b/README.adoc
@@ -283,23 +283,21 @@ it could look like this:
 ---------------
 { pkgs, ... }:
 
-let
-  flipdot-gschichtler = import /path/to/flipdot-gschichtler {
-    inherit pkgs;
-  };
-
-in {
+{
   imports = [
     /path/to/flipdot-gschichtler/nixos/flipdot-gschichtler.nix
   ];
 
-  _module.args = { inherit flipdot-gschichtler; };
-
   services.flipdot-gschichtler = {
     enable = true;
     virtualHost = "flipdot.openlab-augsburg.de";
     tokensFile = "/var/secrets/flipdot-gschichtler/tokens";
     saltFile = "/var/secrets/flipdot-gschichtler/salt";
+    # if you want to change the derivations to use
+    # packages = {
+    #   warteraum = …;
+    #   bahnhofshalle = …;
+    # };
   };
 
   services.nginx.enable = true;
@@ -343,13 +341,19 @@ Changelog
 ** Trim whitespace on input text
 ** Instead of compiling in salt and tokens, read them from the
    files specified via the `WARTERAUM_SALT_FILE` and
-   `WARTERAUM_TOKENS_FILE` environment variables. In the NixOS
-   service this is reflected by the usage of `saltFile` and
+   `WARTERAUM_TOKENS_FILE` environment variables.
+* NixOS module
+** Reflect change to `warteraum` by using `saltFile` and
    `tokensFile` respectively over the previous `salt` and
    `tokens`.
 ** Fix sandboxing in `nixos/flipdot-gschichtler.nix`: Now only
-  the secret files and the nix store will be readable to the
-  `warteraum` process.
+   the secret files and the nix store will be readable to the
+   `warteraum` process.
+** Allow changing `bahnhofshalle` and `warteraum` derivation
+   to use via `packages`.
+** Don't require `flipdot-gschichtler` to be passed as module
+   argument, instead import directly from file system (unless
+   a non-default derivation is configured).
 
 2.0.0
 ~~~~~
diff --git a/nixos/flipdot-gschichtler.nix b/nixos/flipdot-gschichtler.nix
index 35af0b3..bf6797e 100644
--- a/nixos/flipdot-gschichtler.nix
+++ b/nixos/flipdot-gschichtler.nix
@@ -1,13 +1,14 @@
-{ config, lib, pkgs, flipdot-gschichtler, ... }:
+{ config, lib, pkgs, ... }:
 
 with lib;
 
 let
   cfg = config.services.flipdot-gschichtler;
-  inherit (flipdot-gschichtler)
-    bahnhofshalle
-    warteraum-static
-    ;
+
+  flipdot-gschichtler = import ../. {
+    inherit pkgs;
+  };
+  importClause = "(import ../. { inherit pkgs; })";
 
   userGroupName = "warteraum";
 in {
@@ -15,6 +16,25 @@ in {
     services.flipdot-gschichtler = {
       enable = mkEnableOption "flipdot-gschichtler";
 
+      packages = {
+        warteraum = mkOption {
+          type = types.package;
+          default = flipdot-gschichtler.warteraum;
+          defaultText = literalExample "${importClause}.warteraum";
+          description = ''
+            <literal>warteraum</literal> derivation to use.
+          '';
+        };
+        bahnhofshalle = mkOption {
+          type = types.package;
+          default = flipdot-gschichtler.bahnhofshalle;
+          defaultText = literalExample "${importClause}.bahnhofshalle";
+          description = ''
+            <literal>bahnhofshalle</literal> derivation to use.
+          '';
+        };
+      };
+
       virtualHost = mkOption {
         type = types.str;
         default = "localhost";
@@ -59,7 +79,7 @@ in {
 
       serviceConfig = {
         Type = "simple";
-        ExecStart = "${warteraum-static}/bin/warteraum";
+        ExecStart = "${cfg.packages.warteraum}/bin/warteraum";
 
         # make only /nix/store and the salt and token file accessible
         TemporaryFileSystem = "/:ro";
@@ -112,7 +132,7 @@ in {
     services.nginx.virtualHosts."${cfg.virtualHost}" = {
       enableACME = true;
       forceSSL = true;
-      root = bahnhofshalle;
+      root = cfg.packages.bahnhofshalle;
       extraConfig = ''
         location /api {
           proxy_pass http://127.0.0.1:9000/api;