From 7ff4ad5c49e7933841cb358091882e50cd215d1a Mon Sep 17 00:00:00 2001
From: cinereal <cinereal@riseup.net>
Date: Sat, 3 May 2025 11:39:24 +0200
Subject: [PATCH] wip: templates

---
 backends/on-machine.nix |  9 +++++++++
 options.nix             | 17 +++++++++++++++++
 2 files changed, 26 insertions(+)

diff --git a/backends/on-machine.nix b/backends/on-machine.nix
index df072b0..bddc83e 100644
--- a/backends/on-machine.nix
+++ b/backends/on-machine.nix
@@ -60,6 +60,15 @@ let
           echo "All secrets for ${gen.name} are present"
         elif [ $all_files_missing = true ] ; then
 
+          # templates
+          templates=$(mktemp -d)
+          trap 'rm -rf $templates' EXIT
+          export templates
+          mkdir -p "$templates"
+          ${lib.concatMapStringsSep "\n" (file: ''
+            cp "${file.template}" "$templates/${file.name}"
+          '') (lib.filter (file: file.template != null) (lib.attrValues gen.files))}
+
           # prompts
           prompts=$(mktemp -d)
           trap 'rm -rf $prompts' EXIT
diff --git a/options.nix b/options.nix
index 377b2d4..2d668ff 100644
--- a/options.nix
+++ b/options.nix
@@ -119,6 +119,21 @@
                       type = lib.types.nullOr lib.types.str;
                       default = null;
                     };
+                    placeholder = lib.mkOption {
+                      description = ''
+                        A placeholder that may be used to safely reference the variable in a template.
+                      '';
+                      readOnly = true;
+                      default = "<VARS:${builtins.hashString "sha256" "${generator.config.name}:${file.config.name}"}:PLACEHOLDER>";
+                    };
+                    template = lib.mkOption {
+                      description = ''
+                        A template file with placeholders from the generator's dependencies.
+                        These will be substituted.
+                      '';
+                      type = lib.types.nullOr lib.types.path;
+                      default = null;
+                    };
                   };
                 })
               );
@@ -185,6 +200,8 @@
                   - $in: The directory containing the output values of all declared dependencies
                   - $out: The output directory to put the generated files
                   - $prompts: The directory containing the prompted values as files
+                  - $templates: The template files, with placeholders - to be replaced in the script like
+                      cat $templates/foo | sed "s/''${config.vars.generators.bar.files.baz.placeholder}/$(cat "$in/bar/baz")/g" > "$out/foo"
                 The script should produce the files specified in the 'files' attribute under $out.
               '';
               type = lib.types.either lib.types.str lib.types.path;