Use ETags instead of Last-Modified for caching

flake.nix

@@ -30,12 +30,22 @@
           pname = "my-static-site";
           version = "1.0.0";
           src = ./.;
-          buildInputs = [ eleventy ];
+          buildInputs = with pkgs; [
+            eleventy
+            fd
+            coreutils
+          ];
           buildPhase = "eleventy";
           installPhase = ''
             mkdir -p $out/
             echo $out
             cp -r _site/* $out/
+
+            # Generate .etag files for cache validation
+            for file in $(fd --type f . "$out"); do
+              hash=$(md5sum "$file" | cut -d" " -f1)
+              echo "\"$hash\"" > "$file.etag"
+            done;
           '';
         };
       in