Add direnv cache

Signed-off-by: Nikolaos Karaolidis <nick@karaolidis.com>

.envrc

@@ -0,0 +1 @@
+use flake self#nix

hosts/common/user/configs/console/nix-direnv/default.nix

@@ -4,14 +4,30 @@
 }:
 { inputs, ... }:
 {
-  home-manager.users.${user} = {
-    programs.direnv = {
+  home-manager.users.${user}.programs = {
+    direnv = {
       enable = true;
       silent = true;
       nix-direnv.enable = true;
       enableZshIntegration = true;
     };
+
+    # https://github.com/direnv/direnv/wiki/Customizing-cache-location
+    zsh.initExtra = ''
+      declare -A direnv_layout_dirs
+      direnv_layout_dir() {
+        local hash path
+        echo "''${direnv_layout_dirs[$PWD]:=$(
+          hash="$(sha1sum - <<< "$PWD" | head -c40)"
+          path="''${PWD//[^a-zA-Z0-9]/-}"
+          echo "${home}/.cache/direnv/layouts/''${hash}''${path}"
+        )}"
+      }
+    '';
   };
 
-  environment.persistence."/persist"."${home}/.config/direnv/direnv.toml" = { };
+  environment.persistence = {
+    "/persist"."${home}/.config/direnv/direnv.toml" = { };
+    "/cache"."${home}/.cache/direnv" = { };
+  };
 }