open-webui: fix database location

hosts/library/ai.nix

@@ -4,6 +4,9 @@
   ...
 }:
 
+let
+  stateDir = "/var/lib/open-webui";
+in
 {
   age.secrets.open-webui-env = {
     rekeyFile = ./secrets/open-webui-env.age;
@@ -28,10 +31,33 @@
         OFFLINE_MODE = "True";
         OPENID_PROVIDER_URL = "https://auth.vimium.com/oauth2/openid/${clientId}/.well-known/openid-configuration";
         OPENID_REDIRECT_URI = "${publicUrl}/oauth/oidc/callback";
+
+        # Fix from https://github.com/NixOS/nixpkgs/pull/431395
+        STATIC_DIR = "${stateDir}/static";
+        DATA_DIR = "${stateDir}/data";
+        HF_HOME = "${stateDir}/hf_home";
+        SENTENCE_TRANSFORMERS_HOME = "${stateDir}/transformers_home";
       };
     environmentFile = config.age.secrets.open-webui-env.path;
   };
 
+  # Fix from https://github.com/NixOS/nixpkgs/pull/432897
+  systemd.services.open-webui.preStart = ''
+    if [ -d "${stateDir}/data" ] && [ -n "$(ls -A "${stateDir}/data" 2>/dev/null)" ]; then
+      exit 0
+    fi
+
+    mkdir -p "${stateDir}/data"
+
+    [ -f "${stateDir}/webui.db" ] && mv "${stateDir}/webui.db" "${stateDir}/data/"
+
+    for dir in cache uploads vector_db; do
+      [ -d "${stateDir}/$dir" ] && mv "${stateDir}/$dir" "${stateDir}/data/"
+    done
+
+    exit 0
+  '';
+
   modules.services.borgmatic.directories = [
     "/var/lib/private/open-webui"
   ];