factorio: improve backup logic

hosts/monolith/factorio-server.nix

@@ -1,10 +1,49 @@
 {
   config,
   pkgs,
-  lib,
   ...
 }:
+let
+  mkBackup = time: {
+    systemd.services."factorio-backup-save-${time}" = {
+      description = "Backup factorio saves";
+      script = ''
+        set -exuo pipefail
+
+        FILENAME="space-age-$(date --iso=seconds | tr ':' '_').zip"
+        DEST_DIR=~lelgenio/Documentos/GameSaves/factorio_saves/space-age-1/${time}
+
+        mkdir -p "$DEST_DIR"
+        cp /var/lib/factorio/saves/default.zip "$DEST_DIR"/$FILENAME
+        chown lelgenio "$DEST_DIR" "$DEST_DIR"/$FILENAME
+
+        # list all files, from oldest to newest
+        # remove the last 10 from the list
+        # delete the rest
+        cd "$DEST_DIR"
+        ls | head -n-10 | xargs -r rm -v
+      '';
+      serviceConfig.Type = "oneshot";
+    };
+
+    systemd.timers."factorio-backup-save-${time}" = {
+      timerConfig = {
+        # Systemd accepts descriptive names such as "daily"
+        # The times are at midnight, Persistent makes sure that the backups get executed
+        OnCalendar = time;
+        Persistent = true;
+        Unit = "factorio-backup-save-${time}.service";
+      };
+      wantedBy = [ "timers.target" ];
+    };
+  };
+in
 {
+  imports = [
+    (mkBackup "daily")
+    (mkBackup "monthly")
+  ];
+
   services.factorio = {
     enable = true;
     package = pkgs.my-factorio-headless;
@@ -20,29 +59,6 @@
     wants = [ "network-online.target" ];
   };
 
-  systemd.services.factorio-backup-save = {
-    description = "Backup factorio saves";
-    script = ''
-      FILENAME="space-age-$(date --iso=seconds | tr ':' '_').zip"
-      ${lib.getExe pkgs.rsync} \
-        -av  \
-        --chown=lelgenio \
-        /var/lib/factorio/saves/default.zip \
-        ~lelgenio/Documentos/GameSaves/factorio_saves/$FILENAME
-    '';
-    serviceConfig.Type = "oneshot";
-    wantedBy = [ "multi-user.target" ];
-  };
-
-  systemd.timers.factorio-backup-save = {
-    timerConfig = {
-      OnCalendar = "*-*-* 18:00:00";
-      Persistent = true;
-      Unit = "factorio-backup-save.service";
-    };
-    wantedBy = [ "timers.target" ];
-  };
-
   sops.secrets."factorio/server-config.json" = {
     mode = "777";
   };