home: add a timer to fetch mic92's nix-index database

home/misterio/cli/nix-index.nix

@@ -1,7 +1,38 @@
-{ lib, persistence, ... }: {
+{ lib, persistence, pkgs, ... }:
+let update-script = pkgs.writeShellApplication {
+  name = "fetch-nix-index-database";
+  runtimeInputs = with pkgs; [ wget coreutils ];
+  text = ''
+    filename="index-x86_64-linux"
+    mkdir -p ~/.cache/nix-index
+    cd ~/.cache/nix-index
+    wget -N "https://github.com/Mic92/nix-index-database/releases/latest/download/$filename"
+    ln -f "$filename" files
+  '';
+};
+in
+{
   programs.nix-index.enable = true;
 
   home.persistence = lib.mkIf persistence {
     "/persist/home/misterio".directories = [ ".cache/nix-index" ];
   };
+
+  systemd.user.services.nix-index-database-sync = {
+    Unit = { Description = "fetch mic92/nix-index-database"; };
+    Service = {
+      Type = "oneshot";
+      ExecStart = "${update-script}/bin/fetch-nix-index-database";
+      Restart = "on-failure";
+      RestartSec = "5m";
+    };
+  };
+  systemd.user.timers.nix-index-database-sync = {
+    Unit = { Description = "Automatic github:mic92/nix-index-database fetching"; };
+    Timer = {
+      OnBootSec = "10m";
+      OnUnitActiveSec = "24h";
+    };
+    Install = { WantedBy = [ "timers.target" ]; };
+  };
 }