{ config, pkgs, ... }:
let
  # We point directly to 'gnugrep' instead of 'grep'
  grep = pkgs.gnugrep;
  # 1. Declare the Flatpaks you *want* on your system
  desiredFlatpaks = [];
in {
  system.userActivationScripts.flatpakManagement = {
    text = ''
      # 2. Ensure the Flathub repo is added
      ${pkgs.flatpak}/bin/flatpak remote-add --if-not-exists flathub \
        https://flathub.org/repo/flathub.flatpakrepo

      # 3. Get currently installed Flatpaks
      installedFlatpaks=$(${pkgs.flatpak}/bin/flatpak list --app --columns=application)

      # 4. Remove any Flatpaks that are NOT in the desired list
      for installed in $installedFlatpaks; do
        if ! echo ${toString desiredFlatpaks} | ${grep}/bin/grep -q $installed; then
          echo "Removing $installed because it's not in the desiredFlatpaks list."
          ${pkgs.flatpak}/bin/flatpak uninstall -y --noninteractive $installed
        fi
      done

      # 5. Install or re-install the Flatpaks you DO want
      for app in ${toString desiredFlatpaks}; do
        echo "Ensuring $app is installed."
        ${pkgs.flatpak}/bin/flatpak install -y flathub $app
      done

      # 6. Remove unused Flatpaks
      ${pkgs.flatpak}/bin/flatpak uninstall --unused -y

      # 7. Update all installed Flatpaks
      ${pkgs.flatpak}/bin/flatpak update -y
    '';
  };
}