{ config, pkgs, ... }:
let
  grep = pkgs.gnugrep;
  desiredFlatpaks = [
    "com.spotify.Client"
    "io.github.huderlem.porymap"
  ];
in {
  system.userActivationScripts.flatpakManagement = {
    text = ''
      ${pkgs.flatpak}/bin/flatpak remote-add --if-not-exists flathub \
        https://flathub.org/repo/flathub.flatpakrepo

      installedFlatpaks=$(${pkgs.flatpak}/bin/flatpak list --app --columns=application)

      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

      for app in ${toString desiredFlatpaks}; do
        echo "Ensuring $app is installed."
        ${pkgs.flatpak}/bin/flatpak install -y flathub $app
      done

      ${pkgs.flatpak}/bin/flatpak uninstall --unused -y

      ${pkgs.flatpak}/bin/flatpak update -y
    '';
  };
}