{ config, pkgs, lib, ... }:

let
  # Adjust this path if your module lives elsewhere in the repo
  flatpakConfPath = ../../../files/conf/apps/flatpak.conf;

  # Parse flatpak.conf: ignore empty lines and comments
  flatpakApps =
    let
      lines = lib.splitString "\n" (builtins.readFile flatpakConfPath);
      cleaned = map (l: lib.strings.trim l) lines;
    in
      builtins.filter (l: l != "" && !(lib.hasPrefix "#" l)) cleaned;

  # Shell script that:
  # - adds Flathub if missing
  # - installs missing apps
  # - (optional) removes apps not in the list
  syncFlatpaks = pkgs.writeShellScript "sync-flatpaks" ''
    set -euo pipefail

    # Ensure Flathub remote exists (system-wide)
    if ! flatpak remotes --system --columns=name | grep -qx flathub; then
      flatpak remote-add --system --if-not-exists flathub https://dl.flathub.org/repo/flathub.flatpakrepo
    fi

    desired_apps=(
      ${lib.concatStringsSep "\n" (map (a: ''"${a}"'') flatpakApps)}
    )

    # Install desired apps if missing
    for app in "''${desired_apps[@]}"; do
      if ! flatpak info --system "$app" >/dev/null 2>&1; then
        flatpak install --system -y --noninteractive flathub "$app"
      fi
    done

    # OPTIONAL: remove system apps not listed (uncomment to enforce strictly)
    # installed="$(flatpak list --system --app --columns=application | sed '/^$/d')"
    # for app in $installed; do
    #   keep=0
    #   for want in "''${desired_apps[@]}"; do
    #     if [ "$app" = "$want" ]; then keep=1; break; fi
    #   done
    #   if [ "$keep" -eq 0 ]; then
    #     flatpak uninstall --system -y --noninteractive "$app" || true
    #   fi
    # done
  '';
in
{
  # Native NixOS Flatpak support
  services.flatpak.enable = true; # enables Flatpak on NixOS :contentReference[oaicite:1]{index=1}

  # Strongly recommended for Flatpak desktop integration
  # (Adjust portals to your DE/WM if you want, this is a safe default.)
  xdg.portal = {
    enable = true;
    extraPortals = [ pkgs.xdg-desktop-portal-gtk ];
  };

  # Ensure the config file is present on the system (optional but convenient)
  environment.etc."flatpak/flatpak.conf".source = flatpakConfPath;

  # Run sync after boot and after rebuilds, once networking is up
  systemd.services.flatpak-sync = {
    description = "Install Flatpak apps listed in flatpak.conf";
    wantedBy = [ "multi-user.target" ];
    wants = [ "network-online.target" ];
    after = [ "network-online.target" ];

    serviceConfig = {
      Type = "oneshot";
      ExecStart = syncFlatpaks;
    };

    # Re-run when the config changes (best-effort)
    restartTriggers = [ flatpakConfPath ];
    path = [ pkgs.flatpak pkgs.coreutils pkgs.gnugrep pkgs.gnused ];
  };
}