{ config, lib, ... }:

{
  config = lib.mkIf (
    (config.fileSystems ? "/persist")
    && (config.fileSystems."/persist".fsType or "" == "btrfs")
  ) {
    boot.initrd.supportedFilesystems = [ "btrfs" ];

    boot.initrd.postDeviceCommands = lib.mkAfter ''
      mkdir -p /mnt
      mount -t btrfs -o subvol=/ /dev/disk/by-label/nixos /mnt

      if [ ! -d /mnt/root-blank ]; then
        btrfs subvolume snapshot -r /mnt/root /mnt/root-blank
      fi

      if [ -d /mnt/root ]; then
        btrfs subvolume delete /mnt/root
      fi

      btrfs subvolume snapshot /mnt/root-blank /mnt/root
      umount /mnt
    '';

    fileSystems."/persist".neededForBoot = true;

    environment.persistence."/persist" = {
      hideMounts = true;
      directories = [
        "/etc/nixos"
        "/etc/ssh"
        "/etc/cups"
        "/var/lib/cups"
        "/var/lib/libvirt"
        "/var/lib/secureboot"
        "/var/lib/tailscale"
        "/var/lib/systemd"
        "/var/lib/nixos"
      ];
      files = [
        "/etc/machine-id"
      ];
    };
  };
}