# Requires boot.initrd.enable = true and boot.initrd.systemd.enable = true!
{ config, lib, pkgs, ... }:

with lib;

let
  cfg = config.sydnix.impermanence;
in {
  options = {
    sydnix.impermanence = {
      enable = mkOption {
        description = "Enable Impermanence";
        type = types.bool;
        default = false;
      };

      directories = mkOption {
        description = "";
        type = with types; listOf anything;
        default = [];
      };

      files = mkOption {
        description = "";

        type = with types; listOf anything;
        default = [];
      };
    };
  };

  config = mkIf cfg.enable {
    boot.initrd.systemd.initrdBin = with pkgs; [
      zfs
    ];

    boot.initrd.systemd.services.erase-darlings = {
      description = "Rollback filesystem to a blank state on boot";
      wantedBy = [
        "initrd.target"
      ];
      after = [
        # "zfs-import.service"
        "zfs-import-rpool.service"
      ];
      before = [
        "sysroot.mount"
      ];
      path = [ pkgs.zfs ];
      unitConfig.DefaultDependencies = "no";
      serviceConfig = {
        Type = "oneshot";
        RemainAfterExit = true;
      };
      script = /* bash */ ''
      zfs rollback -r rpool/local/root@blank \
        && echo ">> >> rollback complete << <<"
    '';
    };

    environment.persistence."/persist" = {
        directories = cfg.directories;
        files = cfg.files;
    };
  };
}