dotfiles/nixos/systems/heater/impermenance.nix

{
  inputs',
  pkgs,
  ...
}: let
  rollbackStart = pkgs.writeText "rollback-start" ''
    ${pkgs.rolling_datasets}/bin/roll_dataset "heater-ssd/ephemeral/home" "10"
    ${pkgs.rolling_datasets}/bin/roll_dataset "heater-ssd/ephemeral/root" "10"
    ${pkgs.rolling_datasets}/bin/roll_dataset "heater-ssd/ephemeral/nix-tmp" "10"
  '';
in {
  nixpkgs.overlays = [
    inputs'.self.overlays.show-files-to-be-deleted
    inputs'.self.overlays.rolling_datasets
  ];

  environment.systemPackages = [
    pkgs.show-files-to-be-deleted
  ];

  environment.persistence."/nix/persist" = {
    hideMounts = true;

    directories = [
      "/var/log"
      "/var/lib/nixos"
      "/var/lib/systemd/coredump"
      "/var/lib/arma3"
    ];
    files = [
      "/etc/machine-id"
      "/etc/ssh/ssh_host_rsa_key"
      "/etc/ssh/ssh_host_rsa_key.pub"
      "/etc/ssh/ssh_host_ed25519_key"
      "/etc/ssh/ssh_host_ed25519_key.pub"
    ];
  };

  boot.initrd.systemd.storePaths = with pkgs; [
    zfs
    busybox
    rolling_datasets
    rollbackStart
  ];
  boot.initrd.systemd.services.rollback = {
    description = "Rollback ZFS datasets to a pristine state";
    wantedBy = [
      "initrd.target"
    ];
    after = [
      "zfs-import-heater-ssd.service"
    ];
    before = [
      "sysroot.mount"
    ];
    path = with pkgs; [
      zfs
      busybox
    ];
    unitConfig.DefaultDependencies = "no";
    serviceConfig.Type = "oneshot";
    serviceConfig.ExecStart = "/bin/sh ${rollbackStart}";
  };

  systemd.services."mount-old-datasets" = {
    description = "Mount old versions of datasets";

    wantedBy = ["local-fs.target"];
    after = ["local-fs.target"];

    script = ''
      ${pkgs.rolling_datasets}/bin/mount_datasets "heater-ssd/ephemeral/home" "/home/.old"
      ${pkgs.rolling_datasets}/bin/mount_datasets "heater-ssd/ephemeral/root" "/root/.old"
      ${pkgs.rolling_datasets}/bin/mount_datasets "heater-ssd/ephemeral/nix-tmp" "/nix/tmp/.old"
    '';

    serviceConfig = {
      Type = "oneshot";
      RemainAfterExit = "yes";
      TimeoutStartSec = "5m";
    };
  };
}