dotfiles/nixos/systems/omen/impermenance.nix

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

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

  environment.persistence."/nix/persist" = {
    hideMounts = true;
    directories = [
      "/var/log"
      "/var/lib/bluetooth"
      "/var/lib/nixos"
      "/var/lib/systemd/coredump"
      "/var/lib/iwd"
      "/var/lib/syncthing"
      "/var/lib/containers"
    ];
    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"
    ];
    users.main = {
      directories = [
        "sync"
        ".steam"
        ".local/share/Steam"
        ".emacs.d"
        "roam"
        "dotfiles"
        "Documents"
        { directory = ".gnupg"; mode = "0700"; }
        { directory = ".ssh"; mode = "0700"; }
        ".local/share/direnv"
        "repos"
        ".config/SchildiChat"
        ".config/matlab"
        ".matlab"
        "MATLAB"
        ".stack"
        ".cache/nix"
        ".cache/fontconfig"
        ".cache/mesa_shader_cache"
        ".cache/ghcide"
        ".local/share/pantalaimon"
        "Mail"
        ".cache/mu"
        ".gradle"
        ".password-store"
      ];
      files = [
        { file = ".config/wallpaper"; method = "symlink"; }
        { file = ".gitignore"; method = "symlink"; }
      ];
    };
  };

  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-omen-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-homes" = {
    description = "Mount old versions of home dataset";

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

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

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

  systemd.services."home-manager-main-pre.service" = {
    description = "Home Manager environment prestart for main";

    wantedBy = [ "multi-user.target" ];
    before = [ "home-manager-main.service" ];

    script = ''
      set -e
      mkdir -p /home/main
      chown 1000:1000 /home/main
    '';

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