# sudo nix --experimental-features "nix-command flakes" run github:nix-community/disko/latest -- --mode disko /nixos/hosts/nixos-testbed/disko-config.nix
# time sudo nixos-install --flake /nixos#nixos-testbed
{ lib, ... }:
{
  # imports = [ inputs.disko.nixosModules.disko ];
  boot.zfs.extraPools = [ "rpool" ];
  boot.zfs.devNodes = "/dev/disk/by-path";
  boot.initrd.supportedFilesystems = [ "zfs" ];
  boot.supportedFilesystems = [ "zfs" ];

  disko.devices = {
    disk = {
      broot = {
        type = "disk";
        device = "/dev/vda";
        content = {
          type = "gpt";
          partitions = {
            ESP = {
              size = "512M";
              # start = "1MiB";
              # end = "512M";
              type = "EF00";
              content = {
                type = "filesystem";
                format = "vfat";
                mountpoint = "/boot";
                mountOptions = [ "umask=0077" ];
              };
            };
            root = {
              # start = "512M";
              # end = "100%";
              size = "100%";
              content = {
                type = "zfs";
                pool = "rpool";
              };
            };
          };
        };
      };
    };
    zpool = {
      rpool = {
        type = "zpool";

        # Workaround: cannot import 'rpool': I/O error in disko tests
        # options.cachefile = "none";

        # rootFsOptions = {
        #   # I don't know.
        #   # https://wiki.archlinux.org/title/Systemd#systemd-tmpfiles-setup.service_fails_to_start_at_boot
        #   acltype = "posixacl";
        #   # atime = "off";
        #   # compression = "zstd";
        #   mountpoint = "none";
        #   # xattr = "sa";
        #   "com.sun:auto-snapshot" = "false";
        # };

        # mountpoint = "/";

        datasets =
          let dataset = options:
                let default = {
                      type = "zfs_fs";
                      mountOptions = [ "noauto" ];
                      options = {
                        "com.sun:auto-snapshot" = "false";
                      };
              };
              in lib.recursiveUpdate default options;
          in
          {
            "local" = dataset {};
            "darlings" = dataset {};
            "local/root" = dataset {
              mountpoint = "/";
              postCreateHook = ''
                zfs list -t snapshot -H -o name \
                  | grep -E '^rpool/local/root@blank$' \
                  || zfs snapshot rpool/local/root@blank
              '';
            };
            "local/nix" = dataset { mountpoint = "/nix"; };
            "local/home" = dataset {
              mountpoint = "/home";
              postCreateHook = ''
                zfs list -t snapshot -H -o name \
                  | grep -E '^rpool/local/home@blank$' \
                  || zfs snapshot rpool/local/home@blank
              '';
            };
            "darlings/persist" = dataset { mountpoint = "/persist"; };
            "darlings/home" = dataset {
              mountpoint = "/persist/home";
            };
            "reserved" = dataset {
              mountpoint = null;
              options = {
                canmount = "off";
                mountpoint = "none";
                reservation = "5GiB";
              };
            };
          # "local" = {
          #   type = "zfs_fs";
          #   options.mountpoint = "none";
          # };
          # "safe" = {
          #   type = "zfs_fs";
          #   options.mountpoint = "none";
          # };
          # "local/root" = {
          #   type = "zfs_fs";
          #   options.mountpoint = "legacy";
          #   mountpoint = "/";
          #   options."com.sun:auto-snapshot" = "false";
          #   postCreateHook = ''
          #     zfs list -t snapshot -H -o name \
          #       | grep -E '^rpool/local/root@blank$' \
          #       || zfs snapshot rpool/local/root@blank
          #   '';
          # };
          # "local/home" = {

          # };
          # "local/nix" = {
          #   type = "zfs_fs";
          #   options.mountpoint = "legacy";
          #   mountpoint = "/nix";
          #   options."com.sun:auto-snapshot" = "false";
          # };
          # "safe/persist" = {
          #   type = "zfs_fs";
          #   options.mountpoint = "legacy";
          #   mountpoint = "/persist";
          #   options."com.sun:auto-snapshot" = "false";
          # };
          #  # zfs uses copy on write and requires some free space to delete files when the disk is completely filled
          # "reserved" = lib.recursiveUpdate (dataset "reserved") {
          #   mountpoint = null;
          #   options = {
          #     canmount = "off";
          #     mountpoint = "none";
          #     reservation = "5GiB";
          #   };
          #   type = "zfs_fs";
          # };
        };
      };
    };
  };
}