{ ... }:

# Declarative OS-disk layout (disko). UEFI: GPT with an ESP + btrfs root.
# disko both PARTITIONS/FORMATS this disk and generates the NixOS
# `fileSystems.*` entries, so hardware-configuration.nix must NOT define
# fileSystems for "/" or "/boot".
#
# ⚠️  disko's `mkfs` create step SKIPS formatting when `blkid` still detects a
#     filesystem signature on the freshly-cut partition:
#
#       if ! (blkid "$device" -o export | grep -q '^TYPE='); then
#         mkfs.btrfs "$device" -f     # ← -f only runs WHEN this line runs
#       fi
#
#     The disk previously held a CachyOS btrfs root. The whole-disk `wipefs`
#     disko runs before partitioning clears the signature at the OLD layout's
#     offsets, but `sgdisk --clear --align-end` then re-cuts the partitions, so
#     a stale btrfs superblock survives at the NEW root partition's own 64 KiB
#     offset. `blkid` sees TYPE=btrfs, `mkfs` is skipped entirely, and the
#     later `mount` fails on the leftover bytes ("wrong fs type / bad
#     superblock"). Switching ext4→btrfs did NOT fix this: `mkfs.btrfs -f` is
#     never reached, because the guard is on whether `mkfs` runs at all, not on
#     its flags. The ESP hits the same trap (its `mkfs.vfat` gets skipped too).
#
#     Fix: `preCreateHook = wipefs --all --force "$device"` on each partition's
#     content. The hook runs AFTER sgdisk re-cuts the partition but BEFORE the
#     `blkid` guard, so it erases the stale signature at the FINAL offset;
#     `blkid` then comes back empty and `mkfs` actually runs.
#
# ⚠️  This disk is WIPED on install. This is the Kingston SA400 SSD that
#     currently holds CachyOS (btrfs root+subvols on sdb2, ESP on sdb1).
#     The dev-data disks (sdc ext4 /mnt/hdd_01, LVM vg_ssd /mnt/ssd_01) and the
#     leftover ntfs disks (sda, sdf, nvme0n1) are NOT listed here — they are
#     mounted as plain fileSystems in configuration.nix (or, for the ntfs
#     disks, ignored entirely) so they are never touched.
{
  disko.devices.disk.os = {
    type = "disk";
    device = "/dev/disk/by-id/ata-KINGSTON_SA400S37480G_50026B738072F6C6";
    content = {
      type = "gpt";
      partitions = {
        ESP = {
          size = "512M";
          type = "EF00";
          content = {
            type = "filesystem";
            format = "vfat";
            mountpoint = "/boot";
            mountOptions = [ "umask=0077" ];
            # erase any stale signature before disko's blkid format-guard (above)
            preCreateHook = ''wipefs --all --force "$device"'';
          };
        };
        root = {
          size = "100%";
          content = {
            type = "btrfs";
            extraArgs = [ "-f" ];
            mountpoint = "/";
            # erase the stale CachyOS btrfs superblock before disko's blkid
            # format-guard, otherwise mkfs.btrfs is skipped (see header comment)
            preCreateHook = ''wipefs --all --force "$device"'';
          };
        };
      };
    };
  };
}