#!/usr/bin/env bash
# Deploy a NixOS host from this flake. ALL arguments are mandatory (no defaults).
#
#   ./deploy kexec   <config> <host>  headless kexec into a RAM installer, for a
#                                     read-only-root box (ZimaOS) where
#                                     nixos-anywhere can't ssh-copy-id. Ships our
#                                     SSH login key. Then run `install`. <config>
#                                     is only used to look up the vault item.
#   ./deploy kexec-local [--yes]      kexec THIS machine into the RAM installer,
#                                     no ssh/second machine involved. Run as root,
#                                     locally, on the box you're installing onto.
#                                     Disks are untouched; console drops for
#                                     ~1-2 min then comes back as the installer.
#                                     Prompts for confirmation (--yes skips it),
#                                     because run on the wrong terminal this
#                                     kexecs your laptop. TMPDIR (default
#                                     /var/tmp) must be exec-capable and hold
#                                     ~3x the tarball.
#                                     Then run `install <config> localhost`.
#   ./deploy install <config> <host>  first install. Wipes the OS disk. Ships the
#                                     host's sops key. <host>=localhost/127.0.0.1
#                                     skips nixos-anywhere/ssh and runs disko +
#                                     nixos-install directly against /mnt — but
#                                     ONLY once actually inside a live installer
#                                     (hostname nixos-installer, from kexec, or
#                                     homelab-installer, from installer-iso).
#                                     Run from the REAL running OS instead (e.g.
#                                     a box where kexec-local doesn't work),
#                                     it builds installer-iso, stages its
#                                     kernel/initrd on the ESP + the iso file on
#                                     a non-OS-disk partition, sets a systemd-boot
#                                     one-shot entry with homelab.install=<config>
#                                     on its kernel cmdline, and reboots — a real
#                                     ACPI reboot, not a kexec jump. The booted
#                                     installer's homelab-auto-install.service
#                                     reads that cmdline param and re-runs this
#                                     exact command itself once its repo checkout
#                                     (homelab-checkout.service) succeeds, finishing
#                                     the install unattended. See CLAUDE.md.
#   ./deploy switch  <config> <host>  rebuild + activate on a running host.
#   ./deploy boot    <config> <host>  stage for next boot, don't activate now.
#   ./deploy test    <config> <host>  activate without adding a boot entry.
#   ./deploy image   <config>         build an SD-card image (e.g. rpi mercury).
#   ./deploy flash   <config> <dev>   build SD image, write to <dev>, and (if
#                                     ~/.config/homelab/<config>/age.txt exists)
#                                     drop the sops key on its boot partition.
#
# <config> = a nixosConfigurations name (e.g. jupiter, vps). Its pre-generated
# SSH host key must be at ~/.config/homelab/<config>/ssh_host_ed25519_key.
#
# Runs from a non-NixOS host too (nixos-rebuild / nixos-anywhere via `nix run`).
#
# Password prompts are auto-filled from the "HomeLab" Proton Pass vault when
# `pass-cli` is installed and logged in; otherwise every command prompts exactly
# as before. Both items are keyed by <config>, never by <host>: the address is
# incidental (DHCP, a new box, localhost) while the config name is the stable
# identity of the machine being built.
#   darman@<config>   darman's sudo password  (switch/boot/test)
#   root@<config>     root's ssh password     (kexec/install)
# Override with HOMELAB_PASS_ITEM / HOMELAB_PASS_ROOT_ITEM / HOMELAB_PASS_VAULT.
set -euo pipefail
shopt -s nullglob

# Captured before anything shifts/parses $@, so require_root() below can
# re-exec the ORIGINAL invocation under sudo — inside a function, "$@"/"$1"
# refer to the function's own args (empty here), not the script's, so this
# has to be a global array instead of relying on positional-parameter scoping.
SCRIPT_ARGS=("$@")

# Locate the repo root (flake dir) regardless of where this script lives on disk.
SCRIPT_PATH="$(realpath "$0")"           # absolute — "$0" itself may be relative,
                                          # and require_root() re-execs after cd "$REPO"
SCRIPT_DIR="$(dirname "$SCRIPT_PATH")"
REPO="$(git -C "$SCRIPT_DIR" rev-parse --show-toplevel 2>/dev/null || dirname "$SCRIPT_DIR")"
cd "$REPO"
export PATH="/nix/var/nix/profiles/default/bin:$PATH"

die() { echo "error: $*" >&2; exit 1; }

need() { command -v "$1" >/dev/null 2>&1 || die "missing required tool: $1"; }

# Self-elevate instead of dying: re-exec this exact invocation under sudo.
# -E preserves the environment (HOMELAB_* overrides, Proton Pass vault vars)
# across the re-exec. A no-op once already root.
require_root() {
  [ "$(id -u)" = 0 ] && return 0
  echo ">> $1 needs root — re-executing under sudo" >&2
  exec sudo -E -- "$SCRIPT_PATH" "${SCRIPT_ARGS[@]}"
}

# Exactly one path matching a glob, or die. `ls glob | head -1` silently yields
# an empty string when nothing matches (head exits 0, so set -e never fires) and
# the failure only surfaces later as a confusing tar/dd error.
one_match() {
  local what="$1"; shift
  local f=("$@")                       # caller expands the glob (nullglob is on)
  [ "${#f[@]}" -gt 0 ] || die "no $what found — did the build actually produce one?"
  printf '%s\n' "${f[0]}"
}

# Sets tb / cpio / bbox — the kexec tarball plus the static cpio+gzip that
# kexec-run.sh needs on PATH to rebuild its initrd.
#
# HOMELAB_KEXEC_TARBALL (with _CPIO / _GZIP) short-circuits the build and uses a
# prebuilt installer instead. That lets the VM test in flake.nix drive this
# script offline, and lets you re-kexec a box without rebuilding ~500MB.
kexec_artifacts() {
  if [ -n "${HOMELAB_KEXEC_TARBALL:-}" ]; then
    tb="$HOMELAB_KEXEC_TARBALL"
    [ -f "$tb" ] || die "HOMELAB_KEXEC_TARBALL=$tb is not a file"
    cpio="${HOMELAB_KEXEC_CPIO:-$(command -v cpio || true)}"
    bbox="${HOMELAB_KEXEC_GZIP:-$(command -v gzip || true)}"
    { [ -n "$cpio" ] && [ -n "$bbox" ]; } \
      || die "set HOMELAB_KEXEC_CPIO / HOMELAB_KEXEC_GZIP, or put cpio+gzip on PATH"
    echo ">> using prebuilt kexec installer: $tb"
  else
    need nix
    echo ">> building kexec installer + static tools"
    nix build .#nixosConfigurations.kexec.config.system.build.kexecInstallerTarball \
      -o result-kexec
    tb="$(one_match 'kexec tarball' result-kexec/*.tar.gz)"
    cpio="$(nix build --no-link --print-out-paths nixpkgs#pkgsStatic.cpio)/bin/cpio"
    bbox="$(nix build --no-link --print-out-paths nixpkgs#pkgsStatic.busybox)/bin/busybox"
  fi
}

# True inside one of the throwaway live-installer environments this repo
# produces (kexec's nixos-installer, or installer-iso's homelab-installer) —
# i.e. `install <config> localhost` should wipe/install right here. False on
# any real running OS, where the same command instead means "prepare and
# reboot into an installer for THIS box" (see local_install_prepare_and_reboot).
is_live_installer() {
  case "$(uname -n)" in
    nixos-installer | homelab-installer) return 0 ;;
    *) return 1 ;;
  esac
}

# `install <config> localhost` run on a REAL running OS (not already inside a
# live installer): builds installer-iso, stages its kernel/initrd + iso file
# locally, points a systemd-boot one-shot entry at them with
# homelab.install=<config> on the kernel cmdline, and reboots — a real ACPI
# reboot through firmware POST, deliberately NOT a kexec jump (see terra's
# kexec-local gotcha in CLAUDE.md). The booted installer's
# homelab-auto-install.service reads that cmdline param and re-runs this exact
# `install <config> localhost` command itself (now genuinely inside the
# installer) once homelab-checkout.service has fetched the repo, finishing the
# job unattended.
local_install_prepare_and_reboot() {
  local config="$1"
  require_root "preparing a local reinstall"
  [ -d /sys/firmware/efi ] || die "not booted UEFI — the one-shot boot entry needs systemd-boot"
  need bootctl
  need nix
  need lsblk
  need findmnt

  # No default/auto-picked location — the wrong disk here is destroyed
  # mid-install (see the OS-disk check below), so this always asks rather
  # than guessing. HOMELAB_INSTALLER_STAGE_DIR skips the prompt for scripted
  # use, but is otherwise just as explicit a choice as typing it in.
  local stagedir="${HOMELAB_INSTALLER_STAGE_DIR:-}"
  if [ -z "$stagedir" ]; then
    echo ">> currently mounted filesystems:"
    lsblk -o NAME,SIZE,FSTYPE,MOUNTPOINT
    read -rp ">> path to stage the installer iso on (must NOT be on the OS disk being wiped): " stagedir
  fi
  [ -n "$stagedir" ] || die "no staging path given"
  [ -d "$stagedir" ] \
    || die "staging dir $stagedir doesn't exist — needs to be an existing partition that is NOT the OS disk being wiped"

  # Refuse if the staging partition turns out to live on the same disk
  # disko is about to wipe — the iso file (and the running installer
  # loopback-mounted from it) would be destroyed mid-install.
  local osdisk osdisk_real stage_src stage_pkname stage_disk_real
  osdisk="$(nix eval --raw ".#nixosConfigurations.$config.config.disko.devices.disk" \
    --apply 'd: (builtins.head (builtins.attrValues d)).device' 2>/dev/null)" \
    || die "couldn't read the OS disk device from hosts/$config/disk-config.nix"
  osdisk_real="$(readlink -f "$osdisk")"
  stage_src="$(findmnt -no SOURCE --target "$stagedir")" \
    || die "$stagedir doesn't resolve to a mounted filesystem"
  stage_pkname="$(lsblk -no PKNAME "$stage_src" 2>/dev/null || true)"
  if [ -n "$stage_pkname" ]; then
    stage_disk_real="$(readlink -f "/dev/$stage_pkname")"
    [ "$stage_disk_real" = "$osdisk_real" ] \
      && die "$stagedir is on the OS disk ($osdisk) that install would wipe — re-run and pick a different disk"
  fi

  echo ">> building installer-iso (kernel + initrd + iso image)"
  local kernel initrd isodir iso mnt_point iso_relpath
  kernel="$(nix build --no-link --print-out-paths .#nixosConfigurations.installer-iso.config.system.build.kernel)/bzImage"
  initrd="$(nix build --no-link --print-out-paths .#nixosConfigurations.installer-iso.config.system.build.initialRamdisk)/initrd"
  isodir="$(nix build --no-link --print-out-paths .#nixosConfigurations.installer-iso.config.system.build.isoImage)"
  iso="$(one_match 'installer iso' "$isodir"/iso/*.iso)"

  echo ">> staging kernel/initrd on the ESP, iso image on $stagedir"
  install -Dm644 "$kernel" /boot/homelab-installer/bzImage
  install -Dm644 "$initrd" /boot/homelab-installer/initrd
  install -Dm644 "$iso"    "$stagedir/homelab-installer.iso"

  # findiso= is a path relative to whatever partition the initrd finds it on
  # (it mounts every blkid-visible partition looking for it) — not necessarily
  # relative to `/`, if $stagedir is a subdirectory of a bigger filesystem
  # rather than a mountpoint itself.
  mnt_point="$(findmnt -no TARGET --target "$stagedir")"
  iso_relpath="${stagedir#"$mnt_point"}/homelab-installer.iso"

  cat >/boot/loader/entries/homelab-installer.conf <<EOF
title Homelab Installer ($config, findiso)
linux /homelab-installer/bzImage
initrd /homelab-installer/initrd
options nohibernate root=fstab loglevel=4 lsm=landlock,yama,bpf findiso=$iso_relpath homelab.install=$config
EOF

  echo ">> one-shot boot into the installer, then rebooting — it will finish this install itself"
  bootctl set-oneshot homelab-installer.conf
  systemctl reboot
}

# Flakes only see git-tracked files: an untracked hosts/<config>/ is silently
# invisible to `nix build`/`nixos-install`, which then fails obscurely or builds
# a stale config. Check before doing anything destructive.
require_tracked() {
  local config="$1" cfgfile="hosts/$1/configuration.nix"
  [ -e "$cfgfile" ] || die "no $cfgfile in the repo"
  # No .git at all (e.g. a tarball export of the repo, no working tree) means
  # there's nothing that CAN be untracked — nothing to check. Only skip on a
  # MISSING .git, not on any other git failure.
  git -C "$REPO" rev-parse --is-inside-work-tree >/dev/null 2>&1 || return 0
  git -C "$REPO" ls-files --error-unmatch "$cfgfile" >/dev/null 2>&1 \
    || die "$cfgfile is untracked — 'git add hosts/$config' first (flakes ignore untracked files)"
}

# The password field of a Proton Pass item ("--field password" prints the bare
# value, one line), or empty if pass-cli is missing / logged out / has no such
# item — every caller then falls back to the normal interactive prompt.
#
# Resolve the title to an item id among ACTIVE items first, because `item view
# --item-title` has no state filter: Proton Pass keeps deleted items in the
# trash, and if a trashed item shares the title, view can match THAT one and
# return an empty password with exit 0. Empty is indistinguishable from "no such
# item", so the only symptom is a silent fall back to the interactive prompt
# even though the vault clearly holds the entry. (Hit for real on darman@neptun,
# which had an Active and a Trashed copy.)
proton_pass_password() {
  local title="$1" vault="${HOMELAB_PASS_VAULT:-HomeLab}" id pw
  command -v pass-cli >/dev/null 2>&1 || return 0

  # Lines look like:  - [ITEM_ID]: the title (state=Active)
  id="$(pass-cli item list --vault-name "$vault" --filter-state active \
          --output human 2>/dev/null \
        | awk -v t="$title" '
            { i = index($0, "]: "); if (i == 0) next
              id   = substr($0, 4, i - 4)
              rest = substr($0, i + 3)
              sub(/ \(state=[^)]*\)$/, "", rest)
              if (rest == t) { print id; exit } }' || true)"

  if [ -n "$id" ]; then
    pw="$(pass-cli item view --vault-name "$vault" --item-id "$id" \
            --field password --output human 2>/dev/null | head -1 || true)"
    # Resolved an active item but its password field is blank: worth saying so,
    # otherwise this looks identical to having no vault entry at all.
    [ -n "$pw" ] || echo ">> vault item '$title' resolved but its password field is empty" >&2
  else
    # No active match — fall back to the title lookup so an older pass-cli
    # without --filter-state still works exactly as it used to.
    pw="$(pass-cli item view --vault-name "$vault" --item-title "$title" \
            --field password --output human 2>/dev/null | head -1 || true)"
  fi

  printf '%s' "$pw"
}

# Path to an sshpass binary (system one, else built from nixpkgs). Empty if
# neither is available.
sshpass_bin() {
  command -v sshpass 2>/dev/null && return 0
  nix build --no-link --print-out-paths nixpkgs#sshpass 2>/dev/null \
    | sed 's|$|/bin/sshpass|'
}

cmd="${1:-}"; [ -n "$cmd" ] || die "usage: ./deploy <kexec|kexec-local|install|switch|boot|test|image|flash> ..."

case "$cmd" in
  kexec)
    config="${2:-}"; host="${3:-}"
    { [ -n "$config" ] && [ -n "$host" ]; } || die "usage: ./deploy kexec <config> <host>"

    need ssh; need scp

    # kexec/run rebuilds an initrd with `cpio` + `gzip` from PATH — ZimaOS lacks
    # both. Ship static ones: GNU cpio (reliable -o -H newc), busybox as gzip.
    kexec_artifacts

    # One password prompt: multiplex scp + ssh over a shared control connection.
    cm="/tmp/homelab-cm-%r@%h:%p"
    o=(-o ControlMaster=auto -o "ControlPath=$cm" -o ControlPersist=300 \
       -o StrictHostKeyChecking=accept-new)

    # Root's password from Proton Pass, fed to ssh/scp via sshpass -e. Only the
    # first (master) connection authenticates; the rest ride the control socket.
    #
    # SSHPASS is exported here rather than passed as `env SSHPASS=... sshpass`.
    # Both end up equally safe at rest: `env` execs its target immediately, so
    # the assignment is only in argv for the sub-millisecond before exec, after
    # which /proc/PID/cmdline reads plain `sshpass -e`. Exporting just closes
    # that race window and drops a process. Either way the secret lives in the
    # child's environ, which is readable by the owner and root only.
    sp=()
    root_item="${HOMELAB_PASS_ROOT_ITEM:-root@$config}"
    root_pw="$(proton_pass_password "$root_item" || true)"
    if [ -n "$root_pw" ]; then
      sshpass="$(sshpass_bin || true)"
      if [ -n "$sshpass" ]; then
        export SSHPASS="$root_pw"
        sp=("$sshpass" -e)
        # sshpass drives the password prompt; don't let a key/agent short-circuit
        # into an interactive one for a host that only accepts passwords.
        o+=(-o PreferredAuthentications=password -o PubkeyAuthentication=no)
      else
        echo ">> sshpass unavailable — falling back to the interactive prompt" >&2
      fi
    fi
    unset root_pw

    if [ "${#sp[@]}" -gt 0 ]; then
      echo ">> connecting to root@$host  (password from Proton Pass: $root_item)"
    else
      echo ">> connecting to root@$host  (enter the root password once)"
    fi
    "${sp[@]+"${sp[@]}"}" ssh "${o[@]}" "root@$host" 'mkdir -p /tmp/bin'
    scp "${o[@]}" "$cpio" "root@$host:/tmp/bin/cpio"
    scp "${o[@]}" "$bbox" "root@$host:/tmp/bin/gzip"   # busybox as gzip (argv0)

    echo ">> streaming installer + kexec-ing. SSH drops as the box jumps into the"
    echo "   RAM installer. Disks are untouched."
    rc=0
    ssh "${o[@]}" "root@$host" \
      'chmod +x /tmp/bin/*; mkdir -p /tmp/k && tar -C /tmp/k -xzf - && PATH=/tmp/bin:$PATH /tmp/k/kexec/run' \
      < "$tb" || rc=$?
    # A dropped connection IS the success case here, so this can't be fatal —
    # but a full /tmp, a tar error or a missing static tool looks identical from
    # the outside, so at least surface the code instead of swallowing it.
    [ "$rc" -eq 0 ] || echo ">> ssh exited $rc — expected if the box jumped; suspect this if install can't connect" >&2

    ssh "${o[@]}" -O exit "root@$host" 2>/dev/null || true  # close control socket
    unset SSHPASS

    # NB: no ssh-keygen -R here on purpose. kexec-run.sh copies /etc/ssh/ssh_host_*
    # into the appended initrd and restore-remote-access.nix installs them back
    # into the installer's /etc/ssh, so the host key SURVIVES the jump. Clearing
    # known_hosts would just throw away the TOFU record for no reason.

    echo ">> box is kexec-ing. Wait ~1-2 min for the installer + network, then:"
    echo "   ./deploy install $config $host"
    ;;

  kexec-local)
    # No ssh, no second machine: build the same RAM installer as `kexec`, but
    # run it directly on this box (you're sitting at it). The current shell
    # drops when the kernel switches, same as any reboot — that's expected,
    # not a failure. Disks are untouched; only the running kernel changes.
    #
    # This is a one-way trip on the machine you are typing at, so every check
    # that can fail is done BEFORE the point of no return, and nothing that the
    # jump depends on is cleaned up behind it (see the trap discussion below).
    require_root "kexec-local"

    assume_yes=""
    [ "${2:-}" = "--yes" ] && assume_yes=1

    need tar; need install; need mktemp; need find; need sync; need nohup

    # --- preflight: reasons the jump would fail, checked while it's still safe --
    # CONFIG_KEXEC. Without it kexec --load fails and you've built ~1GB for
    # nothing; with lockdown it fails at load time too (Secure Boot blocks the
    # kexec_load syscall unless the image is signed).
    [ -e /sys/kernel/kexec_loaded ] \
      || die "this kernel has no kexec support (CONFIG_KEXEC) — boot install media instead"
    if [ -r /sys/kernel/security/lockdown ] \
       && ! grep -q '\[none\]' /sys/kernel/security/lockdown 2>/dev/null; then
      die "kernel lockdown is active — kexec_load is blocked. Disable Secure Boot, or boot install media."
    fi

    kexec_artifacts

    # Staging lives on /var/tmp, not /tmp: kexec-run.sh APPENDS a fresh cpio to
    # kexec/initrd in place and runs binaries out of this directory, so it needs
    # real space and exec permission. A tmpfs /tmp is both size-capped (ENOSPC
    # mid-append = a half-written initrd) and frequently noexec.
    stage="$(TMPDIR="${TMPDIR:-/var/tmp}" mktemp -d)"
    trap 'rm -rf "$stage"' EXIT

    # noexec would only surface as a cryptic "Permission denied" on kexec/run.
    printf '#!/bin/sh\nexit 0\n' > "$stage/.execmove"
    chmod +x "$stage/.execmove"
    "$stage/.execmove" 2>/dev/null \
      || die "$stage is mounted noexec — set TMPDIR to an exec-capable filesystem"
    rm -f "$stage/.execmove"

    # Need room for the tarball, its extracted contents, and the appended cpio.
    tb_sz="$(stat -Lc %s "$tb")"
    avail="$(df -B1 --output=avail "$stage" | tail -1 | tr -d ' ')"
    [ "$avail" -ge $(( tb_sz * 3 )) ] \
      || die "only $(( avail / 1024 / 1024 ))MB free on $stage, need ~$(( tb_sz * 3 / 1024 / 1024 ))MB — set TMPDIR elsewhere"

    install -Dm755 "$cpio" "$stage/bin/cpio"
    install -Dm755 "$bbox" "$stage/bin/gzip"   # busybox as gzip (argv0)
    mkdir -p "$stage/k" && tar -C "$stage/k" -xzf "$tb"

    # Fail loudly here rather than with a bare "not found" from kexec/run.
    for f in run kexec bzImage initrd ip; do
      [ -f "$stage/k/kexec/$f" ] || die "kexec tarball is missing kexec/$f — bad build?"
    done

    # The installer root is a RAM disk: the initrd has to fit in memory with
    # room to unpack. Refuse rather than OOM halfway into the new kernel, where
    # there is no way back except the power button.
    img_sz="$(( $(stat -Lc %s "$stage/k/kexec/initrd") + $(stat -Lc %s "$stage/k/kexec/bzImage") ))"
    mem_kb="$(awk '/^MemTotal:/{print $2}' /proc/meminfo)"
    [ "$(( mem_kb * 1024 ))" -ge "$(( img_sz * 3 ))" ] \
      || die "only $(( mem_kb / 1024 ))MB RAM for a $(( img_sz / 1024 / 1024 ))MB RAM-disk installer — too tight, boot install media instead"

    # --- confirmation: this script normally runs on the LAPTOP ------------------
    # A stray `kexec-local` here would jump the machine you develop on, not the
    # target. Name it explicitly so a wrong-terminal mistake is visible.
    echo ">> about to kexec THIS machine:"
    echo "   hostname: $(uname -n)"
    echo "   kernel:   $(uname -r)"
    echo "   root:     $(findmnt -no SOURCE / 2>/dev/null || echo '?')"
    echo "   Disks are untouched; only the running kernel changes. Console drops"
    echo "   for ~1-2 min, then comes back as the installer."
    if [ -z "$assume_yes" ]; then
      read -rp ">> type 'yes' to kexec $(uname -n) into the RAM installer: " ok
      [ "$ok" = yes ] || die "aborted"
    fi

    # kexec -e jumps straight to the new kernel: no unmount, no journal flush,
    # no systemd shutdown. Anything still in page cache is lost and the OS disk
    # is left dirty. Cheap insurance, since the box may yet be rebooted back.
    sync

    echo ">> loading the new kernel"
    if ! PATH="$stage/bin:$PATH" "$stage/k/kexec/run"; then
      rm -rf "$stage"
      die "kexec/run failed — machine untouched, still on the old kernel"
    fi

    # kexec --load succeeded iff the kernel now reports a loaded image. If this
    # is 0 the background `kexec -e` below will do nothing and we'd hang forever
    # waiting for a jump that cannot happen.
    [ "$(cat /sys/kernel/kexec_loaded 2>/dev/null || echo 0)" = 1 ] \
      || { rm -rf "$stage"; die "kexec reported success but no image is loaded — aborting"; }

    # THE trap MUST GO NOW. kexec-run.sh backgrounds `nohup sh -c "sleep 6 &&
    # $SCRIPT_DIR/kexec -e"` and returns immediately, so the binary that
    # performs the jump still has to exist ~6s after this script would normally
    # exit. Letting the EXIT trap rm -rf "$stage" deletes it out from under that
    # sleeping shell and the machine silently never jumps.
    trap - EXIT

    sync
    echo ">> kernel loaded; jumping in ~6s. (staging left at $stage on purpose —"
    echo "   the backgrounded kexec still needs it; it's gone after the jump.)"
    # Outlive the sleep 6 so the jump happens while this script is still alive.
    sleep 60
    die "still here after 60s — the jump did not happen. Check dmesg; the old system is intact."
    ;;

  install)
    config="${2:-}"; host="${3:-}"
    { [ -n "$config" ] && [ -n "$host" ]; } || die "usage: ./deploy install <config> <host>"
    hostkey="$HOME/.config/homelab/$config/ssh_host_ed25519_key"
    [ -f "$hostkey" ] || die "missing host key: $hostkey"
    [ -d "./hosts/$config" ] || die "no ./hosts/$config directory in the repo"
    require_tracked "$config"

    if [ "$host" = "localhost" ] || [ "$host" = "127.0.0.1" ]; then
      if ! is_live_installer; then
        # Not already inside a live installer: build one, stage it, one-shot
        # boot into it, and let it finish this exact command itself. See
        # local_install_prepare_and_reboot above and CLAUDE.md.
        local_install_prepare_and_reboot "$config"
        exit 0
      fi

      # Local install: no ssh, no nixos-anywhere. Run after `kexec-local` (or
      # from a live ISO) so /mnt is free to wipe — this IS the box, no second
      # machine in the loop, so skip straight to disko + nixos-install.
      require_root "local install"
      [ -f "./hosts/$config/disk-config.nix" ] || die "no ./hosts/$config/disk-config.nix"

      echo ">> disko .#$config onto this box's OS disk (WILL be wiped)"
      nix run github:nix-community/disko -- \
        --mode disko "./hosts/$config/disk-config.nix"

      echo ">> installing sops host key so it can decrypt on boot #1"
      install -Dm600 "$hostkey"     /mnt/etc/ssh/ssh_host_ed25519_key
      install -Dm644 "$hostkey.pub" /mnt/etc/ssh/ssh_host_ed25519_key.pub

      echo ">> nixos-install .#$config into /mnt"
      nixos-install --root /mnt --flake ".#$config"
    else
      # Stage the pre-generated SSH host key so sops can decrypt on boot #1.
      stage="$(mktemp -d)"
      trap 'rm -rf "$stage"' EXIT
      install -Dm600 "$hostkey"      "$stage/etc/ssh/ssh_host_ed25519_key"
      install -Dm644 "$hostkey.pub"  "$stage/etc/ssh/ssh_host_ed25519_key.pub"

      echo ">> nixos-anywhere .#$config onto root@$host (OS disk WILL be wiped)"
      anywhere=(--flake ".#$config"
                --extra-files "$stage"
                --generate-hardware-config nixos-generate-config "./hosts/$config/hardware-configuration.nix"
                --target-host "root@$host")

      # nixos-anywhere's --env-password reads root's ssh password from $SSHPASS
      # (it ships its own sshpass), so a vault hit skips the ssh-copy-id prompt.
      # Exported rather than `env SSHPASS=...` for consistency with `kexec`;
      # see the note there — it's a marginal win, not a leak fix.
      root_item="${HOMELAB_PASS_ROOT_ITEM:-root@$config}"
      root_pw="$(proton_pass_password "$root_item" || true)"
      if [ -n "$root_pw" ]; then
        echo ">> root ssh password from Proton Pass ($root_item)"
        export SSHPASS="$root_pw"
        unset root_pw
        nix run github:nix-community/nixos-anywhere -- \
          --env-password "${anywhere[@]}"
        unset SSHPASS
      else
        nix run github:nix-community/nixos-anywhere -- "${anywhere[@]}"
      fi
    fi
    ;;

  switch|boot|test)
    config="${2:-}"; host="${3:-}"
    { [ -n "$config" ] && [ -n "$host" ]; } || die "usage: ./deploy $cmd <config> <host>"
    require_tracked "$config"

    echo ">> nixos-rebuild $cmd .#$config on darman@$host"
    # --ask-sudo-password, not the deprecated --use-remote-sudo: common.nix sets
    # security.sudo.wheelNeedsPassword = true, and --use-remote-sudo only
    # prefixes with sudo without ever prompting. Asks for darman's password
    # (the darman_password hash in each host's sops file).
    rebuild=(nix run nixpkgs#nixos-rebuild -- "$cmd"
             --flake ".#$config"
             --target-host "darman@$host"
             --ask-sudo-password)

    item="${HOMELAB_PASS_ITEM:-darman@$config}"
    pw="$(proton_pass_password "$item" || true)"
    if [ -n "$pw" ] && command -v setsid >/dev/null 2>&1; then
      # nixos-rebuild prompts with getpass(), which reads /dev/tty and ignores a
      # piped stdin. setsid drops the controlling terminal, so getpass falls back
      # to stdin and takes the vault password (it warns about echo — harmless,
      # nothing is echoed since the password never reaches the terminal).
      #
      # Caveat of dropping the tty: EVERY prompt in the subtree now reads this
      # stdin, not just the sudo one. Feed the line a few times so a retry or a
      # second sudo ask doesn't hit EOF and hang. Anything else that prompts
      # (an ssh key passphrase, a host-key confirmation) will still fail — fix
      # those out of band rather than by feeding more lines here.
      echo ">> sudo password from Proton Pass ($item)"
      printf '%s\n%s\n%s\n' "$pw" "$pw" "$pw" | setsid -w "${rebuild[@]}"
    else
      "${rebuild[@]}"
    fi
    unset pw
    ;;

  image|flash)
    if [ "$cmd" = flash ]; then
      config="${2:-}"; dev="${3:-}"
      { [ -n "$config" ] && [ -n "$dev" ]; } \
        || die "usage: ./deploy flash <config> <dev>  (e.g. /dev/sdX)"
      # Validate the device and the tools BEFORE building, so a bad `flash`
      # fails fast instead of dying halfway through writing the card.
      [ -b "$dev" ] || die "$dev is not a block device"
      need zstdcat; need dd; need lsblk
    else
      config="${2:-}"; [ -n "$config" ] || die "usage: ./deploy image <config>"
    fi
    require_tracked "$config"

    echo ">> building SD image for .#$config (aarch64 needs qemu binfmt)"
    nix build ".#nixosConfigurations.$config.config.system.build.sdImage" -o result-sd
    img="$(one_match 'SD image' result-sd/sd-image/*.img.zst)"
    echo ">> image: $img"
    [ "$cmd" = image ] && exit 0

    echo ">> TARGET DEVICE — everything on it will be ERASED:"
    lsblk -o NAME,SIZE,MODEL,TRAN,MOUNTPOINTS "$dev"
    read -rp ">> type 'yes' to write $config to $dev: " ok
    [ "$ok" = yes ] || die "aborted"
    zstdcat "$img" | sudo dd of="$dev" bs=4M status=progress oflag=sync
    sync

    # If this config has a dedicated sops age key, drop it on the ROOT ext4
    # partition at /var/lib/sops-nix/age.txt so sops decrypts on first boot.
    # (The Pi's vfat partition isn't mounted at runtime, so the key can't live
    # there.) Key stays off-repo, out of the nix store, and out of the image.
    keyfile="$HOME/.config/homelab/$config/age.txt"
    if [ -f "$keyfile" ]; then
      echo ">> installing sops age key onto the root partition"
      sudo partprobe "$dev" 2>/dev/null || sudo blockdev --rereadpt "$dev" 2>/dev/null || true
      sudo udevadm settle 2>/dev/null || true
      # Largest ext4 partition = the NixOS root. -P (KEY="value" pairs) instead
      # of a columnar listing: an empty FSTYPE collapses under whitespace
      # splitting and shifts every later field.
      rootpart="$(lsblk -bPo PATH,FSTYPE,SIZE "$dev" \
        | sed -n 's/^PATH="\([^"]*\)" FSTYPE="ext4" SIZE="\([0-9]*\)"$/\2 \1/p' \
        | sort -rn | head -1 | cut -d' ' -f2)"
      [ -n "$rootpart" ] || die "no ext4 root partition found on $dev — place $keyfile at /var/lib/sops-nix/age.txt manually"
      mnt="$(mktemp -d)"
      sudo mount "$rootpart" "$mnt"
      sudo install -Dm600 "$keyfile" "$mnt/var/lib/sops-nix/age.txt"
      sudo sync
      sudo umount "$mnt"; rmdir "$mnt"
      echo ">> age key installed (/var/lib/sops-nix/age.txt)"
    fi
    echo ">> done — insert the card into the Pi and boot."
    ;;

  *)
    die "unknown command '$cmd' (kexec|kexec-local|install|switch|boot|test|image|flash)"
    ;;
esac
