#!/usr/bin/env bash
# Update the running GL-MT6000 over SSH without reflashing.
#
#   ./deploy-mt6000.sh                build mt6000.scm, copy, switch, reboot
#   ./deploy-mt6000.sh --no-reboot    ... activate only (the new kernel and
#                                     services start on the next boot)
#   ./deploy-mt6000.sh switch N       make existing generation N the default
#                                     (roll back), activate, reboot
#   ./deploy-mt6000.sh list           show the router's system generations
#
# As deploy-rpi.sh: the system is cross-built here and sent with `guix copy'.
# GL's U-Boot boots one FIT from the `kernel' partition (p6), with no menu,
# so switching to a generation means writing its FIT (scripts/mt6000-fit.sh,
# built here) to p6.  If a new generation doesn't come up, roll back from
# ssh if it gets that far, else through U-Boot's TFTP recovery
# (docs/PITFALLS.md #51) -- an interrupted p6 write needs that too.
#
# Needs: ~/.ssh/config entry for $ROUTER, /etc/guix/signing-key.* on this
# host, and that key in the router's guix-service-type authorized-keys
# (mt6000.scm).
set -euo pipefail
cd "$(dirname "$0")"
export PATH=$HOME/.local/bin:$PATH
export GUIX_PACKAGE_PATH="$PWD/packages:$HOME/channels/nonguix"
ROUTER=${ROUTER:-mt6000}
PROFILES=/var/guix/profiles
KERNEL_PART=/dev/mmcblk0p6

# -n: never read stdin (it would swallow `while read` loop input).
router() { ssh -n -o BatchMode=yes "$ROUTER" "$@"; }

# "N /gnu/store/…-system" for each generation, ascending.
generations() {
  router "cd $PROFILES && for l in system-*-link; do n=\${l#system-}; echo \"\${n%-link} \$(readlink \$l)\"; done" |
    sort -n
}

current() { router "readlink -f $PROFILES/system"; }

# Write the FIT for system $1 to p6 and check it.  The system's kernel and
# initrd must be in this host's store (they are: it built them).
install_fit() {
  local sys=$1 tmp sum
  [ -d "$sys" ] || guix build "$sys" >/dev/null
  tmp=$(mktemp -d)
  scripts/mt6000-fit.sh "$sys" "$tmp/boot.itb"
  ssh -o BatchMode=yes "$ROUTER" "dd of=$KERNEL_PART bs=64k conv=fsync 2>/dev/null" < "$tmp/boot.itb"
  sum=$(router "head -c $(stat -c %s "$tmp/boot.itb") $KERNEL_PART | sha256sum" | cut -c1-64)
  if [ "$sum" != "$(sha256sum < "$tmp/boot.itb" | cut -c1-64)" ]; then
    rm -rf "$tmp"
    echo "FIT on $KERNEL_PART does not match: rewrite it before rebooting" >&2
    exit 1
  fi
  rm -rf "$tmp"
  echo "FIT written to $KERNEL_PART"
}

# Point the system profile at generation $1, write its FIT, activate it.
switch_to() {
  local n=$1 path
  path=$(router "readlink $PROFILES/system-$n-link")
  install_fit "$path"
  router "ln -sfn system-$n-link $PROFILES/system.new && mv -T $PROFILES/system.new $PROFILES/system"
  echo "activating generation $n ($path)"
  # activate.scm picks the system from GUIX_NEW_SYSTEM (set by reconfigure
  # and at boot); without it, it re-activates /run/current-system.
  router "GUIX_NEW_SYSTEM=$path $path/activate" ||
    echo "warning: activation reported errors" >&2
}

reboot_router() {
  echo "rebooting $ROUTER"
  router "sync; (sleep 1; reboot) >/dev/null 2>&1 &" || true
}

case "${1:-deploy}" in
  list)
    cur=$(current)
    generations | while read -r n path; do
      echo "$n $path$( [ "$path" = "$cur" ] && echo '  (current)')"
    done ;;
  switch)
    n=${2:?usage: deploy-mt6000.sh switch N}
    switch_to "$n"
    [ "${3:-}" = --no-reboot ] || reboot_router ;;
  deploy|--no-reboot)
    sys=$(guix system build --target=aarch64-linux-gnu mt6000.scm | tail -1)
    echo "built $sys"
    if [ "$sys" = "$(current)" ]; then echo "already running $sys"; exit 0; fi
    guix copy --to="$ROUTER" "$sys"
    last=$(generations | tail -1 | cut -d' ' -f1)
    n=$((last + 1))
    router "ln -sfn $sys $PROFILES/system-$n-link"
    echo "registered generation $n"
    switch_to "$n"
    [ "${1:-deploy}" = --no-reboot ] || reboot_router ;;
  *)
    sed -n '2,10p' "$0"; exit 1 ;;
esac