#!/bin/sh
# /etc/rc.d/rc.snapd - snapd with socket activation, no systemd
LIBEXEC=/usr/lib@LIB@/snapd
PIDFILE=/run/snapd-activate.pid
UNITDIR=${SNAPD_UNIT_DIR:-/etc/systemd/system}

# snapd.mounts.target equivalent: snapd records each snap mount as a .mount
# unit file; with SNAPD_NO_SYSTEMD=1 nothing re-mounts them at boot, so do it here
mount_snaps() {
  for f in "$UNITDIR"/*.mount; do
    [ -f "$f" ] || continue
    grep -q '^Description=Mount unit for' "$f" || continue
    what=$(sed -n 's/^What=//p' "$f" | head -n1)
    where=$(sed -n 's/^Where=//p' "$f" | head -n1)
    type=$(sed -n 's/^Type=//p' "$f" | head -n1)
    opts=$(sed -n 's/^Options=//p' "$f" | head -n1)
    [ -n "$what" ] && [ -n "$where" ] || continue
    mountpoint -q "$where" && continue
    mkdir -p "$where"
    mount -t "$type" -o "${opts:-ro}" "$what" "$where" ||
      echo "rc.snapd: cannot mount $what on $where" >&2
  done
}

# snapd tracks snap processes through a name=systemd (or name=elogind) cgroup v1
# hierarchy; v2 needs nothing. Only create an empty one if the host has neither.
mount_cgroup() {
  [ "$(stat -f -c %T /sys/fs/cgroup 2>/dev/null)" = cgroup2fs ] && return
  grep -qE 'name=(systemd|elogind)' /proc/self/cgroup && return
  [ -e /sys/fs/cgroup/systemd ] && return
  mkdir -p /sys/fs/cgroup/systemd
  mount -t cgroup -o none,name=systemd cgroup /sys/fs/cgroup/systemd ||
    echo "rc.snapd: cannot mount name=systemd cgroup" >&2
}

snapd_start() {
  [ -s $PIDFILE ] && kill -0 "$(cat $PIDFILE)" 2>/dev/null && { echo "snapd already running"; return; }
  mkdir -p /var/lib/snapd/snap /var/lib/snapd/environment
  [ -e /snap ] || ln -s /var/lib/snapd/snap /snap

  # EnvironmentFile= equivalents (must set SNAPD_NO_SYSTEMD=1)
  set -a
  [ -r /etc/default/snapd ] && . /etc/default/snapd
  [ -r /var/lib/snapd/environment/snapd.conf ] && . /var/lib/snapd/environment/snapd.conf
  set +a

  mount_cgroup
  mount_snaps

  echo -900 > /proc/self/oom_score_adj 2>/dev/null   # OOMScoreAdjust=-900
  # snapd.socket: /run/snapd.socket /run/snapd-snap.socket, mode 0666 root:root
  setsid /usr/sbin/snapd-activate -m 0666 /run/snapd.socket /run/snapd-snap.socket -- \
    $LIBEXEC/snapd >>/var/log/snapd.log 2>&1 </dev/null &
  echo $! > $PIDFILE
}

snapd_stop() {
  [ -s $PIDFILE ] && kill "$(cat $PIDFILE)" 2>/dev/null   # activator forwards SIGTERM to snapd
  rm -f $PIDFILE /run/snapd.socket /run/snapd-snap.socket
}

case "$1" in
  start)   snapd_start ;;
  stop)    snapd_stop ;;
  restart) snapd_stop; sleep 1; snapd_start ;;
  mount)   mount_snaps ;;
  *) echo "usage: $0 {start|stop|restart|mount}" ;;
esac