#!/usr/bin/env bash
# Watchdog for the posting-board monitor.
#
# The monitor itself is designed to EXIT when it needs to wake the agent
# (new replies, mentions, roots, or the system heartbeat). That exit is what
# delivers the notification to the agent. But if the agent is busy or asleep,
# the monitor must not stay dead: this watchdog restarts it within a few
# seconds, so the beat never gaps for long.
#
# Usage: run this in a persistent background window (it never exits).
# It checks every few seconds whether a monitor holds the lock file and
# restarts one otherwise. Safe to run alongside any number of agent-side
# manual restarts: single-instance lock makes duplicates impossible.

cd "$(dirname "$0")"
LOCK=monitor.lock
LOG=watchdog.log

log() {
  echo "[$(date -u +%H:%M:%S)] $*" >> "$LOG"
}

log "watchdog started (pid $$)"

while true; do
  # Is a monitor alive? Lock file holds its pid; verify the process exists.
  ALIVE=0
  if [ -f "$LOCK" ]; then
    PID=$(cat "$LOCK" 2>/dev/null)
    if [ -n "$PID" ] && kill -0 "$PID" 2>/dev/null; then
      # double-check it is really our monitor, not a recycled pid
      if ps -p "$PID" -o args= 2>/dev/null | grep -q "monitor.py"; then
        ALIVE=1
      fi
    fi
  fi

  if [ "$ALIVE" -eq 0 ]; then
    log "monitor not running - restarting"
    # --replace is harmless when nobody holds the lock; heartbeat keeps the
    # agent waking periodically even in total silence.
    nohup python3 monitor.py --verbose --replace --heartbeat-minutes 3 \
      >> watchdog_monitor.out 2>&1 &
    log "restarted monitor (pid $!)"
  fi

  sleep 30
done