#!/usr/bin/env bash
# i3bar-watchdog [session-pid] (module i3status-rust, novox/hq ADR 0208): respawns a bar that died.
#
# i3 starts one i3bar per `bar { }` block and never restarts one that exits, and a reload does not
# either. Changing the monitor setup reliably kills the bar that owns the tray. This brings back the
# one missing i3bar, without restarting i3, and logs the outputs at that moment: the evidence for the
# cause, which is i3bar's.
#
# Started once per session from the session's start, with the session's own pid; it ends when that
# process does. Adopted from the predecessor's i3-bar-watchdog user unit of 2026-10-04.
set -uo pipefail

session_pid="${1:-}"
interval="${I3_BAR_WATCHDOG_INTERVAL:-5}"
# Two misses in a row before acting: an i3 restart tears every bar down and starts them again.
confirm="${I3_BAR_WATCHDOG_CONFIRM:-2}"
# Never respawn the same bar more often than this, so a bar that dies at once is not a tight loop.
cooldown="${I3_BAR_WATCHDOG_COOLDOWN:-30}"

log() { printf 'i3bar-watchdog: %s\n' "$*" >&2; }

for tool in i3-msg i3bar pgrep; do
	command -v "$tool" >/dev/null 2>&1 || {
		log "$tool is missing; not watching"
		exit 1
	}
done

declare -A missed=() fixed=()

bar_ids() { i3-msg -t get_bar_config 2>/dev/null | grep -oE '"[^"]+"' | tr -d '"'; }
outputs() { xrandr --listmonitors 2>/dev/null | tail -n +2 | awk '{print $2" "$3}' | tr '\n' ' '; }
session_alive() { [ -z "$session_pid" ] || kill -0 "$session_pid" 2>/dev/null; }

while session_alive; do
	sleep "$interval"
	socket="$(i3 --get-socketpath 2>/dev/null)"
	[ -n "$socket" ] && [ -S "$socket" ] || continue
	ids="$(bar_ids)"
	[ -n "$ids" ] || continue
	while read -r id; do
		[ -n "$id" ] || continue
		if pgrep -u "$EUID" -f -- "i3bar --bar_id=$id" >/dev/null 2>&1; then
			missed[$id]=0
			continue
		fi
		missed[$id]=$((${missed[$id]:-0} + 1))
		[ "${missed[$id]}" -ge "$confirm" ] || continue
		now="$(date +%s)"
		if [ $((now - ${fixed[$id]:-0})) -lt "$cooldown" ]; then
			continue
		fi
		log "$id is gone; respawning it. Outputs now: $(outputs)"
		nohup i3bar --bar_id="$id" --socket="$socket" >/dev/null 2>&1 &
		disown 2>/dev/null || true
		fixed[$id]="$now"
		sleep 2
		if pgrep -u "$EUID" -f -- "i3bar --bar_id=$id" >/dev/null 2>&1; then
			missed[$id]=0
		else
			log "$id exited within 2s of respawning; check its status_command"
		fi
	done <<<"$ids"
done