#!/bin/bash
# capture-watchdog.sh — monitor image output for a camera and send a
# notification if no new frame arrives within CAPTURE_STALE_SECS seconds.
# Sends a recovery notification once capture resumes.
#
# Runs as a long-running systemd service alongside sky-cam-capture-<cam>.
# One instance per camera, camera name passed as $1.

set -euo pipefail

SCRIPT_DIR="$(dirname "$(realpath "$0")")"
source "$SCRIPT_DIR/sky-cam.conf"
export TZ="$TIMEZONE"

CAM="${1:-}"
if [ -z "$CAM" ]; then
    echo "Usage: $0 <camera-name>"
    exit 1
fi
STALE_SECS="${CAPTURE_STALE_SECS:-30}"
CHECK_INTERVAL=$(( STALE_SECS / 3 ))
[ "$CHECK_INTERVAL" -lt 5 ] && CHECK_INTERVAL=5

echo "Watchdog started for ${CAM} — alerting after ${STALE_SECS}s without a new frame"

last_good=0       # epoch seconds of the newest frame we have seen
stale_notified=false

while true; do
    sleep "$CHECK_INTERVAL"

    today=$(date +%Y-%m-%d)
    dir="$BASE_DIR/$CAM/$today"
    now=$(date +%s)

    # Find newest JPEG in today's directory
    if [ -d "$dir" ]; then
        latest_file=$(ls -t "$dir"/*.jpg 2>/dev/null | head -1 || true)
        if [ -n "$latest_file" ]; then
            latest_mtime=$(stat -c %Y "$latest_file")
            if [ "$latest_mtime" -gt "$last_good" ]; then
                last_good=$latest_mtime
                # Recovery — was stale, now seeing new frames again
                if $stale_notified; then
                    stale_for=$(( now - last_good + STALE_SECS ))
                    echo "Capture resumed for ${CAM} after ~${stale_for}s stall"
                    "$SCRIPT_DIR/notify.sh" "Capture resumed: ${CAM}" \
                        "New frames arriving again after ~${stale_for}s without capture" || true
                    stale_notified=false
                fi
            fi
        fi
    fi

    # Only alert if we have seen at least one frame (camera was working)
    # and now there's a gap longer than the threshold
    if [ "$last_good" -gt 0 ]; then
        age=$(( now - last_good ))
        if [ "$age" -gt "$STALE_SECS" ] && ! $stale_notified; then
            echo "Capture stalled for ${CAM} — last frame ${age}s ago"
            "$SCRIPT_DIR/notify.sh" "WARNING: capture stalled — ${CAM}" \
                "No new frames for ${age}s — camera may be offline or stream lost" || true
            stale_notified=true
        fi
    fi
done