#!/usr/bin/env bash
# =============================================================
#  check-image-updates.sh
#  Checks all running containers for newer images and caches
#  results to /tmp/.docker-updates for the MOTD to display.
#
#  Usage:
#    bash scripts/check-image-updates.sh
#
#  Add to cron for automatic checks (e.g. daily at 3am):
#    0 3 * * * bash /opt/stacks/matrix/scripts/check-image-updates.sh
# =============================================================

set -euo pipefail

CACHE="/tmp/.docker-updates"
TMP=$(mktemp)

echo "# generated $(date -u +"%Y-%m-%dT%H:%M:%SZ")" > "$TMP"

while IFS='|' read -r name image; do
  OUTPUT=$(docker pull "$image" 2>&1 || true)
  if echo "$OUTPUT" | grep -q "Downloaded newer image"; then
    echo "$name  →  $image" >> "$TMP"
  fi
done < <(docker ps --format '{{.Names}}|{{.Image}}' | sort)

mv "$TMP" "$CACHE"

UPDATES=$(grep -v '^#' "$CACHE" | grep -c . || true)
if [ "$UPDATES" -gt 0 ]; then
  echo "✅  $UPDATES image(s) updated — cache written to $CACHE"
else
  echo "✅  All images current — cache written to $CACHE"
fi