DOMAIN="light-slit.pstatic.net"
COUNT=1000
PARALLEL_JOBS=10
OUTPUT_DIR="/data/www/dns"

# 통신사/공용 DNS 정의
declare -A DNS_SERVERS=(
  ["LG"]="164.124.101.2"
  ["KT"]="168.126.63.1"
  ["SK"]="210.220.163.82"
  ["GOOGLE"]="8.8.8.8"
)

mkdir -p "$OUTPUT_DIR"

echo "===== DNS Check ====="
echo "### $DOMAIN ###"
echo "### Count: $COUNT ###"
echo "================================"

for ISP in "${!DNS_SERVERS[@]}"; do
  DNS_IP=${DNS_SERVERS[$ISP]}
  OUTFILE="$OUTPUT_DIR/${ISP}_dns_results_$(date +%Y%m%d_%H%M%S).txt"

  echo
  echo "▶ ${ISP} DNS Check Start (${DNS_IP})"

  # 1000번 병렬 DNS 조회
  seq 1 "$COUNT" | parallel -j "$PARALLEL_JOBS" \
    "dig +short $DOMAIN @$DNS_IP A" >> "$OUTFILE"

  echo
  echo "▶ ${ISP} DNS IP Unique Results:"
  sort "$OUTFILE" | uniq

  echo
  echo "▶ ${ISP} DNS IP Frequency:"
  sort "$OUTFILE" | uniq -c | sort -nr

  echo "--------------------------------"

  rm -f "$OUTFILE"
done