#!/usr/bin/env bash
# Injects an SOA record + canonical NS records into each raw Vultr zone
# file, then writes the result to zones-prepared/. Source files in zones/
# are never modified.
#
# Corrections applied to each zone:
#  1. Synthesize SOA — Vultr's export omits it. SOA mname is ns1.he.net
#     because Hurricane Electric secondaries serve the public face of
#     these zones (hidden-primary architecture).
#  2. Strip the source's ns1.vultr.com / ns2.vultr.com NS records and
#     replace with the five HE nameservers, so AXFR-pulled zones at HE
#     advertise the correct delegation.
#  3. Apex disambiguation: lines starting with leading-TAB-then-TTL get
#     "@" prepended (Vultr's apex convention vs. RFC 1035 inheritance).
#  4. Dot-terminate NS/MX/CNAME rdata (Vultr exports unqualified names).
set -euo pipefail

SRC_DIR="${SRC_DIR:-zones}"
DST_DIR="${DST_DIR:-zones-prepared}"
SERIAL="${SERIAL:-$(date +%Y%m%d)01}"
ADMIN_EMAIL="${ADMIN_EMAIL:-admin}"   # becomes admin.<zone>.

# Public-facing nameservers (Hurricane Electric free secondary service).
# These appear in NS records inside every zone so that recursive
# resolvers fetching the zone learn the correct delegation.
HE_NAMESERVERS=(
  "ns1.he.net."
  "ns2.he.net."
  "ns3.he.net."
  "ns4.he.net."
  "ns5.he.net."
)

mkdir -p "$DST_DIR"

count=0
for src in "$SRC_DIR"/*.zone; do
  fname=$(basename "$src")
  zone="${fname%.zone}"
  dst="$DST_DIR/$fname"

  {
    echo "; Auto-prepared by scripts/prepare-zones.sh on $(date -Iseconds)"
    echo "; Source: $src"
    echo "\$ORIGIN ${zone}."
    echo "\$TTL 3600"
    echo "@ 3600 IN SOA ns1.he.net. ${ADMIN_EMAIL}.${zone}. ("
    echo "    ${SERIAL}  ; serial — bump per change (SERIAL=YYYYMMDDNN make prep)"
    echo "    3600        ; refresh (1 hour)"
    echo "    1800        ; retry   (30 minutes)"
    echo "    604800      ; expire  (1 week)"
    echo "    300         ; minimum (5 minutes)"
    echo "    )"
    echo ""
    # Inject HE nameservers as the authoritative NS set.
    for ns in "${HE_NAMESERVERS[@]}"; do
      echo "@ 3600 IN NS ${ns}"
    done
    echo ""

    # Strip source's own $ORIGIN / $TTL / comments AND drop ns?.vultr.com
    # NS records (we just emitted HE's NS set above). Then run the awk
    # transformations for apex disambiguation and rdata dot-termination.
    grep -vE '^\$(ORIGIN|TTL)|^;' "$src" \
      | grep -vE '[[:space:]]NS[[:space:]]+ns[12]\.vultr\.com\.?[[:space:]]*$' \
      | awk '
      NF == 0 { print; next }
      {
        # (a) Detect Vultr-style apex line: leading whitespace, then TTL,
        #     then "IN". Prepend "@" so the owner is explicit.
        if ($0 ~ /^[[:space:]]+[0-9]+[[:space:]]+IN[[:space:]]/) {
          sub(/^[[:space:]]+/, "@\t", $0)
        }

        # (b) Dot-terminate trailing hostname for NS/CNAME/MX rdata.
        type = ""
        for (i = 1; i <= NF; i++) {
          if ($i == "NS" || $i == "CNAME" || $i == "MX") { type = $i; break }
        }
        if (type != "") {
          target = $NF
          if (index(target, ".") > 0 && substr(target, length(target), 1) != ".") {
            sub(/[[:space:]]+$/, "", $0)
            print $0 "."
            next
          }
        }
        print
      }
    '
  } > "$dst"
  count=$((count + 1))
done

echo "Prepared ${count} zone files in ${DST_DIR}/ (serial=${SERIAL})"