#!/bin/sh
# Generates CoreDNS configmap YAML from records.yaml
# Usage: ./generate.sh records.yaml > coredns-custom.yaml
set -e

RECORDS_FILE="${1:-records.yaml}"

# Parse records.yaml, group by IP, generate CoreDNS template blocks
# Uses only POSIX tools (awk)

cat <<'HEADER'
apiVersion: v1
kind: ConfigMap
metadata:
  name: coredns-custom
  namespace: kube-system
data:
  homelab.override: |
HEADER

awk '
/^[a-zA-Z0-9]/ && /:/ {
  gsub(/"/, "")
  split($0, parts, ":")
  host = parts[1]
  gsub(/^[ \t]+|[ \t]+$/, "", host)
  ip = parts[2]
  gsub(/^[ \t]+|[ \t]+$/, "", ip)
  if (host != "" && ip != "") {
    ips[ip] = ips[ip] ? ips[ip] "|" host : host
  }
}
END {
  for (ip in ips) {
    n = split(ips[ip], hosts, "|")
    regex = ""
    for (i = 1; i <= n; i++) {
      gsub(/\./, "\\.", hosts[i])
      regex = regex ? regex "|" hosts[i] : hosts[i]
    }
    printf "    template IN A {\n"
    printf "      match \"^(%s)\\.$\"\n", regex
    printf "      answer \"{{ .Name }} 60 IN A %s\"\n", ip
    printf "      fallthrough\n"
    printf "    }\n"
  }
}
' "$RECORDS_FILE"