#!/usr/bin/env bash
# vim: set filetype=sh
set -euo pipefail

api_host="https://api.dnsimple.com/v2"
sleep_interval=${SLEEP_INTERVAL:-300}
record_ttl=${RECORD_TTL:-600}

# Only services with ipv6 supported are listed here.
# And are not using cloudflare or similar services
# that may block requests from this script.
services=(
  "ifconfig.io"
)

info() {
  echo "INFO: $1"
}

warn() {
  echo "WARN: $1"
}

error() {
  warn "$1"
  exit 1
}

test -z "${DNSIMPLE_TOKEN}" && error "DNSIMPLE_TOKEN not set!"
test -z "${DNSIMPLE_ACCOUNT_ID}" && error "DNSIMPLE_ACCOUNT_ID not set!"
test -z "${DOMAIN}" && error "DOMAIN not set!"
test -z "${NAME}" && error "NAME not set!"

dns_list="$api_host/$DNSIMPLE_ACCOUNT_ID/zones/$DOMAIN/records"

configure_record() {
  # disable glob expansion
  set -f

  domain_records=$1
  ip=$2
  type=$3

  for sub in ${NAME//;/ }; do
    record_id=$(echo "$domain_records" | jq ".data[] | select(.type == \"$type\" and .name == \"$sub\") | .id")
    record_data=$(echo "$domain_records" | jq -r ".data[] | select(.type == \"$type\" and .name == \"$sub\") | .content")

    # For all subdomains except "any"
    #  we remove duplicates and only keep one A and AAAA records.
    if [[ "${sub}" != "any" ]]; then
      if [ "$(echo "$record_id" | wc -l)" -ge 2 ]; then
        echo "'$sub' domain name has duplicate DNS records, removing duplicates"
        record_id_to_delete=$(echo "$record_id" | tail -n +2)
        record_id=$(echo "$record_id" | head -1)
        record_data=$(echo "$record_data" | head -1)

        while IFS= read -r line; do
          curl -s -X DELETE \
            -H "Content-Type: application/json" \
            -H "Authorization: Bearer $DNSIMPLE_TOKEN" \
            "$dns_list/$line" &>/dev/null
        done <<<"$record_id_to_delete"
      fi
    fi

    # re-enable glob expansion
    set +f

    data="{\"type\": \"$type\", \"name\": \"$sub\", \"content\": \"$ip\", \"ttl\": $record_ttl}"
    url="$dns_list/$record_id"

    if [[ -z $record_id ]]; then
      info "No record found with '$sub' domain name. Creating record, sending data=$data to url=$url"

      new_record=$(curl -s -X POST \
        -H "Content-Type: application/json" \
        -H "Authorization: Bearer $DNSIMPLE_TOKEN" \
        -d "$data" \
        "$url")

      record_data=$(echo "$new_record" | jq -r ".data")
    fi

    if [[ "$ip" != "$record_data" ]]; then
      info "existing DNS record address ($record_data) doesn't match current IP ($ip), sending data=$data to url=$url"

      curl -s -X PATCH \
        -H "Content-Type: application/json" \
        -H "Authorization: Bearer $DNSIMPLE_TOKEN" \
        -d "$data" \
        "$url" &>/dev/null
    else
      info "existing DNS record address ($record_data) did not need updating"
    fi
  done
}

while (true); do
  domain_records=$(curl -s -X GET \
    -H "Content-Type: application/json" \
    -H "Authorization: Bearer $DNSIMPLE_TOKEN" \
    "$dns_list")

  for service in "${services[@]}"; do
    info "Trying with $service..."

    ipv4="$(curl -4 -s -f --connect-timeout 2 "$service" || echo "")"
    ipv6="$(curl -6 -s -f --connect-timeout 2 "$service" || echo "")"

    if [[ -n "$ipv4$ipv6" ]]; then
      break
    else
      warn "Failed to retrieve IP from $service"
    fi
  done

  if [[ -z $ipv4 ]]; then
    warn "IPv4 wasn't retrieved within allowed interval. Will try $sleep_interval seconds later.."
  else
    info "Found IPv4 address $ipv4"
    configure_record "$domain_records" "$ipv4" "A"
  fi

  if [[ -z $ipv6 ]]; then
    warn "IPv6 wasn't retrieved within allowed interval. Will try $sleep_interval seconds later.."
  else
    info "Found IPv6 address $ipv6"
    configure_record "$domain_records" "$ipv6" "AAAA"
  fi

  sleep "$sleep_interval"
done