#!/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}
destructive=${DESTRUCTIVE:-false}

# 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"
)

log::debug() {
  echo "level=DEBUG $1"
}

log::info() {
  echo "level=INFO $1"
}

log::warn() {
  echo "level=WARN $1"
}

log:error() {
  echo "level=ERROR $1"
  exit 1
}

test -z "${DNSIMPLE_TOKEN}" && log:error "DNSIMPLE_TOKEN not set!"
test -z "${DNSIMPLE_ACCOUNT_ID}" && log:error "DNSIMPLE_ACCOUNT_ID not set!"
test -z "${DOMAIN}" && log:error "DOMAIN not set!"
test -z "${CLOUD_REGION}" && log:error "CLOUD_REGION not set!"

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

dnsimple::record::list() {
  curl -s -X GET \
    -H "Content-Type: application/json" \
    -H "Authorization: Bearer $DNSIMPLE_TOKEN" \
    "$base_zone_url"
}

dnsimple::record::create() {
  local data="$1"

  curl -s -X POST \
    -H "Content-Type: application/json" \
    -H "Authorization: Bearer $DNSIMPLE_TOKEN" \
    -d "$data" \
    "$base_zone_url"
}

dnsimple::record::update() {
  local record="$1"
  local data="$2"

  curl -s -X PATCH \
    -H "Content-Type: application/json" \
    -H "Authorization: Bearer $DNSIMPLE_TOKEN" \
    -d "$data" \
    "$base_zone_url/$record" &>/dev/null
}

dnsimple::record::delete() {
  local record="$1"

  if [[ "$destructive" == "false" ]]; then
    log::warn "record=$record Record deletion is disabled. Set DESTRUCTIVE=true to enable."
    return
  fi

  curl -s -X DELETE \
    -H "Content-Type: application/json" \
    -H "Authorization: Bearer $DNSIMPLE_TOKEN" \
    "$base_zone_url/$record" &>/dev/null

}

configure::single() {
  # disable glob expansion
  set -f

  domain_records=$1
  domain=$2
  ip=$3
  type=$4

  record_id=$(echo "$domain_records" | jq ".data[] | select(.type == \"$type\" and .name == \"$domain\") | .id")
  record_data=$(echo "$domain_records" | jq -r ".data[] | select(.type == \"$type\" and .name == \"$domain\") | .content")

  if [ "$(echo "$record_id" | wc -l)" -ge 2 ]; then
    log::warn "domain=$domain type=$type 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
      log::warn "domain=$domain type=$type record=$line Deleting record"
      dnsimple::record::delete "$line"
    done <<<"$record_id_to_delete"
  fi

  # re-enable glob expansion
  set +f

  data="{\"type\": \"$type\", \"name\": \"$domain\", \"content\": \"$ip\", \"ttl\": $record_ttl}"

  if [[ -z $record_id ]]; then
    log::info "domain=$domain type=$type No record found. Creating record."
    dnsimple::record::create "$data"
  elif [[ "$ip" != "$record_data" ]]; then
    log::info "domain=$domain type=$type Existing DNS record address ($record_data) doesn't match current IP ($ip)"
    dnsimple::record::update "$record_id" "$data"
  else
    log::info "domain=$domain type=$type Existing DNS record address ($record_data) did not need updating"
  fi
}

configure::many() {
  domain_records=$1
  domain=$2
  ip=$3
  type=$4

  record_id=$(echo "$domain_records" | jq ".data[] | select(.type == \"$type\" and .name == \"$domain\" and .content == \"$ip\") | .id")
  record_data=$(echo "$domain_records" | jq ".data[] | select(.type == \"$type\" and .name == \"$domain\" and .content == \"$ip\") | .content")

  data="{\"type\": \"$type\", \"name\": \"$domain\", \"content\": \"$ip\", \"ttl\": $record_ttl}"

  if [[ -z $record_id ]]; then
    log::info "domain=$domain type=$type No record found. Creating record."
    dnsimple::record::create "$data"
  else
    log::info "domain=$domain type=$type Existing DNS record address ($record_data) did not need updating."
  fi
}

healthcheck() {
  local ip="$1"

  code=$(curl -s -o /dev/null -I -w '%{http_code}' "http://$ip:1337/healthz" || echo "")

  if [[ "$code" != "200" ]]; then
    log::warn "ip=$ip code=$code Healthcheck failed."
    return 1
  fi

  log::info "ip=$ip code=$code Healthcheck passed."
  return 0
}

while (true); do
  domain_records=$(dnsimple::record::list)
  log::debug "domain_records=$domain_records"

  for service in "${services[@]}"; do
    log::info "service=$service Discovering public IP address..."

    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
      log::warn "service=$service Failed to retrieve IP address."
    fi
  done

  if [[ -z $ipv4 ]]; then
    log::warn "type=A IPv4 address wasn't found." 
  else
    log::info "type=A ip=$ipv4 Found IPv4 address."
    if healthcheck "$ipv4"; then
      configure::single "$domain_records" "$CLOUD_REGION" "$ipv4" "A"
      configure::many "$domain_records" "any" "$ipv4" "A"
    fi
  fi

  if [[ -z $ipv6 ]]; then
    log::warn "type=AAAA IPv6 address wasn't found." 
  else
    log::info "type=AAAA ip=$ipv6 Found IPv6 address"
    if healthcheck "[$ipv6]"; then
      configure::single "$domain_records" "$CLOUD_REGION" "$ipv6" "AAAA"
      configure::many "$domain_records" "any" "$ipv6" "AAAA"
    fi
  fi

  log::info "type=A Checking for stale records..."
  echo "$domain_records" | jq -r ".data[] | select(.type == \"A\" and .name != \"$CLOUD_REGION\") | .id" | while read -r record_id; do
    record_name=$(echo "$domain_records" | jq -r ".data[] | select(.id == \"$record_id\") | .name")
    record_ip=$(echo "$domain_records" | jq -r ".data[] | select(.id == \"$record_id\") | .content")
    log::info "type=A domain=$record_name ip=$record_ip Checking..."
    if ! healthcheck "$record_ip"; then
      log::warn "type=A domain=$record_name ip=$record_ip Unhealthy..."
      dnsimple::record::delete "$record_id"
    else
      log::info "type=A domain=$record_name ip=$record_ip Healthy..."
    fi
  done

  log::info "type=AAAA Checking for stale records..."
  echo "$domain_records" | jq -r ".data[] | select(.type == \"AAAA\" and .name != \"$CLOUD_REGION\") | .id" | while read -r record_id; do
    record_name=$(echo "$domain_records" | jq -r ".data[] | select(.id == \"$record_id\") | .name")
    record_ip=$(echo "$domain_records" | jq -r ".data[] | select(.id == \"$record_id\") | .content")
    log::info "type=AAAA domain=$record_name ip=$record_ip Checking..."
    if ! healthcheck "[$record_ip]"; then
      log::warn "type=AAAA domain=$record_name ip=$record_ip Unhealthy..."
      dnsimple::record::delete "$record_id"
    else
      log::info "type=AAAA domain=$record_name ip=$record_ip Healthy..."
    fi
  done

  log::info "Sleeping for $sleep_interval seconds..."
  sleep "$sleep_interval"
done