#!/usr/bin/env bash
set -euo pipefail

ENV_FILE="/etc/cf-ddns/cf-ddns.env"
STATE_DIR="/var/lib/cf-ddns"
API="https://api.cloudflare.com/client/v4"

log()  { logger -t cf-ddns "$*"; echo "[cf-ddns] $*"; }
fail() { log "ERROR: $*"; exit 1; }

# --- Load env ---
[[ -f "$ENV_FILE" ]] || fail "Missing $ENV_FILE"
# shellcheck disable=SC1090
source "$ENV_FILE"
: "${CF_API_TOKEN:?CF_API_TOKEN required in env}"
: "${CF_PROXIED:=false}"
: "${CF_TTL:=120}"

# --- Derive zone/record from system hostname ---
CF_RECORD_NAME="$(hostname -f 2>/dev/null || true)"
CF_ZONE_NAME="$(hostname -d 2>/dev/null || true)"

[[ -n "$CF_RECORD_NAME" ]] || fail "hostname -f returned empty"
[[ -n "$CF_ZONE_NAME"  ]] || fail "hostname -d returned empty (set a DNS/search domain)"

if [[ "$CF_RECORD_NAME" != *".${CF_ZONE_NAME}" ]]; then
  log "Warning: record '$CF_RECORD_NAME' does not end with zone '$CF_ZONE_NAME' (continuing anyway)"
fi

# Safe filename for state
safe_name="$(echo "$CF_RECORD_NAME" | tr '/:' '__')"
LAST_IP_FILE="${STATE_DIR}/last_ipv4_${safe_name}"

mkdir -p "$STATE_DIR"

# --- Detect local IPv4 on default route interface ---
detect_ip() {
  local iface ip

  # Prefer ip-route default; fallback to ip route get
  iface="$(ip route show default 2>/dev/null | awk '/default/ {print $5; exit}')"
  if [[ -z "$iface" ]]; then
    iface="$(ip -4 route get 1.1.1.1 2>/dev/null | awk '{for (i=1;i<=NF;i++) if ($i=="dev") {print $(i+1); exit}}')"
  fi
  [[ -n "$iface" ]] || fail "Could not detect default route interface"

  ip="$(ip -4 addr show dev "$iface" | awk '/inet / {print $2}' | cut -d/ -f1 | head -n1)"
  [[ -n "$ip" ]] || fail "No IPv4 found on default interface '$iface'"

  echo "$ip"
}

current_ip="$(detect_ip)"
previous_ip="$( [[ -f "$LAST_IP_FILE" ]] && cat "$LAST_IP_FILE" || echo "" )"

if [[ "$current_ip" == "$previous_ip" && -n "$current_ip" ]]; then
  log "IP unchanged ($current_ip); no update needed for ${CF_RECORD_NAME}."
  exit 0
fi

# --- Cloudflare helpers ---
urlenc() { local s="$1"; s="${s// /%20}"; s="${s//\//%2F}"; echo -n "$s"; }
hdr=(-H "Authorization: Bearer ${CF_API_TOKEN}" -H "Content-Type: application/json")

# 1) Get Zone ID
zone_q="name=$(urlenc "$CF_ZONE_NAME")"
zone_id="$(curl -fsS "${hdr[@]}" "${API}/zones?${zone_q}" \
  | sed -n 's/.*"id":"\([^"]*\)".*"name":"'"$CF_ZONE_NAME"'".*/\1/p' | head -n1)"
[[ -n "$zone_id" ]] || fail "Could not find Zone ID for ${CF_ZONE_NAME}"

# 2) Lookup existing A record by name
rec_q="type=A&name=$(urlenc "$CF_RECORD_NAME")"
record_json="$(curl -fsS "${hdr[@]}" "${API}/zones/${zone_id}/dns_records?${rec_q}")"
record_id="$(echo "$record_json" | sed -n 's/.*"id":"\([^"]*\)".*"type":"A".*"name":"'"$CF_RECORD_NAME"'".*/\1/p' | head -n1)"

# 3) Create payload + create/update
json_payload() {
  cat <<JSON
{"type":"A","name":"${CF_RECORD_NAME}","content":"${current_ip}","ttl":${CF_TTL},"proxied":${CF_PROXIED}}
JSON
}

if [[ -z "$record_id" ]]; then
  log "Creating A ${CF_RECORD_NAME} -> ${current_ip}"
  curl -fsS -X POST "${hdr[@]}" \
    --data "$(json_payload)" \
    "${API}/zones/${zone_id}/dns_records" >/dev/null
  log "Created."
else
  log "Updating A ${CF_RECORD_NAME} -> ${current_ip}"
  curl -fsS -X PUT "${hdr[@]}" \
    --data "$(json_payload)" \
    "${API}/zones/${zone_id}/dns_records/${record_id}" >/dev/null
  log "Updated."
fi

echo "$current_ip" > "$LAST_IP_FILE"