"""DNS interception — spoofs cloud domains to point at us"""

import socket
import struct
from utils.log import log, C_SUCCESS, C_IMPORTANT, C_ERROR

SPOOF_DOMAINS = [b"ubianet.com", b"aliyuncs.com", b"amazonaws.com", b"myqcloud.com"]


def parse_dns_name(data, offset):
    labels = []
    while offset < len(data):
        length = data[offset]
        if length == 0:
            offset += 1
            break
        if (length & 0xC0) == 0xC0:
            ptr = struct.unpack("!H", data[offset:offset + 2])[0] & 0x3FFF
            labels.append(parse_dns_name(data, ptr)[0])
            offset += 2
            break
        offset += 1
        labels.append(data[offset:offset + length])
        offset += length
    return b".".join(labels), offset


def build_dns_response(query, ip):
    resp = bytearray(query[:2])
    resp += b"\x81\x80"
    resp += query[4:6]
    resp += b"\x00\x01\x00\x00\x00\x00"
    resp += query[12:]
    resp += b"\xc0\x0c\x00\x01\x00\x01"
    resp += struct.pack("!I", 60)
    resp += b"\x00\x04"
    resp += socket.inet_aton(ip)
    return bytes(resp)


def run(cfg, flags, running_check):
    sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
    sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
    sock.settimeout(1)
    try:
        sock.bind(("0.0.0.0", 53))
    except OSError as e:
        log(f"DNS: bind :53 failed: {e}", C_ERROR)
        return

    flags["dns"] = True
    log("DNS: listening on :53", C_SUCCESS)

    while running_check():
        try:
            data, addr = sock.recvfrom(1024)
        except socket.timeout:
            continue
        except:
            break
        if len(data) < 12:
            continue

        name, _ = parse_dns_name(data, 12)
        name_str = name.decode("utf-8", errors="replace")
        should_spoof = (addr[0] == cfg["camera_ip"] and
                        any(d in name.lower() for d in SPOOF_DOMAINS))

        if should_spoof:
            resp = build_dns_response(data, cfg["our_ip"])
            sock.sendto(resp, addr)
            log(f"DNS: {name_str} -> SPOOFED", C_IMPORTANT)
        else:
            fwd = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
            fwd.settimeout(3)
            try:
                fwd.sendto(data, (cfg["router_ip"], 53))
                resp, _ = fwd.recvfrom(4096)
                sock.sendto(resp, addr)
            except:
                pass
            fwd.close()

    sock.close()
    flags["dns"] = False