import logging
import socket
import json
import requests
from requests.adapters import HTTPAdapter
from requests.packages.urllib3.util.retry import Retry

logger = logging.getLogger(__name__)

# Cache for resolved IPs to avoid spamming DoH
_DNS_CACHE = {}
_ORIGINAL_GETADDRINFO = socket.getaddrinfo

def resolve_via_doh(hostname):
    """
    Resolve hostname using Google DNS-over-HTTPS.
    Bypasses local system resolver (/etc/resolv.conf).
    """
    if hostname in _DNS_CACHE:
        return _DNS_CACHE[hostname]
        
    try:
        # We must use an IP for the DoH server to avoid DNS loop!
        # 8.8.8.8 is Google DNS.
        doh_url = f"https://8.8.8.8/resolve?name={hostname}&type=A"
        
        # Use a fresh simple session without adapters to avoid recursion
        # But wait, requests might try to resolve 8.8.8.8? No, it's an IP.
        resp = requests.get(doh_url, timeout=5, verify=False) # Skip verify for DoH to be fast/safe
        data = resp.json()
        
        if 'Answer' in data:
            for answer in data['Answer']:
                if answer['type'] == 1: # A Record
                    ip = answer['data']
                    logger.debug(f"🔍 DoH Resolved {hostname} -> {ip}")
                    _DNS_CACHE[hostname] = ip
                    return ip
    except Exception as e:
        logger.error(f"⚠️ DoH Resolution failed for {hostname}: {e}")
    
    return None

def patched_getaddrinfo(host, port, family=0, type=0, proto=0, flags=0):
    """
    Custom getaddrinfo that attempts DoH if system resolution fails or for specific hosts.
    """
    # Only intervene for Facebook/Instagram APIs which are failing in this environment
    if host in ('graph.facebook.com', 'www.facebook.com', 'api.instagram.com', 'graph.instagram.com'):
        ip = resolve_via_doh(host)
        if ip:
            # Call original with IP instead of hostname
            # Log usage for debugging
            # logger.debug(f"Redirecting {host} to {ip}")
            return _ORIGINAL_GETADDRINFO(ip, port, family, type, proto, flags)
            
    # Fallback to system resolver
    return _ORIGINAL_GETADDRINFO(host, port, family, type, proto, flags)

def force_ipv4_requests():
    """
    Installs the DNS patch.
    Named 'force_ipv4_requests' for backward compatibility with existing calls.
    """
    if socket.getaddrinfo != patched_getaddrinfo:
        socket.getaddrinfo = patched_getaddrinfo
        logger.debug("🛡️ Installed DoH-based DNS patch for Facebook API")
    else:
        logger.debug("🛡️ DNS patch already active")

def get_resilient_session():
    """
    Returns a session with retry logic.
    """
    session = requests.Session()
    retry = Retry(total=3, backoff_factor=1, status_forcelist=[500, 502, 503, 504])
    adapter = HTTPAdapter(max_retries=retry)
    session.mount('https://', adapter)
    session.mount('http://', adapter)
    
    # Ensure patch is applied whenever we get a session
    force_ipv4_requests()
    
    return session