import os
import argparse
import logging
import requests
import socket
import time
from requests.exceptions import RequestException
from dotenv import load_dotenv
from retry_queue import enqueue as enqueue_retry

logging.basicConfig(level=logging.INFO, format="%(asctime)s %(levelname)s %(message)s")
logger = logging.getLogger(__name__)


def _append_log(entry: str):
    try:
        with open("log.txt", "a", encoding="utf-8") as lf:
            lf.write(entry + "\n")
    except Exception:
        logger.exception("Failed to write to log.txt")


def post_to_facebook(page_id: str, access_token: str, message: str, link: str | None = None):
    url = f"https://graph.facebook.com/{page_id}/feed"
    payload = {"message": message, "access_token": access_token}
    if link:
        payload["link"] = link
    logger.info("Posting to Facebook page %s", page_id)
    # Ensure graph.facebook.com resolves before attempting to POST to avoid long, noisy stack traces
    try:
        socket.getaddrinfo("graph.facebook.com", 443)
    except Exception as e:
        logger.error("DNS resolution failed for graph.facebook.com: %s", e)
        _append_log(f"[{__import__('time').strftime('%Y-%m-%d %H:%M:%S')}] FB_DNS_RESOLUTION_FAILED {e}")
        # enqueue for later retry
        try:
            enqueue_retry({"type": "message", "page_id": page_id, "access_token": access_token, "message": message, "link": link})
        except Exception:
            logger.exception("Failed to enqueue message after DNS failure")
        raise

    # Retry with exponential backoff for transient network issues
    attempts = 4
    backoff = 2
    last_exc = None
    for attempt in range(1, attempts + 1):
        try:
            resp = requests.post(url, data=payload, timeout=15)
            resp.raise_for_status()
            last_exc = None
            break
        except RequestException as e:
            last_exc = e
            logger.warning("Attempt %s/%s: Facebook POST failed: %s", attempt, attempts, e)
            if attempt < attempts:
                time.sleep(backoff)
                backoff *= 2
            else:
                logger.error("All Facebook POST attempts failed")
                _append_log(f"[{__import__('time').strftime('%Y-%m-%d %H:%M:%S')}] FB_POST_ERROR page={page_id} message={message[:120]!r} exception={e}")
                # enqueue for retry
                try:
                    enqueue_retry({"type": "message", "page_id": page_id, "access_token": access_token, "message": message, "link": link})
                except Exception:
                    logger.exception("Failed to enqueue failed message post")
                raise
    data = resp.json()
    logger.info("Post successful: %s", data)
    # append a concise entry to log.txt for auditing
    try:
        _append_log(f"[{__import__('time').strftime('%Y-%m-%d %H:%M:%S')}] FB_POST_SUCCESS page={page_id} id={data.get('id')} post_id={data.get('post_id')}")
    except Exception:
        logger.exception("Failed to append FB success to log.txt")
    return data


def main():
    load_dotenv()
    parser = argparse.ArgumentParser(description="Post a message to a Facebook Page using Page Access Token from .env")
    parser.add_argument("-m", "--message", help="Message text to post (or set MESSAGE in .env)")
    parser.add_argument("-l", "--link", help="Optional link to include")
    parser.add_argument("--use-app-access", action="store_true", help="Attempt to post using the app access token (APP_ID|APP_SECRET)")
    args = parser.parse_args()

    # Prefer explicit env names already present in the repo
    page_id = os.getenv("FB_PAGE_ID") or os.getenv("PAGE_ID")
    access_token = os.getenv("FB_PAGE_ACCESS_TOKEN") or os.getenv("PAGE_ACCESS_TOKEN")
    message = args.message or os.getenv("MESSAGE")
    link = args.link or os.getenv("LINK")
    use_app_access = args.use_app_access

    # build app access token if requested
    if use_app_access:
        app_id = os.getenv("FB_APP_ID")
        app_secret = os.getenv("FB_APP_SECRET")
        if not app_id or not app_secret:
            print("ERROR: FB_APP_ID and FB_APP_SECRET required to build app access token")
            raise SystemExit(1)
        access_token = f"{app_id}|{app_secret}"

    if not page_id or not access_token:
        logger.error("Missing FB_PAGE_ID or FB_PAGE_ACCESS_TOKEN in environment (.env)")
        raise SystemExit(1)

    if not message:
        logger.error("No message provided (use --message or set MESSAGE in .env)")
        raise SystemExit(1)

    try:
        result = post_to_facebook(page_id, access_token, message, link)
    except requests.HTTPError as e:
        details = e.response.text if e.response is not None else str(e)
        logger.error("Facebook API request failed: %s", details)
        raise SystemExit(1)

    logger.info("Posted to Facebook page successfully: %s", result)
    print("Posted to Facebook page successfully:", result)


if __name__ == "__main__":
    main()