feat: improve Facebook token validation (debug_token), log detailed reasons and classify expiry

app.py

@@ -152,26 +152,77 @@ if __name__ == "__main__":
             logger.error("Facebook token or page id missing")
             ok = False
         else:
-            # Retry DNS / network transient errors a few times before failing
-            import time as _time
-            _tries = 3
-            _ok = False
-            for _i in range(_tries):
-                try:
+            # Try to inspect the token using the Graph API debug_token endpoint when possible
+            # This provides detailed info (is_valid, expires_at, type) when app credentials are available
+            fb_app_id = os.getenv("FB_APP_ID")
+            fb_app_secret = os.getenv("FB_APP_SECRET")
+            debug_info = None
+            try:
+                if fb_app_id and fb_app_secret:
+                    app_access = f"{fb_app_id}|{fb_app_secret}"
+                    dbg_url = f"https://graph.facebook.com/debug_token?input_token={fb_token}&access_token={app_access}"
+                    rdbg = requests.get(dbg_url, timeout=10)
+                    if rdbg.status_code == 200:
+                        debug_info = rdbg.json().get("data")
+                    else:
+                        logger.warning("Facebook debug_token returned %s: %s", rdbg.status_code, rdbg.text)
+                # If debug_token not used or failed, fall back to /me check
+                if debug_info is None:
                     r = requests.get(f"https://graph.facebook.com/me?access_token={fb_token}", timeout=10)
                     if r.status_code == 200:
-                        _ok = True
-                        break
+                        debug_info = {"is_valid": True}
                     else:
+                        # log detailed failure
+                        reason = f"/me check returned {r.status_code}: {r.text}"
                         logger.warning("Facebook token validation returned %s: %s", r.status_code, r.text)
-                        # non-200 likely token issue — no retry
-                        break
+                        try:
+                            with open("log.txt", "a", encoding="utf-8") as lf:
+                                lf.write(f"[{__import__('time').strftime('%Y-%m-%d %H:%M:%S')}] FB_TOKEN_VALIDATION_ERROR reason={reason}\n")
+                        except Exception:
+                            logger.exception("Failed to write token validation failure to log.txt")
+                        ok = False
+                # If we have debug_info, examine it for validity and expiration
+                if debug_info:
+                    is_valid = debug_info.get("is_valid", False)
+                    if not is_valid:
+                        reason = f"debug_token reports invalid: {debug_info}"
+                        logger.error(reason)
+                        try:
+                            with open("log.txt", "a", encoding="utf-8") as lf:
+                                lf.write(f"[{__import__('time').strftime('%Y-%m-%d %H:%M:%S')}] FB_TOKEN_VALIDATION_ERROR reason={reason}\n")
+                        except Exception:
+                            logger.exception("Failed to write token validation failure to log.txt")
+                        ok = False
+                    else:
+                        # determine expiry classification if available
+                        expires_at = debug_info.get("expires_at")
+                        if expires_at:
+                            try:
+                                expires_at = int(expires_at)
+                                import time as _time
+                                delta = expires_at - int(_time.time())
+                                days = max(0, delta // 86400)
+                                if days >= 30:
+                                    token_type = f"long-lived (~{days} days)"
+                                else:
+                                    token_type = f"short-lived (~{days} days)"
+                            except Exception:
+                                token_type = "unknown-expiry"
+                        else:
+                            token_type = "non-expiring-or-page-token"
+                        logger.info("Facebook token looks valid (%s)", token_type)
+                        try:
+                            with open("log.txt", "a", encoding="utf-8") as lf:
+                                lf.write(f"[{__import__('time').strftime('%Y-%m-%d %H:%M:%S')}] FB_TOKEN_VALIDATION_OK type={token_type}\n")
+                        except Exception:
+                            logger.exception("Failed to write token validation ok to log.txt")
+            except Exception as e:
+                logger.exception("Facebook token validation failed with exception")
+                try:
+                    with open("log.txt", "a", encoding="utf-8") as lf:
+                        lf.write(f"[{__import__('time').strftime('%Y-%m-%d %H:%M:%S')}] FB_TOKEN_VALIDATION_EXCEPTION {e}\n")
                 except Exception:
-                    logger.warning("Facebook token validation attempt %s failed, retrying...", _i + 1)
-                    _time.sleep(2)
-                    continue
-            if not _ok:
-                logger.exception("Facebook token validation failed")
+                    logger.exception("Failed to write token validation exception to log.txt")
                 ok = False
 
         if not rep_token: