"""HTTP session with connection pooling and retries."""
from __future__ import annotations

import requests
from requests.adapters import HTTPAdapter
from urllib3.util.retry import Retry

_SESSION: requests.Session | None = None


def get_session() -> requests.Session:
    """Get or create a global requests Session with connection pooling and retries."""
    global _SESSION
    if _SESSION is None:
        _SESSION = requests.Session()
        retry_strategy = Retry(
            total=3,
            backoff_factor=0.5,
            status_forcelist=[429, 500, 502, 503, 504],
            allowed_methods=["HEAD", "GET", "OPTIONS", "POST"],
        )
        adapter = HTTPAdapter(
            pool_connections=20,
            pool_maxsize=20,
            max_retries=retry_strategy,
            pool_block=False,
        )
        _SESSION.mount("http://", adapter)
        _SESSION.mount("https://", adapter)
    return _SESSION