"""Shared HTTP session for SFDA / ADE scraping."""

from __future__ import annotations

import time
from typing import Any

import requests

DEFAULT_HEADERS = {
    "User-Agent": (
        "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 "
        "(KHTML, like Gecko) Chrome/120.0.0.0 Safari/537.36"
    ),
    "Accept": "text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8",
    "Accept-Language": "en-US,en;q=0.9",
}

SFDA_BASE = "https://www.sfda.gov.sa"
ADE_BASE = "https://ade.sfda.gov.sa"

# Rate-limit protection for ADE (DownloadDocument throttles after ~10 rapid calls).
ADE_REQUEST_DELAY_SECONDS = 3
ADE_MAX_RETRIES = 3
ADE_RETRY_BACKOFF_SECONDS = 30
ADE_RETRY_STATUS_CODES = {429, 503}


def create_session() -> requests.Session:
    session = requests.Session()
    session.headers.update(DEFAULT_HEADERS)
    return session


def _retry_wait_seconds(response: requests.Response, attempt: int) -> float:
    retry_after = response.headers.get("Retry-After")
    if retry_after:
        try:
            return max(float(retry_after), 1.0)
        except ValueError:
            pass
    return ADE_RETRY_BACKOFF_SECONDS * (2**attempt)


def request_with_retry(
    session: requests.Session,
    method: str,
    url: str,
    *,
    max_retries: int = ADE_MAX_RETRIES,
    retry_status_codes: set[int] | None = None,
    **kwargs: Any,
) -> requests.Response:
    """Perform an HTTP request with exponential backoff on rate-limit responses."""
    retry_status_codes = retry_status_codes or ADE_RETRY_STATUS_CODES
    last_response: requests.Response | None = None

    for attempt in range(max_retries + 1):
        response = session.request(method, url, **kwargs)
        last_response = response

        if response.status_code not in retry_status_codes:
            response.raise_for_status()
            return response

        if attempt >= max_retries:
            response.raise_for_status()

        wait_seconds = _retry_wait_seconds(response, attempt)
        time.sleep(wait_seconds)

    if last_response is not None:
        last_response.raise_for_status()
    raise requests.HTTPError(f"Request failed for {url}")