import asyncio
import logging
import time

import httpx

from backend.config import settings

logger = logging.getLogger(__name__)

BASE_URL = "https://www.reddit.com"

# Simple in-process rate limiter: track request timestamps
_request_times: list[float] = []
MAX_REQUESTS_PER_MINUTE = 9  # Stay under Reddit's ~10/min limit


async def _wait_for_rate_limit():
    """Block until we have budget for another request."""
    now = time.monotonic()
    # Remove timestamps older than 60 seconds
    while _request_times and _request_times[0] < now - 60:
        _request_times.pop(0)
    if len(_request_times) >= MAX_REQUESTS_PER_MINUTE:
        wait = 60 - (now - _request_times[0]) + 0.5
        logger.info(f"Rate limit: waiting {wait:.1f}s")
        await asyncio.sleep(wait)
    _request_times.append(time.monotonic())


async def fetch_json(client: httpx.AsyncClient, path: str, params: dict | None = None) -> dict | None:
    """Fetch a Reddit .json endpoint with rate limiting and error handling."""
    await _wait_for_rate_limit()
    url = f"{BASE_URL}{path}.json"
    try:
        response = await client.get(url, params=params)
        if response.status_code == 429:
            retry_after = int(response.headers.get("Retry-After", 60))
            logger.warning(f"Rate limited, waiting {retry_after}s")
            await asyncio.sleep(retry_after)
            return await fetch_json(client, path, params)
        if response.status_code >= 500:
            logger.warning(f"Reddit returned {response.status_code} for {path}")
            return None
        response.raise_for_status()
        return response.json()
    except httpx.HTTPError as e:
        logger.error(f"HTTP error fetching {path}: {e}")
        return None


def create_client() -> httpx.AsyncClient:
    """Create an httpx client configured for Reddit."""
    return httpx.AsyncClient(
        headers={"User-Agent": settings.reddit_user_agent},
        timeout=30.0,
        follow_redirects=True,
    )