"""
Shared HTTP clients for performance.

Why:
- Creating a new httpx.AsyncClient per request is expensive (TLS handshakes, no connection reuse).
- For high-frequency lookups (RDAP), we keep one pooled AsyncClient per process.

Notes:
- Per-request timeouts can still be overridden in client.get(..., timeout=...).
- Call close_* on shutdown for clean exit (optional but recommended).
"""

from __future__ import annotations

import asyncio
from typing import Optional

import httpx

_rdap_client: Optional[httpx.AsyncClient] = None
_rdap_client_lock = asyncio.Lock()


def _rdap_limits() -> httpx.Limits:
    # Conservative but effective defaults (works well for bursty traffic).
    return httpx.Limits(max_connections=50, max_keepalive_connections=20, keepalive_expiry=30.0)


def _rdap_timeout() -> httpx.Timeout:
    # Overall timeout can be overridden per request.
    return httpx.Timeout(15.0, connect=5.0)


async def get_rdap_http_client() -> httpx.AsyncClient:
    """
    Get a shared httpx.AsyncClient for RDAP requests.
    Safe for concurrent use within the same event loop.
    """
    global _rdap_client
    if _rdap_client is not None and not _rdap_client.is_closed:
        return _rdap_client

    async with _rdap_client_lock:
        if _rdap_client is not None and not _rdap_client.is_closed:
            return _rdap_client

        _rdap_client = httpx.AsyncClient(
            timeout=_rdap_timeout(),
            follow_redirects=True,
            limits=_rdap_limits(),
            headers={
                # Be a good citizen; many registries/redirectors are sensitive.
                "User-Agent": "pounce/1.0 (+https://pounce.ch)",
                "Accept": "application/rdap+json, application/json",
            },
        )
        return _rdap_client


async def close_rdap_http_client() -> None:
    """Close the shared RDAP client (best-effort)."""
    global _rdap_client
    if _rdap_client is None:
        return
    try:
        if not _rdap_client.is_closed:
            await _rdap_client.aclose()
    finally:
        _rdap_client = None