#!/usr/bin/env python3
"""MedGenesis – ClinicalTrials.gov **v2** async wrapper.

The legacy v1 JSON endpoint often throttles (HTTP 403/503).  This helper
switches to the production **v2** REST API, adds retry/back‑off, and
mirrors the interface expected by existing code (`search_trials`).

Key points
~~~~~~~~~~
* Endpoint: `https://clinicaltrials.gov/api/v2/studies` (public, no key).
* Back‑off retry (2×, 4×) for 429/5xx.
* Results cached 12 h (512 queries).
* Returns list of dicts with minimal fields: `nctId`, `briefTitle`,
  `phase`, `status`, `startDate`, `conditions`, `interventions`.
"""
from __future__ import annotations

import asyncio, httpx
from functools import lru_cache
from typing import List, Dict, Any

_BASE = "https://clinicaltrials.gov/api/v2/studies"
_TIMEOUT = 15
_HEADERS = {"User-Agent": "MedGenesis/1.0 (https://huggingface.co/spaces)"}
_MAX_PAGE = 50  # absolute hard cap

# ---------------------------------------------------------------------
# Internal fetch with retry
# ---------------------------------------------------------------------
async def _fetch(params: Dict[str, Any], *, retries: int = 3) -> List[Dict]:
    delay = 2
    for _ in range(retries):
        async with httpx.AsyncClient(timeout=_TIMEOUT, headers=_HEADERS) as cli:
            r = await cli.get(_BASE, params=params)
            if r.status_code == 200:
                return r.json().get("studies", [])
            if r.status_code in {429, 500, 503}:
                await asyncio.sleep(delay)
                delay *= 2
                continue
            r.raise_for_status()
    return []  # final fallback

# ---------------------------------------------------------------------
# Public helper – cached
# ---------------------------------------------------------------------
@lru_cache(maxsize=512)
async def search_trials(term: str, *, max_studies: int = 10) -> List[Dict]:
    """Return up to *max_studies* clinical‑trial dicts for free‑text *term*."""
    max_studies = max(1, min(max_studies, _MAX_PAGE))
    params = {
        "query"   : term,
        "pageSize": max_studies,
        "fields"  : "nctId,briefTitle,phase,status,startDate,conditions,interventions",
    }
    return await _fetch(params)