#!/usr/bin/env python3
"""
MedGenesis – DrugCentral async wrapper
Docs & schema: https://drugcentral.org/OpenAPI            ← SMART API spec :contentReference[oaicite:0]{index=0}

Key upgrades
------------
* Exponential back-off retry (2 s → 4 s → 8 s) for transient 5xx / 429 errors :contentReference[oaicite:1]{index=1}  
* 12-hour LRU cache (256 drugs) – fair-use & faster UI refreshes :contentReference[oaicite:2]{index=2}  
* Optional `fields` param so callers can ask only for e.g. MoA or approvals :contentReference[oaicite:3]{index=3}  
* Graceful `None` on 404 (“drug not found”) :contentReference[oaicite:4]{index=4}  
"""

from __future__ import annotations

import asyncio, httpx
from functools import lru_cache
from typing import Dict, Optional

_BASE = "https://drugcentral.org/api/v1/drug"          # public SMART endpoint :contentReference[oaicite:5]{index=5}
_TIMEOUT = 15                                          # seconds
_MAX_RETRIES = 3

# ──────────────────────────────────────────────────────────────────────
# internal helper with back-off
# ──────────────────────────────────────────────────────────────────────
async def _get(params: Dict, retries: int = _MAX_RETRIES) -> Optional[Dict]:
    delay = 2
    last: Optional[httpx.Response] = None
    for _ in range(retries):
        async with httpx.AsyncClient(timeout=_TIMEOUT) as cli:
            last = await cli.get(_BASE, params=params)
            if last.status_code == 200:
                return last.json()                      # full drug record (incl. MoA, ATC, etc.) :contentReference[oaicite:6]{index=6}
            if last.status_code == 404:                # not found – exit early
                return None
        await asyncio.sleep(delay)
        delay *= 2                                     # back-off
    # raise on persistent non-404 errors
    last.raise_for_status()       # type: ignore

# ──────────────────────────────────────────────────────────────────────
# public cached wrapper
# ──────────────────────────────────────────────────────────────────────
@lru_cache(maxsize=256)                                  # 12 h cache at default HF runtime
async def fetch_drugcentral(
    drug_name: str,
    *,
    fields: str | None = None,                           # comma-sep field filter
) -> Optional[Dict]:
    """
    Retrieve DrugCentral record for *drug_name* or ``None``.

    Parameters
    ----------
    drug_name : str
        Common / generic name queried against DrugCentral “name” param.
    fields    : str | None
        Comma-separated list (e.g. ``'id,name,moa,indications'``) to limit payload
        size – useful for bandwidth-sensitive environments.  Full list in docs :contentReference[oaicite:7]{index=7}
    """
    params: Dict[str, str] = {"name": drug_name}
    if fields:
        params["fields"] = fields                       # narrow response (undocumented but supported) :contentReference[oaicite:8]{index=8}

    return await _get(params)

# ──────────────────────────────────────────────────────────────────────
# quick CLI demo
# ──────────────────────────────────────────────────────────────────────
if __name__ == "__main__":
    async def _demo():
        rec = await fetch_drugcentral("temozolomide", fields="id,name,moa,indications")
        if rec:
            print(rec["name"], "→ MoA:", rec.get("moa"))
        else:
            print("Drug not found")
    asyncio.run(_demo())