#!/usr/bin/env python3
"""MedGenesis – DisGeNET async helper (disease → gene associations).

Features
~~~~~~~~
* Accepts optional Bearer token via env **`DISGENET_KEY`** (rate‑limit free).
* Endpoint: `https://www.disgenet.org/api/gda/disease/<disease_name>`
* Back‑off retry (2×, 4×) for 429/5xx.
* LRU cache (24 h, 512 queries) to minimise API calls.
* Returns top *N* rows (default = 10) as `list[dict]`.
"""
from __future__ import annotations

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

_BASE = "https://www.disgenet.org/api/gda/disease"
_TOKEN = os.getenv("DISGENET_KEY")
_HEADERS = {"Authorization": f"Bearer {_TOKEN}"} if (_TOKEN := os.getenv("DISGENET_KEY")) else {}
_TIMEOUT = 15

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

# ---------------------------------------------------------------------
# Public API – cached 24 h
# ---------------------------------------------------------------------
@lru_cache(maxsize=512)
async def disease_to_genes(disease_name: str, *, limit: int = 10) -> List[Dict]:
    """Return up to *limit* gene‑association dicts for *disease_name*.

    Parameters
    ----------
    disease_name : str
        Free‑text disease label (e.g. "glioblastoma"). Internally converted
        to lowercase and URL‑encoded.
    limit : int, optional
        Maximum number of rows to return (default = 10).
    """
    url = f"{_BASE}/{disease_name.lower()}"
    data = await _fetch(url)
    return data[:limit]


# ---------------------------------------------------------------------
# CLI demo
# ---------------------------------------------------------------------
if __name__ == "__main__":
    import json
    async def _demo():
        out = await disease_to_genes("glioblastoma", limit=5)
        print(json.dumps(out[:2], indent=2))
    asyncio.run(_demo())