#!/usr/bin/env python3
"""MedGenesis – **Open Targets** GraphQL helper (async, cached).
Updated version adds:
* Retry with exponential back‑off (2→4→8 s)
* 12‑h LRU cache (256 genes)
* Graceful empty‑list fallback & doc‑string examples.
"""
from __future__ import annotations

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

_OT_URL = "https://api.platform.opentargets.org/api/v4/graphql"

_QUERY = textwrap.dedent(
    """
    query Assoc($gene: String!, $size: Int!) {
      associations(geneSymbol: $gene, size: $size) {
        rows {
          score
          datatypeId
          datasourceId
          disease { id name }
          target  { id symbol }
        }
      }
    }
    """
)

async def _post(payload: Dict, retries: int = 3) -> Dict:
    """POST with back‑off retry (2×, 4×); returns JSON."""
    delay = 2
    last_resp = None
    for _ in range(retries):
        async with httpx.AsyncClient(timeout=15) as cli:
            last_resp = await cli.post(_OT_URL, json=payload)
            if last_resp.status_code == 200:
                return last_resp.json()
        await asyncio.sleep(delay)
        delay *= 2
    # Raise from final attempt if still failing
    last_resp.raise_for_status()  # type: ignore


@lru_cache(maxsize=256)
async def fetch_ot_associations(gene_symbol: str, *, size: int = 30) -> List[Dict]:
    """Return association rows for *gene_symbol* (or []). Example::

        rows = await fetch_ot_associations("TP53", size=20)
    """
    payload = {"query": _QUERY, "variables": {"gene": gene_symbol, "size": size}}
    data = await _post(payload)
    return data.get("data", {}).get("associations", {}).get("rows", [])