Update mcp/targets.py

mcp/targets.py

@@ -1,14 +1,19 @@
-"""Open Targets GraphQL client – fetch gene ↔ disease ↔ drug associations.
-     Docs: https://platform.opentargets.org/
-     No API‑key required (public endpoint).
+#!/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 httpx, textwrap, asyncio
+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_TEMPLATE = textwrap.dedent(
+_QUERY = textwrap.dedent(
     """
     query Assoc($gene: String!, $size: Int!) {
       associations(geneSymbol: $gene, size: $size) {
@@ -24,9 +29,27 @@ _QUERY_TEMPLATE = textwrap.dedent(
     """
 )
 
+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]:
-    payload = {"query": _QUERY_TEMPLATE, "variables": {"gene": gene_symbol, "size": size}}
-    async with httpx.AsyncClient(timeout=15) as client:
-        resp = await client.post(_OT_URL, json=payload)
-        resp.raise_for_status()
-        return resp.json()["data"]["associations"]["rows"]
+    """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", [])