feat: add AlphaFold version proxy endpoint

- New /api/v1/alphafold-files/version endpoint (CORS-safe)
- Fetches upstream XML index, handles optional namespace
- Extracts model version from NextMarker (model_vN) and returns {"version": "v6"} (lowercased)
- Error responses: upstream fetch failure (status passthrough), malformed ID (500), XML parse error (502)

Author: davereinhart

src/mavedb/routers/alphafold.py

@@ -0,0 +1,52 @@
+from fastapi import APIRouter, HTTPException, Query
+from fastapi.responses import StreamingResponse
+import httpx
+from urllib.parse import quote
+import xml.etree.ElementTree as ET
+import re
+
+from mavedb.lib.logging.logged_route import LoggedRoute
+
+ALPHAFOLD_BASE = "https://alphafold.ebi.ac.uk/files/"
+
+router = APIRouter(
+    prefix="/api/v1",
+    tags=["alphafold files"],
+    responses={404: {"description": "Not found"}},
+    route_class=LoggedRoute,
+)
+
+@router.get("/alphafold-files/version")
+async def proxy_alphafold_index():
+    """
+    Proxy the AlphaFold files index (XML document).
+    """
+    async with httpx.AsyncClient(follow_redirects=True, timeout=30) as client:
+        resp = await client.get(ALPHAFOLD_BASE, headers={"Accept": "application/xml"})
+    if resp.status_code != 200:
+        raise HTTPException(status_code=resp.status_code, detail="Upstream error fetching AlphaFold files index")
+
+    # parse XML response
+    try:
+        root = ET.fromstring(resp.content)
+
+        # Detect default namespace
+        if root.tag.startswith("{"):
+            ns_uri = root.tag.split("}", 1)[0][1:]
+            ns = {"x": ns_uri}
+            next_marker_tag = "x:NextMarker"
+        else:
+            ns = {}
+            next_marker_tag = "NextMarker"
+
+        next_marker_el = root.find(next_marker_tag, ns)
+        next_marker = next_marker_el.text if next_marker_el is not None else None
+
+        match = re.search(r"model_(v\d+)\.pdb$", next_marker, re.IGNORECASE)
+        if not match:
+            raise HTTPException(status_code=500, detail="Malformed AlphaFold PDB ID in XML")
+        version = match.group(1)
+        return {"version": version.lower()}
+
+    except ET.ParseError as e:
+        raise HTTPException(status_code=502, detail=f"Failed to parse upstream XML: {e}")

src/mavedb/server_main.py

@@ -58,6 +58,7 @@
     taxonomies,
     users,
     variants,
+    alphafold,
 )
 
 logger = logging.getLogger(__name__)
@@ -106,6 +107,7 @@
 app.include_router(taxonomies.router)
 app.include_router(users.router)
 app.include_router(variants.router)
+app.include_router(alphafold.router)
 
 
 @app.exception_handler(PermissionException)