app/services/aggregator.py

from collections import defaultdict
import numpy as np

def aggregate_by_user(matches):
    per_user = defaultdict(list)
    for m in matches:
        u = (m.get("metadata") or {}).get("user", "Unknown")
        per_user[u].append(m["score"])
    agg = [(u, float(np.max(v))) for u, v in per_user.items()]
    agg.sort(key=lambda x: x[1], reverse=True)
    return agg