# utils/seen_store.py
import os, redis
from typing import Iterable

REDIS_URL = os.environ.get("REDIS_URL", "redis://localhost:6379/0")
r = redis.from_url(REDIS_URL, decode_responses=True)

def seen_key(username: str) -> str:
    return f"ig:seen:{username}"

def mark_seen(username: str, ids: Iterable[str]) -> None:
    if not ids: return
    r.sadd(seen_key(username), *ids)

def filter_unseen(username: str, ids: Iterable[str]) -> list[str]:
    # pipeline for speed
    key = seen_key(username)
    pipe = r.pipeline()
    for i in ids:
        pipe.sismember(key, i)
    flags = pipe.execute()
    return [i for i, seen in zip(ids, flags) if not seen]