# File : app/cache/redis_cache.py
# Purpose : Redis caching for RAG query responses

import json
import hashlib
import redis.asyncio as aioredis
from typing import Optional
from app.config import get_settings

settings = get_settings()

_redis_client: Optional[aioredis.Redis] = None


async def get_redis() -> aioredis.Redis:
    global _redis_client
    if _redis_client is None:
        _redis_client = aioredis.from_url(
            settings.redis_url,
            encoding="utf-8",
            decode_responses=True,
        )
    return _redis_client


def make_cache_key(user_id: str, query: str) -> str:
    raw = f"{user_id}:{query.strip().lower()}"
    return "rag:" + hashlib.md5(raw.encode()).hexdigest()


async def get_cached_response(user_id: str, query: str) -> Optional[dict]:
    try:
        redis = await get_redis()
        key = make_cache_key(user_id, query)
        cached = await redis.get(key)
        if cached:
            print(f"[CACHE] Hit for key: {key}")
            return json.loads(cached)
    except Exception as e:
        print(f"[CACHE] Redis get error: {e}")
    return None


async def set_cached_response(user_id: str, query: str, response: dict) -> None:
    try:
        redis = await get_redis()
        key = make_cache_key(user_id, query)
        await redis.setex(key, settings.redis_ttl_seconds, json.dumps(response))
        print(f"[CACHE] Stored key: {key}")
    except Exception as e:
        print(f"[CACHE] Redis set error: {e}")