"""Service for retrieving relevant documents from vector store."""

import hashlib
import json
from src.db.postgres.vector_store import get_vector_store
from src.db.redis.connection import get_redis
from sqlalchemy.ext.asyncio import AsyncSession
from src.middlewares.logging import get_logger
from typing import List, Dict, Any

logger = get_logger("retriever")

_RETRIEVAL_CACHE_TTL = 3600  # 1 hour


class RetrieverService:
    """Service for retrieving relevant documents."""

    def __init__(self):
        self.vector_store = get_vector_store()

    async def retrieve(
        self,
        query: str,
        user_id: str,
        db: AsyncSession,
        k: int = 5
    ) -> List[Dict[str, Any]]:
        """Retrieve relevant chunks for a query, scoped to the user's documents.

        Returns:
            List of dicts with keys: content, metadata
            metadata includes: document_id, user_id, filename, chunk_index, page_label (if PDF)
        """
        try:
            redis = await get_redis()
            query_hash = hashlib.md5(query.encode()).hexdigest()
            cache_key = f"retrieval:{user_id}:{query_hash}:{k}"

            cached = await redis.get(cache_key)
            if cached:
                logger.info("Returning cached retrieval results")
                return json.loads(cached)

            logger.info(f"Retrieving for user {user_id}, query: {query[:50]}...")

            docs = await self.vector_store.asimilarity_search(
                query=query,
                k=k,
                filter={"user_id": user_id}
            )

            results = [
                {
                    "content": doc.page_content,
                    "metadata": doc.metadata,
                }
                for doc in docs
            ]

            logger.info(f"Retrieved {len(results)} chunks")
            await redis.setex(cache_key, _RETRIEVAL_CACHE_TTL, json.dumps(results))
            return results

        except Exception as e:
            logger.error("Retrieval failed", error=str(e))
            return []


retriever = RetrieverService()