import json
import os
import logging
import torch
from typing import List
from langchain_core.documents import Document
from sentence_transformers import SentenceTransformer
try:
    from datasets import load_dataset
except ImportError:
    load_dataset = None

logger = logging.getLogger(__name__)

def get_device():
    """
    Determine the appropriate device for PyTorch.
    
    Returns:
        str: Device name ('cuda', 'mps', or 'cpu').
    """
    if torch.cuda.is_available():
        return "cuda"
    elif torch.backends.mps.is_available():
        return "mps"
    return "cpu"

def load_guest_dataset(dataset_path: str = "agents-course/unit3-invitees") -> List[Document]:
    """
    Load guest dataset from a local JSON file or Hugging Face dataset.
    
    Args:
        dataset_path (str): Path to local JSON file or Hugging Face dataset name.
    
    Returns:
        List[Document]: List of Document objects with guest information.
    """
    try:
        # Try loading from Hugging Face dataset if datasets library is available
        if load_dataset and not os.path.exists(dataset_path):
            logger.info(f"Attempting to load Hugging Face dataset: {dataset_path}")
            guest_dataset = load_dataset(dataset_path, split="train")
            docs = [
                Document(
                    page_content="\n".join([
                        f"Name: {guest['name']}",
                        f"Relation: {guest['relation']}",
                        f"Description: {guest['description']}",
                        f"Email: {guest['email']}"
                    ]),
                    metadata={
                        "name": guest["name"],
                        "relation": guest["relation"],
                        "description": guest["description"],
                        "email": guest["email"]
                    }
                )
                for guest in guest_dataset
            ]
            logger.info(f"Loaded {len(docs)} guests from Hugging Face dataset")
            return docs

        # Try loading from local JSON file
        if os.path.exists(dataset_path):
            logger.info(f"Loading guest dataset from local path: {dataset_path}")
            with open(dataset_path, 'r') as f:
                guests = json.load(f)
            docs = [
                Document(
                    page_content=guest.get('description', ''),
                    metadata={
                        'name': guest.get('name', ''),
                        'relation': guest.get('relation', ''),
                        'description': guest.get('description', ''),
                        'email': guest.get('email', '')  # Optional email field
                    }
                )
                for guest in guests
            ]
            logger.info(f"Loaded {len(docs)} guests from local JSON")
            return docs

        # Fallback to mock dataset if both fail
        logger.warning(f"Dataset not found at {dataset_path}, using mock dataset")
        docs = [
            Document(
                page_content="\n".join([
                    "Name: Dr. Nikola Tesla",
                    "Relation: old friend from university days",
                    "Description: Dr. Nikola Tesla is an old friend from your university days. He's recently patented a new wireless energy transmission system.",
                    "Email: nikola.tesla@gmail.com"
                ]),
                metadata={
                    "name": "Dr. Nikola Tesla",
                    "relation": "old friend from university days",
                    "description": "Dr. Nikola Tesla is an old friend from your university days. He's recently patented a new wireless energy transmission system.",
                    "email": "nikola.tesla@gmail.com"
                }
            )
        ]
        logger.info("Loaded mock dataset with 1 guest")
        return docs

    except Exception as e:
        logger.error(f"Failed to load guest dataset: {e}")
        # Return mock dataset as final fallback
        docs = [
            Document(
                page_content="\n".join([
                    "Name: Dr. Nikola Tesla",
                    "Relation: old friend from university days",
                    "Description: Dr. Nikola Tesla is an old friend from your university days. He's recently patented a new wireless energy transmission system.",
                    "Email: nikola.tesla@gmail.com"
                ]),
                metadata={
                    "name": "Dr. Nikola Tesla",
                    "relation": "old friend from university days",
                    "description": "Dr. Nikola Tesla is an old friend from your university days. He's recently patented a new wireless energy transmission system.",
                    "email": "nikola.tesla@gmail.com"
                }
            )
        ]
        logger.info("Loaded mock dataset with 1 guest due to error")
        return docs

class BM25Retriever:
    """
    A retriever class using SentenceTransformer for embedding-based search.
    """
    def __init__(self, dataset_path: str):
        """
        Initialize the retriever with a SentenceTransformer model.
        
        Args:
            dataset_path (str): Path to the dataset for retrieval.
        
        Raises:
            Exception: If embedder initialization fails.
        """
        try:
            self.model = SentenceTransformer("all-MiniLM-L6-v2", device=get_device())
            self.dataset_path = dataset_path
            logger.info("Initialized SentenceTransformer")
        except Exception as e:
            logger.error(f"Failed to initialize embedder: {e}")
            raise

    def search(self, query: str) -> List[dict]:
        """
        Search the dataset for relevant guest information.
        
        Args:
            query (str): Search query (e.g., guest name or relation).
        
        Returns:
            List[dict]: List of matching guest metadata dictionaries.
        """
        try:
            # Load dataset
            docs = load_guest_dataset(self.dataset_path)
            if not docs:
                logger.warning("No documents available for search")
                return []

            # Convert documents to text for BM25 (using metadata for consistency)
            texts = [f"{doc.metadata['name']} {doc.metadata['relation']} {doc.metadata['description']}" for doc in docs]
            from langchain_community.retrievers import BM25Retriever
            retriever = BM25Retriever.from_texts(texts)
            retriever.k = 3  # Limit to top 3 results

            # Perform search
            results = retriever.invoke(query)
            # Map results back to original metadata
            matches = [
                docs[i].metadata
                for i in range(len(docs))
                if any(f"{docs[i].metadata['name']} {docs[i].metadata['relation']} {docs[i].metadata['description']}" in r.page_content for r in results)
            ]
            logger.info(f"Found {len(matches)} matches for query: {query}")
            return matches[:3]  # Return top 3 matches

        except Exception as e:
            logger.error(f"Search failed for query '{query}': {e}")
            return []