tools/answer_generator.py

import nltk
import logging
import numpy as np
from typing import List, Any
from langchain_core.prompts import ChatPromptTemplate
from langchain_core.messages import SystemMessage, HumanMessage
from sentence_transformers import SentenceTransformer

# Setup logging
logging.basicConfig(level=logging.INFO, format='%(asctime)s - %(levelname)s - %(name)s - %(message)s')
logger = logging.getLogger(__name__)

# Download NLTK data
try:
    nltk.download('punkt', quiet=True)
    nltk.download('stopwords', quiet=True)
except Exception as e:
    logger.warning(f"NLTK data download failed: {e}")

# Global embedder
_embedder = None

def get_embedder():
    global _embedder
    if _embedder is None:
        try:
            _embedder = SentenceTransformer(
                "all-MiniLM-L6-v2",
                device="cpu",
                cache_folder="./cache"
            )
            logger.info("SentenceTransformer initialized")
        except Exception as e:
            logger.error(f"Failed to initialize SentenceTransformer: {e}")
            raise RuntimeError(f"Embedder initialization failed: {e}")
    return _embedder

def filter_results(search_results: List[str], question: str) -> List[str]:
    try:
        if not search_results or not question:
            return search_results
        
        embedder = get_embedder()
        question_embedding = embedder.encode([question], convert_to_numpy=True)
        result_embeddings = embedder.encode(search_results, convert_to_numpy=True)
        
        similarities = np.dot(result_embeddings, question_embedding.T).flatten()
        filtered_results = [
            search_results[i] for i in range(len(search_results))
            if similarities[i] > 0.5 and search_results[i].strip()
        ]
        
        return filtered_results if filtered_results else search_results[:3]
    except Exception as e:
        logger.warning(f"Result filtering failed: {e}")
        return search_results[:3]

async def preprocess_question(question: str) -> str:
    """Preprocess the question to clean and standardize it."""
    try:
        question = question.strip().lower()
        if not question.endswith("?"):
            question += "?"
        logger.debug(f"Preprocessed question: {question}")
        return question
    except Exception as e:
        logger.error(f"Error preprocessing question: {e}")
        return question

async def generate_answer(
    task_id: str,
    question: str,
    search_results: List[str],
    file_results: str,
    llm_client: Any
) -> str:
    """Generate an answer using LLM with search and file results."""
    try:
        if not search_results:
            search_results = ["No search results available."]
        if not file_results:
            file_results = "No file results available."

        context = "\n".join([str(r) for r in search_results]) + "\n" + file_results
        prompt = ChatPromptTemplate.from_messages([
            SystemMessage(content="""You are an assistant answering questions using provided context. 
            - Use ONLY the context to formulate a concise, accurate answer.
            - If the context is insufficient, state: 'Insufficient information to answer.'
            - Do NOT generate or assume information beyond the context.
            - Return a single, clear sentence or phrase as the answer."""),
            HumanMessage(content=f"Context: {context}\nQuestion: {question}")
        ])
        
        messages = [
            {"role": "system", "content": prompt[0].content},
            {"role": "user", "content": prompt[1].content}
        ]
        
        if isinstance(llm_client, tuple):  # hf_local
            model, tokenizer = llm_client
            inputs = tokenizer.apply_chat_template(messages, return_tensors="pt").to(model.device)
            outputs = model.generate(inputs, max_new_tokens=100, temperature=0.7)
            response = tokenizer.decode(outputs[0], skip_special_tokens=True)
        elif hasattr(llm_client, "chat"):  # together
            response = llm_client.chat.completions.create(
                model="meta-llama/Llama-3.3-70B-Instruct-Turbo-Free",
                messages=messages,
                max_tokens=100,
                temperature=0.7,
                top_p=0.9,
                frequency_penalty=0.5
            )
            response = response.choices[0].message.content.strip()
        else:  # hf_api
            response = llm_client.chat.completions.create(
                messages=messages,
                max_tokens=100,
                temperature=0.7
            )
            response = response.choices[0].message.content.strip()
        
        answer = response.strip()
        if not answer or answer.lower() == "none":
            answer = "Insufficient information to answer."
        logger.info(f"Task {task_id}: Generated answer: {answer}")
        return answer
    except Exception as e:
        logger.error(f"Task {task_id}: Answer generation failed: {e}")
        return "Error generating answer."