services/topic_service.py

"""Service for topic extraction from text using LangChain Groq"""

import logging
from typing import Optional, List
from langchain_core.messages import HumanMessage, SystemMessage
from langchain_groq import ChatGroq
from pydantic import BaseModel, Field
from langsmith import traceable

from config import GROQ_API_KEY

logger = logging.getLogger(__name__)


class TopicOutput(BaseModel):
    """Pydantic schema for topic extraction output"""
    topic: str = Field(..., description="A specific, detailed topic description")


class TopicService:
    """Service for extracting topics from text arguments"""
    
    def __init__(self):
        self.llm = None
        self.model_name = "openai/gpt-oss-safeguard-20b"  # another model meta-llama/llama-4-scout-17b-16e-instruct
        self.initialized = False
        
    def initialize(self, model_name: Optional[str] = None):
        """Initialize the Groq LLM with structured output"""
        if self.initialized:
            logger.info("Topic service already initialized")
            return
            
        if not GROQ_API_KEY:
            raise ValueError("GROQ_API_KEY not found in environment variables")
        
        if model_name:
            self.model_name = model_name
            
        try:
            logger.info(f"Initializing topic extraction service with model: {self.model_name}")
            
            llm = ChatGroq(
                model=self.model_name,
                api_key=GROQ_API_KEY,
                temperature=0.0,
                max_tokens=512,
            )
            
            # Bind structured output directly to the model
            self.llm = llm.with_structured_output(TopicOutput)
            self.initialized = True
            
            logger.info("✓ Topic extraction service initialized successfully")
            
        except Exception as e:
            logger.error(f"Error initializing topic service: {str(e)}")
            raise RuntimeError(f"Failed to initialize topic service: {str(e)}")
    
    @traceable(name="extract_topic")
    def extract_topic(self, text: str) -> str:
        """
        Extract a topic from the given text/argument
        
        Args:
            text: The input text/argument to extract topic from
            
        Returns:
            The extracted topic string
        """
        if not self.initialized:
            self.initialize()
        
        if not text or not isinstance(text, str):
            raise ValueError("Text must be a non-empty string")
        
        text = text.strip()
        if len(text) == 0:
            raise ValueError("Text cannot be empty")
        
        system_message = """You are an information extraction model.
Extract a topic from the user text. The topic should be a single sentence that captures the main idea of the text in simple english.

Examples:
- Text: "Governments should subsidize electric cars to encourage adoption."
  Output: topic="government subsidies for electric vehicle adoption"

- Text: "Raising the minimum wage will hurt small businesses and cost jobs."
  Output: topic="raising the minimum wage and its economic impact on small businesses"
"""
        
        try:
            result = self.llm.invoke(
                [
                    SystemMessage(content=system_message),
                    HumanMessage(content=text),
                ]
            )
            
            return result.topic
            
        except Exception as e:
            logger.error(f"Error extracting topic: {str(e)}")
            raise RuntimeError(f"Topic extraction failed: {str(e)}")
    
    def batch_extract_topics(self, texts: List[str]) -> List[str]:
        """
        Extract topics from multiple texts
        
        Args:
            texts: List of input texts/arguments
            
        Returns:
            List of extracted topics
        """
        if not self.initialized:
            self.initialize()
        
        if not texts or not isinstance(texts, list):
            raise ValueError("Texts must be a non-empty list")
        
        results = []
        for text in texts:
            try:
                topic = self.extract_topic(text)
                results.append(topic)
            except Exception as e:
                logger.error(f"Error extracting topic for text '{text[:50]}...': {str(e)}")
                results.append(None)  # Or raise, depending on desired behavior
        
        return results


# Initialize singleton instance
topic_service = TopicService()