LangChain/app/services/qa.py

from langchain_community.llms import Ollama
from langchain.chains import LLMChain
from langchain.prompts import PromptTemplate
import os
from dotenv import load_dotenv

# Load environment variables
load_dotenv()

# Global dictionary to store chat history (in-memory for simplicity)
chat_history = {}

# Initialize Ollama LLM with tinyllama
llm = Ollama(
    model="tinyllama",
    temperature=0.7
)

# Define a prompt template that includes history
def get_prompt_with_history(session_id):
    history = chat_history.get(session_id, [])
    history_text = "\n".join([f"User: {msg['question']}\nAI: {msg['answer']}" for msg in history]) if history else "No previous conversation."
    return PromptTemplate(
        input_variables=["question"],
        template=f"Previous conversation:\n{history_text}\n\nResponda à seguinte pergunta: {{question}}"
    )

def get_answer(session_id: str, question: str) -> str:
    # Get or initialize chat history for this session
    if session_id not in chat_history:
        chat_history[session_id] = []
    
    # Create chain with dynamic prompt including history
    prompt = get_prompt_with_history(session_id)
    chain = LLMChain(llm=llm, prompt=prompt)
    
    # Get response
    response = chain.run(question=question)
    response = response[:100] if len(response) > 100 else response  # Truncate if needed
    
    # Store the interaction in history
    chat_history[session_id].append({"question": question, "answer": response})
    
    return response

if __name__ == "__main__":
    session_id = "test_session"
    print(get_answer(session_id, "Qual a capital da França?"))
    print(get_answer(session_id, "E a capital da Espanha?"))