app.py

import os
import gradio as gr
from dotenv import load_dotenv
import traceback # For detailed error logging
import torch # Required for Hugging Face transformers

# --- LangChain and Hugging Face Transformers Imports ---
from langchain_neo4j import Neo4jGraph
# from langchain_openai import ChatOpenAI # We will replace this
from langchain_community.llms import HuggingFacePipeline # For using HuggingFace models
from langchain_community.chains.graph_qa.cypher import GraphCypherQAChain
from langchain_core.prompts import PromptTemplate

from transformers import AutoTokenizer, AutoModelForCausalLM, pipeline

# --- Environment Variable Loading ---
load_dotenv()
print("Environment variables loaded:")
print(f"NEO4J_URI: {'Set' if os.getenv('NEO4J_URI') else 'Not Set'}")
print(f"NEO4J_USER: {'Set' if os.getenv('NEO4J_USER') else 'Not Set'}")
print(f"NEO4J_PASSWORD: {'Set' if os.getenv('NEO4J_PASSWORD') else 'Not Set'}")
# OPENAI_API_KEY is no longer the primary concern if using local/HF models
# print(f"OPENAI_API_KEY: {'Set' if os.getenv('OPENAI_API_KEY') else 'Not Set'}")
print(f"HUGGINGFACE_HUB_TOKEN: {'Set' if os.getenv('HUGGINGFACE_HUB_TOKEN') else 'Not Set (may be needed for certain models)'}")


# --- Global LangChain chain variable ---
chain = None
graph_connection_error = None # To store graph connection error
llm_initialization_error = None # To store LLM setup error

# --- Neo4j, Hugging Face LLM, and LangChain Setup ---
try:
    print("Attempting to connect to Neo4j...")
    graph = Neo4jGraph(
        url=os.getenv("NEO4J_URI"),
        username=os.getenv("NEO4J_USER"),
        password=os.getenv("NEO4J_PASSWORD"),
    )
    print("Successfully connected to Neo4j.")

    # --- Hugging Face LLM Setup ---
    print("Initializing Hugging Face LLM...")
    # IMPORTANT: Replace "gpt2" with your desired Hugging Face model.
    # For larger models like Llama-2, ensure you have enough resources (VRAM/RAM)
    # and handle authentication if it's a gated model (e.g., using huggingface-cli login
    # or by passing use_auth_token=os.getenv("HUGGINGFACE_HUB_TOKEN") if supported and necessary).
    model_id = "gpt2" # REPLACE THIS with your chosen model, e.g., "NousResearch/Llama-2-7b-chat-hf"
    # model_id = "meta-llama/Llama-2-7b-chat-hf" # Example from the prompt, requires auth and resources

    try:
        tokenizer = AutoTokenizer.from_pretrained(model_id, trust_remote_code=True) # trust_remote_code might be needed for some models
        # For large models, device_map='auto' and torch_dtype are crucial.
        # For smaller models like gpt2, they might not be strictly necessary or could be simplified.
        hf_model = AutoModelForCausalLM.from_pretrained(
            model_id,
            trust_remote_code=True,
            device_map='auto', # Automatically distributes model layers across available devices (CPU/GPU)
            torch_dtype=torch.float16, # Use float16 for memory efficiency if GPU supports it
            # use_auth_token=os.getenv("HUGGINGFACE_HUB_TOKEN") # If your model requires a token
        )
        hf_model.eval() # Set the model to evaluation mode

        # Create a text-generation pipeline
        # Adjust max_new_tokens, do_sample, top_k as needed for your model and task
        pipe = pipeline(
            "text-generation",
            model=hf_model,
            tokenizer=tokenizer,
            # torch_dtype=torch.bfloat16, # Alternative dtype
            # device_map="auto", # Already set in model loading
            max_new_tokens=512,  # Max tokens for the generated Cypher query + answer synthesis
            do_sample=True,
            top_k=30,
            num_return_sequences=1,
            eos_token_id=tokenizer.eos_token_id,
            pad_token_id=tokenizer.eos_token_id # Often good to set for open-ended generation
        )

        # Wrap the pipeline in LangChain's HuggingFacePipeline
        llm = HuggingFacePipeline(
            pipeline=pipe,
            # model_kwargs can be used to pass additional arguments to the pipeline's __call__ method
            # or to the model's generate method.
            model_kwargs={'temperature': 0.1, 'max_length': 2000} # max_length here includes prompt
        )
        print(f"Hugging Face LLM ({model_id}) initialized successfully.")

    except Exception as e_llm:
        llm_initialization_error_message = f"Error initializing Hugging Face LLM ({model_id}): {str(e_llm)}\n"
        llm_initialization_error_message += "Full Traceback:\n" + traceback.format_exc()
        print(llm_initialization_error_message)
        llm_initialization_error = llm_initialization_error_message
        llm = None


    if llm: # Proceed only if LLM initialized successfully
        # --- GraphCypherQAChain Setup ---
        print("Initializing GraphCypherQAChain...")
        CYPHER_GENERATION_TEMPLATE = """You are an expert Neo4j Cypher translator.
        Task: Convert the natural language question into a Cypher query that can retrieve relevant information from a Neo4j graph.
        Instructions:
        1. Use only the provided schema details. Do not use any other node labels or relationship types.
        2. Understand the question and identify the key entities and relationships.
        3. Construct a Cypher query that accurately reflects the question's intent.
        4. Output ONLY the Cypher query. No explanations, no introductory text, no markdown. Just the query.

        Schema:
        {schema}

        Question: {question}
        Cypher Query:"""
        cypher_prompt = PromptTemplate.from_template(CYPHER_GENERATION_TEMPLATE)

        # For the QA part, the default prompt is often okay, but you might want to customize it too.
        # Here's an example if you choose to:
        # QA_TEMPLATE = """You are an assistant that answers questions based on query results from a graph database.
        # Use the provided query result to answer the question.
        # If the result is empty or does not contain the answer, say so.
        # Do not make up information.
        # Question: {question}
        # Cypher Query Result: {context}
        # Answer:"""
        # qa_prompt = PromptTemplate.from_template(QA_TEMPLATE)

        chain = GraphCypherQAChain.from_llm(
            llm=llm,
            graph=graph,
            verbose=True,
            return_intermediate_steps=True,
            cypher_prompt=cypher_prompt,
            # qa_prompt=qa_prompt # Uncomment if you want to use a custom QA prompt
        )
        print("LangChain integration with GraphCypherQAChain initialized successfully.")
    else:
        # This case is now handled by the llm_initialization_error check in process_query
        pass


except Exception as e_graph:
    graph_connection_error_message = f"Error setting up Neo4j connection: {str(e_graph)}\n"
    graph_connection_error_message += "Full Traceback:\n" + traceback.format_exc()
    print(graph_connection_error_message)
    graph_connection_error = graph_connection_error_message
    chain = None

# --- Gradio Interface Function ---
def process_query(message: str, history: list):
    if graph_connection_error:
        return f"Application Initialization Error (Neo4j): {graph_connection_error}"
    if llm_initialization_error:
        return f"Application Initialization Error (LLM): {llm_initialization_error}"
    if not chain:
        return "Error: LangChain QA Chain is not available. Please check server logs for initialization issues."

    print(f"Processing message: {message}")
    try:
        result = chain.invoke({"query": message})
        print(f"Chain result: {result}")

        answer = result.get("result", "No answer found or an error occurred in processing.")
        intermediate_steps = result.get("intermediate_steps", [])
        generated_cypher = "Could not extract Cypher query from intermediate steps."

        if intermediate_steps and isinstance(intermediate_steps, list) and len(intermediate_steps) > 0:
            if isinstance(intermediate_steps[0], dict) and "query" in intermediate_steps[0]:
                generated_cypher = intermediate_steps[0]["query"]
            # Sometimes the Cypher query might be in a different structure or a later step
            # depending on the chain's verbosity and internal structure.
            # You might need to inspect intermediate_steps more closely if the above doesn't work.

        return f"📝 Generated Cypher:\n```cypher\n{generated_cypher}\n```\n\n💬 Answer:\n{answer}"

    except Exception as e:
        error_message = f"Error processing query: {str(e)}"
        print(error_message)
        print(traceback.format_exc())
        # Specific error check for Hugging Face model issues (e.g. out of memory)
        if "CUDA out of memory" in str(e):
            return "LLM Error: CUDA out of memory. The model may be too large for your GPU. Try a smaller model or reduce batch size if applicable."
        return error_message

# --- Gradio Interface Definition ---
print("Setting up Gradio interface...")
demo = gr.ChatInterface(
    fn=process_query,
    chatbot=gr.Chatbot(height=600, type="messages"),
    title="Neo4j Graph Database Assistant (with Hugging Face LLM)",
    description="Ask questions about your Neo4j database. Model responses depend on the chosen Hugging Face LLM.",
    examples=[
        "How many nodes are in the database?",
        "What types of nodes exist?",
        "List all relationship types.",
    ],
    theme=gr.themes.Soft(),
    cache_examples=False
)

# --- Main Execution ---
if __name__ == "__main__":
    print("Launching Gradio interface...")
    # To make accessible on the network (e.g., in Docker):
    # demo.launch(server_name="0.0.0.0")
    demo.launch()