app.py

import gradio as gr
from langchain_huggingface import HuggingFaceEmbeddings
from langchain_chroma import Chroma
from transformers import AutoTokenizer, AutoModelForSeq2SeqLM, pipeline
import torch
import os
from data_cutter import create_db

# Constants
CHROMA_PATH = "chroma_db"
MODEL_ID = "google/flan-t5-small"  # Better for French Q&A

print("🚀 Starting app...")

# 1️⃣ Initialize / Load Database
print("🔄 Initializing database from data folder...")
try:
    vectorstore = create_db()
    print("✅ Database created successfully!")
except Exception as e:
    print(f"❌ Error creating database: {e}")
    if os.path.exists(CHROMA_PATH):
        print("⚠️ Attempting to load existing database...")
        embeddings = HuggingFaceEmbeddings(model_name="sentence-transformers/all-MiniLM-L6-v2")
        vectorstore = Chroma(persist_directory=CHROMA_PATH, embedding_function=embeddings)
    else:
        raise e

# 2️⃣ Load LLM
print(f"🤖 Loading AI Model ({MODEL_ID})...")
tokenizer = AutoTokenizer.from_pretrained(MODEL_ID)
model = AutoModelForSeq2SeqLM.from_pretrained(
    MODEL_ID,
    torch_dtype=torch.float32,
    low_cpu_mem_usage=True
)

pipe = pipeline(
    "text2text-generation",
    model=model,
    tokenizer=tokenizer,
    max_new_tokens=300,
    device=-1,  # CPU
    do_sample=True,
    temperature=0.7,
    top_p=0.9,
)
print("✅ AI Model loaded successfully!")

# 3️⃣ Chat function
def chat_function(message, history):
    print(f"📨 Question received: {message}")
    
    try:
        # Search for relevant chunks
        results = vectorstore.similarity_search(message, k=3)
        context = "\n\n".join([doc.page_content for doc in results])
        
        # Build prompt optimized for Flan-T5
        prompt = f"""Contexte du document:
{context}

Question: {message}

Répondez en français en vous basant uniquement sur le contexte ci-dessus. Si l'information n'est pas dans le contexte, dites "Je ne trouve pas cette information dans le document"."""
        
        # Generate response
        outputs = pipe(prompt, max_new_tokens=300, num_return_sequences=1)
        response = outputs[0]['generated_text'].strip()
        
        # Fallback if response is too short or empty
        if len(response) < 10:
            response = "Je n'ai pas trouvé d'information pertinente dans le document pour répondre à votre question."
        
        print(f"✅ Response generated: {response[:100]}...")
        return response
        
    except Exception as e:
        error_msg = f"Erreur lors de la génération de la réponse: {str(e)}"
        print(f"❌ {error_msg}")
        return error_msg


# 4️⃣ Gradio Interface
demo = gr.ChatInterface(
    fn=chat_function,
    title="💬 RAG Chat - Documents en Français",
    description=f"Posez des questions sur vos documents PDF en français. Propulsé par {MODEL_ID}.",
    examples=[
        "Quel est le sujet principal du document ?",
        "Résume le contenu principal.",
        "Quelles sont les informations importantes ?"
    ]
)

if __name__ == "__main__":
    demo.launch()