app.py

import gradio as gr
from transformers import pipeline, set_seed
from functools import lru_cache

# === 1. Cache the model loader once per session ===
@lru_cache(maxsize=1)
def get_generator(model_name: str):
    return pipeline(
        "text-generation",
        model=model_name,
        trust_remote_code=True,
        device_map="auto"
    )

# === 2. Chat callback ===
def chat(user_input, history, model_name, max_length, temperature, seed):
    # Set seed if provided
    if seed and seed > 0:
        set_seed(seed)
    # Lazy-load the model
    generator = get_generator(model_name)

    # Build prompt in Mistral’s instruction format
    prompt = (
        "[INST] <<SYS>>\nYou are a helpful assistant.\n<</SYS>>\n\n"
        f"{user_input}\n[/INST]"
    )
    # Generate response
    outputs = generator(
        prompt,
        max_length=max_length,
        temperature=temperature,
        do_sample=True,
        num_return_sequences=1
    )
    response = outputs[0]["generated_text"].split("[/INST]")[-1].strip()

    # Append to history as dicts for "messages" format
    history.append({"role": "user",      "content": user_input})
    history.append({"role": "assistant", "content": response})
    return history, history

# === 3. Build Gradio UI ===
with gr.Blocks() as demo:
    gr.Markdown("## 🤖 Mistral-7B-Instruct Chatbot (Gradio)")

    # Chatbot and session-state
    chatbot = gr.Chatbot(type="messages")                          # :contentReference[oaicite:3]{index=3}
    state   = gr.State([])                                         # :contentReference[oaicite:4]{index=4}

    with gr.Row():
        with gr.Column(scale=3):
            inp    = gr.Textbox(placeholder="Type your message...", lines=2, show_label=False)
            submit= gr.Button("Send")
        with gr.Column(scale=1):
            gr.Markdown("### Settings")
            model_name  = gr.Textbox(value="mistralai/Mistral-7B-Instruct-v0.3", label="Model name")
            max_length  = gr.Slider(50, 1024, 256, step=50, label="Max tokens")
            temperature = gr.Slider(0.0, 1.0, 0.7, step=0.05, label="Temperature")
            seed        = gr.Number(42, label="Random seed (0 disables)")

    # Wire the button: inputs include the gr.State; outputs update both Chatbot and state
    submit.click(
        fn=chat,
        inputs=[inp, state, model_name, max_length, temperature, seed],
        outputs=[chatbot, state]
    )

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