app.py

import gradio as gr
from transformers import pipeline
from PIL import Image
import torch
import os
import spaces

# --- Configuration & Model Loading ---
print("Loading MedGemma model via pipeline...")
model_loaded = False
pipe = None
try:
    # Using the "image-to-text" pipeline is the standard for these models
    pipe = pipeline(
        "image-to-text",
        model="google/medgemma-4b-it",
        model_kwargs={"torch_dtype": torch.bfloat16},
        device_map="auto",
        token=os.environ.get("HF_TOKEN")
    )
    model_loaded = True
    print("Model loaded successfully!")
except Exception as e:
    print(f"Error loading model: {e}")


# --- Core Chatbot Function ---
@spaces.GPU(duration=120)
def symptom_checker_chat(user_input, history_for_display, new_image_upload, image_state):
    """
    Manages the conversation by correctly separating the image object from the
    text-based message history in the pipeline call.
    """
    if not model_loaded:
        if user_input:
            history_for_display.append((user_input, "Error: The model could not be loaded."))
        return history_for_display, image_state, None, ""

    current_image = new_image_upload if new_image_upload is not None else image_state

    # 1. Build a simple list of text messages for the conversation history.
    messages = []
    for user_msg, assistant_msg in history_for_display:
        messages.append({"role": "user", "content": user_msg})
        if assistant_msg:
            messages.append({"role": "assistant", "content": assistant_msg})
    
    # Add the current user's text message
    messages.append({"role": "user", "content": user_input})

    try:
        # 2. Call the pipeline differently based on whether an image is present.
        generate_kwargs = {"max_new_tokens": 512, "do_sample": True, "temperature": 0.7}

        if current_image:
            # For multimodal calls, the image is the FIRST argument.
            output = pipe(current_image, prompt=messages, generate_kwargs=generate_kwargs)
        else:
            # For text-only calls, we ONLY use the `prompt` keyword argument.
            output = pipe(prompt=messages, generate_kwargs=generate_kwargs)
        
        # 3. Extract the response from the last message in the full conversation history.
        clean_response = output[0]["generated_text"][-1]['content']

    except Exception as e:
        print(f"Caught a critical exception during generation: {e}", flush=True)
        clean_response = (
            "An error occurred during generation. Details:\n\n"
            f"```\n{type(e).__name__}: {e}\n```"
        )

    # Update history and return values for the Gradio UI
    history_for_display.append((user_input, clean_response))
    return history_for_display, current_image, None, ""

# --- Gradio Interface ---
with gr.Blocks(theme=gr.themes.Soft(), css="footer {display: none !important}") as demo:
    gr.Markdown(
        """
        # AI Symptom Checker powered by MedGemma
        Describe your symptoms below. For visual symptoms (e.g., a skin rash), upload an image.
        """
    )
    
    image_state = gr.State(None)
    chatbot = gr.Chatbot(label="Conversation", height=500, bubble_full_width=False, avatar_images=("user.png", "bot.png"))
    chat_history = gr.State([])

    with gr.Row():
        image_box = gr.Image(type="pil", label="Upload Image of Symptom (Optional)")

    with gr.Row():
        text_box = gr.Textbox(label="Describe your symptoms...", placeholder="e.g., I have a rash on my arm that is red and itchy...", scale=4)
        submit_btn = gr.Button("Send", variant="primary", scale=1)

    # The helper functions need to be defined at this indentation level,
    # inside the `with gr.Blocks` scope but before they are used.
    def clear_all():
        return [], None, None, ""

    def on_submit(user_input, display_history, new_image, persisted_image):
        if not user_input.strip() and not new_image:
            return display_history, persisted_image, None, ""
        # The return statement is correctly indented inside this function
        return symptom_checker_chat(user_input, display_history, new_image, persisted_image)

    # Event Handlers for UI components
    clear_btn.click(fn=clear_all, outputs=[chat_history, image_state, image_box, text_box], queue=False)
    
    submit_btn.click(
        fn=on_submit,
        inputs=[text_box, chat_history, image_box, image_state],
        outputs=[chat_history, image_state, image_box, text_box]
    )
    
    text_box.submit(
        fn=on_submit,
        inputs=[text_box, chat_history, image_box, image_state],
        outputs=[chat_history, image_state, image_box, text_box]
    )

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