app.py

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

# --- Configuration & Model Loading ---
# Use the pipeline, which is more robust as seen in the working example
print("Loading MedGemma model via pipeline...")
model_loaded = False
pipe = None
try:
    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) # Increase timeout duration for long first-time generation
def symptom_checker_chat(user_input, history_for_display, new_image_upload, image_state):
    """
    Manages the conversation by embedding the image directly into the message structure,
    which is the correct way to use this pipeline and prevents hanging.
    """
    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

    # --- THE CORRECT IMPLEMENTATION ---
    # Build the 'messages' list by embedding the image object directly inside the content.
    messages = []
    
    # Reconstruct the conversation from history.
    for i, (user_msg, assistant_msg) in enumerate(history_for_display):
        # We define the content for the user's turn
        user_content = [{"type": "text", "text": user_msg}]
        # If it's the very first turn of the conversation AND an image exists for it,
        # we embed the image object here.
        if i == 0 and current_image is not None:
            user_content.append({"type": "image", "image": current_image})
        
        messages.append({"role": "user", "content": user_content})
        
        if assistant_msg:
            # The assistant's response is always text
            messages.append({"role": "assistant", "content": [{"type": "text", "text": assistant_msg}]})

    # Add the current user's input to the conversation
    current_user_content = [{"type": "text", "text": user_input}]
    # If this is the start of a NEW conversation (no history) AND an image was just uploaded,
    # embed the image object in this first turn.
    if not history_for_display and current_image is not None:
        current_user_content.append({"type": "image", "image": current_image})
    
    messages.append({"role": "user", "content": current_user_content})

    try:
        # The pipeline call is now simple and correct.
        # It ONLY takes the `messages` structure. The pipeline unpacks it internally.
        output = pipe(messages, max_new_tokens=512, do_sample=True, temperature=0.7)
        
        # The pipeline returns the full conversation. The last message is the model's reply.
        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 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)
    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)

    def clear_all():
        return [], None, None, ""

    clear_btn = gr.Button("Start New Conversation")
    clear_btn.click(fn=clear_all, outputs=[chat_history, image_state, image_box, text_box], queue=False)
    
    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, ""
        return symptom_checker_chat(user_input, display_history, new__image, persisted_image)

    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)