src/streamlit_app.py

import streamlit as st
import torch
import torch.nn.functional as F
from torchvision import transforms
from PIL import Image
import numpy as np
import timm
from pathlib import Path
import traceback


# ----------------------
# Page config
# ----------------------
st.set_page_config(
    page_title="Pneumonia X-ray Classifier",
    layout="centered"
)

st.title("🫁 Pneumonia Detection from Chest X-ray")
st.write("Upload a chest X-ray image to classify it as **Normal** or **Pneumonia**.")

DEVICE = "cpu"
CLASS_NAMES = ["Normal", "Pneumonia"]

MODEL_PATH = Path(__file__).resolve().parent / "efficientnet_b3_best.pt"

@st.cache_resource
def load_model():
    # Recreate model architecture EXACTLY as training
    model = timm.create_model(
        "efficientnet_b3",
        pretrained=False,
        num_classes=2   # Normal vs Pneumonia
    )

    state_dict = torch.load(MODEL_PATH, map_location=DEVICE)
    model.load_state_dict(state_dict)

    model.to(DEVICE)
    model.eval()
    return model

model = load_model()

# ----------------------
# File uploader
# ----------------------
uploaded_file = st.file_uploader(
    "Upload Chest X-ray Image",
    type=["jpg", "jpeg", "png"]
)

if uploaded_file is not None:
    try:
        # --- Image loading (HF-safe) ---
        image = Image.open(uploaded_file)
        image = image.convert("RGB")
        image = image.resize((300, 300))  # resize

        st.image(image, caption="Uploaded X-ray", use_column_width=True)

        # --- Preprocess ---
        input_tensor = transforms.ToTensor()(image)
        input_tensor = transforms.Normalize(
            mean=[0.485, 0.456, 0.406],
            std=[0.229, 0.224, 0.225]
        )(input_tensor)
        
        input_tensor = input_tensor.unsqueeze(0)


        # --- Inference ---
        with torch.no_grad():
            logits = model(input_tensor)
            probs = F.softmax(logits, dim=1).cpu().numpy()[0]

        st.subheader("🔍 Prediction Results")

        for i, class_name in enumerate(CLASS_NAMES):
            st.write(f"**{class_name}**: {probs[i]*100:.2f}%")

        pred_idx = np.argmax(probs)
        st.success(f"🩺 Diagnosis: **{CLASS_NAMES[pred_idx]}**")

    except Exception as e:
        st.error("❌ Error while processing the image")
        st.code(traceback.format_exc())
    pred_idx = np.argmax(probs)
    st.success(f"🩺 Diagnosis: **{CLASS_NAMES[pred_idx]}**")