app.py

from fastapi import FastAPI, File, UploadFile, HTTPException
import torch
import torch.nn as nn
from torchvision import models, transforms
from PIL import Image, UnidentifiedImageError
import io
import uvicorn


app = FastAPI(title="Food Spoilage Detection API (Swin)")

# Load model
device = torch.device("cuda" if torch.cuda.is_available() else "cpu")

# Swin architecture
model = models.swin_t()
num_ftrs = model.head.in_features
model.head = nn.Linear(num_ftrs, 2)

# Load Swin weights
model.load_state_dict(torch.load("models/spoilage_model_swin_finetuned.pth", map_location=device))
model = model.to(device)
model.eval()

# Preprocessing transforms
preprocess = transforms.Compose([
    transforms.Resize(256),
    transforms.CenterCrop(224),
    transforms.ToTensor(),
    transforms.Normalize([0.485, 0.456, 0.406], [0.229, 0.224, 0.225])
])

CLASS_NAMES = ["fresh", "spoiled"]
MAX_FILE_SIZE = 20 * 1024 * 1024  # 20 MB

@app.post("/predict")
async def predict(file: UploadFile = File(...)):
    contents = await file.read()

    if len(contents) > MAX_FILE_SIZE:
        raise HTTPException(status_code=400, detail="File too large. Maximum size is 10 MB.")

    try:
        image = Image.open(io.BytesIO(contents)).convert("RGB")
    except UnidentifiedImageError:
        raise HTTPException(status_code=400, detail="Could not read image. Please upload a valid image file.")

    try:
        input_tensor = preprocess(image)
        input_batch = input_tensor.unsqueeze(0).to(device)

        with torch.inference_mode():
            outputs = model(input_batch)
            probabilities = torch.nn.functional.softmax(outputs[0], dim=0)
            confidence, index = torch.max(probabilities, 0)

        conf_score = float(confidence.item())

        if conf_score < 0.70:
            return {
                "status": "ambiguous",
                "message": "Model confidence too low. The image might not be a recognized food item or is too low quality.",
                "confidence": conf_score,
                "suggestion": "Please provide a clearer image of a fruit or vegetable."
            }

        return {
            "prediction": CLASS_NAMES[index.item()],
            "confidence": conf_score,
            "status": "success",
            "model": "swin_transformer_tiny_finetuned"
        }

    except Exception as e:
        raise HTTPException(status_code=500, detail=f"Error processing image: {str(e)}")

@app.get("/")
def read_root():
    return {
        "message": "Food Spoilage Detection API is running.",
        "usage": "POST an image to /predict",
        "supported_classes": CLASS_NAMES
    }

@app.get("/health")
def health():
    return {"status": "ok"}

if __name__ == "__main__":
    uvicorn.run(app, host="0.0.0.0", port=7860)