models/yolov8_model.pt

# scripts/download_yolov8_model.py
from ultralytics import YOLO
import os
import torch
import requests
import shutil

# Directory to save the model
MODEL_DIR = "models"
os.makedirs(MODEL_DIR, exist_ok=True)

# Path to save the model
MODEL_PATH = os.path.join(MODEL_DIR, "yolov8_model.pt")

# URL for yolov8n.pt from Ultralytics GitHub releases
MODEL_URL = "https://github.com/ultralytics/assets/releases/download/v8.2.0/yolov8n.pt"

def download_model(url, output_path):
    """Download model file from URL and save to output_path."""
    print(f"Downloading model from {url}...")
    try:
        response = requests.get(url, stream=True)
        if response.status_code == 200:
            with open(output_path, 'wb') as f:
                shutil.copyfileobj(response.raw, f)
            print(f"Model downloaded to {output_path}")
        else:
            raise Exception(f"Failed to download model: HTTP {response.status_code}")
    except Exception as e:
        raise Exception(f"Download error: {str(e)}")

def verify_model(path):
    """Verify that the model file is a valid PyTorch checkpoint."""
    print(f"Verifying model at {path}...")
    try:
        checkpoint = torch.load(path, map_location='cpu', weights_only=False)
        print(f"Model verified as valid PyTorch checkpoint")
        return True
    except Exception as e:
        raise Exception(f"Verification failed: {str(e)}")

# Download and verify model
try:
    # Remove existing file to avoid using corrupted version
    if os.path.exists(MODEL_PATH):
        os.remove(MODEL_PATH)
        print(f"Removed existing file at {MODEL_PATH}")

    # Download yolov8n.pt
    download_model(MODEL_URL, MODEL_PATH)

    # Verify the downloaded file
    verify_model(MODEL_PATH)

    # Load with YOLO to ensure compatibility
    model = YOLO(MODEL_PATH)
    print(f"Model successfully loaded with Ultralytics YOLO")
except Exception as e:
    print(f"Failed to download or verify model: {str(e)}")
    print("Please manually download yolov8n.pt from https://github.com/ultralytics/assets/releases and place it in backend/models/yolov8_model.pt")