import csv
from io import TextIOWrapper
from models import db, Asset  # Import your database and model

def process_csv(file):
    """
    Processes the uploaded CSV file and returns a list of Asset objects.
    Raises an exception if the file is invalid or data is incorrect.
    """
    csv_file = TextIOWrapper(file, encoding='utf-8')
    reader = csv.DictReader(csv_file)

    # Validate CSV headers
    required_headers = ['assettag', 'hostname', 'warrantyfrom', 'status', 'staffnum']
    if not all(header in reader.fieldnames for header in required_headers):
        raise ValueError("CSV file must include headers: assettag, hostname, warrantyfrom, status, staffnum.")

    # Process each row
    assets = []
    for row in reader:
        # Validate required fields
        if not row['assettag']:
            raise ValueError("Missing 'assettag' in one or more rows.")

        # Create Asset object
        assets.append(Asset(
            assettag=row['assettag'],
            hostname=row['hostname'],
            warrantyfrom=row['warrantyfrom'],
            status=row['status'],
            staffnum=row['staffnum']
        ))

    return assets