From the work you do.
To a system of your own.

// Illustration only — not IMS implementation code.
enum StockState { OutOfStock, LowStock, Healthy }

fn stock_state(quantity: i64, threshold: i64) -> StockState {
    if quantity <= 0 {
        StockState::OutOfStock
    } else if quantity <= threshold {
        StockState::LowStock
    } else {
        StockState::Healthy
    }
}

struct StockItem {
    name: String,
    quantity: i64,
    threshold: i64,
}

fn receive(item: &mut StockItem, quantity: i64) {
    item.quantity += quantity;
}

fn main() {
    let mut item = StockItem {
        name: String::from("Sample product"),
        quantity: 8,
        threshold: 3,
    };
    receive(&mut item, 2);
    let state = stock_state(item.quantity, item.threshold);
}