BrokenOpenClosePrinciple.swift

struct Order {
    
    let lineItems: [String]
    let shipping: String
    
    func getShippingCost() -> Double {
        if shipping == "ground" {
            if getTotal() > 100 {
                return 0
            }
            // $1.5 per kilogram, but $10 minimum
            return max(10, getTotalWeight() * 1.5)
        }
        if shipping == "air" {
            return max(20, getTotalWeight() * 3)
        }
        return 0.0
    }
    
    func getTotal() -> Double {
        // calculate the total
        return 0.0
    }
    
    func getTotalWeight() -> Double {
        // calculate the total weight
        return 0.0
    }
}