ReplacingConditionalLogicWithStrategy1.swift

protocol CapitalStrategy {
    func capital(loan: Loan) -> Double
    func riskFactor() -> Double
}

extension CapitalStrategy {
    func riskFactor() -> Double {
        return 0.0
    }
}

class RevolverCapitalStrategy: CapitalStrategy {
    func capital(loan: Loan) -> Double {
        return 250 * riskFactor()
    }
}

class TermLoanCapitalStrategy: CapitalStrategy {
    func capital(loan: Loan) -> Double {
        if loan.expiryDate != nil && loan.maturityDate != nil {
            return 10.0 * loan.duration() * riskFactor()
        }
        if loan.expiryDate != nil && loan.maturityDate == nil {
            if loan.getUnusedPercentage() > 1.0 {
                return 150.0 * loan.getUnusedPercentage()
            } else {
                return 200.0 * loan.getUnusedPercentage()
            }
        }
        
        return 0.0
    }
}