//定義所有演算法的共用介面
abstract class HotelPriceStrategy {
    //取得總價錢
    abstract fun getHotelPrice(price :Int, roomNight: Int) : Int
}

//打折策略，建構子傳入折數
class DiscountOffRateStrategy(private val discountRate:Double):HotelPriceStrategy() {

    //計算售價
    override fun getHotelPrice(price :Int, roomNight: Int) : Int {
        return (price * roomNight * discountRate).toInt()
    }
}

//折扣價錢，建構子傳入折扣金額
class DiscountOffDollarStrategy(private val discountDollar:Int):HotelPriceStrategy() {

    //計算售價
    override fun getHotelPrice(price :Int, roomNight: Int) : Int {
        return ( price * roomNight ) - discountDollar
    }
}

fun main(args : Array<String>) {

    val hotelPrice = 2000
    val roomNight = 3

    //選擇使用打折
    val type = DiscountType.DISCOUNT_RATE

    val price: Int

    if ( type ==  DiscountType.DISCOUNT_RATE ) {
        //使用打折策略，打9折
        val strategy = DiscountOffRateStrategy(0.9)
        //計算售價
        price = strategy.getHotelPrice(hotelPrice, roomNight)
        println("totalPrice:$price") //5400
    }else{
        //使用折價策略，折200元
        val strategy2 = DiscountOffDollarStrategy(200)
        //計算售價
        price = strategy2.getHotelPrice(hotelPrice, roomNight)
        println("totalPrice:$price") //5800
    }
}

//簡單工廠，依照折扣方式，回傳演算法策略
internal class StrategyFactory{
    companion object {
        fun createStrategy(type: DiscountType): HotelPriceStrategy {
            return when (type) {
                //這裡不知道該怎麼傳入不同的參數
                DiscountType.DISCOUNT_RATE -> DiscountOffRateStrategy() //這裡要傳入折數
                DiscountType.DISCOUNT_DOLLAR -> DiscountOffDollarStrategy() //這裡要傳入折扣金額
            }
        }
    }
}

enum class DiscountType {
    DISCOUNT_RATE, DISCOUNT_DOLLAR
}