chapter8.kt

import kotlin.time.Duration

fun <T> Collection<T>.joinToString(
        separator: String = ", ",
        prefix: String = "",
        postfix: String = "",
        transform: ((T) -> String)? = null
): String {
    val result = StringBuilder(prefix)
    for ((index, element) in this.withIndex()) {
        if (index > 0) result.append(separator)
        val str = transform?.invoke(element)?: element.toString()
        result.append(str)
    }
    result.append(postfix)
    return result.toString()
}

enum class Delivery { STANDARD, EXPEDITED }

class Order(val itemCount: Int)

fun getShippingCostCalculator(
        delivery: Delivery): (Order) -> Double {
    if (delivery == Delivery.EXPEDITED) {
        return { order -> 6 + 2.1 * order.itemCount }
    }
    return { order ->  1.2 * order.itemCount }
}

enum class OS { WINDOWS, LINUX, MAC, IOS, ANDROID }
data class SiteVisit(
        val path: String,
        val duration: Double,
        val os: OS
)

val log = listOf(
        SiteVisit("/", 34.0, OS.WINDOWS),
        SiteVisit("/", 22.0, OS.MAC),
        SiteVisit("/login", 12.0, OS.WINDOWS),
        SiteVisit("/signup", 8.0, OS.IOS),
        SiteVisit("/", 16.3, OS.ANDROID)
)

fun List<SiteVisit>.averageDurationFor(predicate: (SiteVisit) -> Boolean) =
        filter(predicate).map(SiteVisit::duration).average()

println(log.averageDurationFor { it.os in setOf(OS.ANDROID, OS.IOS) })
println(log.averageDurationFor { it.os == OS.IOS && it.path == "/signup" })

// Labels
fun lookForAlice(people: List<Person>) {
    people.forEach label@{
        if (it.name == "Alice") return@label
    }
}

fun lookForAlice(people: List<Person>) {
    people.forEach {
        if (it.name == "Alice") return@forEach
    }
}