package kotlin

/**
 * The root of the Kotlin class hierarchy. Every Kotlin class has [Any] as a superclass.
 */
public open class Any {
    public open operator fun equals(other: Any?): Boolean

    public open fun hashCode(): Int

    public open fun toString(): String
}

var a: String? = "abc"
a = null // ok

/* 
* Si a es null el length
* también devolverá null 
*/
val l = a?.length

/*
* Si a es null se lanzará
* un kotlin.KotlinNullPointerException
*/
val l = a!!.size

// Java
int l = a != null ? a.length : -1

// Kotlin (Operador Elvis)
val l = a?.length ?: -1

// Kotlin
class Mensaje {
    //fun mostrar(text: String?) {
    fun mostrar(text: String) { //java.lang.IllegalArgumentException
        println("Text: $text")
    }
}

// Java
public class Invoker {
    public static void main(String[] args) {
        new Mensaje().mostrar(null);
    }
}

val a = "ABCD"
val l = if(a != null) a.length else -1
//a != null ? a.length : -1 No se puede usar

val l2 = when(a) {
    null -> -1
    else -> a.length
}

fun isNumeric(text: String): Boolean {
    return try {
        text.toDouble()
        true
    } catch(error: Exception) {
        false
    }
}

// Lambdas
val x = 2.0
val sin = { n: Double -> Math.sin(n) }
val cos = { n: Double -> Math.cos(n) }
val r = (if(x > 1) sin else cos)(x)
println("R = $r")


//Función anónima
val toInSafety = fun(s: String): Int { return s.toIntOrNull() ?: 0 }
val s = "Carlos"
println("${toInSafety(s)}")

fun Date.toISODate(): String? {
    return Constants.DEFAULT_DATE_FORMAT.format(this)
}

fun Date.toISOTime(withSeconds: Boolean = true): String? {
    var formatedTime = Constants.DEFAULT_TIME_FORMAT.format(this)
    if(!withSeconds) {
        formatedTime = formatedTime.substring(0, formatedTime.lastIndexOf(":"))
    }
    return formatedTime
}

val colors = listOf("Rojo", "Amarillo", "Azul", "Rojo")
val colorsHex = mapOf("Amarillo" to "#123", "Azul" to "#456", "Rojo" to "#789")

fun main(args: Array<String>) {
    val unitHex = colors
        .map { colorsHex[it] }
        .toSet()
    println(unitHex)
}

fun Date.toISODate(): String? {
    return Constants.DEFAULT_DATE_FORMAT.format(this)
}

fun Date.toISOTime(withSeconds: Boolean = true): String? {
    var formatedTime = Constants.DEFAULT_TIME_FORMAT.format(this)
    if(!withSeconds) {
        formatedTime = formatedTime.substring(0, formatedTime.lastIndexOf(":"))
    }
    return formatedTime
}

class User(val map: Map<String, Any?>) {
    val name: String by map
    val age: Int     by map
}

val user = User(mapOf(
    "name" to "John Doe",
    "age"  to 25
))

import kotlin.properties.Delegates

class User {
    var name: String by Delegates.observable("<no name>") {
        prop, old, new ->
        println("$old -> $new")
    }
}

fun main() {
    val user = User()
    user.name = "first"
    user.name = "second"
}

import kotlinx.coroutines.*

fun main() = runBlocking {
    launch { doWorld() }
    println("Hello,")
}

// this is your first suspending function
suspend fun doWorld() {
    delay(1000L)
    println("World!")
}

🤓   Mantén un pensamiento al rededor de lo básico
🐢   Empieza despacio pero hazlo real
😵   No intentes aprender todo el lenguaje de una vez
🔀   Aprende del convertidor automático
🤔   Cuestiona todos tus hábitos de Java
🏕️   Deja el parque más limpio de lo que lo encontraste
👴🏻   Frenar el entusiasmo
💸   No olvides a tus clientes


// Por Dan Kim