class Person (val name: String, val age: Int) {
    fun greeting() = println("嗨！年紀 $age 歲的 $name！")
    fun greeting2() = println("YOYO！年紀 $age 歲的 $name！")
}

fun operateWithSonic(f: Person.() -> Unit) =
    f(Person("Sonic", 30))

// 節錄自 Kotlin 官方教學程式碼
fun happyBirthday(name: String, age: Int): String {
    return "Happy ${age}th birthday, $name!"
}

// 如果函式只有一行 return 的話，可簡寫成等式
fun happyBirthday2(name: String, age: Int) =
    "Happy ${age}th birthday, $name!"

// 無回傳參數的型態為 Unit 或不寫亦可
fun happyBirthday3(name: String, age: Int): Unit =
    println("Happy ${age}th birthday, $name!")

val greeting = happyBirthday("Anne", 32)

// try-catch
fun divideOrZero(numerator: Int, denominator: Int): Int {
    try {
        return numerator / denominator
    } catch (e: ArithmeticException) {
        println("error: x/0")
        return 0
    }
}

fun main() {

    // declare variables - val (read-only) var (writable)
    val a_1: Int = 2
    var a_2: Double = 2.0
    var a_3: Boolean = true
    var a_4: String = "heyMan"

    // String Interpolation
    var b_1: Int = 10
    var b_2: Int = 20
    var b_3: String = "The number ($b_1 + $b_2 + 100) = ${b_1 + b_2 + 100}"
    println(b_3)

    // Condition Flow: if
    val c_1: Int = 10
    if (c_1 > 10) {
        println("big number")
    }else {
        println("small number")
    }
    // Condition Flow: if-expression
    var c_result = if (c_1 > 10) {
        "big number"
    }else {
        "small number"
    }
    println("c_result: " + c_result)

    // Condition Flow: when (like switch in JAVA)
    when (c_1) {
        in 0..9 -> println("big number")
        else -> println("small number")
    }
    // Condition Flow: when-expression
    var c_result_2 = when (c_1) {
        in 0..9 -> "big number"
        else -> "small number"
    }
    println("c_result_2: " + c_result_2)

    // Collection: array (like int[] in JAVA)
    val integers = intArrayOf(1, 2, 3)
    val doubles = doubleArrayOf(1.0, 2.0, 3.0)

    // Collection: array (like Integer[] in JAVA)
    val generalIntegers = arrayOf(1, 2, 3)
    val generalDoubles = arrayOf(1.0, 2.0, 3.0)

    // Collection: List, Map, Set (Read-only)
    val strings = listOf("A","B","C")
    val map = mapOf("A" to 1, "B" to 2, "C" to 3);
    val set = setOf("a", "b", "c")

    // Collection: List, Map, Set (Writable)
    val strings_w = mutableListOf("A","B","C")
    val map_w = mutableMapOf("A" to 1, "B" to 2, "C" to 3);
    val set_w = mutableSetOf("a", "b", "c")

    // for loop
    for (word in strings) {
        print(word + " , ")
    }
    println()

    // while loop
    var d_1: Int = 3
    while (d_1 > 0) {
        println("d_1 is still positive number: $d_1")
        d_1--;
    }

    // special continue, break to jump out of outer-outer-outer loop !
    outer@ for (n in 2..100) {
        for (d in 2 until n) {
            if (n % d == 0) break@outer
        }
        println("$n is prime")
    }

    operateWithSonic {  // 參數只有 Function Type 的話，連括弧都可不寫。
        greeting2()
        println("$name 真的很棒。")
    }

    divideOrZero(10,0);


    // TODO: null ? !!
    // TODO: Lambda function

}