import kotlinx.coroutines.experimental.GlobalScope
import kotlinx.coroutines.experimental.async
import kotlinx.coroutines.experimental.runBlocking
import java.util.*

data class GiftCard(val id: Int, val code: String)

class GiftCardService {

    /**
     * Just plain Kotlin code, might throw an Exception
     *
     * In our case this would be a call to a RESTful service
     */
    fun getGiftCard(id: Int): GiftCard {
        println("Getting GiftCard with id: $id")
        if (id == 8) throw Exception("Boom!")
        return GiftCard(id = id, code = UUID.randomUUID().toString())
    }

    /**
     * Async invoke getGiftCard() for the whole list of GiftCard ids
     *
     * Suspend keyword is mandatory due to the await() function call
     */
    suspend fun getGiftCards(): List<GiftCard> = listOf(1, 2, 3, 4, 5, 6, 7, 8, 9, 0)
            .map {
                // Launch the Coroutine and returns immediately
                GlobalScope.async { getGiftCard(it) }
            }
            .map {
                // Will Throw an Exception when calling await() for id=8
                val await = it.await()
                println("Fetched GiftCard: $await")
                await
            }

    /**
     * Async invoke getGiftCard() for the whole list of GiftCard ids, ignoring the failed ones.
     *
     * Suspend keyword is mandatory due to the await() function call
     */
    suspend fun getSuccessfullyFetchedGiftCards(): List<GiftCard> = listOf(1, 2, 3, 4, 5, 6, 7, 8, 9, 0)
            .map {
                // Launch the coroutine and returns immediately
                GlobalScope.async { getGiftCard(it) }
            }
            .mapNotNull {
                // Will Throw an Exception when awaiting for id=8
                if (!it.isCompletedExceptionally) it.await() else null
            }
}

fun main(args: Array<String>) = runBlocking {
    try {
        val giftCards = GiftCardService().getGiftCards() // Will throw an Exception
    } catch (e: Exception) {
        println("Shit exploded: ${e.message}")
    }

    val giftCards = GiftCardService().getSuccessfullyFetchedGiftCards().forEach {
        println(it)
    }
}