coroutines.kt

package com.usabilla.coroutines

import kotlinx.coroutines.CoroutineScope
import kotlinx.coroutines.Dispatchers
import kotlinx.coroutines.Job
import kotlinx.coroutines.async
import kotlinx.coroutines.delay
import kotlinx.coroutines.flow.Flow
import kotlinx.coroutines.flow.catch
import kotlinx.coroutines.flow.collect
import kotlinx.coroutines.flow.flowOf
import kotlinx.coroutines.flow.map
import kotlinx.coroutines.launch
import kotlinx.coroutines.runBlocking

fun main() {
    val job = Job()
    val scope = CoroutineScope(Dispatchers.Default + job)

    scope.launch {
        delay(1000)
        worldHelloFlow().collect {
            println(it)
        }
    }

    // main thread scope
    runBlocking {
        // co-routine scope with a context derived from the main thread
        //
        // scope is the environment where the co-routine operations will run
        // context is the origin of such environment

        launch {
            delay(1000)
            worldHelloFlow().collect {
                println(it)
            }
        }

        val async = async {
            delay(2000)
            "async"
        }
        println(async.await())

        println("ending")
    }
}

fun helloWorldFlow(): Flow<String> {
    return flowOf("hello world")
}

fun worldHelloFlow(): Flow<String> {
    return helloWorldFlow()
        .catch {
            println("error here")
        }
        .map {
            "$it world hello"
        }
}