Merge pull request #45 from burned42/add_coffee_maker_challenge_code

add coffee maker challenge code

slides/2019/031_go-to-grpc/coffee-maker-challenge/README.md

@@ -0,0 +1,10 @@
+We (@dersell and @burned42) tried to solve the challenge :)
+It's not pretty but it works and we thought it would be nice to share
+the code anyway.
+
+As we remembered the constrains where that the coffee maker should be
+able to make multiple coffees at the same time and you should be able
+to abort each coffee if you like, so that's what we implemented. The
+coffee maker produces 10 coffees and you can abort a specific coffee by
+typing in the number of the coffee.
+

slides/2019/031_go-to-grpc/coffee-maker-challenge/main.go

@@ -0,0 +1,86 @@
+package main
+
+import (
+	"fmt"
+	"sync"
+	"time"
+)
+
+var waitGroup sync.WaitGroup
+
+const coffeeCount = 10
+
+func main() {
+	var coffeeFinished [coffeeCount]chan bool
+	for i := 0; i < coffeeCount; i++ {
+		coffeeFinished[i] = make(chan bool)
+	}
+	go runAbortScreen(coffeeFinished)
+
+	for i := 0; i < coffeeCount; i++ {
+		waitGroup.Add(1)
+		go func(i int) {
+			go makeCoffee(i+1, coffeeFinished[i])
+			<-coffeeFinished[i]
+			waitGroup.Done()
+		}(i)
+
+		time.Sleep(time.Second)
+	}
+
+	waitGroup.Wait()
+}
+
+func runAbortScreen(isAbort [coffeeCount]chan bool) {
+	fmt.Println("Press a number to cancel making coffee!")
+
+	for {
+		var key int
+		fmt.Scanf("%d", &key)
+		fmt.Println("Cancelling coffee #", key)
+
+		close(isAbort[key-1])
+	}
+}
+
+func makeCoffee(number int, isFinished chan bool) {
+	select {
+	case <-isFinished:
+		return
+	default:
+		fmt.Println("Making coffee #", number)
+		grindBeans(number)
+	}
+
+	select {
+	case <-isFinished:
+		return
+	default:
+		prepareCoffee(number)
+	}
+
+	select {
+	case <-isFinished:
+		return
+	default:
+		steamMilk(number)
+	}
+
+	fmt.Println("Coffee #", number, " is ready!")
+	isFinished <- true
+}
+
+func grindBeans(number int) {
+	fmt.Println("Grinding beans #", number, " ...")
+	time.Sleep(3 * time.Second)
+}
+
+func prepareCoffee(number int) {
+	fmt.Println("Preparing coffee #", number, " ...")
+	time.Sleep(1 * time.Second)
+}
+
+func steamMilk(number int) {
+	fmt.Println("Steaming milk #", number, " ...")
+	time.Sleep(2 * time.Second)
+}