package main

import "fmt"

func paintNeeded(width float64, height float64) (paintNeededCalculated float64, anError error) {
	area := width * height
	if width < 0.0 {
		return 0, fmt.Errorf("a width of %0.2f is invalid", width)
	}
	if height < 0.0 {
		return 0, fmt.Errorf("a height of %0.2f is invalid", height)
	}
	return area / 10.0, nil
}

func printLitersNeeded(amount float64) {
	fmt.Printf("%.2f liters needed\n", amount)
}

func wallArea() {
	var amount, total float64
	amount, err := paintNeeded(4.2, 3.0)
	if err != nil {
		fmt.Println(err)
	} else {
		printLitersNeeded(amount)
	}
	total += amount
	amount, err = paintNeeded(-5.2, 3.5)
	if err != nil {
		fmt.Println(err)
	} else {
		printLitersNeeded(amount)
	}
	total += amount
	amount, err = paintNeeded(5.2, 5.0)
	if err != nil {
		fmt.Println(err)
	} else {
		printLitersNeeded(amount)
	}
	total += amount
	fmt.Printf("Total: %.2f liters\n", total)
}