added Go variant

- using homegrown approval test function

go/theatre/StatementPrinter.go

@@ -0,0 +1,53 @@
+package theatre
+
+import (
+	"fmt"
+	"math"
+
+	"github.com/leekchan/accounting"
+)
+
+type StatementPrinter struct{}
+
+func (StatementPrinter) Print(invoice Invoice, plays map[string]Play) (string, error) {
+	totalAmount := 0
+	volumeCredits := 0
+	result := fmt.Sprintf("Statement for %s\n", invoice.Customer)
+
+	ac := accounting.Accounting{Symbol: "$", Precision: 2}
+
+	for _, perf := range invoice.Performances {
+		play := plays[perf.PlayID]
+		thisAmount := 0
+
+		switch play.Type {
+		case "tragedy":
+			thisAmount = 40000
+			if perf.Audience > 30 {
+				thisAmount += 1000 * (perf.Audience - 30)
+			}
+		case "comedy":
+			thisAmount = 30000
+			if perf.Audience > 20 {
+				thisAmount += 10000 + 500*(perf.Audience-20)
+			}
+			thisAmount += 300 * perf.Audience
+		default:
+			return "", fmt.Errorf("unknown type: %s", play.Type)
+		}
+
+		// add volume credits
+		volumeCredits += int(math.Max(float64(perf.Audience)-30, 0))
+		// add extra credit for every ten comedy attendees
+		if play.Type == "comedy" {
+			volumeCredits += int(math.Floor(float64(perf.Audience) / 5))
+		}
+
+		// print line for this order
+		result += fmt.Sprintf("  %s: %s (%d seats)\n", play.Name, ac.FormatMoney(float64(thisAmount)/100), perf.Audience)
+		totalAmount += thisAmount
+	}
+	result += fmt.Sprintf("Amount owed is %s\n", ac.FormatMoney(float64(totalAmount)/100))
+	result += fmt.Sprintf("You earned %d credits\n", volumeCredits)
+	return result, nil
+}