cmd: add die roller

cmd/rolldie/main.go

@@ -0,0 +1,48 @@
+package main
+
+import (
+	"flag"
+	"fmt"
+	"math/rand"
+	"os"
+	"regexp"
+	"strconv"
+
+	"git.wntrmute.dev/kyle/goutils/die"
+)
+
+var dieRollFormat = regexp.MustCompile(`^(\d+)[dD](\d+)$`)
+
+func rollDie(count, sides int) []int {
+	sum := 0
+	var rolls []int
+
+	for i := 0; i < count; i++ {
+		roll := rand.Intn(sides) + 1
+		sum += roll
+		rolls = append(rolls, roll)
+	}
+
+	rolls = append(rolls, sum)
+	return rolls
+}
+
+func main() {
+	flag.Parse()
+
+	for _, arg := range flag.Args() {
+		if !dieRollFormat.MatchString(arg) {
+			fmt.Fprintf(os.Stderr, "invalid die format %s: should be XdY\n", arg)
+			os.Exit(1)
+		}
+
+		dieRoll := dieRollFormat.FindAllStringSubmatch(arg, -1)
+		count, err := strconv.Atoi(dieRoll[0][1])
+		die.If(err)
+
+		sides, err := strconv.Atoi(dieRoll[0][2])
+		die.If(err)
+
+		fmt.Println(rollDie(count, sides))
+	}
+}