Fail fast if count value is invalid when count-prompt is not set.

move lottery draw logic into runLottery()

move MarkFlagsMutuallyExclusive into init()

cmd/lottery/validate.go

@@ -0,0 +1,41 @@
+package main
+
+import (
+	"fmt"
+	"strconv"
+	"strings"
+
+	"github.com/spf13/viper"
+)
+
+// validateNonPromptCount checks if the count is valid when the count-prompt flag is not set.
+func validateNonPromptCount() error {
+	if viper.GetBool("count-prompt") {
+		return nil
+	}
+
+	return validateCount(viper.GetInt("count"))
+}
+
+// validateCount checks if the count is valid.
+func validateCount(count int) error {
+	if count < 1 {
+		return fmt.Errorf("count must be greater than 0")
+	}
+
+	return nil
+}
+
+// parseCount parses the count from a string and validates it.
+func parseCount(raw string) (int, error) {
+	count, err := strconv.Atoi(strings.TrimSpace(raw))
+	if err != nil {
+		return 0, fmt.Errorf("count must be a whole number")
+	}
+
+	if err := validateCount(count); err != nil {
+		return 0, err
+	}
+
+	return count, nil
+}