init

main.go

@@ -0,0 +1,37 @@
+package main
+
+import (
+	"fmt"
+	"os"
+	"strings"
+
+	"golang.org/x/net/publicsuffix"
+)
+
+func main() {
+	if len(os.Args) != 2 {
+		fmt.Fprintf(os.Stderr, "Usage: %s <domain>\n", os.Args[0])
+		os.Exit(1)
+	}
+
+	domain := strings.TrimSpace(os.Args[1])
+	if domain == "" {
+		fmt.Println("invalid")
+		os.Exit(1)
+	}
+
+	// Get the effective TLD+1 (registrable domain)
+	etld1, err := publicsuffix.EffectiveTLDPlusOne(domain)
+	if err != nil {
+		fmt.Println("invalid")
+		os.Exit(1)
+	}
+
+	// If the domain is exactly the effective TLD+1, it's a valid domain
+	// If it's longer, it's a subdomain
+	if domain == etld1 {
+		fmt.Println("valid")
+	} else {
+		fmt.Println("subdomain")
+	}
+}