goipgrep: refactor into module; pure-Go ping/resolve; cache+CI; drop binary

projects/go-tools/go/goipgrep/internal/normalize/ip.go

@@ -0,0 +1,27 @@
+package normalize
+
+import (
+	"fmt"
+	"net"
+	"strings"
+)
+
+// NormalizeIP validates an IP string and returns a canonical string form.
+// If allowIPv6 is false, only IPv4 is accepted.
+func NormalizeIP(s string, allowIPv6 bool) (string, bool) {
+	s = strings.TrimSpace(s)
+	if s == "" {
+		return "", false
+	}
+	ip := net.ParseIP(s)
+	if ip == nil {
+		return "", false
+	}
+	if v4 := ip.To4(); v4 != nil {
+		return fmt.Sprintf("%d.%d.%d.%d", v4[0], v4[1], v4[2], v4[3]), true
+	}
+	if !allowIPv6 {
+		return "", false
+	}
+	return ip.String(), true
+}