refactor structure

utils.go

@@ -0,0 +1,70 @@
+package main
+
+import (
+	"bufio"
+	"errors"
+	"io"
+	"log/slog"
+	"net"
+	"net/netip"
+	"strings"
+)
+
+func Iterate(reader io.Reader) <-chan net.IP {
+	scanner := bufio.NewScanner(reader)
+	ipChan := make(chan net.IP)
+	go func() {
+		defer close(ipChan)
+		for scanner.Scan() {
+			line := strings.TrimSpace(scanner.Text())
+			if line == "" {
+				continue
+			}
+			ip := net.ParseIP(line)
+			if ip != nil && (ip.To4() != nil || enableIPv6) {
+				// ip address
+				ipChan <- ip
+				continue
+			}
+			_, _, err := net.ParseCIDR(line)
+			if err == nil {
+				// ip cidr
+				p, err := netip.ParsePrefix(line)
+				if err != nil {
+					slog.Warn("Invalid cidr", "cidr", line, "err", err)
+				}
+				if !p.Addr().Is4() && !enableIPv6 {
+					continue
+				}
+				p = p.Masked()
+				addr := p.Addr()
+				for {
+					if !p.Contains(addr) {
+						break
+					}
+					ip = net.ParseIP(addr.String())
+					if ip != nil {
+						ipChan <- ip
+					}
+					addr = addr.Next()
+				}
+				continue
+			}
+			ips, err := net.LookupIP(line)
+			if err == nil {
+				// domain
+				for _, ip = range ips {
+					if ip.To4() != nil || enableIPv6 {
+						ipChan <- ip
+					}
+				}
+				continue
+			}
+			slog.Warn("Not a valid IP, IP CIDR or domain", "line", line)
+		}
+		if err := scanner.Err(); err != nil && !errors.Is(err, io.EOF) {
+			slog.Error("Read file error", "err", err)
+		}
+	}()
+	return ipChan
+}