ParseNetworks belongs in report

report/networks.go

@@ -2,11 +2,30 @@ package report
 
 import (
 	"net"
+	"strings"
 )
 
 // Networks represent a set of subnets
 type Networks []*net.IPNet
 
+// ParseNetworks converts a string of space-separated CIDRs to a Networks.
+func ParseNetworks(v string) Networks {
+	set := map[string]struct{}{}
+	for _, s := range strings.Fields(v) {
+		_, ipNet, err := net.ParseCIDR(s)
+		if err != nil {
+			continue
+		}
+		set[ipNet.String()] = struct{}{}
+	}
+	nets := Networks{}
+	for s := range set {
+		_, ipNet, _ := net.ParseCIDR(s)
+		nets = append(nets, ipNet)
+	}
+	return nets
+}
+
 // Interface is exported for testing.
 type Interface interface {
 	Addrs() ([]net.Addr, error)

report/networks_test.go

@@ -1,6 +1,7 @@
 package report_test
 
 import (
+	"fmt"
 	"net"
 	"reflect"
 	"testing"
@@ -24,6 +25,28 @@ func TestContains(t *testing.T) {
 	}
 }
 
+func TestParseNetworks(t *testing.T) {
+	var (
+		bignetStr   = "10.1.0.1/16"
+		smallnetStr = "5.6.7.8/32"
+		bignet      = mustParseCIDR(bignetStr)
+		smallnet    = mustParseCIDR(smallnetStr)
+	)
+	for _, tc := range []struct {
+		input string
+		want  report.Networks
+	}{
+		{"", report.Networks{}},
+		{fmt.Sprintf("%s", bignetStr), report.Networks([]*net.IPNet{bignet})},
+		{fmt.Sprintf("%s %s", bignetStr, bignetStr), report.Networks([]*net.IPNet{bignet})},
+		{fmt.Sprintf("%s foo %s oops  %s", smallnetStr, smallnetStr, smallnetStr), report.Networks([]*net.IPNet{smallnet})},
+	} {
+		if want, have := tc.want, report.ParseNetworks(tc.input); !reflect.DeepEqual(want, have) {
+			t.Error(test.Diff(want, have))
+		}
+	}
+}
+
 func mustParseCIDR(s string) *net.IPNet {
 	_, ipNet, err := net.ParseCIDR(s)
 	if err != nil {