Fix Varnish version reporting (#38)

* GH-37 Add version test for Varnish 4.1.10

* GH-37 Fix version parsing regex

* GH-37 Improve regex matching of Varnish version

varnish.go

@@ -224,10 +224,18 @@ func (v *varnishVersion) queryVersion() error {
 }
 
 func (v *varnishVersion) parseVersion(version string) error {
-	r := regexp.MustCompile(`(\d)\.?(\d)?\.?(\d)?(?:.*revision\s(.*)\))?`)
-	parts := r.FindStringSubmatch(version)
+	r := regexp.MustCompile(`(?P<major>\d+)(\.(?P<minor>\d+))?(\.(?P<patch>\d+))?(.*revision\s(?P<revision>[0-9a-f]*)\))?`)
+	match := r.FindStringSubmatch(version)
+
+	parts := make(map[string]string)
+	for i, name := range r.SubexpNames() {
+		if i != 0 && name != "" {
+			parts[name] = match[i]
+		}
+	}
+
 	if len(parts) > 1 {
-		if err := v.set(parts[1:]); err != nil {
+		if err := v.set(parts); err != nil {
 			return err
 		}
 	}
@@ -255,25 +263,30 @@ func (v *varnishVersion) Labels() map[string]string {
 	return labels
 }
 
-func (v *varnishVersion) set(parts []string) error {
-	for i, part := range parts {
-		if len(part) == 0 {
+func (v *varnishVersion) set(parts map[string]string) error {
+	for name, value := range parts {
+		// skip empty value
+		if len(value) == 0 {
 			continue
 		}
-		if i == 3 {
-			v.Revision = part
-			break
+
+		// save revision as-is (string)
+		if name == "revision" {
+			v.Revision = value
+			continue
 		}
-		num, err := strconv.Atoi(part)
+
+		// convert semver parts to integer and save it
+		num, err := strconv.Atoi(value)
 		if err != nil {
 			return err
 		}
-		switch i {
-		case 0:
+		switch name {
+		case "major":
 			v.Major = num
-		case 1:
+		case "minor":
 			v.Minor = num
-		case 2:
+		case "patch":
 			v.Patch = num
 		}
 	}

varnish_test.go

@@ -20,6 +20,9 @@ func Test_VarnishVersion(t *testing.T) {
 		"varnishstat (varnish-5.2.0 revision 4c4875cbf)": &varnishVersion{
 			Major: 5, Minor: 2, Patch: 0, Revision: "4c4875cbf",
 		},
+		"varnishstat (varnish-4.1.10 revision 1d090c5a08f41c36562644bafcce9d3cb85d824f)": &varnishVersion{
+			Major: 4, Minor: 1, Patch: 10, Revision: "1d090c5a08f41c36562644bafcce9d3cb85d824f",
+		},
 		"varnishstat (varnish-4.1.0 revision 3041728)": &varnishVersion{
 			Major: 4, Minor: 1, Patch: 0, Revision: "3041728",
 		},