Extract useragent package

Fixes #30

useragent/useragent.go

@@ -0,0 +1,38 @@
+package useragent
+
+import (
+	"strings"
+)
+
+type UserAgent struct {
+	Product string
+	Version string
+	Comment string
+}
+
+func Parse(s string) UserAgent {
+	parts := strings.SplitN(s, "/", 2)
+	var version, comment string
+	if len(parts) > 1 {
+		// If first character is a number, treat it as version
+		if parts[1][0] >= 48 && parts[1][0] <= 57 {
+			rest := strings.SplitN(parts[1], " ", 2)
+			version = rest[0]
+			if len(rest) > 1 {
+				comment = rest[1]
+			}
+		} else {
+			comment = parts[1]
+		}
+	} else {
+		parts = strings.SplitN(s, " ", 2)
+		if len(parts) > 1 {
+			comment = parts[1]
+		}
+	}
+	return UserAgent{
+		Product: parts[0],
+		Version: version,
+		Comment: comment,
+	}
+}