custom: custom operation separated

custom.go

@@ -0,0 +1,32 @@
+package main
+
+import "log"
+
+type callerFunc func(collector, ...string) string
+
+const (
+	CustomCustom = "custom"
+)
+
+var (
+	call = map[string]callerFunc{
+		CustomCustom: callCustom,
+	}
+)
+
+func customCall(data collector, tokens []string) string {
+	if len(tokens) < 1 {
+		log.Println("error: invalid number of arguments in call")
+		return ""
+	}
+
+	if caller, ok := call[tokens[0]]; ok {
+		return caller(data, tokens[1:]...)
+	}
+
+	return ""
+}
+
+func callCustom(data collector, tokens ...string) string {
+	return "this is a custom field"
+}