Caller interface applies to both units and chains

core/chain.go

@@ -0,0 +1,34 @@
+package core
+
+type (
+	Chain struct {
+		Flow  Flow
+		Links []Caller
+	}
+	Caller interface {
+		Call([]byte) ([]byte, error)
+		Units() []string
+	}
+)
+
+func (c *Chain) Call(data []byte) (resp []byte, err error) {
+	return data, nil
+}
+
+func (c *Chain) Units() []string {
+	// Collecting unique unit names using map
+	units := map[string]*struct{}{}
+	for _, caller := range c.Links {
+		for _, unit := range caller.Units() {
+			units[unit] = nil
+		}
+	}
+
+	// Extracting names to a slice
+	uniq := []string{}
+	for unit, _ := range units {
+		uniq = append(uniq, unit)
+	}
+
+	return uniq
+}