Move selector type and read logic

internal/types/selector.go

@@ -0,0 +1,51 @@
+package types
+
+import (
+	"encoding/json"
+	"errors"
+)
+
+type SelectorElement struct {
+	Any    bool
+	String string
+	Group  []string
+}
+
+func (se *SelectorElement) UnmarshalJSON(input []byte) error {
+	if input[0] == '"' {
+		if err := json.Unmarshal(input, &se.String); err != nil {
+			return err
+		}
+
+		if se.String == "*" {
+			se.Any = true
+			se.String = ""
+		}
+
+		return nil
+	}
+
+	if input[0] == '[' {
+		return json.Unmarshal(input, &se.Group)
+	}
+
+	return errors.New("the Go SelectorElement type can only be a string or an array of strings")
+}
+
+func (se *SelectorElement) MarshalJSON() ([]byte, error) {
+	if se.Any {
+		return []byte("\"*\""), nil
+	}
+
+	if se.String != "" {
+		return json.Marshal(se.String)
+	}
+
+	if se.Group != nil {
+		return json.Marshal(se.Group)
+	}
+
+	return nil, errors.New("a Go Selector must be a non-empty string or a non-empty slice of strings")
+}
+
+type Selector []SelectorElement