func marshalUDT()

in marshal.go [2407:2490]
69 lines of code
21 McCabe index (conditional complexity)

func marshalUDT(info TypeInfo, value interface{}) ([]byte, error) {
	udt := info.(UDTTypeInfo)

	switch v := value.(type) {
	case Marshaler:
		return v.MarshalCQL(info)
	case unsetColumn:
		return nil, unmarshalErrorf("invalid request: UnsetValue is unsupported for user defined types")
	case UDTMarshaler:
		var buf []byte
		for _, e := range udt.Elements {
			data, err := v.MarshalUDT(e.Name, e.Type)
			if err != nil {
				return nil, err
			}

			buf = appendBytes(buf, data)
		}

		return buf, nil
	case map[string]interface{}:
		var buf []byte
		for _, e := range udt.Elements {
			val, ok := v[e.Name]

			var data []byte

			if ok {
				var err error
				data, err = Marshal(e.Type, val)
				if err != nil {
					return nil, err
				}
			}

			buf = appendBytes(buf, data)
		}

		return buf, nil
	}

	k := reflect.ValueOf(value)
	if k.Kind() == reflect.Ptr {
		if k.IsNil() {
			return nil, marshalErrorf("cannot marshal %T into %s", value, info)
		}
		k = k.Elem()
	}

	if k.Kind() != reflect.Struct || !k.IsValid() {
		return nil, marshalErrorf("cannot marshal %T into %s. Accepted types: Marshaler, UDTMarshaler, map[string]interface{}, struct, UnsetValue.", value, info)
	}

	fields := make(map[string]reflect.Value)
	t := reflect.TypeOf(value)
	for i := 0; i < t.NumField(); i++ {
		sf := t.Field(i)

		if tag := sf.Tag.Get("cql"); tag != "" {
			fields[tag] = k.Field(i)
		}
	}

	var buf []byte
	for _, e := range udt.Elements {
		f, ok := fields[e.Name]
		if !ok {
			f = k.FieldByName(e.Name)
		}

		var data []byte
		if f.IsValid() && f.CanInterface() {
			var err error
			data, err = Marshal(e.Type, f.Interface())
			if err != nil {
				return nil, err
			}
		}

		buf = appendBytes(buf, data)
	}

	return buf, nil
}