func marshalTuple()

in marshal.go [2177:2266]
73 lines of code
19 McCabe index (conditional complexity)

func marshalTuple(info TypeInfo, value interface{}) ([]byte, error) {
	tuple := info.(TupleTypeInfo)
	switch v := value.(type) {
	case unsetColumn:
		return nil, unmarshalErrorf("Invalid request: UnsetValue is unsupported for tuples")
	case []interface{}:
		if len(v) != len(tuple.Elems) {
			return nil, unmarshalErrorf("cannont marshal tuple: wrong number of elements")
		}

		var buf []byte
		for i, elem := range v {
			if elem == nil {
				buf = appendInt(buf, int32(-1))
				continue
			}

			data, err := Marshal(tuple.Elems[i], elem)
			if err != nil {
				return nil, err
			}

			n := len(data)
			buf = appendInt(buf, int32(n))
			buf = append(buf, data...)
		}

		return buf, nil
	}

	rv := reflect.ValueOf(value)
	t := rv.Type()
	k := t.Kind()

	switch k {
	case reflect.Struct:
		if v := t.NumField(); v != len(tuple.Elems) {
			return nil, marshalErrorf("can not marshal tuple into struct %v, not enough fields have %d need %d", t, v, len(tuple.Elems))
		}

		var buf []byte
		for i, elem := range tuple.Elems {
			field := rv.Field(i)

			if field.Kind() == reflect.Ptr && field.IsNil() {
				buf = appendInt(buf, int32(-1))
				continue
			}

			data, err := Marshal(elem, field.Interface())
			if err != nil {
				return nil, err
			}

			n := len(data)
			buf = appendInt(buf, int32(n))
			buf = append(buf, data...)
		}

		return buf, nil
	case reflect.Slice, reflect.Array:
		size := rv.Len()
		if size != len(tuple.Elems) {
			return nil, marshalErrorf("can not marshal tuple into %v of length %d need %d elements", k, size, len(tuple.Elems))
		}

		var buf []byte
		for i, elem := range tuple.Elems {
			item := rv.Index(i)

			if item.Kind() == reflect.Ptr && item.IsNil() {
				buf = appendInt(buf, int32(-1))
				continue
			}

			data, err := Marshal(elem, item.Interface())
			if err != nil {
				return nil, err
			}

			n := len(data)
			buf = appendInt(buf, int32(n))
			buf = append(buf, data...)
		}

		return buf, nil
	}

	return nil, marshalErrorf("cannot marshal %T into %s. Accepted types: struct, []interface{}, array, slice, UnsetValue.", value, tuple)
}