// if it could not be found.
func findIndex(idx tag.Index, key []byte, form string) (index int, err error) {
	if !tag.FixCase(form, key) {
		return 0, ErrSyntax
	}
	i := idx.Index(key)
	if i == -1 {
		return 0, NewValueError(key)
	}
	return i, nil
}

func searchUint(imap []uint16, key uint16) int {
	return sort.Search(len(imap), func(i int) bool {
		return imap[i] >= key
	})
}

type Language uint16

// input is well-formed but the respective subtag is not recognized
// as a valid value.
type ValueError struct {
	v [8]byte
}

// NewValueError creates a new ValueError.
func NewValueError(tag []byte) ValueError {
	var e ValueError
	copy(e.v[:], tag)
	return e
}

func (e ValueError) tag() []byte {
	n := bytes.IndexByte(e.v[:], 0)
	if n == -1 {
		n = 8
	}

		if recover() != nil {
			v = Variant{}
			err = ErrSyntax
		}
	}()

	s = strings.ToLower(s)
	if id, ok := variantIndex[s]; ok {
		return Variant{id, s}, nil
	}
	return Variant{}, NewValueError([]byte(s))
}

// String returns the string representation of the variant.
func (v Variant) String() string {
	return v.str