license_plate.go

package record

import (
	"errors"
	"fmt"
	"strings"
	"unicode"
)

// LicensePlate represents a license plate that can be attempted normalized.
type LicensePlate struct {
	string
}

const maxLength = 8

// NewLicensePlate returns a new LicensePlate
func NewLicensePlate(s string) *LicensePlate {
	return &LicensePlate{s}
}

// Normalize returns a pointer reference to a new uppercase LicensePlate without whitespace.
// If the LicensePlate cannot be normalized, an error is returned.
// A LicensePlate cannot be normalized if:
// It has more than 8 non-whitespace characters, contains special characters or
// contains no alphanumerics (digits and letters).
func (lp *LicensePlate) Normalize() (nlp *LicensePlate, err error) {
	if len(lp.string) == 0 {
		return nil, errors.New("empty string")
	}

	var b strings.Builder
	b.Grow(len(lp.string))

	runes := 0

	for index, r := range lp.string {
		if unicode.IsDigit(r) || unicode.IsLetter(r) {
			if runes < maxLength {
				b.WriteRune(unicode.ToUpper(r))
				runes++
			} else {
				return nil, fmt.Errorf("more than %d characters", maxLength)
			}
		} else if !unicode.IsSpace(r) {
			return nil, fmt.Errorf("invalid character %#U at byte position %d", r, index)
		}
	}

	if b.Len() == 0 {
		return nil, errors.New("no alphanumerics")
	}

	return &LicensePlate{b.String()}, nil
}

func (lp *LicensePlate) String() string {
	return lp.string
}