prefixed.go

package prefixed

import (
	"encoding/base32"
	"errors"
	"strings"

	"github.com/lsl/uuid"
)

var encoder = base32.NewEncoding("0123456789abcdefghjkmnpqrstvwxyz").WithPadding(base32.NoPadding)

func Encode(prefix string, u uuid.UUIDv7) string {
	// Pre-allocate buffer: prefix + '_' + 26 base32 chars
	result := make([]byte, len(prefix)+1+26)
	copy(result, prefix)
	result[len(prefix)] = '_'

	// Encode directly into the buffer after the prefix and underscore
	encoder.Encode(result[len(prefix)+1:], u[:])

	return string(result)
}

func New(prefix string) string {
	u := uuid.NewV7()
	return Encode(prefix, u)
}

func Parse(input string) (prefix, encodedUUID string, err error) {
	if input == "" {
		return "", "", errors.New("input cannot be empty")
	}

	var found bool
	prefix, encodedUUID, found = strings.Cut(input, "_")
	if !found {
		return "", "", errors.New("invalid format: missing underscore separator")
	}

	if len(encodedUUID) != 26 {
		// 128 bits = 16 bytes → ceil(16 * 8 / 5) = 26 base32 characters
		return "", "", errors.New("invalid encoded UUID length: must be 26 base32 characters")
	}

	return prefix, encodedUUID, nil
}

func Decode(input string) (string, uuid.UUIDv7, error) {
	prefix, encodedUUID, err := Parse(input)
	if err != nil {
		return "", uuid.UUIDv7{}, err
	}

	var result uuid.UUIDv7
	n, err := encoder.Decode(result[:], []byte(encodedUUID))
	if err != nil {
		return "", uuid.UUIDv7{}, errors.New("invalid base32 encoding")
	}

	if n != 16 {
		return "", uuid.UUIDv7{}, errors.New("decoded UUID has invalid length")
	}

	return prefix, result, nil
}

func Validate(input string) bool {
	if input == "" {
		return false
	}

	_, encodedUUID, found := strings.Cut(input, "_")
	if !found {
		return false
	}

	if len(encodedUUID) != 26 {
		return false
	}

	return true
}