ace-teknologi/abra

package abra

import (
    "fmt"
    "strconv"
    "strings"
)

// ACN represents an actual Australian Company Number
type ACN struct {
    IdentifierValue         string  `xml:"identifierValue,omitempty"`
    IsCurrentIndicator      string  `xml:"isCurrentIndicator,omitempty"`
    ReplacedIdentifierValue string  `xml:"replacedIdentifierValue,omitempty"`
    ReplacedFrom            abnDate `xml:"replacedFrom,omitempty"`
}

// IsValid checks whether your ACN has a valid identifier
// (https://asic.gov.au/for-business/registering-a-company/steps-to-register-a-company/australian-company-numbers/australian-company-number-digit-check/)
func (a *ACN) IsValid() (bool, error) {
    return ValidateACN(a.IdentifierValue)
}

// ValidateACN tests a string to see if it is a valid ACN
func ValidateACN(acn string) (bool, error) {
    // Strip whitespace
    raw := strings.Replace(acn, " ", "", -1)
    if len(raw) != 9 {
        return false, fmt.Errorf("Invalid ACN: found a %d character string", len(raw))
    }

    var checksum int
    var mapVal int
    var checkDigit int
    // compute the mapped values
    for i, char := range raw {
        digit, err := strconv.Atoi(string(char))
        if err != nil {
            return false, fmt.Errorf("Invalid ACN: found character %s", string(char))
        }
        if i < 8 {
            mapVal += (8 - i) * digit
        }
        if i == 8 {
            checkDigit = digit
        }
    }
    checksum = (10 - (mapVal % 10)) % 10

    if checkDigit != checksum {
        return false, fmt.Errorf("Invalid checksum: %d", checksum)
    }

    return true, nil
}