Belin.Validation

0.2.0

Sources/Validators/CreditCard.ps1

using namespace Belin.Validation

<#
.SYNOPSIS
    Creates a new validator that ensures the validated value is a well formed credit card number.
.OUTPUTS
    The newly created validator.
#>
function New-ValidatorCreditCard {
    [CmdletBinding()]
    [OutputType([Belin.Validation.Validator])]
    param (
        # The error message describing the validation failure.
        [Parameter(Mandatory, Position = 0)]
        [string] $Reason
    )

    New-Validator $Reason {
        $number = $_ -replace "[-. ]", ""
        if ($number -notmatch "^\d{8,19}$") { return $false }

        $characters = $number.ToCharArray()
        [Array]::Reverse($characters)

        $checksum = 0
        $evenDigit = $false

        foreach ($character in $characters) {
            $digit = ($character - [char] "0") * ($evenDigit ? 2 : 1)
            $evenDigit = -not $evenDigit

            while ($digit -gt 0) {
                $checksum += $digit % 10
                $digit = [int] [Math]::Truncate($digit / 10)
            }
        }

        ($checksum % 10) -eq 0
    }
}