Another PowerShell Math Challenge - IronScripter Challenge - 2021-02-09 (Intermediate Only)

1-Intermediate.ps1

#requires -Version 7
function Get-SumTotal {
    [CmdLetBinding()]
    param(
        [Parameter(Mandatory,Position = 0,ValueFromPipeline)]
        [ValidatePattern('^\d{1,10}$', ErrorMessage = '"{0}" does not match only numbers 0-9 with a maximum of 10.')]
        #[ValidatePattern('^\d{1,10}$')]
        #[ValidateScript({ if ($_ -notmatch '^\d{1,10}$') { throw ('{0}"{1}" does not match only numbers 0-9 with a maximum of 10.' -f [System.Environment]::NewLine,$_) } else { $true }})]
        [string]$Value,

        [switch]$Full
    )

    process {
        $NumberList = [System.Collections.ArrayList]::new()
        $Value.ToCharArray() | ForEach-Object {
            [void]$NumberList.Add([System.Char]::GetNumericValue($_))
        }
        $SumTotal = $NumberList | Measure-Object -Sum
        $Calculation = '{0} = {1}' -f ($NumberList -join ' + '),$SumTotal.Sum

        $SumTotalOutput = [PsCustomObject]@{
            Value = $Value
            NumberCount = $SumTotal.Count
            Sum = $SumTotal.Sum
            Calculation = $Calculation
        }

        $Calculation | Write-Verbose

        if ($PSBoundParameters.ContainsKey('Full')) {
            $SumTotalOutput
        } else {
            $SumTotalOutput.Sum
        }
    }
}

There are 2 Validate* attributes that have been commented out.

The ValidatePattern attribute, prior to PowerShell Core, displays a generic, hard-to-read error message. The commented out attribute shows how to validate in Windows PowerShell 5.1. The other, uncommented, shows how to validate with PowerShell Core (6.x) and PowerShell (7.x).

The commented ValidateScript shows one way to provide the user with a more specific error message. This requires more code than the targeted validate attributes and can support more complex validation rules. I could have easily stayed with this attribute, but I chose to go with PowerShell 7 hence the #Requires statement.