Roll-Dice

function Roll-Dice {
param(
    [Parameter(
  	Mandatory = $true,
		#Position = 0,
		ValueFromPipeline = $true,
		ValueFromPipelineByPropertyName = $true)]
        [string]$ndm
    )
    #should probably check for input not matching ndm pattern
    if (-not ($ndm -match "\dd\d")){
      Write-Error -Message "Invalid Input, format must be ndm where 1<=n<=100 and 2<=m<=200." -Category InvalidArgument; 
      return $null
    }
    [system.int32]$n = $ndm.split("d")[0]
    [system.int32]$m = $ndm.split("d")[1]
    
    #validate input    
    if (($n -lt 1) -or ($n -gt 100) -or ($m -lt 2) -or ($m -gt 100)){
      Write-Error -Message "Invalid Input, format must be ndm where 1<=n<=100 and 2<=m<=200." -Category InvalidArgument
      return $null
    }
    
    $result = @();    
    while ($i++ -lt $n){$result += Get-Random -Minimum 1 -Maximum ($m+1) }
    return $result    
}

#region UnitTests
function verify-diceroll($n, $m) {
  $output = roll-dice ("" + $n + "d" + $m)
  if ($output -eq $null) {write-error "FAIL OUTPUT NULL"; return; }
  if ($output.count -ne $n) { Write-Error "FAIL! number of rolls doesn't match input: actual:$output.count. expected:$n."; return;}
  foreach($a in $output) {
    if (($a -gt $m) -or ($a -lt 1)){ write-error "FAIL Resulting roll result ($a) is out of expected bounds 1..$m."; return;}
  }
  write-host "looks good"
}

function test-ValidateOutput() {
  Write-Host "Test Valid Values"
  verify-diceroll 1 2 #min
  verify-diceroll 1 100 #max
  verify-diceroll 100 100 #max
  verify-diceroll 2 6 #most common
}

function test-invalidinputs() {
#invalid
  write-host "Test Invalid Values"
 "abd" | Roll-Dice
 "0d6" | Roll-Dice
 "101d6" | ROll-Dice
 "2d1" | Roll-Dice
 "2d101" | Roll-Dice
}

function test-PipelineInputs(){
  Write-Host "Test Pipeline Inputs"
  "2d6" | Roll-Dice
  "1d2" | Roll-Dice
  "100d100" | Roll-Dice
}

function Run-Tests()
{
  test-PipelineInputs
  test-invalidinputs
  test-ValidateOutput
}

#endregion