#----------------------------------------------------------------
# Dirname.ps1
#----------------------------------------------------------------
param
(
  [string]$name = $null
);

$script:SEPARATOR = "\";

#----------------------------------------------------------------
# function Do-Dirname
#----------------------------------------------------------------
function Do-Dirname()
{
  param
  (
    [string]$name = $null
  );
  
  $dirname = ".";
  
  if ( $name  )
  {
    if ( $name -ne $script:SEPARATOR )
    {
      $start_index = $name.Length-1;
      
      # for paths like \foo\bar\, bypass the trailing separator
      if ( ($name.Length -gt 1) -and $name.EndsWith($script:SEPARATOR) )
      {
        $start_index--;
      }
      
      # Reverse Iterate through the string until we find a path separator
      for($dirlen=$start_index; $dirlen -ge 0; $dirlen--)
      {
        if ( $name[$dirlen] -eq $script:SEPARATOR )
        {
          break;
        }
      }
      if ( $dirlen -eq -1 )
      {
        # No path separators found, default to the current directory
        $dirname = "."
      }
      else
      {
        $dirname = $name.Substring(0, $dirlen);
        
        #sanity checks
        if ( $dirname.Length -eq 0 ) { $dirname = $script:SEPARATOR; }
        if ( $dirname -like "[a-zA-Z]:" ) { $dirname += $script:SEPARATOR; }
      }
    }
  }
  $dirname;
}

#----------------------------------------------------------------
# function Do-DirnameUnitTests
#----------------------------------------------------------------
function Do-DirnameUnitTests()
{
  $tests = @( 
    @("foo", "."),
    @("foo\", "."),
    @("", "."),
    @("\foo", "\"),
    @("\foo\", "\"),
    @("\foo\bar", "\foo"),
    @("\foo\bar\", "\foo"),
    @("c:\foo", "c:\"),
    @("c:\foo\bar", "c:\foo"),
    @("c:\foo\bar\", "c:\foo")
  );
  
  $success = "PASS";
  
  "  {0,-15}      {1,-15}       {2,-15}    {3}" -f ("Test", "Expected", "Found", "Pass");
  foreach ($test in $tests)
  {
    $result = Do-Dirname $test[0];
    $status = $result -eq $test[1];
    "(""{0,-15}"" -> ""{1,-15}"") -> ""{2,-15}"" : {3}" -f ($test[0], $test[1], $result, $status);
    #Write-Host "TEST: (""$($test[0])"" -> ""$($test[1])"") -> ""$result"" : $status";
    if ( ! $status ) { $success = "FAIL"; }
  }
  ""
  "RESULT: $success";

}

Do-Dirname -name $name;