Write-Log

Function Get-CurrentLineNumber { 
  $Invocation = Get-Variable MyInvocation -value -ea 0 2>$Null
  If (!$Invocation) { $Invocation = $MyInvocation } 
  $Invocation.ScriptLineNumber 
}

Function Get-CurrentFileLine   { 
  if ($MyInvocation.PSCommandPath) {
    "$(split-path -leaf $MyInvocation.PSCommandPath):$($MyInvocation.ScriptLineNumber)" 
  } else {"GLOBAL:$(LINE)"} 
}
New-Alias -Name   LINE   -Value Get-CurrentLineNumber -Description 'Returns the current (caller''s) line number in a script.' -force -scope Global
New-Alias -Name __LINE__ -Value Get-CurrentLineNumber -Description 'Returns the current (caller''s) line number in a script.' -force -scope Global
New-Alias -Name   FILE   -Value Get-CurrentFileName   -Description 'Returns the name of the current script file.'             -force -scope Global
New-Alias -Name   FLINE  -Value Get-CurrentFileLine   -Description 'Returns the name of the current script file.'             -force -scope Global
New-Alias -Name __FILE__ -Value Get-CurrentFileName   -Description 'Returns the name of the current script file.'             -force -scope Global

# Typically I alias Write-Log to Write-Verbose WHEN Function Write-Log isn't defined
# so remove the alias when we define Write-Log
if (Get-Command Write-Log -alias -ea 0) { remove-item Alias:Write-Log -force -ea 0 }

Function Write-Log {
  param (
    [string]$Message,
    [int]$Severity = 3, ## Default to a high severity. Otherwise, override
    [string]$File = $LogFilePath  # default to caller's $LogFilePath if defined
  )
  try {
    if (!$LogLevel) { $LogLevel = 3 }
    if ($Severity -lt $LogLevel) { return }
    write-verbose $Message
    $line = [pscustomobject]@{
      'DateTime' = (Get-Date -f "yyyy-MM-dd-ddd-HH:mm:ss") #### (Get-Date)
      'Severity' = $Severity
      'Message'  = $Message
    }
    if (-not $LogFilePath) { 
      $LogFilePath  =  "$($MyInvocation.ScriptName)" -replace '(\.ps1)?$', ''    
      $LogFilePath += '-Log.txt'
    }
    if ($File) { $LogFilePath = $File }
    if ($psversiontable.psversion.major -lt 3) {
      $Entry = "`"$($line.DateTime)`", `"$($line.$Severity)`", `"$($line.$Message)`""
      $null = Out-file -enc utf8 -filepath $LogFilePath -input $Entry -append -erroraction Silentlycontinue -force 
    } else {
      $line | Export-Csv -Path $LogFilePath -Append -NoTypeInformation -erroraction Silentlycontinue -force -enc ASCII
    }
  } catch {
    $ec   = ('{0:x}' -f $_.Exception.ErrorCode); $em = $_.Exception.Message; $in = $_.InvocationInfo.PositionMessage
    $description =  "$(FLINE) Catch $in $ec, $em"
    "Logging: $description" >> $LogFilePath
  }  
}