Write-Log.ps1

# Function to write to the log file
function Write-Log
{
     <#
     .SYNOPSIS
     Function to write formatted information to the log file.

     .DESCRIPTION
     Function takes provided message and severity level (1,2,3), formats the message and writes it to the log file. The message parameter is required.
     If a severity level other than 1 is needed, specify it as the second parameter.
     Default logging output level can be defined at the script level using the $LogLevel variable. Options are:
     1: Info
     2: Warning (Default)
     3: Error

     .NOTES
     The following variable need to be set for this function to work correctly:

     $date = (Get-Date -Format "M-d-yyyy")
     $logFile = "<Full path to log file>"

     .EXAMPLE
     Write-Log -Message "<message>" -Severity "<severity level: 1,2,3>"

     Write-Log -Message "Hello World" -Severity 3

     #>

     param (
        [Parameter(Mandatory)]
        [string]$Message,

        [Parameter()]
        [ValidateSet('1','2','3')]
        [int]$Severity = 1 # Default to a low severity. Otherwise, override
     )

     # Functions
     function readableErrorLevel($Severity)
     {
          # Convert Severity level to human readable
          if ( $Severity -eq 1 )
          {
              return "Info"
          }
          elseif ( $Severity -eq 2 )
          {
              return "Warning"
          }
          elseif ( $Severity -eq 3 )
          {
              return "Error"
          }
     }

     # Check if log file exists. If no, create it
     if ( !(Test-Path -Path $logFile) )
     {
         # Create log file
         write-host "Creating log file: $scriptPath\$fileBase\gpuDomainJoin-$(Get-Date -Format "MM-dd-yyyy").log`n"
         New-Item $logFile -type file > $null
     }

     # Set time for log entry
     $time = (Get-Date -Format "HH:mm:ss")

     if ( $LogLevel -eq 3 -and $Severity -eq 3 )
     {
          # Convert error level to human readable
          [string]$Severity = readableErrorLevel $Severity

          # Add formatted message to log file
          Add-Content -Path $logFile -Value "$date $time : $Severity : $Message"
     }
     elseif ( $LogLevel -eq 2 -and $Severity -ge 2 )
     {
          # Convert error level to human readable
          [string]$Severity = readableErrorLevel $Severity

          # Add formatted message to log file
          Add-Content -Path $logFile -Value "$date $time : $Severity : $Message"
     }
     elseif ( $LogLevel -eq 1 -and $Severity -ge 1 )
     {
          # Convert error level to human readable
          [string]$Severity = readableErrorLevel $Severity

          # Add formatted message to log file
          Add-Content -Path $logFile -Value "$date $time : $Severity : $Message"
     }
}