<#
.SYNOPSIS
This filewatcher is specifically to watch for new files in a directory
below where the project root of the project script exists AND logs its creation (for management) in an adjacent force-written subdirectory

.DESCRIPTION
for ChangeType choose from option [Created/Deleted/Changed]

Arguments:
    - watcherDirectory: name a string (will be created if not exists) for a subdirectory to watch
    - directoryChangeType [Created/Deleted/Changed]
    - watcherNameDescription: single unspaced string describing purpose or name of file/subfolder watching context
    - filenameFilter (for watcher): type of file

.EXAMPLE
./scripts/filewatcher-helper.ps1 -WatcherDirectory -DirectoryChangeType Created


.NOTES
This script will:
-  watch the given directory (WatcherDirectory) from argument
-  clearing any existing of the same name
-  register a new Powershell FileSystemWatcher

.LINK

#>

[CmdletBinding()]
Param(
    [Parameter(Mandatory=$True,Position=1)]
    [string]$WatcherDirectory,
    [Parameter(Mandatory=$True,Position=2)]
    [string]$DirectoryChangeType,
    [Parameter(Mandatory=$True,Position=3)]
    [string]$WatcherNameDescription,
    [Parameter(Mandatory=$True,Position=4)]
    [string]$FilenameFilter
)

function Write-Log {
    Param(
        $Message,
        $Path
    )
    function TS {Get-Date -Format 'yyyy-MMM-dd hh:mm:ss'}
    "[$(TS)]$Message" | Tee-Object -FilePath $Path -Append | Write-Verbose
}


$loggingOutputDirectory = $($(Split-path -Path  $PSScriptRoot -Parent) + '\logging')
New-Item -EA SilentlyContinue -ItemType Directory -Force -Path $loggingOutputDirectory
$loggingOutput = $loggingOutputDirectory + '\' + $WatcherNameDescription + '_' + $DirectoryChangeType + '_output_log.txt'
Write-Log -Message $("Logging subscriber creation initialization to:" + $loggingOutputDirectory) -Path $loggingOutput

$fullWatcherDirectory = $($(Split-path -Path  $PSScriptRoot -Parent) + '\' + $WatcherDirectory)
Write-Log -Message $("Initializing subscriber creation for directory:" + $fullWatcherDirectory) -Path $loggingOutput
New-Item -EA SilentlyContinue -ItemType Directory -Force -Path $fullWatcherDirectory | Out-Null

$fileSystemWatcher = New-Object IO.FileSystemWatcher -EA SilentlyContinue  $fullWatcherDirectory, $filter -Property @{IncludeSubdirectories = $false;NotifyFilter = [IO.NotifyFilters]'FileName, LastWrite'}
$subscriberName = $null
$subscriberName =  $($WatcherDirectory + '_' + $WatcherNameDescription + '_' + $DirectoryChangeType)
Write-Log -Message $("Unregistering previous version of Event type " + $subscriberName + " on " + $fullWatcherDirectory) -Path $loggingOutput
Unregister-Event $subscriberName # clear event subscription in case of change/name collision
if ($null -eq $(Get-EventSubscriber $subscriberName -EA SilentlyContinue | Format-List -Property SourceIdentifier))
    {
        Write-Log -Message $("Registering " + $subscriberName + " on " + $fullWatcherDirectory) -Path $loggingOutput
        Write-Output $("Registering " + $subscriberName + " on " + $fullWatcherDirectory)
        Register-ObjectEvent $fileSystemWatcher $DirectoryChangeType -SourceIdentifier $subscriberName -Action {
        $name = $Event.SourceEventArgs.Name
        $changeType = $Event.SourceEventArgs.ChangeType
        $timeStamp = $Event.TimeGenerated
        Write-Host "The file '$name' was $DirectoryChangeType at $timeStamp" -fore red
        Out-File -FilePath $loggingOutput -Append -InputObject "The file '$name' was $DirectoryChangeType at $timeStamp"}
    }