Recursion Logic

I've been working on a PowerShell script that will preserve directory structure when cabbing nested folders. I'm having a bit of difficulty getting the recursion logic right, though.

This is a rough, so there isn't any try/catch error code yet. I've commented out the Remove-Item to prevent accidental runs.

The logic I worked out for this is as follows.

Check & get base tree for subdirectories
Go one level in and check again
Continue until no directories and then return one level up.
Cab directory, remove directory, write log for automated extraction (file names of subdirectory cabs).
Repeat process next level up and continue until base directory

function Chkfordir ($clevel)
{
    $dir = dir $clevel | ? { $_.PSIsContainer -eq $true } #Does Current Level have Folders?
    if($dir -ne $null)    # Yes
    {
        Chkfordir $dir        #Go Deeper
    }
    if ($dir -eq $null)   #Deepest Branch
    {
        return                # Go Back One Level and begin Cabbing
    }

    $dir | % { 
        Compress-Directory $_.FullName (".\" + [string]$_.Name + ".cab")
        echo ($_.FullName + ".cab" >> .\cleaf.log"
        #Remove-Item -Recurse $_.FullName
        return
    } 
}

The function call Compress-Directory is from here.

Edit Changes:

Will Re-Post Code Soon (08/18)

Edit 08/18 So I finally had a chance to test it and the logic seems to work now. There were some problems.

Most of the difficulty came with a powershell gotcha and the unnoticed problem that Compress-Directory is not path independent. Looks like I'll be needing to re-write this function later to be path independent.

The powershell gotcha was in a type change for a value on the pipeline. Apparently after returning from a function directory items are changed from System.IO.FileInfo to System.IO.DirectoryInfo with differently named member functions.

Echo was replaced with Add-Content as the redirection operators don't work in powershell.

There were some unaccounted states to contend with as well. A leaf directory which had no files would cause Compress-Directory to error or complete silently with no file creation (thus not preserving hierarchy).

Solution was to add an Add-Content for leaf folders before return, and moved Add-Content to before the Compress-Directory so there is at least one file in each directory.

I've included my current version below but it is a work in progress.

function Chkfordir ($clevel)
{
    $dir = dir $clevel | ? { $_.PSIsContainer -eq $true } # Get Folders?
    if ($dir -eq $null) {  #Check if deepest branch
        Add-Content (Join-Path $_.PSPath "\leaf.log") ([string]$_.FullName + ".cab")
        return $_                # Return one level up and cab
    }

    $dir | % { #for each sub go deeper
        Chkfordir $_.FullName
        Add-Content (Join-Path $_.PSParentPath "\branch.log") ([string]$_.FullName + ".cab")
        Compress-Directory $_.FullName ([string]$_.Name + ".cab")
        #Remove-Item $_.FullName -recurse
    }          
}

Solution

You need to recurse for each subdirectory and compress it after the recursive call returns:

function Chkfordir($clevel) {
    Get-ChildItem $clevel |
        Where-Object { $_.PSIsContainer } |
        ForEach-Object {
            Chkfordir $_
            Compress-Directory ...
            ...
        }
}

That way you automatically descend first, then create the archives as you return.