This script archives documents in a folder (and its subfolders) that may benefit from archiving (i.e. jpg, epub are skipped; pdf's and other files are left archived if they can be compressed to a certain percentage, etc.)

book-archiver.ps1

<#
.SYNOPSIS

.PARAMETER Ratio
    A real number within (0, 1). Ratio of the compressed file that is accepted as the archive.
    Files that cannot be compressed better or equal to this ratio compared to the original,
    are not archived (left as is).
#>

param(
    $Ratio = 0.97
)

$7zFound = $true
try{
    7z.exe | out-null
}
catch{
    $7zFound = $false
}
if(-not $7zFound -or $LASTEXITCODE -ne 0 -or -not $?){
    write-host "7z.exe not found" -ForegroundColor Red
    write-host "Add 7z.exe to your PATH environment variable" -ForegroundColor Yellow
    exit
}

$skippedFileExt = @(
    'zip',
    '7z',
    'arj',
    'rar',
    'epub',
    #'mp4',
    'mpeg',
    'png',
    'jpeg',
    'jpg',
    'png',
    'webp'
)

$files = Get-ChildItem -Recurse -File

$fileCnt = $files.Length
$fileNum = 1

foreach($file in $files){    

    Write-Progress -Activity "Archiving files..." -Status "Complete:" -PercentComplete $($fileNum++ * 100 / $fileCnt)

    if($file.Name -eq 'book-archiver.ps1') {
        continue
    }

    # TODO: exclude folders with 'video' in their names

    $fileExt = [System.IO.Path]::GetExtension($file).ToLower()
    if([string]::IsNullOrWhiteSpace($fileExt)) {
        write-host "File $file does not have extension" -ForegroundColor Red
        exit
    }
    $fileExt = $fileExt.Substring(1)
    $filePath = $file.FullName
    $filePathWithoutExt = $filePath.Remove($file.FullName.Length - $fileExt.Length - 1)

    # remove certain files, because I personally don't need them
    if($fileExt -eq 'zip' `
        -and (
                $filePathWithoutExt.EndsWith("_code") `
            -or $filePathWithoutExt.EndsWith("-code") `
            -or $filePathWithoutExt.EndsWith("_master") `
            -or $filePathWithoutExt.EndsWith("-master") `
            -or $filePathWithoutExt.EndsWith("_main") `
            -or $filePathWithoutExt.EndsWith("-main") `
        ))
    {
        rm $filePath
        continue
    }

    # archiving
    if($skippedFileExt.IndexOf($fileExt) -gt -1){
        continue
    }

    $archPath = $filePath + '.7z'
    $archErr = $false
    try{
        7z.exe a -mx9  $archPath $filePath # | out-null
    }
    catch{
        $archErr = $true
    }
    if($archErr -or $LASTEXITCODE -ne 0 -or -not $?){
        write-host "Error archiving $filePath" -ForegroundColor Red
        exit        
    }

    $size = (Get-item $filePath).Length
    $archSize = (Get-item $archPath).Length
    if([float]$archSize / $size -gt $Ratio){
        rm $archPath
    }
    else {
        rm $filePath
    }
}