param([Parameter(Mandatory=$true)] $ComputerFile, $jobCount = 50)

# Initialize the models hash which will be populated while processing job output
$models = @{}

# This function strips stuff in parentheses and trailing whitespace from the string passed,
# which in my experience is usually what you want when looking at the BIOS model string.
function Massage-Model {
    
    param([Parameter(Mandatory=$true)][string] $private:model)
    
    $private:model = $private:model -replace '\s*\([^)]+\)\s*', ''
    $private:model = $private:model -replace '\s+$', ''
    
    return $private:model
    
}

function Process-Jobs {
    
    param($private:runningJobs)
    
    #''
    'Processing job batch...'
    Write-Host -NoNewLine 'Processing jobs: '
    $private:jobCounter = 0
    
    foreach ($private:jobHash in $private:runningJobs) {
        
        $private:jobCounter++
        
        $private:computerName = $private:jobHash.Name
        
        if ($private:jobCounter -eq 8) {
            
            $private:jobCounter = 0
            Write-Host $private:computerName
            Write-Host -NoNewLine 'Processing jobs: '
            
        }
        
        else {
            
            Write-Host -NoNewLine "$private:computerName, "
            
        }
        
        Wait-Job $private:jobHash.Job | Out-Null
        $private:output = Receive-Job -ErrorAction SilentlyContinue $private:JobHash.Job
        
        if ($private:output -ieq 'No ping reply') {
            
            $private:computerName | Out-File -Append $noPingFile
            
        }
        
        elseif ($private:output -match '\S+') {
            
            $models.$private:computerName = Massage-Model $private:output
            
        }
        
        else {
            
            $models.$private:computerName = 'ERROR'
            
        }
        
    }
    
    ''
    Write-Host -NoNewLine 'Starting jobs: '
    
}


# Output files, didn't bother making them parameters...
$modelsFile = 'computer-models-with-computername.txt'
$modelsCountFile = 'computer-models-count.txt'
$noPingFile = 'computer-models-noping.txt'

# Prompt before overwriting files.
if ( (Test-Path $modelsFile) -or (Test-Path $modelsCountFile) -or (Test-Path $noPingFile) ) {
    
    "Output file(s) '$modelsFile', '$modelsCountFile' or '$noPingFile' exist."
    $private:answer = Read-Host 'Overwrite? (Y/n) [yes]'
    if ($private:answer -match '^n') { 'Aborting.'; exit 0 }
    
    Remove-Item $noPingFile -ErrorAction SilentlyContinue
    
}

# Get the start time and display it before starting processing.
$startTime = Get-Date
"Start time: $startTime"

if (!(Test-Path -PathType leaf $computerFile)) {
    
    "Error: $computerFile does not exist. Exiting..."
    exit 0
    
}

# Get the computers. Skip lines with only whitespace (including blank lines).
$computers = Get-Content $ComputerFile | Where-Object { $_ -match '\S+' }

'Found ' + $computers.Count + ' computers.'
'Starting jobs.'
'This might take a good long while depending on the amount of computers and the hardware being used.'

# Having issues with passing large arrays to GWMI -computer and many concurrent jobs,
# trying batches of 50 jobs
$runningJobs = @()
$private:computerCounter = 0
$private:tempComputerCounter = 0
$private:jobCounter = 0

Write-Host -NoNewLine 'Starting jobs: '

foreach ($computer in $computers) {
    
    $private:computerCounter++
    $private:tempComputerCounter++
    
    if ($private:tempComputerCounter -eq 8) {
        
        $private:tempComputerCounter = 0
        Write-Host $computer
        Write-Host -NoNewLine 'Starting jobs: '
        
    }
    
    else {
        
        Write-Host -NoNewLine "$computer, "
        
    }
    
    #Start-Sleep -Milliseconds 500
    
    $private:job = Start-Job -ArgumentList $computer -ScriptBlock {
        
        param($private:computer)
        
        if (Test-Connection -Quiet -Count 1 $private:computer) {
            
            (Get-WMIObject -computer $private:computer -Class Win32_ComputerSystem).Model
            
        }
        
        else {
            
            'No ping reply'
            
        }
        
    }
    
    $runningJobs += @{ 'Name' = $computer; 'Job' = $private:job; }
    
    $private:jobCounter++
    
    if ($private:jobCounter -eq $jobCount) {
        
        ''; "Total computer count: $private:computerCounter"
        
        Process-Jobs $runningJobs
        
        $private:jobCounter = 0
        $runningJobs = @()
        
    }
    
}

''

# Process the remainder
Process-Jobs $runningJobs

''

$models.GetEnumerator() | Sort-Object -property @{Expression='Name';Descending=$false},@{Expression='Value';Descending=$false} |
    Format-Table -AutoSize | Out-File $modelsFile

$modelsCount = @{}
$models.Keys | Foreach { $modelsCount.$($models.$_) += 1 }

'Found ' + $modelsCount.Count + ' unique models'

$modelsCount.GetEnumerator() | Sort-Object -property @{Expression='Value';Descending=$true},@{Expression='Name';Descending=$false} |
    Format-Table -AutoSize | Out-File $modelsCountFile

@"
Start time: $startTime
End time:   $(Get-Date)
Output files: $modelsFile, $modelsCountFile, $noPingFile
"@