param([Parameter(Mandatory=$true)][string] $ComputerFile)

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

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

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

# 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.'
'Processing computers with Get-WMIObject.'
'This might take a good long while depending on the amount of computers and their availability.'

$models = @{}

# Looks like it doesn't like, say, 1000 computers in the array passed to GWMI,
# so I'm splitting it into chunks of 50
$computerCounter = 0
$tempComputers = @()

foreach ($computer in $computers) {
    
    $computerCounter++
    
    $tempComputers += $computer
    
    if ($computerCounter -eq 50) {
        
        Write-Host 'Processing a chunk of 50 computers (first:' $tempComputers[0] ', last:' $tempComputers[49]
        
        Get-WMIObject -computer $tempComputers -ErrorAction SilentlyContinue -Class Win32_ComputerSystem |
            Foreach {
                
                if ($_.Model) {
                    
                    $private:model = massageModel $_.Model
                    $models.$(($_.Name).ToLower()) = $private:model
                    
                }
                
                else {
                    
                    $models.$(($_.Name).ToLower()) = 'ERROR: No model'
                    
                }
                
            }
        
        # Reset counter and empty temporary array
        $computerCounter = 0
        $tempComputers = @()
        
    } # end of if $computerCounter -eq 50
    
}

$models.GetEnumerator() | Sort-Object -property @{Expression='Name';Descending=$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
"@