[CmdletBinding()]
Param (
    # InputFile
    [Parameter(Mandatory = $true)]
    [string]
    $InputFile,

    # OutputFile
    [Parameter(Mandatory = $true)]
    [string]
    $OutputFile
)
$ErrorActionPreference = 'Stop'
try {
    $File = Get-ChildItem $InputFile
}
catch {
    throw $_
}

if ($File.Extension -eq '.csv') {
    $InputFile = Import-Csv $InputFile
}
else{
    throw "Only CSV files are currently supported."
}

if (Test-Path -Path $OutputFile){
    Clear-Content -Path $OutputFile
}

function ConvertTo-DecimalOctet{
    Param (
        # Octet Bits
        [Parameter(Mandatory=$true)]
        [int]
        $Bits
    )

    $Octet = 0

    for ($x=7;$Bits -gt 0;$Bits--){
        $Octet = $Octet + [math]::Pow(2,$x)
        $x--
    }

    return $Octet
}
function ConvertTo-DecimalMask{
    Param (
        [Parameter(Mandatory=$True)]
        [int]
        $CIDRNumber
    )

    # Validate input based on numerical range
    if ($CIDRNumber -lt 0 -or $CIDRNumber -gt 32){
        Throw "Invalid input detected. CIDRNumber must be between 0 and 32."
        Exit
    }

    # Define the network and host bits
    [int]$NetworkOctets = [Math]::DivRem($CIDRNumber,8,[ref]0)
    [int]$HostBits = ($CIDRNumber%8)
    $Octets = New-Object System.Collections.ArrayList

    # Fill each decimal octet for the network bit allocation
    if ($NetworkOctets -gt 0){
        for ($NetworkOctets; $NetworkOctets -gt 0; $NetworkOctets--){
            $Octets.Add(255) | Out-Null
        }
    }
    
    # Add the decimal octet for the host bit allocation
    if ($HostBits -ne 0){
        $Octets.Add((ConvertTo-DecimalOctet -Bits $HostBits)) | Out-Null
    }


    # Add remaining zeros for each empty octet
    if ($Octets.Count -ne 5){
        for ($OctCount = $Octets.Count;$OctCount -lt 4;$OctCount++){
        $Octets.Add(0) | Out-Null
        }
    }

    # Return the octets in full decimal format
    return ($Octets -join '.')

}
function New-Route{
    Param(
        # Destination IP
        [Parameter(Mandatory = $true)]
        [String]
        $DestinationIP,

        # Parameter help description
        [Parameter(Mandatory = $false)]
        [Int]
        $CIDRNumber,

        # Parameter help description
        [Parameter(Mandatory = $false)]
        [string]
        $SubnetMask,

        # Parameter help description
        [Parameter(Mandatory = $false)]
        [string]
        $NextHopIP,

        # Sets destination to an interface
        [Parameter(Mandatory = $false)]
        [string]
        $Interface
    )

    if ($CIDRNumber -ne "") {
        $Mask = ConvertTo-DecimalMask -CIDRNumber ([int]$CIDRNumber)
    }
    elseif ($SubnetMask -ne "") {
        $Mask = [string]$SubnetMask
    }
    else {
        Throw "No Input for 'SubnetMask' or 'CIDRNumber' detected."
    }

    if ($NextHopIP -ne "") {
        $Destination = [string]$NextHopIP
    }
    elseif ($Interface -ne "") {
        $Destination = [string]$Interface
    }
    else {
        Throw "No Input for 'NextHopIP' or 'Interface' detected."
    }

    $Command = "ip route $DestinationIP $Mask $Destination"

    return $Command
}

foreach ($route in $InputFile) {
    
    $routeObj = @{
        'DestinationIP' = $route.DestinationIP
        'CIDRNumber'    = $route.CIDRNumber
        'SubnetMask'    = $route.SubnetMask
        'NextHopIP'     = $route.NextHopIP
        'Interface'     = $route.Interface
    }

    New-Route @routeObj | Out-File -FilePath $OutputFile -Append
}