[CmdletBinding()]
Param (
    [Parameter()]
    [String]$ManageAlchemyPath = "[redacted]",
    [Parameter()]
    [String]$VshadowPath = "[redacted]",
    [Parameter()]
    [String]$SourceDrive = "[redacted]",
    [Parameter()]
    [String]$ShadowDrive = "[redacted]",
    [Parameter()]
    [String]$ShadowPath = "[redacted]"
)

###############################################################################
#
# BackupVMs.ps1 - alchemy.nodomain.net VM backup script
#
# Copyright 2017-2020 - Josh Moyer <JMoyer@NODOMAIN.NET>, all rights reserved.
#
###############################################################################

# To do:
# Support automated restartability - i.e. without having to manually destroy the shadow and offline the drive

# Known Issues:
# - If VM config references files in a different directory than the config then the files might get skipped
# - No verbose logging
# - C style error handling is not as modern as PowerShell can be
# - If the backup drive is full the script will never complete, as robocopy keeps retrying the failed copy.

# Test cases:
# - Destination path does/does not exist
# - Disk failure/removal
# - Disk full
# - Disk offline
# - Disk online
# - Disk read only
# - Disk subsystem configuration changes
# - Multiple backup disks connected
# - Multiple script instances started

Begin
{
    Function Send-Alert($Subject, $Body)
    {
        $Message = [System.Web.Mail.MailMessage]::new()
        $Message.To = "[redacted]"
        $Message.To = "[redacted]"
        $Message.From = "$($Env:COMPUTERNAME).NODOMAIN.NET"
        $Message.Subject = $Subject
        $Message.Body = $Body

        [System.Web.Mail.SmtpMail]::SmtpServer = '[redacted]'
        [System.Web.Mail.SmtpMail]::Send($Message)
    }

    Function ConcatStringCollection ($Object)
    {
        For ($I = 0 ; $I -LT $Object.Length ; $I++)
        {
            $Output = -Join ($Output, $Object[$I], "`n")
        }
        Return $Output
    }

    # -5: failed to copy at least one file
    Function CopyVMs ($BackupPath)
    {
        <#
        some of the things we'll need to do:
        check disk size $disk = Get-WmiObject Win32_LogicalDisk -ComputerName remotecomputer -Filter "DeviceID='C:'" |
        Select-Object Size,FreeSpace

        $disk.Size
        $disk.FreeSpace
        check free space: $disk = Get-WmiObject Win32_LogicalDisk -ComputerName remotecomputer -Filter "DeviceID='C:'" |
        Select-Object Size,FreeSpace; $disk.FreeSpace
        check the size of files and/or directories: gci -Recurse | measure-object -sum length
        have a priority ranked list of vms to backup, according to storage class and an alert if a certain class of machine is not backedup
        #>

       If (!(Test-Path $BackupPath)) {Return -5}

        $BackupItems = Get-ChildItem $BackupPath

        ForEach ($BackupItem In $BackupItems)
        {
            If (Test-Path $ShadowPath$BackupItem)
            {
                #If vm.length -LT (freespace + vm.backup.length) 
                #Requires -RunAsAdministrator
                RoboCopy $ShadowPath$BackupItem $BackupPath$BackupItem /COPYALL /B /J /MIR /SL /DCOPY:DAT /NP #| Out-Null
                #If ($Notify -EQ $True) { Notify vm.specification }
            }
        }
    }

    # -6: failed to create or expose shadow
    Function CreateShadow 
    {
        #Requires -RunAsAdministrator
        $Output = & $VshadowPath "-p" "-nw" "$($SourceDrive)"
        $Output = ConcatStringCollection($Output)
        #If ($Output -EQ $Null)
        #{
        #    Write-Output "VC Redist installed?"
        #    Return -61
        #}
        Write-Debug $Output
        
        $ShadowCopySet = ($Output | Select-String "Shadow copy Set: ({[a-f0-9-]*})").Matches.Groups[1].Value
        $SnapshotId = ($Output | Select-String "SNAPSHOT ID = ({[a-f0-9-]*})").Matches.Groups[1].Value

        If (($ShadowCopySet -EQ $Null -OR $SnapshotId -EQ $Null)) 
        { Return -6 }

        If (Test-Path $ShadowDrive)
        { Return -6 }
        
        #Requires -RunAsAdministrator
        $Output = & $VshadowPath "-el=`"$($SnapshotId),$($ShadowDrive)`""
        $Output = ConcatStringCollection($Output)
        Write-Debug $Output
        
        If (!(Test-Path $ShadowDrive))
        { Return -6 }

        Return $ShadowCopySet
    }
    
    # -7: unable to destroy shadow
    Function DestroyShadow($ShadowCopySet)
    {
        #Requires -RunAsAdministrator
        $Output = & $VshadowPath "-dx=`"$ShadowCopySet`""

        If (Test-Path $ShadowDrive)
        { Return -7 }
    }

    # -4: offline disks was not equal to 1
    Function OnlineDrive {
        $Drives = "list disk" | DISKPART | Where {$_ -Match "Disk ([0-9]+)\s+Offline"}
        If ($Matches.Count -NE 2) {Return -4}
        $Drive = $Matches[1]
        "select disk $Drive`nattributes disk clear readonly`nonline disk" | DISKPART | Out-Null
        $Drive
    }

    # -3: failed to offline backup drive
    Function OfflineDrive ($Drive) {
        "select disk $Drive`noffline disk" | DISKPART | Out-Null
    }

    # -2: backup drive signature not found
    Function ReturnDrive {
        $IDFile = "vmbackupdrive.id"
        $Drives = Get-WmiObject -Query "SELECT * from win32_logicaldisk WHERE DriveType = 3”
        $Drives | ForEach-Object -Process {
            $Drive = $_.DeviceID
            $Candidate = Get-ChildItem "$Drive\$IDFile" -ErrorAction Ignore
            If ($Candidate) {Return $Drive}
            }
        If ($Drive -LT 0) {Return -2}
       }

    # -1: failure in main
    Function Main
    {
        $DebugPreference = "Continue"
        $ErrorActionPreference = "Stop"

        Date
        Echo "Suspending VMs."
        & $ManageAlchemyPath -Command Suspend-VMs

        Date
        Echo "Creating shadow copy."
        $ShadowSet = CreateShadow
        If ($ShadowSet.Length -NE 38) {Return $ShadowSet}

        Date
        Echo "Resuming VMs."
        & $ManageAlchemyPath -Command Start-VMs

        Date
        Echo "Bringing backup drive online."
        $Drive = OnlineDrive
        If ($Drive -LT 0) {Return $Drive}

        Date
        Echo "Identifying backup drive."
        $BackupDrive = ReturnDrive
        If ($BackupDrive -LT 0) {Return $BackupDrive}
        
        Date
        Echo "Copying items."
        CopyVMs $BackupDrive
        Pause

        Date
        Echo "Destroying shadow copy."
        DestroyShadow $ShadowSet
        
        Date
        Echo "Taking backup drive offline."
        OfflineDrive $Drive

        Date
    }
}

Process
{
    Main
}

End
{}