Auto-Backup, SMB Server Simple Backup

#
# Samba, Auto-Backup Script
# Useage: Auto-Backup.ps1 -Source "\\SourceServer" -Destination D:\Backups -RetentionPolicy 5 -Incremental $true
# Switches;
#    -Source, Specify the source SMB server where all accessible shares will be backed up.
#    -Destination, Specify the path to store backups. A folder Named "Auto-Backup" will be created here.
#    -RetentionPolicy, Specify a number of days to keep backups for. The default is 3.
#    -Incremental, When $true - only changed and new files will be backed up. A full back will be taken every three days.
#    -SingleBackupPerDay, when $false - the script will be allowed to run multiple times in one day.
#

# Default script parameters.
$Incremental = $true
$RetentionPolicy = 3
$SingleBackupPerDay = $true

# Set script parameters.
Param(
    [string]$Source,
    [string]$Destination,
    [int]$RetentionPolicy,
    [switch]$Incremental,
    [switch]$SingleBackupPerDay
)

# Set global variables
$ScriptStart = Get-Date

# Error Count, Counted throughout the script for a clean exit
$Errors = 0

if (!(Test-Path -Path $Destination)) {
    try {
        New-Item -ItemType Directory -Path $Destination"\Auto-Backup"
    }
    catch {
        scriptLog("Unable to create / access backup destination")
        $Errors++
        Exit 1
    }
}

# Notify if the source or destination has not been configured
if (!($Source) -or !($Destination)) {
    scriptLog("You must specify a source and destination before this script can continue.")
    $Errors++
    Exit 1
}

# Test if a backup has already been taken today, stop if it has
if (Test-Path -Path ($Destination+"\Auto-Backup\"+(($ScriptStart).ToString("yyyyMMdd"))) -and $SingleBackupPerDay = $true) {
    scriptLog("A backup has already been taken today. The script will now terminate.")
    $Errors++
    Exit 1
}

# Get a list of remote shares
$RemoteShares = (net view \\localhost) | % { if($_.IndexOf(' Disk ') -gt 0){ $_.Split('  ')[0] } }
# If there are no shares, log and stop.
if ($RemoteShares.Count -eq 0) {
    scriptLog("Found no shares on the server.")
    $Errors++
    Exit 1
}
# Otherwise, we've found shares - Log and continue.
scriptLog("Found " + ($RemoteShares.Count) + " SMB Shares; " + ($RemoteShares -join ','))

if (DoFullBackup) {
    # Full backup routine
    scriptLog("A full backup will be taken at this time")
    if (!(Test-Path -Path ($Destination+"\Auto-Backup\"+(($ScriptStart).ToString("yyyyMMdd"))))) {
        New-Item -ItemType Directory -Path ($Destination+"\Auto-Backup\"+(($ScriptStart).ToString("yyyyMMdd")))
        New-Item -ItemType File -Path ($Destination+"\Auto-Backup\"+(($ScriptStart).ToString("yyyyMMdd"))+"\Backup Configuration.txt")
        Add-Content -Path ($Destination+"\Auto-Backup\"+(($ScriptStart).ToString("yyyyMMdd"))+"\Backup Configuration.txt") -Value ("Backup Started: " + $ScriptStart)
        Add-Content -Path ($Destination+"\Auto-Backup\"+(($ScriptStart).ToString("yyyyMMdd"))+"\Backup Configuration.txt") -Value "Backup Type: Full"

        New-Item -ItemType File -Path ($Destination+"\Auto-Backup\"+(($ScriptStart).ToString("yyyyMMdd"))+"\Backup.type")
        Set-Content -Path ($Destination+"\Auto-Backup\"+(($ScriptStart).ToString("yyyyMMdd"))+"\Backup.type") -Value "Full"
    }

    foreach ($Share in $RemoteShares) {
        if (!(Test-Path -Path ($Destination+"\Auto-Backup\"+(($ScriptStart).ToString("yyyyMMdd"))+"\"+$Share))) {
            New-Item -ItemType Directory -Path ($Destination+"\Auto-Backup\"+(($ScriptStart).ToString("yyyyMMdd"))+"\"+$Share)
        }
        scriptLog(("Backing up directory: "+$Share))
        robocopy ($Source+"\"+$Share) ($Destination+"\Auto-Backup\"+(($ScriptStart).ToString("yyyyMMdd"))+"\"+$Share) /E | Out-File ($Destination+"\Auto-Backup\"+(($ScriptStart).ToString("yyyyMMdd"))+"\"+$Share+"-RoboCopy.log")
        if ($LASTEXITCODE -eq 0 -or $LASTEXITCODE -eq 1) { Add-Content -Path ($Destination+"\Auto-Backup\"+(($ScriptStart).ToString("yyyyMMdd"))+"\Backup Configuration.txt") -Value ("Backup of shared folder completed. Folder name: " + $Share) }
        else {
            $Errors++
            Add-Content -Path ($Destination+"\Auto-Backup\"+(($ScriptStart).ToString("yyyyMMdd"))+"\Backup Configuration.txt") -Value ("There was an error during the robocopy of the shared folder. Examine the Robocopy log. Shared Folder: " + $Share + $LASTEXITCODE)
            scriptLog(("There was an error during the robocopy of the shared folder. Examine the Robocopy log. Shared Folder: " + $Share + $LASTEXITCODE))
        }
    }
    scriptLog("Full Backup has finished")
    Add-Content -Path ($Destination+"\Auto-Backup\"+(($ScriptStart).ToString("yyyyMMdd"))+"\Backup Configuration.txt") -Value ("Backup Ended: " + (Get-Date))
    Set-Content -Path $Destination"\Auto-Backup\Integ.bk" -Value (Get-Date)
}
else {
    # Incremental routine
    $FullBackupLocation = LastFullBackup

    # Stop the backup if a full backup cannot be found.
    if ($FullBackupLocation -eq $null) {
        scriptLog("A full backup could not be found.")
        $Errors++
        Exit 1
    }

    # Create Backup Location
    if (!(Test-Path -Path ($Destination+"\Auto-Backup\"+(($ScriptStart).ToString("yyyyMMdd"))))) {
        New-Item -ItemType Directory -Path ($Destination+"\Auto-Backup\"+(($ScriptStart).ToString("yyyyMMdd")))
        New-Item -ItemType File -Path ($Destination+"\Auto-Backup\"+(($ScriptStart).ToString("yyyyMMdd"))+"\Backup Configuration.txt")
        Add-Content -Path ($Destination+"\Auto-Backup\"+(($ScriptStart).ToString("yyyyMMdd"))+"\Backup Configuration.txt") -Value ("Backup Started: " + $ScriptStart)
        Add-Content -Path ($Destination+"\Auto-Backup\"+(($ScriptStart).ToString("yyyyMMdd"))+"\Backup Configuration.txt") -Value "Backup Type: Incremental"

        New-Item -ItemType File -Path ($Destination+"\Auto-Backup\"+(($ScriptStart).ToString("yyyyMMdd"))+"\Backup.type")
        Set-Content -Path ($Destination+"\Auto-Backup\"+(($ScriptStart).ToString("yyyyMMdd"))+"\Backup.type") -Value "Incremental"
    }

    scriptLog("An incremental backup will be taken at this time")
    scriptLog(("Last Full Backup Location: " + $FullBackupLocation))

    foreach ($Share in $RemoteShares) {
        foreach ($Item in Get-ChildItem ($Source+"\"+$Share) -Recurse) {
            $FullItem = ($FullBackupLocation+"\"+($Item.FullName).Remove(0,($Source).Length))
            if (!(Test-Path -Path $FullItem) -or $Item.LastWriteTime -gt (Get-Item -Path $FullItem).LastWriteTime -or $Item.Length -ne (Get-Item -Path $FullItem).Length) {
                try {
                    New-Item -ItemType File -Path ($Destination+"\Auto-Backup\"+(($ScriptStart).ToString("yyyyMMdd"))+"\"+($Item.FullName).Remove(0,($Source).Length)) -Force
                    Copy-Item -Path $Item.FullName -Destination ($Destination+"\Auto-Backup\"+(($ScriptStart).ToString("yyyyMMdd"))+"\"+($Item.FullName).Remove(0,($Source).Length))
                    scriptLog(("[Copied] " + $Item.FullName + " (" + ($Destination+"\Auto-Backup"+(($ScriptStart).ToString("yyyyMMdd"))+"\"+($Item.FullName).Remove(0,($Source).Length)) + ")"))
                }
                catch {
                    $Errors++
                    scriptLog(("[Failed] " + $Item.FullName))
                }
            }
        }
    }
    scriptLog("Incremental Backup has finished")
    Add-Content -Path ($Destination+"\Auto-Backup\"+(($ScriptStart).ToString("yyyyMMdd"))+"\Backup Configuration.txt") -Value ("Backup Ended: " + (Get-Date))
}

# Retention Policy Routine
foreach($Backup in Get-ChildItem -Path ($Destination+"\Auto-Backup\")) {
    if ($Backup.GetType().ToString() -eq "System.IO.DirectoryInfo") {
        try {
            $CreateDate = ([datetime]::ParseExact($Backup.Name,"yyyyMMdd",$null))
        }
        catch {
            $CreateDate = $Backup.CreationTime
        }

        if ($CreateDate -lt $ScriptStart.AddDays(-$RetentionPolicy)) {
            scriptLog("The backup for " + $CreateDate + " has expired due to the retention policy. This will be deleted.")
            Remove-Item $Backup.FullName -Force -Recurse
        }
    }
}

# Script Exit
if ($Errors -eq 0) { scriptLog("Backup finished with no errors.") }
if ($Errors -gt 0) { scriptLog("Errors were found while running the backup.") }
Write-Host $Errors
Exit $Errors

# Global Script for logging.
function scriptLog([string]$LogMessage) {
    if (!(Test-Path $Destination"\Auto-Backup\Auto-Backup.log")) { New-Item -ItemType File -Path $Destination"\Auto-Backup\Auto-Backup.log" }
    $Today = Get-Date
    Add-Content -Path $Destination"\Auto-Backup\Auto-Backup.log" -Value ([String]$Today+": "+$LogMessage)
    Write-Host $Today": " $LogMessage
}

# Should we run a full, or file change backup?
function DoFullBackup {
    if (!(Test-Path -Path $Destination"\Auto-Backup\Integ.bk")) {
        New-Item -Path $Destination"\Auto-Backup\Integ.bk"
        return $true
    }
    if ($Incremental -eq $false) { return $true }
    $AllowedDate = (Get-Date).AddDays(-$RetentionPolicy)
    $IntegContent = Get-Content -Path $Destination"\Auto-Backup\Integ.bk"
    if (([datetime]$IntegContent) -lt $AllowedDate) {
        return $true
    }
    return $false
}

# Function to find last full backup
function LastFullBackup {
    $Latest = $null
    $TimeCheck = (Get-Date).AddDays(-360)
    foreach($Backup in Get-ChildItem -Path ($Destination+"\Auto-Backup\")) {
        if ($Backup.GetType().ToString() -eq "System.IO.DirectoryInfo") {
            if (Test-Path -Path ($Backup.FullName+"\Backup.type")) {
                if ((Get-Content -Path ($Backup.FullName+"\Backup.type")) -eq "Full") {
                    if (([datetime]::ParseExact($Backup.Name,"yyyyMMdd",$null)) -gt $TimeCheck) {
                        $TimeCheck = ([datetime]::ParseExact($Backup.Name,"yyyyMMdd",$null))
                        $Latest = $Backup.FullName
                    }
                }
            }
        }
    }
    return $Latest
}