#!/usr/bin/env pwsh

# Add any email addresses that should be purged to the $Addresses array

$Addresses = @()
$MaxDate = "2023-06-30"

# No modifications below this point.

function Write-Log {
    [CmdletBinding()]
    param
    (
        [Parameter(Mandatory = $true)]
        [string]$Message
    )

    $timestamp = Get-Date -Format "yyyy-MM-dd HH:mm:ss"
    Write-Output "${timestamp}: $Message"
}

# Build query for ComplianceSearch

if (!$Addresses) { 
    Write-Output "Search query is empty - make sure that Addresses array is not empty - exiting"
    exit 1 
}

$From = "from:" + ($Addresses -join " OR from:")
$To = "to:" + ($Addresses -join " OR to:")
$Participants = "$From OR $To"

$Query = "($Participants) AND date<=$MaxDate AND (kind:email)"

# Ask user for admin credentials

$UserCredential = Get-Credential -Title "Office 365 Credentials" -Message "Enter your credentials for Office 365"

# Load PowerShell session for Microsoft Exchange

Import-Module ExchangeOnlineManagement
Connect-IPPSSession -Credential $UserCredential
Connect-ExchangeOnline -Credential $UserCredential

# Define folders that should be ignored by ComplianceSearch

$folders = "/Recoverable Items", "/Deletions", "/Purges", "/Versions"

Write-Output "Finding folders to exclude, this may take a while..."

$mailboxes = Get-Mailbox

$folderQueries = @()

foreach ($mailbox in $mailboxes) {
    $emailAddress = $mailbox.PrimarySmtpAddress
    $folderStatistics = Get-EXOMailboxFolderStatistics $emailAddress
    foreach ($folderStatistic in $folderStatistics) {
        $folderId = $folderStatistic.FolderId;
        $folderPath = $folderStatistic.FolderPath;

        if ($folders -contains $folderPath) {

            # Based on / shamelessly stolen from:
            # https://practical365.com/targeted-collection-content-search/

            $encoding = [System.Text.Encoding]::GetEncoding("us-ascii")
            $nibbler = $encoding.GetBytes("0123456789ABCDEF");
            $folderIdBytes = [Convert]::FromBase64String($folderId);
            $indexIdBytes = New-Object byte[] 48;
            $indexIdIdx = 0;
            $folderIdBytes | Select-Object -skip 23 -First 24 | % { $indexIdBytes[$indexIdIdx++] = $nibbler[$_ -shr 4];
            $indexIdBytes[$indexIdIdx++] = $nibbler[$_ -band 0xF] }
            $folderQuery = "folderid:$($encoding.GetString($indexIdBytes))";

            $folderStat = New-Object PSObject
            Add-Member -InputObject $folderStat -MemberType NoteProperty -Name Mailbox -Value $emailAddress
            Add-Member -InputObject $folderStat -MemberType NoteProperty -Name FolderPath -Value $folderPath
            Add-Member -InputObject $folderStat -MemberType NoteProperty -Name FolderQuery -Value $folderQuery

            $folderQueries += $folderStat

        }
    }
}

$Excluded = ""

foreach ($folder in $folderQueries) {
    $q = $folder.folderQuery
    $Excluded += " NOT $q"
}

$Query += $Excluded

$Looper = $true

while ($Looper) {
    try {
        Write-Output "Creating new search"
        New-ComplianceSearch -Name "WAT Remover" -ContentMatchQuery $Query -ExchangeLocation all -AllowNotFoundExchangeLocationsEnabled $true -Force | Out-Null
        Start-ComplianceSearch -Identity "WAT Remover" | Out-Null

        Write-Output "Waiting for search to complete"
        while (!(Get-ComplianceSearch -Identity "WAT Remover" | Format-List -Property Status | Out-String | Select-String -Pattern "Completed")) {
            Start-Sleep -s 1
        }

        $Results = (Get-ComplianceSearch "WAT Remover").Items
        if ($Results) {
            Write-Output "$Results results found, deleting"
            for ($i = 0; $i -lt 10; $i++) {
                Write-Output "Starting deletion run $i"
                New-ComplianceSearchAction -SearchName "WAT Remover" -Purge -PurgeType HardDelete -Force -Confirm:$false | Out-Null
                while (!(Get-ComplianceSearchAction -Identity "WAT Remover_Purge" | Out-String | Select-String -Pattern "Completed")) {
                    Start-Sleep -s 1
                }
                Write-Output "Results deleted"
                Remove-ComplianceSearchAction -Confirm:$false -Identity "WAT Remover_Purge"
            }
        }
        else {
            Write-Output "No results found, exiting after this run"
            $Looper = $false
        }
    }
    finally {
        Write-Output "Cleaning up"
        Remove-ComplianceSearchAction -Confirm:$false -Identity "WAT Remover_Purge"
        Remove-ComplianceSearch -Identity "WAT Remover" -Confirm:$false
    }
}

Write-Output "Done - exiting"