<#
.SYNOPSIS
  Identify inactive mailboxes based on LastLogonTime

.DESCRIPTION
  Finds mailboxes with no logon activity within specified days.
  Useful for identifying stale accounts, cost optimization, and cleanup planning.

.PARAMETER InactiveDays
  Number of days without logon to consider mailbox inactive (default: 90)

.PARAMETER OutputFolder
  Destination folder for reports. Default: .\InactiveMailboxes-<date>

.PARAMETER IncludeShared
  Include shared mailboxes in the report (default: $false)

.PARAMETER IncludeSize
  Include mailbox size information (slower, default: $true)

.NOTES
  ⚠️  AI-GENERATED SCRIPT - UNTESTED
  This script was generated by Claude AI and has not been tested in production.
  Review and test thoroughly in a non-production environment before use.

  - Run in Exchange Management Shell with appropriate RBAC permissions
  - LastLogonTime may be null for never-accessed mailboxes
  - Size calculation can be slow with large mailbox counts

.EXAMPLE
  .\Get-InactiveMailboxes.ps1

.EXAMPLE
  .\Get-InactiveMailboxes.ps1 -InactiveDays 180 -IncludeShared $true
#>

[CmdletBinding()]
param(
    [int]$InactiveDays = 90,
    [string]$OutputFolder = (Join-Path -Path (Get-Location) -ChildPath ("InactiveMailboxes-" + (Get-Date -Format "yyyyMMdd-HHmm"))),
    [bool]$IncludeShared = $false,
    [bool]$IncludeSize = $true
)

function NowTag { (Get-Date).ToString("yyyy-MM-dd HH:mm:ss") }

Write-Host "[$(NowTag)] ⚠️  AI-GENERATED SCRIPT - UNTESTED" -ForegroundColor Yellow
Write-Host "[$(NowTag)] Searching for mailboxes inactive for $InactiveDays+ days..." -ForegroundColor Green

# Create output folder
New-Item -ItemType Directory -Path $OutputFolder -Force | Out-Null

$cutoffDate = (Get-Date).AddDays(-$InactiveDays)
Write-Host "[$(NowTag)] Cutoff date: $($cutoffDate.ToString('yyyy-MM-dd'))"

# Get mailboxes
Write-Host "[$(NowTag)] Retrieving mailboxes..."
$filter = if ($IncludeShared) {
    { RecipientTypeDetails -notmatch "^Remote" -and Database }
} else {
    { RecipientTypeDetails -eq "UserMailbox" -and Database }
}

$mailboxes = Get-Mailbox -ResultSize Unlimited -ErrorAction SilentlyContinue |
    Where-Object $filter

$mbCount = ($mailboxes | Measure-Object).Count
Write-Host "[$(NowTag)] Found $mbCount mailboxes to check"

# Get statistics per database to avoid prompts
Write-Host "[$(NowTag)] Retrieving mailbox statistics..."
$statsByDb = @{}
$databases = ($mailboxes.Database | Sort-Object -Unique)

$dbIdx = 0
foreach ($db in $databases) {
    $dbIdx++
    Write-Progress -Activity "Collecting Mailbox Statistics" -Status "Database $db ($dbIdx/$($databases.Count))" -PercentComplete ([int](($dbIdx / $databases.Count) * 100))

    try {
        $stats = Get-MailboxStatistics -Database $db -ErrorAction SilentlyContinue
        foreach ($stat in $stats) {
            $statsByDb[$stat.DisplayName] = $stat
        }
    } catch {
        Write-Host "[$(NowTag)] WARNING: Could not get statistics for database $db" -ForegroundColor Yellow
    }
}

Write-Progress -Activity "Collecting Mailbox Statistics" -Completed

# Analyze for inactive mailboxes
Write-Host "[$(NowTag)] Analyzing mailbox activity..."
$inactiveMailboxes = @()

$current = 0
foreach ($mb in $mailboxes) {
    $current++
    $pct = [int](($current / $mbCount) * 100)
    Write-Progress -Activity "Analyzing Mailboxes" -Status "Processing $($mb.DisplayName) ($current/$mbCount)" -PercentComplete $pct

    $stat = $statsByDb[$mb.DisplayName]

    $lastLogon = if ($stat) { $stat.LastLogonTime } else { $null }
    $isInactive = $false
    $reason = ""

    if ($null -eq $lastLogon) {
        $isInactive = $true
        $reason = "Never logged on"
    } elseif ($lastLogon -lt $cutoffDate) {
        $isInactive = $true
        $reason = "Last logon: $($lastLogon.ToString('yyyy-MM-dd'))"
    }

    if ($isInactive) {
        $daysSinceLogon = if ($lastLogon) {
            [int]((Get-Date) - $lastLogon).TotalDays
        } else {
            "N/A"
        }

        $size = $null
        $itemCount = $null

        if ($IncludeSize -and $stat) {
            $size = $stat.TotalItemSize
            $itemCount = $stat.ItemCount
        }

        $inactiveMailboxes += [PSCustomObject]@{
            DisplayName          = $mb.DisplayName
            PrimarySmtpAddress   = $mb.PrimarySmtpAddress
            RecipientTypeDetails = $mb.RecipientTypeDetails
            Database             = $mb.Database
            LastLogonTime        = $lastLogon
            DaysSinceLogon       = $daysSinceLogon
            WhenCreated          = $mb.WhenCreated
            TotalItemSize        = $size
            ItemCount            = $itemCount
            Reason               = $reason
        }
    }
}

Write-Progress -Activity "Analyzing Mailboxes" -Completed

# Export results
Write-Host "[$(NowTag)] Found $($inactiveMailboxes.Count) inactive mailboxes"

if ($inactiveMailboxes.Count -gt 0) {
    $csvFile = Join-Path $OutputFolder "Inactive-Mailboxes.csv"
    $inactiveMailboxes | Sort-Object DaysSinceLogon -Descending |
        Export-Csv -NoTypeInformation -Encoding UTF8 -Path $csvFile
    Write-Host "[$(NowTag)] Report exported: $csvFile" -ForegroundColor Green

    # Summary by type
    $byType = $inactiveMailboxes | Group-Object RecipientTypeDetails
    Write-Host "`nInactive Mailboxes by Type:"
    foreach ($type in $byType) {
        Write-Host "  $($type.Name): $($type.Count)"
    }

    # Calculate potential storage savings
    if ($IncludeSize) {
        $totalBytes = 0
        foreach ($mb in $inactiveMailboxes) {
            if ($mb.TotalItemSize) {
                try {
                    $sizeStr = [string]$mb.TotalItemSize
                    if ($sizeStr -match "([\d\.,]+)\s*(KB|MB|GB|TB)") {
                        $num = [double]($matches[1] -replace ',', '.')
                        $bytes = switch ($matches[2].ToUpper()) {
                            "KB" { $num * 1KB }
                            "MB" { $num * 1MB }
                            "GB" { $num * 1GB }
                            "TB" { $num * 1TB }
                        }
                        $totalBytes += $bytes
                    }
                } catch {}
            }
        }
        $totalGB = [math]::Round($totalBytes / 1GB, 2)
        Write-Host "`nPotential storage savings: $totalGB GB" -ForegroundColor Cyan
    }
} else {
    Write-Host "[$(NowTag)] No inactive mailboxes found!" -ForegroundColor Green
}

Write-Host "`n[$(NowTag)] Analysis complete! Output folder: $OutputFolder"