# Define path for HTML report
$outputFile = "$env:USERPROFILE\Downloads\SharedMailboxesReport_Details.html"
# Define path for server address and credentials
$serverAddressFile = ".\DefaultServer.txt"
$credentialFile = ".\AdminCredential.xml"

# --- Helper function to format mailbox size ---
Function Format-MailboxSize {
    param(
        [Parameter(Mandatory=$true)]
        $SizeObject
    )
    if ($null -eq $SizeObject) { return "N/A" }
    # Example SizeObject format: "1.23 GB (1,320,155,136 bytes)"
    # Extract the part before the parenthesis
    $sizeString = $SizeObject.ToString().Split('(')[0].Trim()
    # If it's just bytes, format it
    if ($sizeString -like "*bytes") {
        $bytes = $SizeObject.ToBytes()
        if ($bytes -gt 1GB) { return ("{0:N2} GB" -f ($bytes / 1GB)) }
        if ($bytes -gt 1MB) { return ("{0:N2} MB" -f ($bytes / 1MB)) }
        if ($bytes -gt 1KB) { return ("{0:N2} KB" -f ($bytes / 1KB)) }
        return ("{0} Bytes" -f $bytes)
    } else {
        # Return the already formatted part (e.g., "1.23 GB")
        return $sizeString
    }
}

# --- HTML Styling (CSS) ---
$cssStyle = @"
<style>
body { font-family: Segoe UI, Calibri, Arial, sans-serif; font-size: 10pt; }
h1 { color: #2E4053; font-size: 16pt; margin-bottom: 15px;}
h2 { color: #17202A; font-size: 14pt; margin-top: 25px; margin-bottom: 10px; border-bottom: 1px solid #AEB6BF; padding-bottom: 5px; } /* DB Name */
h3 { color: #1B4F72; font-size: 12pt; margin-top: 20px; margin-bottom: 5px; } /* Table Title - might not be needed */
table { border-collapse: collapse; width: 98%; margin-top: 10px; margin-bottom: 20px; border: 1px solid #AEB6BF; }
th { background-color: #1E8449; color: white; padding: 8px; text-align: left; border: 1px solid #AEB6BF; } /* Green header */
td { padding: 8px; text-align: left; border: 1px solid #D5DBDB; vertical-align: top; word-wrap: break-word; }
tr:nth-child(even) { background-color: #f2f2f2; }
tr:hover { background-color: #ddd; }
.description { margin-top: 10px; margin-bottom: 20px; padding: 10px; background-color: #f9f9f9; border-left: 4px solid #1E8449; } /* Green border */
.description p { margin-top: 0; margin-bottom: 5px; }
.description code { font-family: Consolas, monospace; background-color: #eee; padding: 2px 4px; border-radius: 3px; }
.never-logged-on { color: #E74C3C; font-style: italic; } /* Style for 'Never' */
.error { color: red; font-weight: bold; }
.timestamp { font-size: 8pt; color: #888; margin-top: 25px; }
</style>
"@

# --- Script Logic ---
$session = $null # Initialize session variable

# --- Initialize Report Body with Title and Descriptions ---
$reportTitle = "<h1>Shared Mailboxes Report</h1>"
$reportDescription = @"
<div class='description'>
<p>This report lists all shared mailboxes, grouped by their mailbox database.</p>
<p>It includes the mailbox size and the last time the mailbox was accessed (<code>LastLogonTime</code>).</p>
<p>Mailboxes listed with a 'Last Logon' date of <span class='never-logged-on'>Never</span> have potentially never been accessed or logon auditing was not enabled when they might have been accessed.</p>
</div>
"@

$reportBody = $reportTitle + $reportDescription

try {
    # --- Input File Validation ---
    if (-not (Test-Path $serverAddressFile)) {
        throw "Server address file not found: $serverAddressFile"
    }
    if (-not (Test-Path $credentialFile)) {
        throw "Credential file not found: $credentialFile"
    }

    # Import admin credentials
    $serverAddress = Get-Content -Path $serverAddressFile
    $credential = Import-Clixml -Path $credentialFile

    # Establish session with Exchange Server
    Write-Host "Connecting to Exchange Server: $serverAddress..."
    $session = New-PSSession -ConfigurationName Microsoft.Exchange -ConnectionUri "http://$serverAddress/PowerShell/" -Authentication Kerberos -Credential $credential -ErrorAction Stop
    Import-PSSession $session -DisableNameChecking -ErrorAction Stop
    Write-Host "Successfully connected to Exchange." -ForegroundColor Green

    # --- Data Retrieval and Processing ---
    Write-Host "Retrieving mailbox databases..."
    # Retrieve all non-recovery databases
    $databases = Get-MailboxDatabase -Status | Where-Object {$_.Recovery -ne $true} | Select-Object Name, Identity

    # Check database count *before* loop
    if (-not $databases -or $databases.Count -eq 0) {
        throw "No non-recovery mailbox databases found. Cannot generate report."
    }

    $totalDbCount = $databases.Count
    Write-Host "Found $totalDbCount databases. Processing mailboxes for each database..."
    $dbProcessed = 0

    foreach ($db in $databases) {
        $dbProcessed++

        # *** ADDED SAFEGUARD FOR Write-Progress calculation ***
        $percentComplete = 0 # Default value
        if ($totalDbCount -gt 0) {
             $percentComplete = [math]::Floor(($dbProcessed / $totalDbCount) * 100)
        }
        # Now safe to call Write-Progress
        Write-Progress -Activity "Processing Databases" -Status "Processing DB: $($db.Name) ($dbProcessed of $totalDbCount)" -PercentComplete $percentComplete

        $dbName = $db.Name
        # Add Database heading to report
        $reportBody += "<h2>Database: $dbName</h2>"

        $sharedMailboxesInDb = @()
        $reportDataForDb = @()

        try {
            # Get only SharedMailboxes directly from this DB
            Write-Host " - Retrieving shared mailboxes for database '$dbName'..."
            $sharedMailboxesInDb = Get-Mailbox -Database $db.Identity -RecipientTypeDetails SharedMailbox -ResultSize Unlimited -ErrorAction Stop

            if ($sharedMailboxesInDb.Count -gt 0) {
                Write-Host "   Found $($sharedMailboxesInDb.Count) shared mailboxes. Getting statistics..."
                # Get stats for all found mailboxes in this DB in one go (more efficient)
                $mailboxStats = $sharedMailboxesInDb | Get-MailboxStatistics -ErrorAction SilentlyContinue # Continue if stats fail for one mailbox

                # Create a hashtable for quick stats lookup
                $statsHashTable = @{}
                $mailboxStats | ForEach-Object { $statsHashTable[$_.MailboxGuid] = $_ }

                # Process each mailbox and combine with its stats
                foreach ($mb in $sharedMailboxesInDb) {
                    $currentStats = $statsHashTable[$mb.ExchangeGuid]
                    $formattedSize = "N/A"
                    $lastLogon = $null

                    if ($currentStats) {
                        $formattedSize = Format-MailboxSize -SizeObject $currentStats.TotalItemSize
                        $lastLogon = $currentStats.LastLogonTime
                    } else {
                        Write-Warning "Could not retrieve statistics for $($mb.PrimarySmtpAddress) in database $dbName."
                    }

                    $formattedLastLogon = if ($lastLogon) {
                         $lastLogon.ToString('yyyy-MM-dd HH:mm:ss')
                    } else {
                         "<span class='never-logged-on'>Never</span>"
                    }

                    $reportDataForDb += [PSCustomObject]@{
                        DisplayName        = $mb.DisplayName
                        PrimarySmtpAddress = $mb.PrimarySmtpAddress
                        Size               = $formattedSize
                        LastLogon          = $formattedLastLogon # Store the formatted string
                    }
                } # End foreach mailbox in DB

                # Generate HTML table for this database if data exists
                 if ($reportDataForDb.Count -gt 0) {
                    Write-Host "   Generating HTML table for '$dbName'..."
                    $htmlTable = $reportDataForDb | Sort-Object DisplayName | ConvertTo-Html -Fragment -Property DisplayName, PrimarySmtpAddress, Size, @{Name='Last Logon Time'; Expression={$_.LastLogon}}
                    $reportBody += [System.Net.WebUtility]::HtmlDecode($htmlTable) # Decode the 'Never' span
                } else {
                    # This case should be rare if $sharedMailboxesInDb.Count was > 0, unless all stats failed
                     $reportBody += "<p>No shared mailbox data processed for this database (potential issue retrieving statistics).</p>"
                }

            } else {
                 Write-Host "   No shared mailboxes found in database '$dbName'."
                 $reportBody += "<p>No shared mailboxes found in this database.</p>"
            }
        } catch {
             Write-Warning "An error occurred processing database '$dbName': $($_.Exception.Message)"
             $reportBody += "<p style='color:orange;'>An error occurred while processing mailboxes for database '$dbName'. Some mailboxes may be missing. Error: $($_.Exception.Message)</p>"
        } # End try-catch for DB processing
    } # End foreach database

    Write-Progress -Activity "Processing Databases" -Completed
    $reportBody += "<p style='margin-top:20px;'>Report generation complete.</p>"

} catch {
    Write-Host "Error: $($_.Exception.Message)" -ForegroundColor Red
    # Append error details to the report body (which already has title/description)
    $reportBody += "<h2 class='error'>Script Execution Error</h2>"
    $reportBody += "<p class='error'>An error occurred while generating the shared mailbox report.</p>"
    $reportBody += "<p class='error'><strong>Error Details:</strong><br/>$([System.Net.WebUtility]::HtmlEncode($_.Exception.Message))</p>"
    if ($_.Exception.StackTrace) {
         $reportBody += "<p class='error'><strong>Stack Trace:</strong><br/>$([System.Net.WebUtility]::HtmlEncode($_.Exception.StackTrace) -replace "`n", "<br/>")</p>"
     }
     if ($_.InvocationInfo) {
         $reportBody += "<p class='error'><strong>Script Line:</strong> $($_.InvocationInfo.ScriptLineNumber)</p>"
     }
} finally {
    # --- Generate Final HTML Report ---
    $reportFooter = "<p class='timestamp'>Report generated on: $(Get-Date -Format 'yyyy-MM-dd HH:mm:ss') by $($env:USERNAME)</p>"

    # Assemble the full HTML page
    ConvertTo-Html -Head $cssStyle `
                   -Title "Shared Mailboxes Report by Database" `
                   -Body $reportBody `
                   -PostContent $reportFooter | Out-File $outputFile -Encoding UTF8 -ErrorAction SilentlyContinue

    # Check if the file was actually created before trying to open it
    if (Test-Path $outputFile) {
        Write-Host "HTML Report saved to: $outputFile" -ForegroundColor Green
        Invoke-Item -Path $outputFile
    } else {
         Write-Host "Failed to create the report file at: $outputFile" -ForegroundColor Red
    }

    # Clean up Exchange session
    if ($session -ne $null) {
        Write-Host "Removing Exchange PSSession..."
        Remove-PSSession $session
        Write-Host "Session removed."
    }
}