<#
.SYNOPSIS
  Analyze Exchange message flow statistics from transport logs

.DESCRIPTION
  Aggregates statistics from Exchange transport logs including top senders/receivers,
  message volume by time period, and potential anomalies. Builds on Get-SMTPTraffic.ps1
  pattern but provides comprehensive analysis.

.PARAMETER LogPath
  Path to transport logs (default: auto-detect from Exchange install)

.PARAMETER DaysBack
  Number of days of logs to analyze (default: 7)

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

.PARAMETER TopCount
  Number of top senders/receivers to include in report (default: 25)

.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
  - Can be slow with large log volumes
  - Analyzes SMTP Receive logs by default

.EXAMPLE
  .\Get-MailflowStats.ps1

.EXAMPLE
  .\Get-MailflowStats.ps1 -DaysBack 30 -TopCount 50
#>

[CmdletBinding()]
param(
    [string]$LogPath = "",
    [int]$DaysBack = 7,
    [string]$OutputFolder = (Join-Path -Path (Get-Location) -ChildPath ("MailflowStats-" + (Get-Date -Format "yyyyMMdd-HHmm"))),
    [int]$TopCount = 25
)

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

Write-Host "[$(NowTag)] ⚠️  AI-GENERATED SCRIPT - UNTESTED" -ForegroundColor Yellow
Write-Host "[$(NowTag)] Starting mail flow analysis..." -ForegroundColor Green

# Auto-detect log path if not specified
if (-not $LogPath) {
    $exchangePath = (Get-ItemProperty -Path "HKLM:\SOFTWARE\Microsoft\ExchangeServer\v15\Setup" -ErrorAction SilentlyContinue).MsiInstallPath
    if ($exchangePath) {
        $LogPath = Join-Path $exchangePath "TransportRoles\Logs\FrontEnd\ProtocolLog\SmtpReceive"
    } else {
        Write-Host "[$(NowTag)] ERROR: Could not auto-detect Exchange log path. Please specify -LogPath parameter" -ForegroundColor Red
        exit 1
    }
}

if (-not (Test-Path $LogPath)) {
    Write-Host "[$(NowTag)] ERROR: Log path not found: $LogPath" -ForegroundColor Red
    exit 1
}

Write-Host "[$(NowTag)] Log path: $LogPath"

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

# Get log files within date range
$cutoffDate = (Get-Date).AddDays(-$DaysBack)
Write-Host "[$(NowTag)] Analyzing logs from $($cutoffDate.ToString('yyyy-MM-dd')) to $(Get-Date -Format 'yyyy-MM-dd')"

$logFiles = Get-ChildItem -Path $LogPath -Filter "*.log" -ErrorAction SilentlyContinue |
    Where-Object { $_.LastWriteTime -ge $cutoffDate } |
    Sort-Object LastWriteTime -Descending

$fileCount = ($logFiles | Measure-Object).Count

if ($fileCount -eq 0) {
    Write-Host "[$(NowTag)] No log files found in specified date range" -ForegroundColor Yellow
    exit 0
}

Write-Host "[$(NowTag)] Found $fileCount log file(s) to analyze"

# Parse logs
$allMessages = @()
$fileIdx = 0

foreach ($logFile in $logFiles) {
    $fileIdx++
    Write-Progress -Activity "Parsing Transport Logs" -Status "Processing $($logFile.Name) ($fileIdx/$fileCount)" -PercentComplete ([int](($fileIdx / $fileCount) * 100))

    # Get header from file
    $header = Get-Content $logFile.FullName -TotalCount 50 | Where-Object { $_ -like '#Fields:*' } | Select-Object -First 1
    if (-not $header) { continue }

    $fields = $header -replace '^#Fields: ', ''
    $columns = $fields -split ','

    # Parse log entries
    Get-Content $logFile.FullName | Where-Object { -not ($_ -like '#*') -and $_ -match ',' } | ForEach-Object {
        try {
            $row = $_ -split ',(?=(?:[^"]*"[^"]*")*[^"]*$)'  # Handle quoted fields
            $entry = [PSCustomObject]@{}

            for ($i = 0; $i -lt $columns.Count -and $i -lt $row.Count; $i++) {
                $entry | Add-Member -NotePropertyName $columns[$i].Trim() -NotePropertyValue ($row[$i] -replace '^"|"$', '') -Force
            }

            # Filter for relevant events (RECEIVE events)
            if ($entry.event -eq 'RECEIVE' -or $entry.event -eq '+') {
                $allMessages += $entry
            }
        } catch {}
    }
}

Write-Progress -Activity "Parsing Transport Logs" -Completed

$totalMessages = $allMessages.Count
Write-Host "[$(NowTag)] Parsed $totalMessages message(s)"

if ($totalMessages -eq 0) {
    Write-Host "[$(NowTag)] No messages found to analyze" -ForegroundColor Yellow
    exit 0
}

# Analyze data
Write-Host "[$(NowTag)] Analyzing message flow patterns..."

# Top senders (by remote-endpoint or client-ip)
$topSenders = $allMessages | Where-Object { $_.'remote-endpoint' } |
    Group-Object -Property 'remote-endpoint' |
    Select-Object @{N = "IPAddress"; E = { $_.Name } }, Count |
    Sort-Object Count -Descending |
    Select-Object -First $TopCount

# Messages by hour
$messagesByHour = $allMessages | Where-Object { $_.'date-time' } |
    ForEach-Object {
        try {
            $dt = [DateTime]::Parse($_.'date-time')
            [PSCustomObject]@{ Hour = $dt.Hour }
        } catch {}
    } |
    Group-Object Hour |
    Select-Object @{N = "Hour"; E = { $_.Name } }, Count |
    Sort-Object Hour

# Messages by day
$messagesByDay = $allMessages | Where-Object { $_.'date-time' } |
    ForEach-Object {
        try {
            $dt = [DateTime]::Parse($_.'date-time')
            [PSCustomObject]@{ Date = $dt.ToString('yyyy-MM-dd') }
        } catch {}
    } |
    Group-Object Date |
    Select-Object @{N = "Date"; E = { $_.Name } }, Count |
    Sort-Object Date

# Connector usage
$connectorStats = $allMessages | Where-Object { $_.'connector-id' } |
    Group-Object -Property 'connector-id' |
    Select-Object @{N = "Connector"; E = { $_.Name } }, Count |
    Sort-Object Count -Descending

# Export results
Write-Host "[$(NowTag)] Exporting results..."

$summaryFile = Join-Path $OutputFolder "Mailflow-Summary.txt"
$topSendersFile = Join-Path $OutputFolder "Top-Senders-By-IP.csv"
$byHourFile = Join-Path $OutputFolder "Messages-By-Hour.csv"
$byDayFile = Join-Path $OutputFolder "Messages-By-Day.csv"
$connectorFile = Join-Path $OutputFolder "Messages-By-Connector.csv"

$topSenders | Export-Csv -NoTypeInformation -Encoding UTF8 -Path $topSendersFile
$messagesByHour | Export-Csv -NoTypeInformation -Encoding UTF8 -Path $byHourFile
$messagesByDay | Export-Csv -NoTypeInformation -Encoding UTF8 -Path $byDayFile
$connectorStats | Export-Csv -NoTypeInformation -Encoding UTF8 -Path $connectorFile

Write-Host "[$(NowTag)] Top senders: $topSendersFile" -ForegroundColor Green
Write-Host "[$(NowTag)] Hourly distribution: $byHourFile" -ForegroundColor Green
Write-Host "[$(NowTag)] Daily distribution: $byDayFile" -ForegroundColor Green
Write-Host "[$(NowTag)] Connector stats: $connectorFile" -ForegroundColor Green

# Summary report
$summary = @"
Mail Flow Statistics Report
Generated: $(Get-Date)
Analysis Period: $($cutoffDate.ToString('yyyy-MM-dd')) to $(Get-Date -Format 'yyyy-MM-dd')
Log Path: $LogPath

SUMMARY:
  Total Messages Analyzed: $totalMessages
  Log Files Processed: $fileCount
  Average Messages Per Day: $([math]::Round($totalMessages / $DaysBack, 0))

TOP $TopCount SENDERS (by IP):
$($topSenders | ForEach-Object { "  $($_.IPAddress): $($_.Count) messages" } | Out-String)

BUSIEST HOURS (24-hour format):
$($messagesByHour | Sort-Object Count -Descending | Select-Object -First 5 | ForEach-Object { "  Hour $($_.Hour): $($_.Count) messages" } | Out-String)

DAILY VOLUME:
$($messagesByDay | ForEach-Object { "  $($_.Date): $($_.Count) messages" } | Out-String)

CONNECTOR USAGE:
$($connectorStats | ForEach-Object { "  $($_.Connector): $($_.Count) messages" } | Out-String)
"@

$summary | Out-File -FilePath $summaryFile -Encoding UTF8
Write-Host "[$(NowTag)] Summary report: $summaryFile" -ForegroundColor Green

# Console output
Write-Host "`nMAIL FLOW SUMMARY:" -ForegroundColor Cyan
Write-Host "  Total Messages: $totalMessages"
Write-Host "  Average Per Day: $([math]::Round($totalMessages / $DaysBack, 0))"
Write-Host "  Peak Hour: $(($messagesByHour | Sort-Object Count -Descending | Select-Object -First 1).Hour):00"
Write-Host "  Busiest Day: $(($messagesByDay | Sort-Object Count -Descending | Select-Object -First 1).Date)"

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