# Hyper-V Performance Diagnostic Script
# Diagnoses issues after checkpoint/merge operations

param(
    [switch]$Detailed,
    [switch]$ExportReport
)

$ReportPath = "C:\Temp\HyperV-Diagnostic-$(Get-Date -Format 'yyyyMMdd_HHmmss').txt"

function Write-Output-And-Log {
    param([string]$Message, [string]$Color = "White")
    Write-Host $Message -ForegroundColor $Color
    if ($ExportReport) {
        Add-Content -Path $ReportPath -Value $Message
    }
}

function Write-Section {
    param([string]$Title)
    Write-Output-And-Log ""
    Write-Output-And-Log "============================================" "Cyan"
    Write-Output-And-Log $Title "Cyan"
    Write-Output-And-Log "============================================" "Cyan"
}

try {
    if ($ExportReport) {
        New-Item -ItemType Directory -Path (Split-Path $ReportPath -Parent) -Force -ErrorAction SilentlyContinue | Out-Null
        Write-Output-And-Log "Diagnostic Report will be saved to: $ReportPath" "Yellow"
    }

    Write-Section "HYPER-V PERFORMANCE DIAGNOSTIC - $(Get-Date)"

    # 1. Check for active merge operations
    Write-Section "1. CHECKING FOR ACTIVE MERGE OPERATIONS"
    $VMs = Get-VM
    $MergingVMs = @()
    
    foreach ($VM in $VMs) {
        $Status = $VM.Status
        if ($Status -like "*Merging*" -or $Status -like "*Deleting*") {
            $MergingVMs += $VM
            Write-Output-And-Log "⚠️  $($VM.Name): $Status" "Yellow"
        } else {
            Write-Output-And-Log "✓  $($VM.Name): $Status" "Green"
        }
    }
    
    if ($MergingVMs.Count -gt 0) {
        Write-Output-And-Log ""
        Write-Output-And-Log "⚠️  WARNING: $($MergingVMs.Count) VM(s) still have merge operations in progress!" "Red"
        Write-Output-And-Log "This is likely causing the slowness. Wait for merges to complete." "Red"
    } else {
        Write-Output-And-Log ""
        Write-Output-And-Log "✓ No active merge operations detected" "Green"
    }

    # 2. Check disk space
    Write-Section "2. DISK SPACE CHECK"
    $Drives = Get-PSDrive -PSProvider FileSystem | Where-Object { $_.Used -gt 0 }
    
    foreach ($Drive in $Drives) {
        $UsedGB = [math]::Round($Drive.Used / 1GB, 2)
        $FreeGB = [math]::Round($Drive.Free / 1GB, 2)
        $TotalGB = $UsedGB + $FreeGB
        $PercentFree = [math]::Round(($FreeGB / $TotalGB) * 100, 1)
        
        $Color = "Green"
        $Warning = ""
        if ($PercentFree -lt 10) {
            $Color = "Red"
            $Warning = " ⚠️  CRITICAL - Less than 10% free!"
        } elseif ($PercentFree -lt 20) {
            $Color = "Yellow"
            $Warning = " ⚠️  WARNING - Less than 20% free"
        }
        
        Write-Output-And-Log "$($Drive.Name) - Free: $FreeGB GB / Total: $TotalGB GB ($PercentFree% free)$Warning" $Color
    }

    # 3. Check checkpoint status for all VMs
    Write-Section "3. CHECKPOINT STATUS FOR ALL VMs"
    
    foreach ($VM in $VMs) {
        $Checkpoints = Get-VMCheckpoint -VMName $VM.Name
        $CheckpointCount = $Checkpoints.Count
        
        if ($CheckpointCount -eq 0) {
            Write-Output-And-Log "$($VM.Name): No checkpoints" "Green"
        } else {
            Write-Output-And-Log "$($VM.Name): $CheckpointCount checkpoint(s)" "Yellow"
            
            foreach ($Checkpoint in $Checkpoints | Sort-Object CreationTime) {
                $Age = [math]::Round((New-TimeSpan -Start $Checkpoint.CreationTime -End (Get-Date)).TotalDays, 1)
                Write-Output-And-Log "  - $($Checkpoint.Name) (Age: $Age days, Created: $($Checkpoint.CreationTime))"
            }
        }
    }

    # 4. Check for AVHDX files and their sizes
    Write-Section "4. DIFFERENCING DISK (AVHDX) FILES"
    
    $TotalAVHDXSize = 0
    $AVHDXFiles = @()
    
    foreach ($VM in $VMs) {
        $VMHardDisks = Get-VMHardDiskDrive -VMName $VM.Name
        
        foreach ($Disk in $VMHardDisks) {
            if ($Disk.Path -match "\.avhdx$") {
                if (Test-Path $Disk.Path) {
                    $FileInfo = Get-Item $Disk.Path
                    $SizeGB = [math]::Round($FileInfo.Length / 1GB, 2)
                    $TotalAVHDXSize += $FileInfo.Length
                    
                    $AVHDXFiles += [PSCustomObject]@{
                        VM = $VM.Name
                        Path = $Disk.Path
                        SizeGB = $SizeGB
                        LastModified = $FileInfo.LastWriteTime
                    }
                }
            }
        }
    }
    
    if ($AVHDXFiles.Count -eq 0) {
        Write-Output-And-Log "✓ No AVHDX files found (no active checkpoints)" "Green"
    } else {
        $TotalAVHDXGB = [math]::Round($TotalAVHDXSize / 1GB, 2)
        Write-Output-And-Log "⚠️  Found $($AVHDXFiles.Count) AVHDX files (Total: $TotalAVHDXGB GB)" "Yellow"
        Write-Output-And-Log ""
        
        foreach ($File in $AVHDXFiles | Sort-Object SizeGB -Descending) {
            Write-Output-And-Log "$($File.VM): $($File.SizeGB) GB - $(Split-Path $File.Path -Leaf)"
            Write-Output-And-Log "  Last Modified: $($File.LastModified)"
        }
    }

    # 5. Check disk I/O performance
    Write-Section "5. CURRENT DISK I/O ACTIVITY"
    
    Write-Output-And-Log "Sampling disk activity for 5 seconds..."
    $DiskCounters = Get-Counter '\PhysicalDisk(*)\Disk Writes/sec', '\PhysicalDisk(*)\Disk Reads/sec' -SampleInterval 1 -MaxSamples 5
    
    $Writes = $DiskCounters.CounterSamples | Where-Object { $_.Path -like "*writes*" } | 
              Group-Object { $_.InstanceName } | 
              ForEach-Object { [PSCustomObject]@{ Disk = $_.Name; AvgWrites = [math]::Round(($_.Group.CookedValue | Measure-Object -Average).Average, 1) }}
    
    $Reads = $DiskCounters.CounterSamples | Where-Object { $_.Path -like "*reads*" } | 
             Group-Object { $_.InstanceName } | 
             ForEach-Object { [PSCustomObject]@{ Disk = $_.Name; AvgReads = [math]::Round(($_.Group.CookedValue | Measure-Object -Average).Average, 1) }}
    
    Write-Output-And-Log ""
    Write-Output-And-Log "Average Disk Activity (5 second sample):"
    foreach ($Disk in $Writes) {
        if ($Disk.Disk -ne "_total") {
            $ReadInfo = $Reads | Where-Object { $_.Disk -eq $Disk.Disk }
            $TotalIO = $Disk.AvgWrites + $ReadInfo.AvgReads
            
            $Color = "Green"
            if ($TotalIO -gt 100) { $Color = "Yellow" }
            if ($TotalIO -gt 500) { $Color = "Red" }
            
            Write-Output-And-Log "$($Disk.Disk): Reads: $($ReadInfo.AvgReads)/sec, Writes: $($Disk.AvgWrites)/sec" $Color
        }
    }

    # 6. Check CPU and Memory usage
    Write-Section "6. SYSTEM RESOURCE USAGE"
    
    $CPU = Get-Counter '\Processor(_Total)\% Processor Time' -SampleInterval 1 -MaxSamples 5
    $AvgCPU = [math]::Round(($CPU.CounterSamples.CookedValue | Measure-Object -Average).Average, 1)
    
    $CPUColor = "Green"
    if ($AvgCPU -gt 70) { $CPUColor = "Yellow" }
    if ($AvgCPU -gt 90) { $CPUColor = "Red" }
    
    Write-Output-And-Log "Average CPU Usage: $AvgCPU%" $CPUColor
    
    $OS = Get-CimInstance -ClassName Win32_OperatingSystem
    $TotalRAM = [math]::Round($OS.TotalVisibleMemorySize / 1MB, 2)
    $FreeRAM = [math]::Round($OS.FreePhysicalMemory / 1MB, 2)
    $UsedRAM = $TotalRAM - $FreeRAM
    $PercentUsed = [math]::Round(($UsedRAM / $TotalRAM) * 100, 1)
    
    $RAMColor = "Green"
    if ($PercentUsed -gt 80) { $RAMColor = "Yellow" }
    if ($PercentUsed -gt 95) { $RAMColor = "Red" }
    
    Write-Output-And-Log "Memory Usage: $UsedRAM GB / $TotalRAM GB ($PercentUsed% used)" $RAMColor

    # 7. Check VM Storage Locations
    Write-Section "7. VM STORAGE LOCATIONS"
    
    foreach ($VM in $VMs) {
        Write-Output-And-Log ""
        Write-Output-And-Log "$($VM.Name):"
        Write-Output-And-Log "  Config: $($VM.ConfigurationLocation)"
        Write-Output-And-Log "  Snapshots: $($VM.SnapshotFileLocation)"
        
        $VMHardDisks = Get-VMHardDiskDrive -VMName $VM.Name
        foreach ($Disk in $VMHardDisks) {
            Write-Output-And-Log "  Disk: $($Disk.Path)"
        }
    }

    # 8. Check recent Hyper-V errors
    Write-Section "8. RECENT HYPER-V ERRORS (Last 24 hours)"
    
    $Yesterday = (Get-Date).AddDays(-1)
    $HyperVErrors = Get-WinEvent -FilterHashtable @{
        LogName = 'Microsoft-Windows-Hyper-V-*'
        Level = 2,3  # Error and Warning
        StartTime = $Yesterday
    } -ErrorAction SilentlyContinue | Select-Object -First 10
    
    if ($HyperVErrors) {
        Write-Output-And-Log "⚠️  Found $($HyperVErrors.Count) recent error/warning entries (showing first 10):" "Yellow"
        foreach ($Error in $HyperVErrors) {
            Write-Output-And-Log ""
            Write-Output-And-Log "[$($Error.TimeCreated)] $($Error.LevelDisplayName): $($Error.Message)" "Yellow"
        }
    } else {
        Write-Output-And-Log "✓ No recent errors found in Hyper-V event logs" "Green"
    }

    # 9. Detailed checkpoint analysis if requested
    if ($Detailed) {
        Write-Section "9. DETAILED CHECKPOINT ANALYSIS"
        
        foreach ($VM in $VMs) {
            $Checkpoints = Get-VMCheckpoint -VMName $VM.Name
            if ($Checkpoints.Count -gt 0) {
                Write-Output-And-Log ""
                Write-Output-And-Log "$($VM.Name) - Detailed Checkpoint Info:"
                
                foreach ($Checkpoint in $Checkpoints) {
                    Write-Output-And-Log "  Checkpoint: $($Checkpoint.Name)"
                    Write-Output-And-Log "    ID: $($Checkpoint.Id)"
                    Write-Output-And-Log "    Type: $($Checkpoint.CheckpointType)"
                    Write-Output-And-Log "    Created: $($Checkpoint.CreationTime)"
                    Write-Output-And-Log "    Parent: $($Checkpoint.ParentCheckpointName)"
                    
                    # Try to get AVHDX sizes for this checkpoint
                    $CheckpointDisks = Get-VMHardDiskDrive -VMCheckpoint $Checkpoint -ErrorAction SilentlyContinue
                    if ($CheckpointDisks) {
                        foreach ($Disk in $CheckpointDisks) {
                            if (Test-Path $Disk.Path) {
                                $Size = [math]::Round((Get-Item $Disk.Path).Length / 1GB, 2)
                                Write-Output-And-Log "    Disk: $Size GB - $(Split-Path $Disk.Path -Leaf)"
                            }
                        }
                    }
                }
            }
        }
    }

    # Summary and Recommendations
    Write-Section "SUMMARY AND RECOMMENDATIONS"
    
    $Issues = @()
    
    if ($MergingVMs.Count -gt 0) {
        $Issues += "⚠️  CRITICAL: Merge operations still in progress on $($MergingVMs.Count) VM(s)"
        $Issues += "   Action: Wait for merges to complete or restart Hyper-V service (risky)"
    }
    
    if ($AVHDXFiles.Count -gt 0) {
        $Issues += "⚠️  WARNING: $($AVHDXFiles.Count) checkpoint differencing disks (AVHDX files) exist"
        $Issues += "   Action: Remove old checkpoints to merge these files"
    }
    
    $LowDiskDrives = $Drives | Where-Object { ($_.Free / ($_.Used + $_.Free)) -lt 0.20 }
    if ($LowDiskDrives) {
        $Issues += "⚠️  WARNING: Low disk space on $($LowDiskDrives.Count) drive(s)"
        $Issues += "   Action: Free up disk space or move VMs to larger drives"
    }
    
    if ($AvgCPU -gt 80) {
        $Issues += "⚠️  WARNING: High CPU usage ($AvgCPU%)"
        $Issues += "   Action: Check for runaway processes or reduce VM load"
    }
    
    if ($PercentUsed -gt 90) {
        $Issues += "⚠️  WARNING: High memory usage ($PercentUsed%)"
        $Issues += "   Action: Reduce VM memory allocations or add more RAM"
    }
    
    if ($Issues.Count -eq 0) {
        Write-Output-And-Log "✓ No major issues detected!" "Green"
        Write-Output-And-Log ""
        Write-Output-And-Log "Your slowness might be due to:"
        Write-Output-And-Log "1. Background merge operations that completed but haven't settled"
        Write-Output-And-Log "2. Disk fragmentation after large merge operations"
        Write-Output-And-Log "3. Windows Search or other background services indexing new data"
        Write-Output-And-Log ""
        Write-Output-And-Log "Recommendations:"
        Write-Output-And-Log "- Restart the Hyper-V Host to clear any stuck states"
        Write-Output-And-Log "- Defragment drives containing VM files"
        Write-Output-And-Log "- Check Windows Task Manager for background processes"
    } else {
        foreach ($Issue in $Issues) {
            Write-Output-And-Log $Issue "Red"
        }
    }
    
    Write-Output-And-Log ""
    Write-Output-And-Log "============================================" "Cyan"
    Write-Output-And-Log "DIAGNOSTIC COMPLETE - $(Get-Date)" "Cyan"
    Write-Output-And-Log "============================================" "Cyan"
    
    if ($ExportReport) {
        Write-Output-And-Log ""
        Write-Output-And-Log "Report saved to: $ReportPath" "Green"
    }
}
catch {
    Write-Output-And-Log "Error running diagnostic: $_" "Red"
}

# Quick commands to try
Write-Output-And-Log ""
Write-Output-And-Log "============================================" "Yellow"
Write-Output-And-Log "QUICK DIAGNOSTIC COMMANDS" "Yellow"
Write-Output-And-Log "============================================" "Yellow"
Write-Output-And-Log ""
Write-Output-And-Log "Check for stuck merge operations:"
Write-Output-And-Log "  Get-VM | Where-Object {`$_.Status -like '*Merging*'}" "Cyan"
Write-Output-And-Log ""
Write-Output-And-Log "Check disk queue length (high = problem):"
Write-Output-And-Log "  Get-Counter '\PhysicalDisk(*)\Avg. Disk Queue Length'" "Cyan"
Write-Output-And-Log ""
Write-Output-And-Log "View all checkpoints:"
Write-Output-And-Log "  Get-VM | ForEach-Object { Get-VMCheckpoint -VMName `$_.Name }" "Cyan"
Write-Output-And-Log ""
Write-Output-And-Log "Restart Hyper-V Management Service (last resort):"
Write-Output-And-Log "  Restart-Service vmms -Force" "Cyan"
Write-Output-And-Log ""