Param(
    [Parameter(Mandatory = $true)]
    [string]$Source,

    [Parameter(Mandatory = $true)]
    [string]$Destination,

    [int]$BufferSizeMB = 4,
    [string]$MoveFiles = "false"
)
$shouldMove = $false
if ($MoveFiles.ToLower() -eq "true") {
    $shouldMove = $true
}

#HASH
function Get-FileHashSHA256 {
    param([string]$Path)
    return (Get-FileHash -Algorithm SHA256 -Path $Path).Hash
}

# Format: YYYY-MM-DD_HH-MM-SS for cross-platform friendliness
$timestamp = (Get-Date -Format "yyyy-MM-dd_HH-mm-ss")
$logFileName = "HashMismatchLog_$timestamp.txt"
$logFilePath = Join-Path $Destination $logFileName

# Create an empty file to start with
New-Item -ItemType File -Path $logFilePath -Force | Out-Null

# Prepare buffer size in bytes
$bufferSize = $BufferSizeMB * 1MB

# Gather all files
$files      = Get-ChildItem -Path $Source -Recurse -File
$totalCount = $files.Count
if ($totalCount -eq 0) {
    Write-Host "No files found under $Source"
    exit
}

$currentIndex = 0

foreach ($file in $files) {
    $currentIndex++

    $relative = $file.FullName.Substring($Source.Length).TrimStart('\')
    $destFull = Join-Path $Destination $relative
    $destDir  = Split-Path $destFull -Parent

    if (-not (Test-Path $destDir)) {
        New-Item -ItemType Directory -Path $destDir | Out-Null
    }

    $bytesCopied = 0
    $fileSize    = $file.Length
    $reader      = [System.IO.File]::OpenRead($file.FullName)
    $writer      = [System.IO.File]::Create($destFull)

    try {
        $buffer = New-Object byte[] ($BufferSizeMB * 1MB)

        while (($read = $reader.Read($buffer, 0, $buffer.Length)) -gt 0) {
            $writer.Write($buffer, 0, $read)
            $bytesCopied += $read

            $percentFile    = [math]::Round(($bytesCopied / $fileSize) * 100, 1)
            $percentOverall = [math]::Round(($currentIndex / $totalCount) * 100, 1)

            Write-Progress `
                -Activity "Copying file $currentIndex of $totalCount" `
                -Status "$percentFile%% of $($file.Name)" `
                -PercentComplete $percentOverall
        }
    }
    finally {
        $reader.Close()
        $writer.Close()
    }

    # Verify hash match
    $srcHash = Get-FileHashSHA256 -Path $file.FullName
    $dstHash = Get-FileHashSHA256 -Path $destFull

    if ($srcHash -eq $dstHash) {
        Write-Host "✅ Verified: $relative"

        if ($shouldMove) {
            try {
                Remove-Item $file.FullName -Force
                Write-Host "🗑️ Moved (source deleted): $relative"
            } catch {
                Write-Warning "⚠️ Failed to delete source file: $relative"
            }
        } else {
            Write-Host "Copied: $relative"
        }
    } else {
        Write-Warning "❌ Hash mismatch for $relative — file NOT deleted!"
        $logEntry = @"
        SOURCE: $($file.FullName)
        DEST:   $destFull

"@
        Add-Content -Path $logFilePath -Value $logEntry
    }
}

# Finalize progress
Write-Progress -Activity "Copy Complete" -Completed
Write-Host "All $totalCount files copied from `"$Source`" to `"$Destination`"."
if ((Get-Content $logFilePath).Length -eq 0) {
    Remove-Item $logFilePath -Force
    Write-Host "✅ No hash mismatches detected — log file auto-deleted."
} else {
    Write-Host "⚠ Hash mismatches logged in: $logFilePath"
}