v1.1.0: Improved file locking handling for eDNC transfers

- Wait for file to stabilize (size stops changing) before processing
- Exponential backoff retry: 500ms -> 1s -> 2s -> up to 16s
- Up to 10 retry attempts (was 3)
- Debouncing to prevent duplicate processing of same file
- Use exclusive file lock during read/write for atomic operations
- Track failed file count in session summary

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

eDNC-SpecialCharFix.ps1

@@ -36,9 +36,15 @@
 
 .NOTES
     Author: GE Aerospace - Rutland
-    Version: 1.0.0
+    Version: 1.1.0
     Date: 2025-12-12
 
+    v1.1.0 - Improved file locking handling:
+    - Wait for file to stabilize (size stops changing)
+    - Exponential backoff retry (500ms -> 16s)
+    - Up to 10 retry attempts
+    - Debouncing to prevent duplicate processing
+
     Common problematic characters:
     - 0xFF (255) - Padding/fill character
     - 0x00 (0)   - NULL character
@@ -62,7 +68,7 @@ param(
 )
 
 # Script info
-$ScriptVersion = "1.0.0"
+$ScriptVersion = "1.1.0"
 $ScriptName = "eDNC Special Character Fix"
 
 # Display banner
@@ -92,6 +98,11 @@ Write-Host ""
 # Statistics
 $script:FilesProcessed = 0
 $script:BytesRemoved = 0
+$script:FailedFiles = 0
+
+# Debounce tracking - prevent processing same file multiple times
+$script:RecentlyProcessed = @{}
+$script:DebounceSeconds = 5
 
 # Create file system watcher
 $watcher = New-Object System.IO.FileSystemWatcher
@@ -106,31 +117,89 @@ $action = {
     $changeType = $Event.SourceEventArgs.ChangeType
     $fileName = Split-Path $path -Leaf
 
-    # Get characters to remove from the outer scope
+    # Get parameters from message data
     $charsToRemove = $Event.MessageData.CharsToRemove
+    $debounceSeconds = $Event.MessageData.DebounceSeconds
+
+    # Debounce check - skip if we processed this file recently
+    $now = Get-Date
+    if ($script:RecentlyProcessed.ContainsKey($path)) {
+        $lastProcessed = $script:RecentlyProcessed[$path]
+        if (($now - $lastProcessed).TotalSeconds -lt $debounceSeconds) {
+            return  # Skip duplicate event
+        }
+    }
 
     Write-Host "$(Get-Date -Format 'yyyy-MM-dd HH:mm:ss') | $changeType | $fileName" -ForegroundColor White
 
-    # Wait for file to finish writing
-    Start-Sleep -Milliseconds 500
+    # STEP 1: Wait for file to stabilize (size stops changing)
+    $stableChecks = 0
+    $lastSize = -1
+    $maxStableWait = 30  # Max 30 seconds waiting for file to stabilize
 
-    # Retry logic for locked files
-    $maxRetries = 3
+    while ($stableChecks -lt $maxStableWait) {
+        Start-Sleep -Milliseconds 500
+        try {
+            if (-not (Test-Path $path)) {
+                Write-Host "  [SKIP] File no longer exists" -ForegroundColor Yellow
+                return
+            }
+            $currentSize = (Get-Item $path).Length
+            if ($currentSize -eq $lastSize -and $currentSize -gt 0) {
+                # File size hasn't changed - likely done writing
+                break
+            }
+            $lastSize = $currentSize
+            $stableChecks++
+            if ($stableChecks % 4 -eq 0) {
+                Write-Host "  [WAIT] File still being written... ($([math]::Round($stableChecks/2))s)" -ForegroundColor DarkGray
+            }
+        }
+        catch {
+            $stableChecks++
+        }
+    }
+
+    # STEP 2: Try to acquire exclusive access with exponential backoff
+    $maxRetries = 10
     $retryCount = 0
+    $baseDelay = 500  # Start with 500ms
 
     while ($retryCount -lt $maxRetries) {
+        $fileStream = $null
         try {
-            # Read file as bytes
-            $bytes = [System.IO.File]::ReadAllBytes($path)
-            $originalCount = $bytes.Count
+            # Try to open file with exclusive access - this confirms it's available
+            $fileStream = [System.IO.File]::Open(
+                $path,
+                [System.IO.FileMode]::Open,
+                [System.IO.FileAccess]::ReadWrite,
+                [System.IO.FileShare]::None
+            )
+
+            # Read all bytes while we have exclusive lock
+            $fileStream.Position = 0
+            $bytes = New-Object byte[] $fileStream.Length
+            $null = $fileStream.Read($bytes, 0, $bytes.Length)
+            $originalCount = $bytes.Length
 
             # Remove specified bytes
-            $cleaned = $bytes | Where-Object { $_ -notin $charsToRemove }
+            $cleaned = [System.Collections.Generic.List[byte]]::new()
+            foreach ($b in $bytes) {
+                if ($b -notin $charsToRemove) {
+                    $cleaned.Add($b)
+                }
+            }
             $newCount = $cleaned.Count
 
             # Only rewrite if we found characters to remove
             if ($originalCount -ne $newCount) {
-                [System.IO.File]::WriteAllBytes($path, [byte[]]$cleaned)
+                # Truncate and rewrite
+                $fileStream.Position = 0
+                $fileStream.SetLength(0)
+                $cleanedArray = $cleaned.ToArray()
+                $fileStream.Write($cleanedArray, 0, $cleanedArray.Length)
+                $fileStream.Flush()
+
                 $removed = $originalCount - $newCount
                 Write-Host "  [CLEANED] Removed $removed byte(s)" -ForegroundColor Green
                 $script:FilesProcessed++
@@ -138,27 +207,41 @@ $action = {
             } else {
                 Write-Host "  [OK] No special characters found" -ForegroundColor Gray
             }
+
+            # Mark as recently processed
+            $script:RecentlyProcessed[$path] = Get-Date
             break
         }
         catch [System.IO.IOException] {
             $retryCount++
             if ($retryCount -lt $maxRetries) {
-                Write-Host "  [RETRY] File locked, waiting... ($retryCount/$maxRetries)" -ForegroundColor Yellow
-                Start-Sleep -Milliseconds 1000
+                # Exponential backoff: 500ms, 1s, 2s, 4s, 8s, 16s...
+                $delay = [math]::Min($baseDelay * [math]::Pow(2, $retryCount - 1), 16000)
+                Write-Host "  [RETRY] File locked, waiting $([math]::Round($delay/1000, 1))s... ($retryCount/$maxRetries)" -ForegroundColor Yellow
+                Start-Sleep -Milliseconds $delay
             } else {
-                Write-Host "  [ERROR] Could not access file after $maxRetries attempts" -ForegroundColor Red
+                Write-Host "  [FAILED] Could not access file after $maxRetries attempts" -ForegroundColor Red
+                $script:FailedFiles++
             }
         }
         catch {
             Write-Host "  [ERROR] $($_.Exception.Message)" -ForegroundColor Red
+            $script:FailedFiles++
             break
         }
+        finally {
+            if ($fileStream) {
+                $fileStream.Close()
+                $fileStream.Dispose()
+            }
+        }
     }
 }
 
 # Create message data object to pass parameters to the action
 $messageData = @{
     CharsToRemove = $CharactersToRemove
+    DebounceSeconds = $script:DebounceSeconds
 }
 
 # Register event handlers
@@ -183,6 +266,9 @@ finally {
     Write-Host "========================================" -ForegroundColor Cyan
     Write-Host "  Files Cleaned:  $script:FilesProcessed"
     Write-Host "  Bytes Removed:  $script:BytesRemoved"
+    if ($script:FailedFiles -gt 0) {
+        Write-Host "  Failed Files:   $script:FailedFiles" -ForegroundColor Red
+    }
     Write-Host ""
     Write-Host "Stopped watching folder" -ForegroundColor Yellow
 }