sync app filled in

apps/macos-sync/Sources/CairnquireSync/Sync/FolderWatcher.swift

@@ -0,0 +1,103 @@
+import Foundation
+import CoreServices
+
+public protocol FolderWatcherDelegate: AnyObject {
+    func folderWatcher(_ watcher: FolderWatcher, didDetectChanges paths: [String])
+}
+
+public class FolderWatcher {
+    public weak var delegate: FolderWatcherDelegate?
+    
+    private var stream: FSEventStreamRef?
+    private let folderPath: String
+    private var debounceTimer: Timer?
+    private var pendingPaths: Set<String> = []
+    private let queue = DispatchQueue(label: "com.cairnquire.folderwatcher")
+    
+    public init(folderPath: String) {
+        self.folderPath = folderPath
+    }
+    
+    public func start() {
+        stop()
+        
+        let pathsToWatch = [folderPath as CFString]
+        var context = FSEventStreamContext(
+            version: 0,
+            info: Unmanaged.passUnretained(self).toOpaque(),
+            retain: nil,
+            release: nil,
+            copyDescription: nil
+        )
+        
+        let callback: FSEventStreamCallback = { (streamRef, clientCallBackInfo, numEvents, eventPaths, eventFlags, eventIds) in
+            let watcher = Unmanaged<FolderWatcher>.fromOpaque(clientCallBackInfo!).takeUnretainedValue()
+            watcher.handleEvents(numEvents: numEvents, eventPaths: eventPaths, eventFlags: eventFlags)
+        }
+        
+        stream = FSEventStreamCreate(
+            kCFAllocatorDefault,
+            callback,
+            &context,
+            pathsToWatch as CFArray,
+            FSEventStreamEventId(kFSEventStreamEventIdSinceNow),
+            0.5, // latency in seconds
+            FSEventStreamCreateFlags(kFSEventStreamCreateFlagFileEvents | kFSEventStreamCreateFlagUseCFTypes)
+        )
+        
+        if let stream = stream {
+            FSEventStreamSetDispatchQueue(stream, queue)
+            FSEventStreamStart(stream)
+        }
+    }
+    
+    public func stop() {
+        if let stream = stream {
+            FSEventStreamStop(stream)
+            FSEventStreamInvalidate(stream)
+            FSEventStreamRelease(stream)
+            self.stream = nil
+        }
+    }
+    
+    private func handleEvents(numEvents: Int, eventPaths: UnsafeMutableRawPointer, eventFlags: UnsafePointer<FSEventStreamEventFlags>) {
+        guard let paths = Unmanaged<CFArray>.fromOpaque(eventPaths).takeUnretainedValue() as? [String] else { return }
+        
+        var changedPaths: [String] = []
+        for i in 0..<numEvents {
+            let path = paths[i]
+            let flags = eventFlags[i]
+            
+            // Filter for relevant file events
+            if flags & UInt32(kFSEventStreamEventFlagItemCreated) != 0 ||
+               flags & UInt32(kFSEventStreamEventFlagItemModified) != 0 ||
+               flags & UInt32(kFSEventStreamEventFlagItemRemoved) != 0 ||
+               flags & UInt32(kFSEventStreamEventFlagItemRenamed) != 0 {
+                
+                // Only track markdown files
+                if path.hasSuffix(".md") {
+                    changedPaths.append(path)
+                }
+            }
+        }
+        
+        guard !changedPaths.isEmpty else { return }
+        
+        DispatchQueue.main.async { [weak self] in
+            guard let self = self else { return }
+            
+            self.pendingPaths.formUnion(changedPaths)
+            self.debounceTimer?.invalidate()
+            self.debounceTimer = Timer.scheduledTimer(withTimeInterval: 1.0, repeats: false) { [weak self] _ in
+                guard let self = self else { return }
+                let paths = Array(self.pendingPaths)
+                self.pendingPaths.removeAll()
+                self.delegate?.folderWatcher(self, didDetectChanges: paths)
+            }
+        }
+    }
+    
+    deinit {
+        stop()
+    }
+}