throttle

Author: ethanndickson

Coder-Desktop/VPNLib/Download.swift

@@ -129,9 +129,14 @@ public func download(
     src: URL,
     dest: URL,
     urlSession: URLSession,
-    progressUpdates: ((DownloadProgress) -> Void)? = nil
+    progressUpdates: (@Sendable (DownloadProgress) -> Void)? = nil
 ) async throws(DownloadError) {
-    try await DownloadManager().download(src: src, dest: dest, urlSession: urlSession, progressUpdates: progressUpdates)
+    try await DownloadManager().download(
+        src: src,
+        dest: dest,
+        urlSession: urlSession,
+        progressUpdates: progressUpdates.flatMap { throttle(interval: .milliseconds(10), $0) },
+    )
 }
 
 func etag(data: Data) -> String {
@@ -173,7 +178,7 @@ private final class DownloadManager: NSObject, @unchecked Sendable {
         src: URL,
         dest: URL,
         urlSession: URLSession,
-        progressUpdates: ((DownloadProgress) -> Void)?
+        progressUpdates: (@Sendable (DownloadProgress) -> Void)?
     ) async throws(DownloadError) {
         var req = URLRequest(url: src)
         if FileManager.default.fileExists(atPath: dest.path) {

Coder-Desktop/VPNLib/Util.swift

@@ -29,3 +29,32 @@ public func makeNSError(suffix: String, code: Int = -1, desc: String) -> NSError
         userInfo: [NSLocalizedDescriptionKey: desc]
     )
 }
+
+private actor Throttler<T: Sendable> {
+    let interval: Duration
+    let send: @Sendable (T) -> Void
+    var lastFire: ContinuousClock.Instant?
+
+    init(interval: Duration, send: @escaping @Sendable (T) -> Void) {
+        self.interval = interval
+        self.send = send
+    }
+
+    func push(_ value: T) {
+        let now = ContinuousClock.now
+        if let lastFire, now - lastFire < interval { return }
+        lastFire = now
+        send(value)
+    }
+}
+
+public func throttle<T: Sendable>(
+    interval: Duration,
+    _ send: @escaping @Sendable (T) -> Void
+) -> @Sendable (T) -> Void {
+    let box = Throttler(interval: interval, send: send)
+
+    return { value in
+        Task { await box.push(value) }
+    }
+}