feat(ios): stream compact LiDAR frames over websocket

integrations/iphone-lidar/native/RuViewLiDAR/WebSocketStreamer.swift

@@ -0,0 +1,93 @@
+import Foundation
+
+actor WebSocketStreamer {
+    enum StreamError: Error {
+        case invalidURL
+    }
+
+    struct WirePacket: Codable {
+        struct Depth: Codable {
+            let width: Int
+            let height: Int
+            let encoding: String
+            let millimetersBase64: String
+            let confidenceBase64: String
+        }
+
+        let type: String
+        let intrinsics: RuViewLiDARFrame.Intrinsics
+        let pose: RuViewLiDARFrame.Pose
+        let depth: Depth
+        let provenance: RuViewLiDARFrame.Provenance
+    }
+
+    private var task: URLSessionWebSocketTask?
+    private let encoder = JSONEncoder()
+    private var lastSentNs: UInt64 = 0
+
+    func connect(to endpoint: String) throws {
+        guard let url = URL(string: endpoint),
+              url.scheme == "ws" || url.scheme == "wss" else {
+            throw StreamError.invalidURL
+        }
+        task?.cancel(with: .goingAway, reason: nil)
+        let socket = URLSession.shared.webSocketTask(with: url)
+        socket.resume()
+        task = socket
+    }
+
+    func disconnect() {
+        task?.cancel(with: .goingAway, reason: nil)
+        task = nil
+    }
+
+    func send(_ frame: RuViewLiDARFrame, maxFPS: UInt64 = 15, sampleStep: Int = 2) async throws {
+        guard let task else { return }
+
+        let timestamp = frame.provenance.timestampNs
+        let minDelta = 1_000_000_000 / max(1, maxFPS)
+        guard timestamp >= lastSentNs + minDelta else { return }
+        lastSentNs = timestamp
+
+        let packet = Self.makeWirePacket(frame, sampleStep: max(1, sampleStep))
+        let data = try encoder.encode(packet)
+        guard let string = String(data: data, encoding: .utf8) else { return }
+        try await task.send(.string(string))
+    }
+
+    static func makeWirePacket(_ frame: RuViewLiDARFrame, sampleStep: Int) -> WirePacket {
+        let step = max(1, sampleStep)
+        let sourceWidth = frame.depth.width
+        let sourceHeight = frame.depth.height
+        let width = (sourceWidth + step - 1) / step
+        let height = (sourceHeight + step - 1) / step
+
+        var millimeters = Data(capacity: width * height * 2)
+        var confidence = Data(capacity: width * height)
+
+        for y in stride(from: 0, to: sourceHeight, by: step) {
+            for x in stride(from: 0, to: sourceWidth, by: step) {
+                let index = y * sourceWidth + x
+                let meters = frame.depth.meters[index]
+                let mm = UInt16(clamping: Int((meters * 1000).rounded()))
+                var littleEndian = mm.littleEndian
+                withUnsafeBytes(of: &littleEndian) { millimeters.append(contentsOf: $0) }
+                confidence.append(frame.depth.confidence[index])
+            }
+        }
+
+        return WirePacket(
+            type: frame.type,
+            intrinsics: frame.intrinsics,
+            pose: frame.pose,
+            depth: Depth(
+                width: width,
+                height: height,
+                encoding: "u16le-mm+u8-confidence",
+                millimetersBase64: millimeters.base64EncodedString(),
+                confidenceBase64: confidence.base64EncodedString()
+            ),
+            provenance: frame.provenance
+        )
+    }
+}