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feat(liveness): add session + websocket client (#134)
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4 files changed

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4 files changed

+282
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‎AmplifyPlugins/Predictions/AWSPredictionsPlugin/Liveness/Service/FaceLivenessSession.swift‎

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//
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// Copyright Amazon.com Inc. or its affiliates.
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// All Rights Reserved.
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//
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// SPDX-License-Identifier: Apache-2.0
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//
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import Foundation
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import Amplify
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@_spi(PredictionsFaceLiveness)
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public final class FaceLivenessSession: LivenessService {
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let websocket: WebSocketSession
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let eventStreamEncoder: EventStream.Encoder
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let eventStreamDecoder: EventStream.Decoder
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let signer: SigV4Signer
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let baseURL: URL
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var serverEventListeners: [LivenessEventKind.Server: (FaceLivenessSession.SessionConfiguration) -> Void] = [:]
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var onComplete: (ServerDisconnection) -> Void = { _ in }
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init(
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websocket: WebSocketSession,
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signer: SigV4Signer,
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baseURL: URL
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) {
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self.eventStreamEncoder = EventStream.Encoder()
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self.eventStreamDecoder = EventStream.Decoder()
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self.signer = signer
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self.baseURL = baseURL
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self.websocket = websocket
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websocket.onMessageReceived { [weak self] result in
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self?.receive(result: result) ?? false
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}
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websocket.onSocketClosed { [weak self] closeCode in
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self?.onComplete(.unexpectedClosure(closeCode))
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}
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}
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public func register(
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onComplete: @escaping (ServerDisconnection) -> Void
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) {
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self.onComplete = onComplete
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}
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public func register(
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listener: @escaping (FaceLivenessSession.SessionConfiguration) -> Void,
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on event: LivenessEventKind.Server
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) {
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serverEventListeners[event] = listener
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}
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public func initializeLivenessStream(withSessionID sessionID: String, userAgent: String = "") throws {
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var components = URLComponents(url: baseURL, resolvingAgainstBaseURL: false)
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components?.queryItems = [
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URLQueryItem(name: "session-id", value: sessionID),
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URLQueryItem(name: "challenge-versions", value: "FaceMovementAndLightChallenge_1.0.0"),
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URLQueryItem(name: "video-width", value: "480"),
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URLQueryItem(name: "video-height", value: "640"),
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URLQueryItem(name: "x-amz-user-agent", value: userAgent)
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]
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guard let url = components?.url
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else { throw FaceLivenessSessionError.invalidURL }
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let signedConnectionURL = signer.sign(url: url)
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websocket.open(url: signedConnectionURL)
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}
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public func send<T>(
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_ event: LivenessEvent<T>,
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eventDate: () -> Date = Date.init
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) {
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let encodedPayload = eventStreamEncoder.encode(
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payload: event.payload,
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headers: [
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":content-type": .string("application/json"),
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":event-type": .string(event.eventTypeHeader),
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":message-type": .string("event")
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]
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)
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let eventDate = eventDate()
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let signedPayload = signer.signWithPreviousSignature(
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payload: encodedPayload,
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dateHeader: (key: ":date", value: eventDate)
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)
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let encodedEvent = eventStreamEncoder.encode(
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payload: encodedPayload,
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headers: [
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":date": .timestamp(eventDate),
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":chunk-signature": .data(signedPayload)
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]
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)
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websocket.send(
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message: .data(encodedEvent),
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onError: { error in }
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)
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}
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private func fallbackDecoding(_ message: EventStream.Message) -> Bool {
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// We only care about two events above.
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// Just in case the header value changes (it shouldn't)
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// We'll try to decode each of these events
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if let payload = try? JSONDecoder().decode(ServerSessionInformationEvent.self, from: message.payload) {
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let sessionConfiguration = sessionConfiguration(from: payload)
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self.serverEventListeners[.challenge]?(sessionConfiguration)
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} else if (try? JSONDecoder().decode(DisconnectEvent.self, from: message.payload)) != nil {
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onComplete(.disconnectionEvent)
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return false
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}
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return true
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}
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private func receive(result: Result<URLSessionWebSocketTask.Message, Error>) -> Bool {
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switch result {
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case .success(.data(let data)):
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do {
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let message = try self.eventStreamDecoder.decode(data: data)
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guard let eventType = message.headers.first(where: { $0.name == ":event-type" })
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else { return fallbackDecoding(message) }
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switch eventType.value {
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case "ServerSessionInformationEvent":
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// :event-type ServerSessionInformationEvent
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let payload = try JSONDecoder().decode(
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ServerSessionInformationEvent.self, from: message.payload
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)
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let sessionConfiguration = sessionConfiguration(from: payload)
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serverEventListeners[.challenge]?(sessionConfiguration)
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case "DisconnectionEvent":
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// :event-type DisconnectionEvent
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onComplete(.disconnectionEvent)
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return false
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default:
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return true
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}
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} catch {}
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return true
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case .success:
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return true
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case .failure:
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return true
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}
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}
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}

‎AmplifyPlugins/Predictions/AWSPredictionsPlugin/Liveness/Service/FaceLivenessSessionRepresentable.swift‎

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//
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// Copyright Amazon.com Inc. or its affiliates.
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// All Rights Reserved.
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//
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// SPDX-License-Identifier: Apache-2.0
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//
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import Foundation
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import Amplify
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@_spi(PredictionsFaceLiveness)
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public protocol LivenessService {
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func send<T>(
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_ event: LivenessEvent<T>,
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eventDate: () -> Date
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)
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func register(onComplete: @escaping (ServerDisconnection) -> Void)
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func initializeLivenessStream(withSessionID sessionID: String, userAgent: String) throws
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func register(
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listener: @escaping (FaceLivenessSession.SessionConfiguration) -> Void,
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on event: LivenessEventKind.Server
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)
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}
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‎AmplifyPlugins/Predictions/AWSPredictionsPlugin/Liveness/Service/ServerDisconnection.swift‎

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//
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// Copyright Amazon.com Inc. or its affiliates.
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// All Rights Reserved.
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//
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// SPDX-License-Identifier: Apache-2.0
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//
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import Foundation
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@_spi(PredictionsFaceLiveness)
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public enum ServerDisconnection {
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case disconnectionEvent
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case unexpectedClosure(URLSessionWebSocketTask.CloseCode)
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}

‎AmplifyPlugins/Predictions/AWSPredictionsPlugin/Liveness/Service/WebSocketSession.swift‎

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//
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// Copyright Amazon.com Inc. or its affiliates.
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// All Rights Reserved.
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//
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// SPDX-License-Identifier: Apache-2.0
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//
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import Foundation
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final class WebSocketSession {
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private let urlSessionWebSocketDelegate: Delegate
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private let session: URLSession
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private var task: URLSessionWebSocketTask?
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private var receiveMessage: ((Result<URLSessionWebSocketTask.Message, Error>) -> Bool)?
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private var onSocketClosed: ((URLSessionWebSocketTask.CloseCode) -> Void)?
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init() {
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self.urlSessionWebSocketDelegate = Delegate()
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self.session = URLSession(
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configuration: .default,
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delegate: urlSessionWebSocketDelegate,
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delegateQueue: .init()
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)
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}
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func onMessageReceived(_ receive: @escaping (Result<URLSessionWebSocketTask.Message, Error>) -> Bool) {
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self.receiveMessage = receive
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}
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func onSocketClosed(_ onClose: @escaping (URLSessionWebSocketTask.CloseCode) -> Void) {
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urlSessionWebSocketDelegate.onClose = onClose
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}
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func receive(shouldContinue: Bool) {
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guard shouldContinue else { return }
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task?.receive(completionHandler: { [weak self] result in
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if let shouldContinue = self?.receiveMessage?(result) {
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self?.receive(shouldContinue: shouldContinue)
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}
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})
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}
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func open(url: URL) {
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var request = URLRequest(url: url)
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request.setValue("no-store", forHTTPHeaderField: "Cache-Control")
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task = session.webSocketTask(with: request)
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receive(shouldContinue: true)
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task?.resume()
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}
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func close(with code: URLSessionWebSocketTask.CloseCode, reason: Data = .init()) {
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task?.cancel(with: code, reason: reason)
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}
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func send(
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message: URLSessionWebSocketTask.Message,
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onError: @escaping (Error) -> Void
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) {
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task?.send(
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message,
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completionHandler: { error in
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guard let error else { return }
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onError(error)
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}
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)
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}
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final class Delegate: NSObject, URLSessionWebSocketDelegate {
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var onClose: (URLSessionWebSocketTask.CloseCode) -> Void = { _ in }
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var onOpen: () -> Void = {}
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func urlSession(
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_ session: URLSession,
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webSocketTask: URLSessionWebSocketTask,
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didOpenWithProtocol protocol: String?
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) {
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onOpen()
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}
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func urlSession(
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_ session: URLSession,
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webSocketTask: URLSessionWebSocketTask,
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didCloseWith closeCode: URLSessionWebSocketTask.CloseCode,
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reason: Data?
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) {
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onClose(closeCode)
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}
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}
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}

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