Add initial version of the WebSocketService

Author: backslash-f

Sources/SwiftTraderWebSocket/Network/WebSocketService.swift

@@ -0,0 +1,77 @@
+//
+//  WebSocketService.swift
+//
+//
+//  Created by Fernando Fernandes on 02.01.24.
+//
+
+import Foundation
+
+#warning("TODO: Observable, propagate received messages")
+public class WebSocketService {
+    public var session: URLSession = .init(configuration: .default)
+
+    private let urlString: String
+    private let token: String
+    private let clientId: String
+
+    private var webSocketTask: URLSessionWebSocketTask?
+
+    public init(urlString: String,
+                token: String,
+                clientId: String) throws {
+        self.urlString = urlString
+        self.token = token
+        self.clientId = clientId
+
+        try initializeWebSocket()
+        receiveMessage()
+    }
+}
+
+// MARK: - Interface
+
+public extension WebSocketService {
+
+    #warning("TODO: handle received messages as models, throw errors?")
+    func receiveMessage() {
+        webSocketTask?.receive { result in
+            switch result {
+            case .success(let message):
+                switch message {
+                case .string(let text):
+                    print("Received string: \(text)")
+                case .data(let data):
+                    print("Received data: \(data)")
+                @unknown default:
+                    fatalError()
+                }
+                
+                // Listen for the next message.
+                self.receiveMessage()
+
+            case .failure(let error):
+                print("Error in receiving message: \(error)")
+            }
+        }
+    }
+}
+
+// MARK: - Private
+
+private extension WebSocketService {
+    func initializeWebSocket() throws {
+        let webSocketURL = try createWebSocketURL()
+        webSocketTask = session.webSocketTask(with: webSocketURL)
+        webSocketTask?.resume()
+    }
+
+    #warning("TODO: remove this logic from here, this should be done previously")
+    func createWebSocketURL() throws -> URL {
+        let fullURL = "\(urlString)?token=\(token)&connectId=\(clientId)"
+        guard let url = URL(string: fullURL) else {
+            throw SwiftTraderWebSocketError.invalidWebSocketURL(urlString: fullURL)
+        }
+        return url
+    }
+}