Use NWConnection instead of URLSessionWebSocketTask (#10)

- Replace URLSessionWebSocketTask with NWConnection
- Conform to published behavior of web browsers' WebSocket
- Add support for Swift Concurrency

Author: atdrendel

.github/workflows/ci.yml

@@ -0,0 +1,12 @@
+on: push
+
+jobs:
+  test:
+    runs-on: macos-12
+    
+    steps:
+      - uses: actions/checkout@v2
+      # Available environments: https://github.com/actions/virtual-environments/blob/main/images/macos/macos-12-Readme.md#xcode
+      - run: xcversion select 13.3
+      - run: swift package resolve
+      - run: swift test --skip-update

.github/workflows/swift.yml

@@ -1,6 +1,8 @@
 --funcattributes prev-line
 --minversion 0.47.2
---maxwidth 100
+--maxwidth 96
 --typeattributes prev-line
 --wraparguments before-first
+--wrapparameters before-first
 --wrapcollections before-first
+--xcodeindentation enabled

.swiftformat

@@ -4,36 +4,23 @@ import PackageDescription
 let package = Package(
     name: "WebSocket",
     platforms: [
-        .macOS(.v10_15), .iOS(.v13), .tvOS(.v13), .watchOS(.v6),
+        .macOS(.v11), .iOS(.v14), .tvOS(.v14), .watchOS(.v7),
     ],
     products: [
         .library(
             name: "WebSocket",
             targets: ["WebSocket"]
-        )],
-    dependencies: [
-        .package(
-            name: "Synchronized",
-            url: "https://github.com/shareup/synchronized.git",
-            from: "3.0.0"
         ),
-        .package(
-            name: "WebSocketProtocol",
-            url: "https://github.com/shareup/websocket-protocol.git",
-            from: "2.3.2"
-        ),
-        .package(name: "swift-nio", url: "https://github.com/apple/swift-nio.git", from: "2.0.0")],
+    ],
+    dependencies: [],
     targets: [
         .target(
             name: "WebSocket",
-            dependencies: ["Synchronized", "WebSocketProtocol"]),
+            dependencies: []
+        ),
         .testTarget(
             name: "WebSocketTests",
-            dependencies: [
-                .product(name: "NIO", package: "swift-nio"),
-                .product(name: "NIOHTTP1", package: "swift-nio"),
-                .product(name: "NIOWebSocket", package: "swift-nio"),
-                "WebSocket",
-            ])
+            dependencies: ["WebSocket"]
+        ),
     ]
 )

Package.resolved

@@ -2,31 +2,32 @@
 
 ## _(macOS, iOS, iPadOS, tvOS, and watchOS)_
 
-A concrete implementation of a WebSocket client implemented by wrapping Apple's `URLSessionWebSocketTask` and conforming to [`WebSocketProtocol`](https://github.com/shareup/websocket-protocol). `WebSocket` exposes a simple API and conforms to Apple's Combine [`Publisher`](https://developer.apple.com/documentation/combine/publisher).
+A concrete implementation of a WebSocket client implemented by wrapping Apple's [`NWConnection`](https://developer.apple.com/documentation/network/nwconnection).
+
+The public "interface" of `WebSocket` is a simple struct whose public "methods" are exposed as closures. The reason for this design is to make it easy to inject fake `WebSocket`s into your code for testing purposes.
+
+The actual implementation is `SystemWebSocket`, but this type is not publicly accessible. Instead, you can access it via `WebSocket.system(url:)`. `SystemWebSocket` tries its best to mirror the documented behavior of web browsers' [`WebSocket`](http://developer.mozilla.org/en-US/docs/Web/API/WebSocket). Please report any deviations as bugs.
+
+`WebSocket` exposes a simple API, makes heavy use of [Swift Concurrency](https://developer.apple.com/documentation/swift/swift_standard_library/concurrency), and conforms to Apple's Combine [`Publisher`](https://developer.apple.com/documentation/combine/publisher).
 
 ## Usage
 
 ```swift
-let socket = WebSocket(url: url(49999))
-
-let sub = socket.sink(
-	receiveCompletion: { print("Socket closed: \(String(describing: $0))") },
-	receiveValue: { (result) in
-		switch result {
-		case .success(.open):
-			socket.send("First message")
-		case .success(.string(let incoming)):
-			print("Received \(incoming)")
-		case .failure:
-			socket.close()
-		default:
-			break
-		}
-	}
-)
-defer { sub.cancel() }
-
-socket.connect()
+// `WebSocket` starts connecting to the specified `URL` immediately.
+let socket = WebSocket.system(url: url(49999))
+
+// Wait for `WebSocket` to be ready to send and receive messages.
+try await socket.open()
+
+// Send a message to the server
+try await socket.send(.text("hello"))
+
+// Receive messages from the server
+for await message in socket.messages {
+    print(message)
+}
+
+try await socket.close()
 ```
 
 ## Tests