Add ConnectionIDGenerator and NoOpKeepAliveBehavior (#418)

Sources/ConnectionPoolModule/ConnectionIDGenerator.swift

@@ -0,0 +1,15 @@
+import Atomics
+
+public struct ConnectionIDGenerator: ConnectionIDGeneratorProtocol {
+    static let globalGenerator = ConnectionIDGenerator()
+
+    private let atomic: ManagedAtomic<Int>
+
+    public init() {
+        self.atomic = .init(0)
+    }
+
+    public func next() -> Int {
+        return self.atomic.loadThenWrappingIncrement(ordering: .relaxed)
+    }
+}

Sources/ConnectionPoolModule/NoKeepAliveBehavior.swift

@@ -0,0 +1,8 @@
+@available(macOS 13.0, iOS 16.0, tvOS 16.0, watchOS 9.0, *)
+public struct NoOpKeepAliveBehavior<Connection: PooledConnection>: ConnectionKeepAliveBehavior {
+    public var keepAliveFrequency: Duration? { nil }
+
+    public func runKeepAlive(for connection: Connection) async throws {}
+
+    public init(connectionType: Connection.Type) {}
+}

Tests/ConnectionPoolModuleTests/ConnectionIDGeneratorTests.swift

@@ -0,0 +1,22 @@
+import _ConnectionPoolModule
+import XCTest
+
+final class ConnectionIDGeneratorTests: XCTestCase {
+    func testGenerateConnectionIDs() async {
+        let idGenerator = ConnectionIDGenerator()
+
+        XCTAssertEqual(idGenerator.next(), 0)
+        XCTAssertEqual(idGenerator.next(), 1)
+        XCTAssertEqual(idGenerator.next(), 2)
+
+        await withTaskGroup(of: Void.self) { taskGroup in
+            for _ in 0..<1000 {
+                taskGroup.addTask {
+                    _ = idGenerator.next()
+                }
+            }
+        }
+
+        XCTAssertEqual(idGenerator.next(), 1003)
+    }
+}

Tests/ConnectionPoolModuleTests/Mocks/MockConnection.swift

@@ -0,0 +1,74 @@
+import DequeModule
+@testable import _ConnectionPoolModule
+
+// Sendability enforced through the lock
+final class MockConnection: PooledConnection, @unchecked Sendable {
+    typealias ID = Int
+
+    let id: ID
+
+    private enum State {
+        case running([@Sendable ((any Error)?) -> ()])
+        case closing([@Sendable ((any Error)?) -> ()])
+        case closed
+    }
+
+    private let lock = NIOLock()
+    private var _state = State.running([])
+
+    init(id: Int) {
+        self.id = id
+    }
+
+    func onClose(_ closure: @escaping @Sendable ((any Error)?) -> ()) {
+        let enqueued = self.lock.withLock { () -> Bool in
+            switch self._state {
+            case .closed:
+                return false
+
+            case .running(var callbacks):
+                callbacks.append(closure)
+                self._state = .running(callbacks)
+                return true
+
+            case .closing(var callbacks):
+                callbacks.append(closure)
+                self._state = .closing(callbacks)
+                return true
+            }
+        }
+
+        if !enqueued {
+            closure(nil)
+        }
+    }
+
+    func close() {
+        self.lock.withLock {
+            switch self._state {
+            case .running(let callbacks):
+                self._state = .closing(callbacks)
+
+            case .closing, .closed:
+                break
+            }
+        }
+    }
+
+    func closeIfClosing() {
+        let callbacks = self.lock.withLock { () -> [@Sendable ((any Error)?) -> ()] in
+            switch self._state {
+            case .running, .closed:
+                return []
+
+            case .closing(let callbacks):
+                self._state = .closed
+                return callbacks
+            }
+        }
+
+        for callback in callbacks {
+            callback(nil)
+        }
+    }
+}

Tests/ConnectionPoolModuleTests/NoKeepAliveBehaviorTests.swift

@@ -0,0 +1,10 @@
+import _ConnectionPoolModule
+import XCTest
+
+@available(macOS 13.0, iOS 16.0, tvOS 16.0, watchOS 9.0, *)
+final class NoKeepAliveBehaviorTests: XCTestCase {
+    func testNoKeepAlive() {
+        let keepAliveBehavior = NoOpKeepAliveBehavior(connectionType: MockConnection.self)
+        XCTAssertNil(keepAliveBehavior.keepAliveFrequency)
+    }
+}