feat: Begins breaking out topic listener and publisher as it's own dependency.

Sources/TopicDependencies/TopicListener.swift

@@ -0,0 +1,133 @@
+import Dependencies
+import DependenciesMacros
+import Foundation
+import MQTTNIO
+
+/// A dependency that can generate an async stream of changes to the given topics.
+///
+/// - Note: This type only conforms to ``TestDependencyKey`` because it requires an MQTTClient
+/// to generate the live dependency.
+@DependencyClient
+public struct TopicListener: Sendable {
+
+  /// Create an async stream that listens for changes to the given topics.
+  private var _listen: @Sendable (_ topics: [String]) async throws -> AsyncThrowingStream<MQTTPublishInfo, any Error>
+
+  /// Shutdown the listener stream.
+  public var shutdown: @Sendable () -> Void
+
+  /// Create a new topic listener.
+  ///
+  /// - Parameters:
+  ///   - listen: Generate an async stream of changes for the given topics.
+  ///   - shutdown: Shutdown the topic listener stream.
+  public init(
+    listen: @Sendable @escaping ([String]) async throws -> AsyncThrowingStream<MQTTPublishInfo, any Error>,
+    shutdown: @Sendable @escaping () -> Void
+  ) {
+    self._listen = listen
+    self.shutdown = shutdown
+  }
+
+  /// Create an async stream that listens for changes to the given topics.
+  ///
+  /// - Parameters:
+  ///   - topics: The topics to listen for changes to.
+  public func listen(to topics: [String]) async throws -> AsyncThrowingStream<MQTTPublishInfo, any Error> {
+    try await _listen(topics)
+  }
+
+  /// Create an async stream that listens for changes to the given topics.
+  ///
+  /// - Parameters:
+  ///   - topics: The topics to listen for changes to.
+  public func listen(_ topics: String...) async throws -> AsyncThrowingStream<MQTTPublishInfo, any Error> {
+    try await listen(to: topics)
+  }
+
+  /// Create the live implementation of the topic listener with the given MQTTClient.
+  ///
+  /// - Parameters:
+  ///   - client: The MQTTClient to use.
+  public static func live(client: MQTTClient) -> Self {
+    let listener = MQTTTopicListener(client: client)
+    return .init(
+      listen: { await listener.listen($0) },
+      shutdown: { listener.shutdown() }
+    )
+  }
+}
+
+extension TopicListener: TestDependencyKey {
+  public static var testValue: TopicListener {
+    Self()
+  }
+}
+
+public extension DependencyValues {
+  var topicListener: TopicListener {
+    get { self[TopicListener.self] }
+    set { self[TopicListener.self] = newValue }
+  }
+}
+
+// MARK: - Helpers
+
+private actor MQTTTopicListener {
+  private let client: MQTTClient
+  private let continuation: AsyncThrowingStream<MQTTPublishInfo, any Error>.Continuation
+  private let name: String
+  let stream: AsyncThrowingStream<MQTTPublishInfo, any Error>
+  private var shuttingDown: Bool = false
+
+  init(
+    client: MQTTClient
+  ) {
+    let (stream, continuation) = AsyncThrowingStream<MQTTPublishInfo, any Error>.makeStream()
+    self.client = client
+    self.continuation = continuation
+    self.name = UUID().uuidString
+    self.stream = stream
+  }
+
+  deinit {
+    if !shuttingDown {
+      let message = """
+      Shutdown was not called on topic listener. This could lead to potential errors or
+      the stream never ending.
+
+      Please ensure that you call shutdown on the listener.
+      """
+      client.logger.warning("\(message)")
+      continuation.finish()
+    }
+    client.removePublishListener(named: name)
+  }
+
+  func listen(_ topics: [String]) async -> AsyncThrowingStream<MQTTPublishInfo, any Error> {
+    assert(client.isActive(), "The client is not connected.")
+    client.addPublishListener(named: name) { result in
+      switch result {
+      case let .failure(error):
+        self.client.logger.error("Received error while listening: \(error)")
+        self.continuation.yield(with: .failure(error))
+      case let .success(publishInfo):
+        if topics.contains(publishInfo.topicName) {
+          self.client.logger.trace("Recieved new value for topic: \(publishInfo.topicName)")
+          self.continuation.yield(publishInfo)
+        }
+      }
+    }
+    return stream
+  }
+
+  private func setIsShuttingDown() {
+    shuttingDown = true
+  }
+
+  nonisolated func shutdown() {
+    client.logger.trace("Closing topic listener...")
+    continuation.finish()
+    Task { await self.setIsShuttingDown() }
+  }
+}

Sources/TopicDependencies/TopicPublisher.swift

@@ -0,0 +1,114 @@
+import Dependencies
+import DependenciesMacros
+import MQTTNIO
+import NIO
+
+/// A dependency that is responsible for publishing values to an MQTT broker.
+///
+/// - Note: This dependency only conforms to `TestDependencyKey` because it
+/// requires an active `MQTTClient` to generate the live dependency.
+@DependencyClient
+public struct TopicPublisher: Sendable {
+
+  private var _publish: @Sendable (PublishRequest) async throws -> Void
+
+  /// Create a new topic publisher.
+  ///
+  /// - Parameters:
+  ///   -  publish: Handle the publish request.
+  public init(
+    publish: @Sendable @escaping (PublishRequest) async throws -> Void
+  ) {
+    self._publish = publish
+  }
+
+  /// Publish a new value to the given topic.
+  ///
+  /// - Parameters:
+  ///   - topicName: The topic to publish the new value to.
+  ///   - payload: The value to publish.
+  ///   - qos: The MQTTQoS.
+  ///   - retain: The retain flag.
+  public func publish(
+    to topicName: String,
+    payload: ByteBuffer,
+    qos: MQTTQoS,
+    retain: Bool = false
+  ) async throws {
+    try await _publish(.init(
+      topicName: topicName,
+      payload: payload,
+      qos: qos,
+      retain: retain
+    ))
+  }
+
+  /// Create the live topic publisher with the given `MQTTClient`.
+  ///
+  /// - Parameters:
+  ///   - client: The mqtt broker client to use.
+  public static func live(client: MQTTClient) -> Self {
+    .init(
+      publish: { request in
+        assert(client.isActive(), "Client not connected.")
+        client.logger.trace("Begin publishing to topic: \(request.topicName)")
+        defer { client.logger.trace("Done publishing to topic: \(request.topicName)") }
+        try await client.publish(
+          to: request.topicName,
+          payload: request.payload,
+          qos: request.qos,
+          retain: request.retain
+        )
+      }
+    )
+  }
+
+  /// Represents the parameters required to publish a new value to the
+  /// MQTT broker.
+  public struct PublishRequest: Equatable, Sendable {
+
+    /// The topic to publish the new value to.
+    public let topicName: String
+
+    /// The value to publish.
+    public let payload: ByteBuffer
+
+    /// The qos of the request.
+    public let qos: MQTTQoS
+
+    /// The retain flag for the request.
+    public let retain: Bool
+
+    /// Create a new publish request.
+    ///
+    /// - Parameters:
+    ///   - topicName: The topic to publish to.
+    ///   - payload: The value to publish.
+    ///   - qos: The qos of the request.
+    ///   - retain: The retain flag of the request.
+    public init(
+      topicName: String,
+      payload: ByteBuffer,
+      qos: MQTTQoS,
+      retain: Bool
+    ) {
+      self.topicName = topicName
+      self.payload = payload
+      self.qos = qos
+      self.retain = retain
+    }
+  }
+}
+
+extension TopicPublisher: TestDependencyKey {
+  public static var testValue: TopicPublisher { Self() }
+}
+
+public extension DependencyValues {
+
+  /// A dependency that is responsible for publishing values to an MQTT broker.
+  var topicPublisher: TopicPublisher {
+    get { self[TopicPublisher.self] }
+    set { self[TopicPublisher.self] = newValue }
+  }
+}