Streamable HTTPCallable functions

FirebaseFunctions/Sources/Functions.swift

@@ -471,6 +471,105 @@ enum FunctionsConstants {
     }
   }
 
+  @available(iOS 13, macCatalyst 13, macOS 10.15, tvOS 13, watchOS 7, *)
+  func stream(at url: URL,
+              withObject data: Any?,
+              options: HTTPSCallableOptions?,
+              timeout: TimeInterval) async throws
+    -> AsyncThrowingStream<HTTPSCallableResult, Error> {
+    let context = try await contextProvider.context(options: options)
+    let fetcher = try makeFetcherForStreamableContent(
+      url: url,
+      data: data,
+      options: options,
+      timeout: timeout,
+      context: context
+    )
+
+    do {
+      let rawData = try await fetcher.beginFetch()
+      return try callableResultFromResponseAsync(data: rawData, error: nil)
+    } catch {
+      // This method always throws when `error` is not `nil`, but ideally,
+      // it should be refactored so it looks less confusing.
+      return try callableResultFromResponseAsync(data: nil, error: error)
+    }
+  }
+
+  @available(iOS 13.0, *)
+  func callableResultFromResponseAsync(data: Data?,
+                                       error: Error?) throws -> AsyncThrowingStream<
+    HTTPSCallableResult, Error
+
+  > {
+    let processedData =
+      try processResponseDataForStreamableContent(
+        from: data,
+        error: error
+      )
+
+    return processedData
+  }
+
+  private func makeFetcherForStreamableContent(url: URL,
+                                               data: Any?,
+                                               options: HTTPSCallableOptions?,
+                                               timeout: TimeInterval,
+                                               context: FunctionsContext) throws
+    -> GTMSessionFetcher {
+    let request = URLRequest(
+      url: url,
+      cachePolicy: .useProtocolCachePolicy,
+      timeoutInterval: timeout
+    )
+    let fetcher = fetcherService.fetcher(with: request)
+
+    let data = data ?? NSNull()
+    let encoded = try serializer.encode(data)
+    let body = ["data": encoded]
+    let payload = try JSONSerialization.data(withJSONObject: body, options: [.fragmentsAllowed])
+    fetcher.bodyData = payload
+
+    // Set the headers for starting a streaming session.
+    fetcher.setRequestValue("application/json", forHTTPHeaderField: "Content-Type")
+    fetcher.setRequestValue("text/event-stream", forHTTPHeaderField: "Accept")
+    fetcher.request?.httpMethod = "POST"
+    if let authToken = context.authToken {
+      let value = "Bearer \(authToken)"
+      fetcher.setRequestValue(value, forHTTPHeaderField: "Authorization")
+    }
+
+    if let fcmToken = context.fcmToken {
+      fetcher.setRequestValue(fcmToken, forHTTPHeaderField: Constants.fcmTokenHeader)
+    }
+
+    if options?.requireLimitedUseAppCheckTokens == true {
+      if let appCheckToken = context.limitedUseAppCheckToken {
+        fetcher.setRequestValue(
+          appCheckToken,
+          forHTTPHeaderField: Constants.appCheckTokenHeader
+        )
+      }
+    } else if let appCheckToken = context.appCheckToken {
+      fetcher.setRequestValue(
+        appCheckToken,
+        forHTTPHeaderField: Constants.appCheckTokenHeader
+      )
+    }
+    // Remove after genStream is updated on the emulator or deployed
+    #if DEBUG
+      fetcher.allowLocalhostRequest = true
+      fetcher.allowedInsecureSchemes = ["http"]
+    #endif
+    // Override normal security rules if this is a local test.
+    if emulatorOrigin != nil {
+      fetcher.allowLocalhostRequest = true
+      fetcher.allowedInsecureSchemes = ["http"]
+    }
+
+    return fetcher
+  }
+
   private func makeFetcher(url: URL,
                            data: Any?,
                            options: HTTPSCallableOptions?,
@@ -556,6 +655,58 @@ enum FunctionsConstants {
     return data
   }
 
+  @available(iOS 13, macCatalyst 13, macOS 10.15, tvOS 13, watchOS 7, *)
+  private func processResponseDataForStreamableContent(from data: Data?,
+                                                       error: Error?) throws
+    -> AsyncThrowingStream<
+      HTTPSCallableResult,
+      Error
+    > {
+    return AsyncThrowingStream { continuation in
+      Task {
+        var resultArray = [String]()
+        do {
+          if let error = error {
+            throw error
+          }
+
+          guard let data = data else {
+            throw NSError(domain: FunctionsErrorDomain.description, code: -1, userInfo: nil)
+          }
+
+          if let dataChunk = String(data: data, encoding: .utf8) {
+            // We remove the "data :" field so it can be safely parsed to Json.
+            let dataChunkToJson = dataChunk.split(separator: "\n").map {
+              String($0.dropFirst(6))
+            }
+            resultArray.append(contentsOf: dataChunkToJson)
+          } else {
+            throw NSError(domain: FunctionsErrorDomain.description, code: -1, userInfo: nil)
+          }
+
+          for dataChunk in resultArray {
+            let json = try callableResult(
+              fromResponseData: dataChunk.data(
+                using: .utf8,
+                allowLossyConversion: true
+              ) ?? Data()
+            )
+            continuation.yield(HTTPSCallableResult(data: json.data))
+          }
+
+          continuation.onTermination = { @Sendable _ in
+            // Callback for cancelling the stream
+            continuation.finish()
+          }
+          // Close the stream once it's done
+          continuation.finish()
+        } catch {
+          continuation.finish(throwing: error)
+        }
+      }
+    }
+  }
+
   private func responseDataJSON(from data: Data) throws -> Any {
     let responseJSONObject = try JSONSerialization.jsonObject(with: data)
 
@@ -564,8 +715,10 @@ enum FunctionsConstants {
       throw FunctionsError(.internal, userInfo: userInfo)
     }
 
-    // `result` is checked for backwards compatibility:
-    guard let dataJSON = responseJSON["data"] ?? responseJSON["result"] else {
+    // `result` is checked for backwards compatibility,
+    // `message` is checked for StramableContent:
+    guard let dataJSON = responseJSON["data"] ?? responseJSON["result"] ?? responseJSON["message"]
+    else {
       let userInfo = [NSLocalizedDescriptionKey: "Response is missing data field."]
       throw FunctionsError(.internal, userInfo: userInfo)
     }

FirebaseFunctions/Sources/HTTPSCallable.swift

@@ -143,4 +143,11 @@ open class HTTPSCallable: NSObject {
     try await functions
       .callFunction(at: url, withObject: data, options: options, timeout: timeoutInterval)
   }
+
+  @available(iOS 13, tvOS 13, macOS 10.15, macCatalyst 13, watchOS 7, *)
+  open func stream(_ data: Any? = nil) async throws
+    -> AsyncThrowingStream<HTTPSCallableResult, Error> {
+    try await functions
+      .stream(at: url, withObject: data, options: options, timeout: timeoutInterval)
+  }
 }

FirebaseFunctions/Tests/Unit/FunctionsTests.swift

@@ -358,4 +358,88 @@ class FunctionsTests: XCTestCase {
     }
     waitForExpectations(timeout: 1.5)
   }
+
+  func testGenerateStreamContent() async throws {
+    let options = HTTPSCallableOptions(requireLimitedUseAppCheckTokens: true)
+    var response = [String]()
+    let responseQueue = DispatchQueue(label: "responseQueue")
+
+    let input: [String: Any] = ["data": "Why is the sky blue"]
+      let stream = try await functions?.stream(
+        at: URL(string: "http://127.0.0.1:5001/demo-project/us-central1/genStream")!,
+        withObject: input,
+        options: options,
+        timeout: 4.0
+      )
+      // First chunk of the stream comes as NSDictionary
+      if let stream = stream {
+        for try await result in stream {
+          if let dataChunk = result.data as? NSDictionary {
+            for (key, value) in dataChunk {
+              responseQueue.sync {
+                response.append("\(key) \(value)")
+              }
+            }
+          } else {
+            // Last chunk is the concatenated result so we have to parse it as String else will
+            // fail.
+            if let dataString = result.data as? String {
+              responseQueue.sync {
+                response.append(dataString)
+              }
+            }
+          }
+        }
+        XCTAssertEqual(
+          response,
+          [
+            "chunk hello",
+            "chunk world",
+            "chunk this",
+            "chunk is",
+            "chunk cool",
+            "hello world this is cool",
+          ]
+        )
+      }
+      XCTExpectFailure("Failed to download stream")
+  }
+
+  func testGenerateStreamContentCanceled() async {
+    let options = HTTPSCallableOptions(requireLimitedUseAppCheckTokens: true)
+    let input: [String: Any] = ["data": "Why is the sky blue"]
+
+    let task = Task.detached { [self] in
+      let stream = try await functions!.stream(
+        at: URL(string: "http://127.0.0.1:5001/demo-project/us-central1/genStream")!,
+        withObject: input,
+        options: options,
+        timeout: 4.0
+      )
+      // First chunk of the stream comes as NSDictionary
+      var response = [String]()
+      for try await result in stream {
+        if let dataChunk = result.data as? NSDictionary {
+          for (key, value) in dataChunk {
+            response.append("\(key) \(value)")
+          }
+        } else {
+          // Last chunk is the concatenated result so we have to parse it as String else will
+          // fail.
+          if let dataString = result.data as? String {
+            response.append(dataString)
+          }
+        }
+      }
+      // Since we cancel the call we are expecting an empty array.
+      XCTAssertEqual(
+        response,
+        []
+      )
+    }
+    // We cancel the task and we expect a null response even if the stream was initiated.
+    task.cancel()
+    let result = await task.result
+    XCTAssertNotNil(result)
+  }
 }