Make HPPS Callable Functions callable like a plain Swift function

Example:

let greeter = functions.httpsCallable("greeter",
                                                                requestType: GreetingRequest.self,
                                                                responseType: GreetingResponse.self)
let result = try await greeter(data)
print(result.greeting)

Signed-off-by: Peter Friese <[email protected]>

Author: peterfriese

FirebaseFunctionsSwift/Sources/Codable/Callable+Codable.swift

@@ -107,6 +107,26 @@ public struct Callable<Request: Encodable, Response: Decodable> {
     }
   }
 
+  /// Creates a directly callable function.
+  ///
+  /// This allows users to call a HTTPS Callable Funciton like a normal Swift function:
+  ///
+  ///     let greeter = functions.httpsCallable("greeter",
+  ///                                           requestType: GreetingRequest.self,
+  ///                                           responseType: GreetingResponse.self)
+  ///     try greeter(data) { result in
+  ///       print(result.greeting)
+  ///     }
+  ///
+  /// - Parameters:
+  ///   - data: Parameters to pass to the trigger.
+  ///   - completion: The block to call when the HTTPS request has completed.
+  public func callAsFunction(_ data: Request,
+                             completion: @escaping (Result<Response, Error>)
+                               -> Void) throws {
+    try call(data, completion: completion)
+  }
+
   #if compiler(>=5.5) && canImport(_Concurrency)
     /**
      * Executes this Callable HTTPS trigger asynchronously.
@@ -138,5 +158,23 @@ public struct Callable<Request: Encodable, Response: Decodable> {
       let result = try await callable.call(encoded)
       return try decoder.decode(Response.self, from: result.data)
     }
+
+    /// Creates a directly callable function.
+    ///
+    /// This allows users to call a HTTPS Callable Funciton like a normal Swift function:
+    ///
+    ///     let greeter = functions.httpsCallable("greeter",
+    ///                                           requestType: GreetingRequest.self,
+    ///                                           responseType: GreetingResponse.self)
+    ///     let result = try await greeter(data)
+    ///     print(result.greeting)
+    ///
+    /// - Parameters:
+    ///   - data: Parameters to pass to the trigger.
+    /// - Returns: The decoded `Response` value
+    @available(iOS 15, tvOS 15, macOS 12, watchOS 8, *)
+    public func callAsFunction(_ data: Request) async throws -> Response {
+      return try await call(data)
+    }
   #endif
 }

FirebaseFunctionsSwift/Tests/IntegrationTests.swift

@@ -531,4 +531,60 @@ class IntegrationTests: XCTestCase {
       }
     }
   #endif
+
+  func testCallAsFunction() throws {
+    let expectation = expectation(description: #function)
+    let data = DataTestRequest(
+      bool: true,
+      int: 2,
+      long: 9_876_543_210,
+      string: "four",
+      array: [5, 6],
+      null: nil
+    )
+    let function = functions.httpsCallable("dataTest",
+                                           requestType: DataTestRequest.self,
+                                           responseType: DataTestResponse.self)
+    try function(data) { result in
+      do {
+        let response = try result.get()
+        let expected = DataTestResponse(
+          message: "stub response",
+          long: 420,
+          code: 42
+        )
+        XCTAssertEqual(response, expected)
+        expectation.fulfill()
+      } catch {
+        XCTAssert(false, "Failed to unwrap the function result: \(error)")
+      }
+    }
+    waitForExpectations(timeout: 5)
+  }
+
+  #if compiler(>=5.5) && canImport(_Concurrency)
+    @available(iOS 15, tvOS 15, macOS 12, watchOS 8, *)
+    func testCallAsFunctionAsync() async throws {
+      let data = DataTestRequest(
+        bool: true,
+        int: 2,
+        long: 9_876_543_210,
+        string: "four",
+        array: [5, 6],
+        null: nil
+      )
+
+      let function = functions.httpsCallable("dataTest",
+                                             requestType: DataTestRequest.self,
+                                             responseType: DataTestResponse.self)
+
+      let response = try await function(data)
+      let expected = DataTestResponse(
+        message: "stub response",
+        long: 420,
+        code: 42
+      )
+      XCTAssertEqual(response, expected)
+    }
+  #endif
 }