From e5ba7d87284da64ec5a1216958c91df61854bba6 Mon Sep 17 00:00:00 2001
From: Jakub Skotnicki <1700160+Skoti@users.noreply.github.com>
Date: Wed, 5 Mar 2025 19:59:41 +0100
Subject: [PATCH] add race and timeout/deadline async functions

---
 Sources/AsyncAlgorithms/AsyncRace.swift    |  57 ++++++++++++
 Sources/AsyncAlgorithms/AsyncTimeout.swift | 101 +++++++++++++++++++++
 2 files changed, 158 insertions(+)
 create mode 100644 Sources/AsyncAlgorithms/AsyncRace.swift
 create mode 100644 Sources/AsyncAlgorithms/AsyncTimeout.swift

diff --git a/Sources/AsyncAlgorithms/AsyncRace.swift b/Sources/AsyncAlgorithms/AsyncRace.swift
new file mode 100644
index 00000000..7a3bd524
--- /dev/null
+++ b/Sources/AsyncAlgorithms/AsyncRace.swift
@@ -0,0 +1,57 @@
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the Swift Async Algorithms open source project
+//
+// Copyright (c) 2025 Apple Inc. and the Swift project authors
+// Licensed under Apache License v2.0 with Runtime Library Exception
+//
+// See https://swift.org/LICENSE.txt for license information
+//
+//===----------------------------------------------------------------------===//
+
+/// Returns the value or throws an error, from the first completed or failed operation.
+public func race(_ operations: (@Sendable () async throws -> Void)...) async throws {
+    try await race(operations)
+}
+
+/// Returns the value or throws an error, from the first completed or failed operation.
+public func race<T: Sendable>(_ operations: (@Sendable () async throws -> T)...) async throws -> T? {
+    try await race(operations)
+}
+
+/// Returns the value or throws an error, from the first completed or failed operation.
+public func race<T: Sendable>(_ operations: [@Sendable () async throws -> T]) async throws -> T? {
+    try await withThrowingTaskGroup(of: T.self) { group in
+        operations.forEach { operation in
+            group.addTask { try await operation() }
+        }
+        defer {
+            group.cancelAll()
+        }
+        return try await group.next()
+    }
+}
+
+/// Returns the value or throws an error, from the first completed or failed operation.
+public func race<T: Sendable>(_ operations: (@Sendable () async throws -> T?)...) async throws -> T? {
+    try await race(operations)
+}
+
+/// Returns the value or throws an error, from the first completed or failed operation.
+public func race<T: Sendable>(_ operations: [@Sendable () async throws -> T?]) async throws -> T? {
+    try await withThrowingTaskGroup(of: T?.self) { group in
+        operations.forEach { operation in
+            group.addTask { try await operation() }
+        }
+        defer {
+            group.cancelAll()
+        }
+        let value = try await group.next()
+        switch value {
+        case .none:
+            return nil
+        case let .some(value):
+            return value
+        }
+    }
+}
diff --git a/Sources/AsyncAlgorithms/AsyncTimeout.swift b/Sources/AsyncAlgorithms/AsyncTimeout.swift
new file mode 100644
index 00000000..7c07363c
--- /dev/null
+++ b/Sources/AsyncAlgorithms/AsyncTimeout.swift
@@ -0,0 +1,101 @@
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the Swift Async Algorithms open source project
+//
+// Copyright (c) 2025 Apple Inc. and the Swift project authors
+// Licensed under Apache License v2.0 with Runtime Library Exception
+//
+// See https://swift.org/LICENSE.txt for license information
+//
+//===----------------------------------------------------------------------===//
+
+/**
+ - Parameters:
+    - customError: The failure returned by this closure is thrown when the operation timeouts.
+    If `customError` is `nil`, then `CancellationError` is thrown.
+ */
+@available(macOS 13.0, iOS 16.0, watchOS 9.0, tvOS 16.0, *)
+public func withTimeout<Success: Sendable>(
+    _ duration: ContinuousClock.Duration,
+    tolerance: ContinuousClock.Duration? = nil,
+    customError: (@Sendable () -> Error)? = nil,
+    operation: @Sendable () async throws -> Success
+) async throws -> Success {
+    let clock = ContinuousClock()
+    return try await withDeadline(after: clock.now.advanced(by: duration), tolerance: tolerance, clock: clock, customError: customError, operation: operation)
+}
+
+#if compiler(<6.1)
+/**
+ - Parameters:
+    - customError: The failure returned by this closure is thrown when the operation timeouts.
+    If `customError` is `nil`, then `CancellationError` is thrown.
+ */
+@available(macOS 13.0, iOS 16.0, watchOS 9.0, tvOS 16.0, *)
+public func withTimeout<C: Clock, Success: Sendable>(
+    _ duration: C.Duration,
+    tolerance: C.Duration? = nil,
+    clock: C,
+    customError: (@Sendable () -> Error)? = nil,
+    operation: @Sendable () async throws -> Success
+) async throws -> Success {
+    try await withDeadline(after: clock.now.advanced(by: duration), tolerance: tolerance, clock: clock, customError: customError, operation: operation)
+}
+#endif
+
+/**
+ - Parameters:
+    - customError: The failure returned by this closure is thrown when the operation timeouts.
+    If `customError` is `nil`, then `CancellationError` is thrown.
+ */
+@available(macOS 13.0, iOS 16.0, watchOS 9.0, tvOS 16.0, *)
+public func withTimeout<Success: Sendable>(
+    _ duration: Duration,
+    tolerance: Duration? = nil,
+    clock: any Clock<Duration>,
+    customError: (@Sendable () -> Error)? = nil,
+    operation: @Sendable () async throws -> Success
+) async throws -> Success {
+    try await withoutActuallyEscaping(operation) { operation in
+        try await race(operation) {
+            try await clock.sleep(for: duration, tolerance: tolerance)
+            throw customError?() ?? CancellationError()
+        }.unsafelyUnwrapped
+    }
+}
+
+/**
+ - Parameters:
+    - customError: The failure returned by this closure is thrown when the operation timeouts.
+    If `customError` is `nil`, then `CancellationError` is thrown.
+ */
+@available(macOS 13.0, iOS 16.0, watchOS 9.0, tvOS 16.0, *)
+public func withDeadline<Success: Sendable>(
+    after instant: ContinuousClock.Instant,
+    tolerance: ContinuousClock.Duration? = nil,
+    customError: (@Sendable () -> Error)? = nil,
+    operation: @Sendable () async throws -> Success
+) async throws -> Success {
+    try await withDeadline(after: instant, tolerance: tolerance, clock: .continuous, customError: customError, operation: operation)
+}
+
+/**
+ - Parameters:
+    - customError: The failure returned by this closure is thrown when the operation timeouts.
+    If `customError` is `nil`, then `CancellationError` is thrown.
+ */
+@available(macOS 13.0, iOS 16.0, watchOS 9.0, tvOS 16.0, *)
+public func withDeadline<C: Clock, Success: Sendable>(
+    after instant: C.Instant,
+    tolerance: C.Duration? = nil,
+    clock: C,
+    customError: (@Sendable () -> Error)? = nil,
+    operation: @Sendable () async throws -> Success
+) async throws -> Success {
+    try await withoutActuallyEscaping(operation) { operation in
+        try await race(operation) {
+            try await clock.sleep(until: instant, tolerance: tolerance)
+            throw customError?() ?? CancellationError()
+        }.unsafelyUnwrapped
+    }
+}