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//===----------------------------------------------------------------------===//
//
// This source file is part of the SwiftNIO open source project
//
// Copyright (c) 2022-2023 Apple Inc. and the SwiftNIO project authors
// Licensed under Apache License v2.0
//
// See LICENSE.txt for license information
// See CONTRIBUTORS.txt for the list of SwiftNIO project authors
//
// SPDX-License-Identifier: Apache-2.0
//
//===----------------------------------------------------------------------===//
/// A ``NIOAsyncChannelOutboundWriter`` is used to write and flush new outbound messages in a channel.
///
/// The writer acts as a bridge between the Concurrency and NIO world. It allows to write and flush messages into the
/// underlying ``Channel``. Furthermore, it respects back-pressure of the channel by suspending the calls to write until
/// the channel becomes writable again.
@available(macOS 10.15, iOS 13, tvOS 13, watchOS 6, *)
public struct NIOAsyncChannelOutboundWriter<OutboundOut: Sendable>: Sendable {
@usableFromInline
typealias _Writer = NIOAsyncChannelOutboundWriterHandler<OutboundOut>.Writer
/// An `AsyncSequence` backing a ``NIOAsyncChannelOutboundWriter`` for testing purposes.
public struct TestSink: AsyncSequence {
public typealias Element = OutboundOut
@usableFromInline
internal let stream: AsyncStream<OutboundOut>
@usableFromInline
internal let continuation: AsyncStream<OutboundOut>.Continuation
@inlinable
init(
stream: AsyncStream<OutboundOut>,
continuation: AsyncStream<OutboundOut>.Continuation
) {
self.stream = stream
self.continuation = continuation
}
public func makeAsyncIterator() -> AsyncIterator {
AsyncIterator(iterator: self.stream.makeAsyncIterator())
}
public struct AsyncIterator: AsyncIteratorProtocol {
@usableFromInline
internal var iterator: AsyncStream<OutboundOut>.AsyncIterator
@inlinable
init(iterator: AsyncStream<OutboundOut>.AsyncIterator) {
self.iterator = iterator
}
public mutating func next() async -> Element? {
await self.iterator.next()
}
}
}
@usableFromInline
enum Backing: Sendable {
case asyncStream(AsyncStream<OutboundOut>.Continuation)
case writer(_Writer)
}
@usableFromInline
internal let _backing: Backing
/// Creates a new ``NIOAsyncChannelOutboundWriter`` backed by a ``NIOAsyncChannelOutboundWriter/TestSink``.
/// This is mostly useful for testing purposes where one wants to observe the written data.
@inlinable
public static func makeTestingWriter() -> (Self, TestSink) {
var continuation: AsyncStream<OutboundOut>.Continuation!
let asyncStream = AsyncStream<OutboundOut> { continuation = $0 }
let writer = Self(continuation: continuation)
let sink = TestSink(stream: asyncStream, continuation: continuation)
return (writer, sink)
}
@inlinable
init(
channel: Channel,
isOutboundHalfClosureEnabled: Bool,
closeOnDeinit: Bool
) throws {
let handler = NIOAsyncChannelOutboundWriterHandler<OutboundOut>(
eventLoop: channel.eventLoop,
isOutboundHalfClosureEnabled: isOutboundHalfClosureEnabled
)
let writer = _Writer.makeWriter(
elementType: OutboundOut.self,
isWritable: true,
finishOnDeinit: closeOnDeinit,
delegate: .init(handler: handler)
)
handler.sink = writer.sink
handler.writer = writer.writer
try channel.pipeline.syncOperations.addHandler(handler)
self._backing = .writer(writer.writer)
}
@inlinable
init(continuation: AsyncStream<OutboundOut>.Continuation) {
self._backing = .asyncStream(continuation)
}
/// Send a write into the ``ChannelPipeline`` and flush it right away.
///
/// This method suspends if the underlying channel is not writable and will resume once the it becomes writable again.
@inlinable
public func write(_ data: OutboundOut) async throws {
switch self._backing {
case .asyncStream(let continuation):
continuation.yield(data)
case .writer(let writer):
try await writer.yield(data)
}
}
/// Send a sequence of writes into the ``ChannelPipeline`` and flush them right away.
///
/// This method suspends if the underlying channel is not writable and will resume once the it becomes writable again.
@inlinable
public func write<Writes: Sequence>(contentsOf sequence: Writes) async throws where Writes.Element == OutboundOut {
switch self._backing {
case .asyncStream(let continuation):
for data in sequence {
continuation.yield(data)
}
case .writer(let writer):
try await writer.yield(contentsOf: sequence)
}
}
/// Send an asynchronous sequence of writes into the ``ChannelPipeline``.
///
/// This will flush after every write.
///
/// This method suspends if the underlying channel is not writable and will resume once the it becomes writable again.
@inlinable
public func write<Writes: AsyncSequence>(contentsOf sequence: Writes) async throws where Writes.Element == OutboundOut {
for try await data in sequence {
try await self.write(data)
}
}
/// Finishes the writer.
///
/// This might trigger a half closure if the ``NIOAsyncChannel`` was configured to support it.
public func finish() {
switch self._backing {
case .asyncStream(let continuation):
continuation.finish()
case .writer(let writer):
writer.finish()
}
}
}
@available(macOS 10.15, iOS 13, tvOS 13, watchOS 6, *)
extension NIOAsyncChannelOutboundWriter.TestSink: Sendable {}
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