TaskQueue

TaskQueue.swift

import Foundation

public actor TaskQueue {
	private let maxConcurrentTasks: Int
	private var runningTasks = 0
	private var queue: [CheckedContinuation<Void, Never>] = []
	
	public init(maxConcurrentTasks: Int) {
		self.maxConcurrentTasks = maxConcurrentTasks
	}
	
	public func enqueue<T: Sendable, E: Error>(_ task: @escaping @Sendable () async throws(E) -> T) async throws(E) -> T {
		if runningTasks >= maxConcurrentTasks {
			await withCheckedContinuation { continuation in
				queue.append(continuation)
			}
		}
		
		runningTasks += 1
		defer {
			runningTasks -= 1
			if runningTasks < maxConcurrentTasks && !queue.isEmpty {
				queue.removeFirst().resume()
			}
		}
		return try await task()
	}	
}