Service to manage repeated execution of tasks at specified intervals.

RepeatedTaskServiceProtocol.swift

import Foundation

/// Protocol defining the behavior of a repeated task service.
protocol RepeatedTaskServiceProtocol {
    /// Schedules a repeated task to be executed at specified intervals.
    /// - Parameters:
    ///   - interval: The time interval between executions.
    ///   - repeatCount: The number of times to repeat the task.
    ///   - identifier: The optional unique identifier for the task. If nil, an identifier will be auto-generated.
    func execute(
        every interval: TimeInterval,
        repeatCount: Int,
        withIdentifier identifier: String?,
        task: @Sendable @escaping () -> Void
    ) throws
    
    /// Stops a task with the specified identifier.
    /// - Parameter identifier: The unique identifier for the task.
    func stopTask(withIdentifier identifier: String)
    
    /// Stops all currently scheduled tasks.
    func stopAllTasks()
    
    /// Stops all tasks without explicit identifiers.
    func stopTasksWithoutIdentifiers()
}

extension RepeatedTaskServiceProtocol {
    /// Schedules a repeated task to be executed at specified intervals without an identifier.
    /// - Parameters:
    ///   - interval: The time interval between executions.
    ///   - repeatCount: The number of times to repeat the task.
    ///   - task: The task to be executed.
    func execute(every interval: TimeInterval, repeatCount: Int, task: @Sendable @escaping () -> Void) throws {
        try execute(every: interval, repeatCount: repeatCount, withIdentifier: nil, task: task)
    }
}

enum RepeatedTaskServiceError: Error {
    case identifierAlreadyInUse
}

/// Service to manage repeated execution of tasks at specified intervals.
final class RepeatedTaskService: RepeatedTaskServiceProtocol {
    private var tasks: [String: (task: DispatchWorkItem, isAutoGenerated: Bool)] = [:]
    private let queue = DispatchQueue(label: "RepeatedTaskServiceQueue")
    private var identifierCounter = 0

    init() { }

    /// Schedules a repeated task to be executed at specified intervals.
    /// - Parameters:
    ///   - interval: The time interval between executions.
    ///   - repeatCount: The number of times to repeat the task.
    ///   - task: The task to be executed.
    ///   - identifier: The optional unique identifier for the task. If nil, an identifier will be auto-generated.
    func execute(
        every interval: TimeInterval,
        repeatCount: Int,
        withIdentifier identifier: String?,
        task: @Sendable @escaping () -> Void
    ) throws {
        // Check if the identifier is auto-generated
        let isAutoGenerated = identifier == nil
        
        // Generate a unique identifier if not provided
        let taskIdentifier = identifier ?? generateUniqueIdentifier()
        
        // Check if the identifier is already in use
        guard tasks[taskIdentifier] == nil else {
            throw RepeatedTaskServiceError.identifierAlreadyInUse
        }
        
        // Create a new DispatchWorkItem to execute the task repeatedly
        let newTask = DispatchWorkItem {
            for _ in 0..<repeatCount {
                // Execute the task
                task()
                // Sleep for the specified interval before the next execution
                Thread.sleep(forTimeInterval: interval)
            }
        }
        
        // Store the task with its identifier
        self.tasks[taskIdentifier] = (task: newTask, isAutoGenerated: isAutoGenerated)
        
        // Perform the following actions asynchronously on the queue
        queue.async {
            // Execute the task on a background queue
            DispatchQueue.global(qos: .background).async(execute: newTask)
        }
    }

    /// Stops a task with the specified identifier.
    /// - Parameter identifier: The unique identifier for the task.
    func stopTask(withIdentifier identifier: String) {
        queue.async {
            guard let task = self.tasks[identifier] else { return }
            task.task.cancel()
            self.tasks.removeValue(forKey: identifier)
        }
    }

    /// Stops all currently scheduled tasks.
    func stopAllTasks() {
        queue.async {
            self.tasks.forEach { $0.value.task.cancel() }
            self.tasks.removeAll()
        }
    }

    /// Stops all tasks without explicit identifiers.
    func stopTasksWithoutIdentifiers() {
        queue.async {
            self.tasks.filter { $0.value.isAutoGenerated }.forEach { $0.value.task.cancel() }
            self.tasks = self.tasks.filter { !$0.value.isAutoGenerated }
        }
    }

    private func generateUniqueIdentifier() -> String {
        UUID().uuidString
    }
}