//
//  BackgroundTaskManager.swift
//  Earthquake Network
//
//  Created by Andrea Busi on 16/08/23.
//  Copyright © 2023 Earthquake Network. All rights reserved.
//

import Foundation
import BackgroundTasks


@objc
class BackgroundTaskManager: NSObject {
    
    @objc
    static let shared = BackgroundTaskManager()
    
    private let identifiers: [BackgroundTaskIdentifiable.Type] = [UpdateUserLocationTask.self]

    // MARK: - Public
    
    @objc
    func registerTasks() {
        identifiers
            .forEach { taskIdentifiable in
                BGTaskScheduler.shared.register(forTaskWithIdentifier: taskIdentifiable.identifier, using: DispatchQueue.global()) { [weak self] task in
                    guard let appTask = task as? BGAppRefreshTask else { return }
                    
                    self?.handleTask(appTask, with: taskIdentifiable)
                    self?.scheduleTaskRequest(for: taskIdentifiable)
                }
            }
    }
    
    // MARK: - Public
    
    @objc
    func scheduleUpdateServerPosition() {
        scheduleTaskRequest(for: UpdateUserLocationTask.self)
    }
    
    
    // MARK: - Private

    private func scheduleTaskRequest(
        for taskIdentifiable: BackgroundTaskIdentifiable.Type
    ) {
        let request = BGAppRefreshTaskRequest(identifier: taskIdentifiable.identifier)
        // Fetch no earlier than X minutes from now
        request.earliestBeginDate = Date(timeIntervalSinceNow: taskIdentifiable.interval)
        //request.requiresNetworkConnectivity = true
        
        do {
            try BGTaskScheduler.shared.submit(request)
            print("[BackgroundTaskManager] Background task scheduler submitted")
        } catch {
            print("[BackgroundTaskManager] Could not schedule background taksk. Error: \(error)")
        }
    }
    
    private func handleTask(
        _ appTask: BGAppRefreshTask,
        with taskIdentifiable: BackgroundTaskIdentifiable.Type
    ) {
        // create a task
        let task = taskIdentifiable.init()
        
        // Provide the background task with an expiration handler that cancels the operation.
        appTask.expirationHandler = {
            task.exipration()
        }
        
        // Handle workload
        task.handle(appTask) { success in
            // Inform the system that the background task is complete
            // when the operation completes.
            appTask.setTaskCompleted(success: success)
        }
    }
}