//
//  BGTask.swift
//  PaiAi
//
//  Created by zhengjianfei on 2016/12/23.
//  Copyright © 2016年 FFIB. All rights reserved.
//

import UIKit

class BGTask: NSObject {
    static let instance = BGTask()
    var bgTaskIdlist = [Int]()
    var masterTasjId = UIBackgroundTaskIdentifier()
    class func shareTask() -> BGTask {
        return instance
    }

    func beginNewBackgroundTask() -> UIBackgroundTaskIdentifier {
        let application = UIApplication.shared
        var bgTaskId = UIBackgroundTaskInvalid
        bgTaskId = application.beginBackgroundTask(expirationHandler: {
            self.bgTaskIdlist = self.bgTaskIdlist.filter({ (taskId) -> Bool in
                return taskId != bgTaskId
            })
        })
        if masterTasjId == UIBackgroundTaskInvalid {
            masterTasjId = bgTaskId
        } else {
            bgTaskIdlist.append(bgTaskId)
            endBackgroundTask(all: false)
        }
        return bgTaskId
    }
    func endBackgroundTask(all: Bool) {
        let application = UIApplication.shared

        for _ in 0..<(all ? bgTaskIdlist.count : bgTaskIdlist.count - 1) {
            let bgTaskId = self.bgTaskIdlist.first
            application.endBackgroundTask(bgTaskId!)
            bgTaskIdlist.removeFirst()
        }

        if self.bgTaskIdlist.count > 0 {
            printLog("后台任务正在保持运行\(String(describing: bgTaskIdlist.first))")
        }
        if all {
            application.endBackgroundTask(masterTasjId)
            self.masterTasjId = UIBackgroundTaskInvalid
        } else {
            printLog("keep master background task id \(masterTasjId)")
        }
    }
}