crawler.swift

import Foundation

let queue = OperationQueue()
let session = URLSession.shared

if let contents = try? String(contentsOfFile: "./url.txt") {
    let urls = contents.trimmingCharacters(in: .newlines).components(separatedBy: "\n")
    
    for url in urls {
        queue.addOperation(URLChecker(url: url))
    }
}

queue.waitUntilAllOperationsAreFinished()

class URLChecker: Operation {
    private let url: URL
    private let lockQueue = DispatchQueue(label: "net.dictav", attributes: .concurrent)

    init(url str: String) {
        url = URL(string: str)!
    }

    override var isAsynchronous: Bool {
        return true
    }

    private var _isExecuting: Bool = false
    override private(set) var isExecuting: Bool {
        get {
            return lockQueue.sync { () -> Bool in
                return _isExecuting
            }
        }
        set {
            willChangeValue(forKey: "isExecuting")
            lockQueue.sync(flags: [.barrier]) {
                _isExecuting = newValue
            }
            didChangeValue(forKey: "isExecuting")
        }
    }

    private var _isFinished: Bool = false
    override private(set) var isFinished: Bool {
        get {
            return lockQueue.sync { () -> Bool in
                return _isFinished
            }
        }
        set {
            willChangeValue(forKey: "isFinished")
            lockQueue.sync(flags: [.barrier]) {
                _isFinished = newValue
            }
            didChangeValue(forKey: "isFinished")
        }
    }

    override func start() {
        isFinished = false
        isExecuting = true
        main()
    }

    override func main() {
        session.dataTask(with: URLRequest(url: self.url)) { (data, response, error) in
            defer {
                self.isExecuting = false
                self.isFinished = true
            }

            if let err = error {
                print(self.url, err.localizedDescription)
                return
            }

            if let res = response as? HTTPURLResponse {
                print("status: \(res.statusCode)")
            }
        }.resume()
    }
}