Download DouYin video from shared link using Swift

//
//  DouYinVideoParser.swift
//  Transformer
//
//  Created by Forever Positive on 2021/2/15.
//

import Foundation
class DouYinVideoDownloader:NSObject,URLSessionTaskDelegate {
    
    private var callback:((URL?)->Void)!
    
    private var queue:OperationQueue!
    
    private static  var detector:NSDataDetector = try! NSDataDetector(types: NSTextCheckingResult.CheckingType.link.rawValue)
    
    /**
     
     杨超越靠什么走上人生巅峰？她看似躺赢的人生背后到底是谁在暗中操控？今天的视频楠哥为你解谜：杨超越背后的资本迷局  https://v.douyin.com/JKEVKVQ/ 椱制此链接，打开Dou音搜索，値接观kan视频！
     
     */
    
    private static func parseURLInShareText(_ text:String) -> String?{
        
        let detector = Self.detector;
        let matches = detector.matches(in: text, options: [], range: NSRange(location: 0, length: text.utf16.count))
        
        if let first = matches.first{
            let range = Range(first.range, in: text)!
            let url = text[range];
            print("分享文字中的URL:\(url)")
            return String(url);
        }
        return nil;
    }
    
    
    
    private  func onFinish(localURL:URL?){
        let callback = self.callback;
        DispatchQueue.main.async {
            callback?(localURL)
        }
    }
    
    
    public  func beginDownloading(_ shareText:String,callback:@escaping (URL?) -> Void){
        
        self.callback = callback;
        
        if let shareUrlStr = Self.parseURLInShareText(shareText),let url = URL(string: shareUrlStr){
            
            
            let queue = OperationQueue()
            self.queue = queue;
            self.queue.addOperation {
                let config = URLSessionConfiguration.default
                let session = URLSession(configuration: config, delegate: self, delegateQueue: queue);
                let task = session.dataTask(with: url) {(data, response, error) in
                }
                task.resume()
            }
            
          
        }
    }
    
    // MARK: - URLSessionDelete
    func urlSession(_ session: URLSession, task: URLSessionTask, willPerformHTTPRedirection response: HTTPURLResponse, newRequest request: URLRequest, completionHandler: @escaping (URLRequest?) -> Void) {
     
        //redirect to: https://www.iesdouyin.com/share/video/6928193122853784845/?region=CN&mid=6928193379415182087&u_code=18mgdm019&titleType=title&did=1662096460754429&iid=2938317180253068&timestamp=1613368782&app=aweme&utm_campaign=client_share&utm_medium=ios&tt_from=copy&utm_source=copy
        
      
        //json url = https://www.iesdouyin.com/web/api/v2/aweme/iteminfo/?item_ids=6928193122853784845
        if let url = request.url{
            let videoId = url.lastPathComponent;
            let dataURL = "https://www.iesdouyin.com/web/api/v2/aweme/iteminfo/?item_ids=\(videoId)"
            let task = URLSession.shared.dataTask(with: URL(string: dataURL)!) {[weak self] (data, response, error) in
                
                
                guard let `self` = self else{
                    return
                }
                
                guard let data = data, let json = try? JSONSerialization.jsonObject(with: data, options: .allowFragments) as? [String:Any] else {
                    self.onFinish(localURL: nil);
                    return
                }
                print("视频JSON:\(json)")
                
                if let item_list = json["item_list"] as? [[String:Any]],let content = item_list.first{
                    guard let video = content["video"] as? [String:Any],
                          let play_addr = video["play_addr"] as? [String:Any],
                          let url_list = play_addr["url_list"] as? [String],
                          let wmVideoURLStr = url_list.first else{
                        
                        self.onFinish(localURL: nil);
                        return;
                    }
                    let videoURLString = wmVideoURLStr.replacingOccurrences(of: "playwm", with: "play")
                    let finalURL = URL(string: videoURLString)!
                    print("最终下载url:\(finalURL)")
                    
                  

                    let task = URLSession.shared.downloadTask(with: finalURL) { localURL, urlResponse, error in
                        if let localURL = localURL {
                            let localFileName = "\(videoId)-\(UInt64(Date.timeIntervalSinceReferenceDate)).mp4";
                            let newLocalPath = (NSTemporaryDirectory() as NSString).appendingPathComponent(localFileName);
                            let newLocalURL = URL(fileURLWithPath: newLocalPath)
                            if let _ = try? FileManager.default.moveItem(at: localURL, to:newLocalURL){
                                self.onFinish(localURL: newLocalURL)
                            }else{
                                self.onFinish(localURL: nil)
                            }
                        }
                    }

                    task.resume()
                    
                    
                    
                    
                }else{
                    self.onFinish(localURL: nil);
                }

            }
            task.resume()
            
            
         
        }else{
            self.onFinish(localURL: nil);
        }

        

    }
}