Download file in JSBox using Objective-C APIs

objc-downloader.js

$define({
  type: "DownloadEventHandler: NSObject<NSURLSessionDownloadDelegate>",
  props: ["handlers"],
  events: {
    "URLSession:downloadTask:didFinishDownloadingToURL:": (session, task, location) => {
      const data = $objc("NSData").$dataWithContentsOfURL(location).$copy();
      const filename = task.$response().$suggestedFilename();
      const result = {
        "url": task.$originalRequest().$URL().$absoluteString().jsValue(),
        "data": data.jsValue(),
        "status": task.$error() == false,
        "response": task.$response().jsValue(),
        "error": task.$error().jsValue(),
      };

      self.$handlers().finished(result);
    },
    "URLSession:downloadTask:didWriteData:totalBytesWritten:totalBytesExpectedToWrite:": (session, task, bytes, written, expected) => {
      const progress = written / expected;
      self.$handlers().downloading(progress);
    },
    "URLSession:task:didCompleteWithError:": (session, task, error) => {
      self.$handlers().failed(error ? error.jsValue() : null);
    }
  }
});

function download(params) {
  params = params || {};
  params.handlers = params.handlers || {};

  const url = params.url;
  const method = params.method || "GET";
  const timeout = params.timeout || 60;
  const header = params.header || {};
  const body = params.body;
  const handlers = params.handlers;

  const request = $objc("NSMutableURLRequest").$requestWithURL($objc("NSURL").$URLWithString(url));
  request.$setHTTPMethod(method);
  request.$setTimeoutInterval(timeout);
  request.$setHTTPShouldUsePipelining(true);

  for (const [key, value] of Object.entries(header)) {
    request.$addValue_forHTTPHeaderField(value, key);
  }

  if (body) {
    request.$setHTTPBody(body.ocValue());
  }

  const config = $objc("NSURLSessionConfiguration").$defaultSessionConfiguration();
  const delegate = $objc("DownloadEventHandler").$new();
  $objc_retain(delegate);

  delegate.$setHandlers({
    downloading: progress => {
      if (handlers.downloading) {
        handlers.downloading(progress);
      }
    },
    finished: result => {
      if (handlers.finished) {
        handlers.finished(result);
      }
      $objc_release(delegate);
    },
    failed: error => {
      if (handlers.failed && error) {
        handlers.failed(error);
      }
      $objc_release(delegate);
    }
  });

  const queue = $objc("NSOperationQueue").$mainQueue();
  const session = $objc("NSURLSession").$sessionWithConfiguration_delegate_delegateQueue(config, delegate, queue);
  session.$setHTTPMaximumConnectionsPerHost(500);

  const task = session.$downloadTaskWithRequest(request);
  task.$resume();
}

// exports.download = download;

download({
  "url": "https://www.apple.com/v/iphone/home/z/images/overview/the_ultimate_iphone_large_2x.jpg",
  "method": "GET",  // Optional, default to GET
  "timeout": 60,    // Optional, default to 60
  "header": {},     // Optional, default to {}
  "body": null,     // Optional, default to null
  "handlers": {
    downloading: progress => {
      console.log(`Downloading: ${progress}`);
    },
    finished: result => {
      console.log(`Finished: ${JSON.stringify(result)}`);

      // props: url, data, status, response, error
      const data = result.data;
      if (data) {
        $share.sheet(data);
      }
    },
    failed: error => {
      console.log(`Failed: ${error}`);
    }
  }
});