Super simple URL unshortener in Dart

unshortener.dart

import 'dart:io' show HttpRequest, HttpClient, HttpServer, ContentType;
import 'dart:convert' show JSON;

void handleRequest(HttpRequest request) {
  // For convenience.
  var response = request.response;

  // No path is expected. Return with 404 for anything else.
  if (request.uri.path != '' && request.uri.path != '/') {
    response.statusCode = 404;
    response.close();
    return;
  }

  var query = request.uri.queryParameters;

  // If there was no url query parameter, return with 400.
  if (query['url'] == null) {
    response.statusCode = 400;
    response.close();
    return;
  }

  var url = Uri.parse(query['url']);

  // We have the information needed to make a request to a remote server. Create a client.
  var client = new HttpClient();

  // Make a HEAD request to resolve redirects, but avoid unnecessary data.
  client.openUrl('HEAD', url)
    .then((req) => req.close())
    .then((res) {
      // The response will be JSON.
      response.headers.contentType = ContentType.parse('application/json; charset=utf-8');

      // Encode a JSON object with the original and resolved URLs and write it to the response.
      response.write(JSON.encode({
        'original': query['url'],
        'resolved': res.redirects.last.location.toString()
      }));

      response.close();
    });
}

void main() {
  HttpServer.bind('127.0.0.1', 8080)
    .then((server) {
      print('Server listening...');
      server.listen(handleRequest);
    });
}

Thanks for posting. Did you consider not using as with the imports? Usually we only use as if there is real uncertainty or name collisions.

You don't need to import dart:core, you get that one for free.

protip: use show with your imports. It protects your app and makes it clear which library provides what name.

import 'dart:io' show HttpServer;

protip: select the import line and hit Cmd-1 (quick fix) and let Dart Editor manage the show for you.

Thoughts?

The choice to import like this comes from my background with Node. I like keeping modules namespaced. Your show recommendation is nice though. That's a little like doing

var EventEmitter = require('events').EventEmitter; // Only needed EventEmitter.

so I may go that way. I figured that core was free when importing it explicitly like this broke prints, but stuck with it because I'm forced to think about what modules particular things come from as I use them.

Updated to use show. Definitely much nicer.