画像のurl入れたらキャッシュしてくれるやつ

app.js

/**
 * Module dependencies.
 */

var express = require('express')
  , http = require('http')
  , path = require('path')
  , crypto = require('crypto')
  , fs = require('fs');

var app = express();

var IMAGES_DIR = 'images/';

app.configure(function(){
  app.set('port', process.env.PORT || 3000);
  app.use(express.favicon());
  app.use(express.logger('dev'));
  app.use(express.bodyParser());
  app.use(express.methodOverride());
  app.use(app.router);
  app.use(express.static(path.join(__dirname, 'public')));
});

app.configure('development', function(){
  app.use(express.errorHandler());
});

// GET /?url=http://hoge.com/hoge.png
app.get('/', function (req, res) {
  var image_url = req.query.url
    , extension = '.' + image_url.split('.').pop();

  if (!image_url.match(/\.(jpg|jpeg|gif|png)$/)) {
    res.send(400, 'Bad Request: url must have extension (.jpg, .jpeg, .gif, .png)');
    return;
  }

  var sha1 = crypto.createHash('sha1');
  sha1.update(image_url, 'ascii');
  var filename = sha1.digest('hex') + extension;

  res.sendfile(IMAGES_DIR + filename, function (err) {
    if (!err) {
      return;
    }

    http.get(image_url, function (res_from_external) {
      if (res_from_external.statusCode !== 200) {
        res.send(404);
        return;
      }

      var ws = fs.createWriteStream(IMAGES_DIR + filename);
      res_from_external.on('data', function (data) {
        ws.write(data, 'binary');
      })
      .on('end', function () {
        ws.end();
        res.sendfile(IMAGES_DIR + filename);
      });
    });
  });
});

http.createServer(app).listen(app.get('port'), function(){
  console.log("Express server listening on port " + app.get('port'));
});

express使うほどじゃなかった