An asset middleware component for Yahoo! Mojito that uses CouchDB attachments

static_assets_from_couchdb.js

/*jslint anon:true, sloppy:true, nomen:true, white:true, stupid:true*/
var http = require('http')
  , path = require('path')
  , url = require('url')
  , ycb = require('ycb')
  , fs = require('fs')
  ;

var uripattern = /^\/static\/([a-zA-Z0-9\-\._~]+)\/([a-zA-Z0-9\-\._~]+)\/([a-zA-Z0-9\-\._~]+)/
  , configPath = path.join(__dirname, '../', 'application.json')
  , appConfig = JSON.parse(fs.readFileSync(configPath, 'utf8'))
  , appConfig = new ycb.Ycb(appConfig, {})
  ;

function getBody(asseturi, res, next) {
  http.get(asseturi, function(dbfile) {
    var headers = dbfile.headers
      ;

    if (dbfile.statusCode !== 200) {
      return next();
    }

    Object.keys(headers).forEach(function(key) {
      res.setHeader(key, headers[key]);
    });
    dbfile.pipe(res);
  }).on('error', function(e) {
    next(e);
  });
}

module.exports = function(req, res, next) {
  var matches = req.url.match(uripattern)
    , noneMatch = req.headers['if-none-match']
    , config = appConfig.read(req.app.store.getStaticContext())
    , appName = config.staticHandling.appName
    , dburi = config[appName].database.server
    , chapter
    , id
    , attachment
    , headopts
    , asseturipath
    , asseturi
    ;

  if(!matches || matches.length === 0) {
    return next();
  }

  chapter = matches[1];
  id = matches[2];
  attachment = matches[3];
  asseturipath = path.join(chapter, id, attachment);
  asseturi = url.resolve(dburi, asseturipath);

  if (noneMatch) {
    headopts = url.parse(asseturi);
    headopts.method = 'HEAD';
    http.request(headopts)
      .on('response', function(headRes) {
        var headers = headRes.headers
          ;
        headRes.resume();
        if (headRes.headers.etag === noneMatch) {
          headers['content-length'] = 0;
          res.writeHead(304, headers);
          res.end();
        } else {
          getBody(asseturi, res, next);
        }
      }).on('error', function(e) {
        next(e);
      }).end();
  } else {
    getBody(asseturi, res, next);
  }
};