architect http plugin for dynamic component building

component-build.js

module.exports = setup;
setup.consumes = ["http"];

function setup(config, imports, register) {
    imports.http.wrap(require('./middleware')(config));
    register();
}

middleware.js

module.exports = function (config) {
    var Builder = require('component-builder');
    var cssUrl = config.cssUrl || "/build/build.css";
    var jsUrl = config.jsUrl || "/build/build.js";

    // Monkeypatch Builder to rewrite urls in css when concatting them.
    var rootLength = config.componentPath.length;
    if (config.componentPath[rootLength - 1] !== "/") rootLength++;
    Builder.prototype.buildStyles = function(fn){
      this.buildType('styles', fn, function (builder, file, css) {
        var prefix = "../" + builder.dir.substr(rootLength) + "/";
        var index = file.lastIndexOf("/");
        if (index >= 0) {
          prefix += file.substr(0, index + 1);
        }
        return css.replace(/url\(['"][^\/][^'"]+['"]\)/g, function (css) {
          css = "url(" + css[4] + prefix + css.substr(5);
          return css;
        });
      });
    };

    var queue;
    function build(callback) {
        if (queue) return queue.push(callback);
        queue = [callback];
        var builder = new Builder(config.componentPath);
        builder.build(function (err, res) {
            var callbacks = queue;
            queue = null;
            callbacks.forEach(function (callback) {
                callback(err, res);
            });
        });
    }

    return function (req, res, next) {
        if (req.uri.pathname === cssUrl) {
            build(function (err, result) {
                if (err) return next(err);
                res.setHeader("Content-Type", "text/css");
                res.setHeader("Content-Length", Buffer.byteLength(result.css));
                res.end(result.css);
            });
        }
        else if (req.uri.pathname === jsUrl) {
            build(function (err, result) {
                if (err) return next(err);
                var js = result.require + result.js;
                res.setHeader("Content-Type", "application/javascript");
                res.setHeader("Content-Length", Buffer.byteLength(js));
                res.end(js);
            });
        }
        else {
            next();
        }
    };

};