strata/lib/cascade.js

A modular, streaming HTTP server

var utils = require('./utils');

/**
 * A middleware that tries each of the given apps in turn, returning the
 * response from the first one that doesn't return a status code the same as
 * cascadeStatus, which defaults to 404.
 */
module.exports = function (apps, cascadeStatus, defaultApp) {
  cascadeStatus = cascadeStatus || 404;
  defaultApp = defaultApp || utils.notFound;

  function tryApp(i, env, callback) {
    var app = apps[i];

    if (!app) {
      defaultApp(env, callback);
      return;
    }

    app(env, function (status, headers, body) {
      if (status == cascadeStatus) {
        tryApp(i + 1, env, callback);
      } else {
        callback(status, headers, body);
      }
    });
  }

  function cascade(env, callback) {
    tryApp(0, env, callback);
  }

  return cascade;
};