polyserve/src/make_app.ts

A simple dev server for bower components

/**
 * @license
 * Copyright (c) 2015 The Polymer Project Authors. All rights reserved.
 * This code may only be used under the BSD style license found at
 * http://polymer.github.io/LICENSE.txt
 * The complete set of authors may be found at
 * http://polymer.github.io/AUTHORS.txt
 * The complete set of contributors may be found at
 * http://polymer.github.io/CONTRIBUTORS.txt
 * Code distributed by Google as part of the polymer project is also
 * subject to an additional IP rights grant found at
 * http://polymer.github.io/PATENTS.txt
 */

import * as express from 'express';
import * as path from 'path';
import {parse as parseUrl} from 'url';

import {bowerConfig} from './bower_config';

import send = require('send');

export interface AppOptions {
  componentDir: string;
  packageName?: string;
  headers?: {[name: string]: string};
  root?: string;
  compile?: 'always'|'never'|'auto';
}

export interface PolyserveApplication extends express.Express {
  packageName: string;
}

/**
 * Make a polyserve express app.
 * @param  {Object} options
 * @param  {string} options.componentDir The directory to serve components from.
 * @param  {string} options.packageName A name for this polyserve package.
 * @param  {Object} options.headers An object keyed by header name containing
 *         header values.
 * @param  {string} options.root The root directory to serve a package from
 * @return {Object} An express app which can be served with `app.get`
 */
export function makeApp(options: AppOptions): PolyserveApplication {
  const root = options.root;
  const baseComponentDir = options.componentDir;
  const componentDir = path.isAbsolute(baseComponentDir) ?
      baseComponentDir :
      path.join(root, baseComponentDir);
  let packageName = options.packageName;
  if (!packageName) {
    packageName = bowerConfig(root).name;
  }
  if (!packageName) {
    packageName = path.basename(root || process.cwd());
    console.log(`no bower.json detected, using name "${packageName}"`);
  }
  let headers = options.headers || {};

  const app: PolyserveApplication = <PolyserveApplication>express();

  app.get('*', (req, res) => {
    // Serve local files from . and other components from bower_components
    const url = parseUrl(req.url, true);
    let splitPath = url.pathname.split('/').slice(1);

    if (splitPath[0] === packageName) {
      if (root) {
        splitPath = [root].concat(splitPath.slice(1));
      } else {
        splitPath = splitPath.slice(1);
      }
    } else {
      splitPath = [componentDir].concat(splitPath);
    }
    const filePath = splitPath.join('/');

    if (headers) {
      for (const header in headers) {
        (<any>res).setHeader(header, headers[header]);
      }
    }
    const _send = send(req, filePath);
    // Uncomment this to disable 304s from send(). This will make the
    // compileMiddleware used in startServer always compile. Useful for testing
    // and working on the compilation middleware.
    // _send.isFresh = () => false;

    // The custom redirect is needed becuase send() redirects to the
    // _file_ path plus a leading slash, not the URL. :(
    // https://github.com/pillarjs/send/issues/132
    _send
        .on('directory',
            () => {
              res.statusCode = 301;
              res.setHeader('Location', req.originalUrl + '/');
              res.end('Redirecting to ' + req.originalUrl + '/');
            })
        .pipe(res);
  });
  app.packageName = packageName;
  return app;
}