decouple start code from CLI

[jdanyow]

Opening to continue discussion from #13 (comment)

What do you think about splitting start.js into two files:

1. cli.js: argv, SIGHUP and file access related code
2. index.js: exports a start and updateWorkerScript functions, re-exports the worker.js and server.js exports?

import { start, updateWorkerScript } from 'cloudflare-worker-local';

const options = {
  port: 4000,
  workerScript: '... javascript ...',
  upstreamHost: 'localhost:3000',
  kvStores: [],
  workerCount: 1
};

start(options);
...
...
updateWorkerScript('... js ...');

This would make the following scenario cleaner / less hacky:

import chokidar from 'chokidar';
import { access, F_OK } from 'fs';

const filename = 'dist/index.js';

let started = false;

async function handler() {
  const exists = await new Promise(resolve => access(filename, F_OK, e => resolve(!e)));
  if (exists && !started) {
    started = true;
    // TEMP: set args expected by cloudflare-worker-local
    process.argv[2] = filename;
    process.argv[3] = 'localhost:7001';
    process.argv[4] = '7000';
    import('cloudflare-worker-local/start.js');
  } else if (exists && started) {
    process.emit('SIGHUP');
  }
}

let timeout = 0;
function debouncedHandler() {
  clearTimeout(timeout);
  timeout = setTimeout(handler, 300);
}

chokidar.watch(filename)
  .on('add', debouncedHandler)
  .on('change', debouncedHandler);

[gja]

Hmmm, Lots of food for thought. I think we should be exporting the following things:

• startServer(pathToWorker, {port}) (this automatically will updating the worker on SIGHUP)
• Worker
• startTestServer(workerContents, upstreamBehavior)

I've updated the readme, turns out watching and listening for SIGHUP is actually much easier than I thought.

[jdanyow]

In my experience so far using cloudflare-worker-local with packagers like parcel and rollup, nodemon hasn't worked well. It leads to complex npm scripts to ensure the packager has built the worker script prior to starting cloudflare-worker-local. Similar to remy/nodemon#1297 and remy/nodemon#797.

The sighup approach seems to be ok for scenarios where the worker source code is a single javascript file.

For increased flexibility I think it would be great if the CLI related logic (process.argv, SIGHUP and fs.readFile(pathToWorker)) was decoupled from the core logic (start server / update worker).

[gja]

I think this will probably be the direction we go in. As a start, I've opened #19, which just exports (by default) Worker and createApp.

[gja]

If you want to use chokidar, the new pseudocode would look something like this

const {createApp} = require("cloudflare-worker-local")

const app = createApp(fs.readFileSync("/path/to/worker.js"), {})
app.listen(3000);

chokidhar.watch("/path/to/worker.js")
  .on('change', () => fs.readFile('/path/to/worker.js', buffer => app.updateWorker(bufferToString(buffer))))