sw-generator.js

/* global require process console */

const { lstatSync, readdirSync, readFileSync, writeFileSync } = require('fs');
const { join } = require('path');

const { log } = console;

const config = require('./web/config');

// Function to get a recursive list of files in a folder
const inflateInput = (inputDirs, parentDir = './') =>
      inputDirs.map(
          inputDir =>
              (
                  item =>
                      lstatSync(item).isDirectory()
                      ? inflateInput(readdirSync(item), item)
                      : [item]
              )(join(parentDir, inputDir))
      ).reduce(
          (a, c) => a.concat(c),
          []
      );

log('Generating service-worker file...');

// Generate list of files in 'public' directory
const listOfFiles = inflateInput(['public']);

// Read sw.js template as string
const swTemplateString = readFileSync('./assets/sw-template.js', 'utf8');

// Get stringified list of files with static path
const stringifiedOutputFileList = JSON.stringify(
    ['/']
        .concat(
            listOfFiles
                .map(
                    filename => filename.replace('public', `/${config.staticPath}`)
                )
        )
);

// Generate output file contents post substitution
const compiledContentOfOutputFile = swTemplateString
      .replace(/'swCacheString'/g, new Date().getTime())
      .replace(/'outputFileList'/g, stringifiedOutputFileList);

// Write final sw.js to public directory
writeFileSync('./public/sw.js', compiledContentOfOutputFile);

log('Service-worker file generated!');