semaphore/bin/build-vercel-json.js

// create the vercel.json file
// Unfortunately this has to be re-run periodically, as AFAICT there is no way to
// give Zeit a script and tell them to run that, instead of using a static vercel.json file.

import path from 'path'
import fs from 'fs'
import { promisify } from 'util'
import { routes } from '../__sapper__/service-worker.js'
import { cloneDeep } from '../src/routes/_utils/lodash-lite.js'
import inlineScriptChecksum from '../src/inline-script/checksum.js'
import { sapperInlineScriptChecksums } from '../src/server/sapperInlineScriptChecksums.js'

const __dirname = path.dirname(new URL(import.meta.url).pathname)
const writeFile = promisify(fs.writeFile)

const JSON_TEMPLATE = {
  version: 2,
  env: {
    NODE_ENV: 'production'
  },
  github: {
    silent: true
  },
  builds: [
    {
      src: 'package.json',
      use: '@now/static-build',
      config: {
        distDir: '__sapper__/export'
      }
    }
  ],
  routes: [
    {
      src: '^/service-worker\\.js$',
      headers: {
        'cache-control': 'public,max-age=0'
      }
    },
    {
      src: '^/(report\\.html|stats\\.json)$',
      headers: {
        'cache-control': 'public,max-age=3600'
      },
      dest: 'client/$1'
    },
    {
      src: '^/client/.*\\.(js|css|map|LICENSE|txt)$',
      headers: {
        'cache-control': 'public,max-age=31536000,immutable'
      }
    },
    {
      src: '^/.*\\.(png|css|json|svg|jpe?g|map|txt|gz|webapp|woff|woff2)$',
      headers: {
        'cache-control': 'public,max-age=3600'
      }
    }
  ]
}

const SCRIPT_CHECKSUMS = [inlineScriptChecksum]
  .concat(sapperInlineScriptChecksums)
  .map(_ => `'sha256-${_}'`)
  .join(' ')

const PERMISSIONS_POLICY = 'sync-xhr=(),document-domain=(),interest-cohort=()'

const HTML_HEADERS = {
  'cache-control': 'public,max-age=3600',
  'content-security-policy': [
    "default-src 'self'",
    `script-src 'self' ${SCRIPT_CHECKSUMS}`,
    "worker-src 'self'",
    "style-src 'self' 'unsafe-inline'",
    "img-src 'self' * data: blob:",
    "media-src 'self' *",
    "connect-src 'self' * data: blob:",
    "frame-src 'none'",
    "frame-ancestors 'none'",
    "object-src 'none'",
    "manifest-src 'self'",
    "form-action 'self'", // we need form-action for the Web Share Target API
    "base-uri 'self'"
  ].join(';'),
  'referrer-policy': 'no-referrer',
  'strict-transport-security': 'max-age=15552000; includeSubDomains',
  'permissions-policy': PERMISSIONS_POLICY,
  'x-content-type-options': 'nosniff',
  'x-download-options': 'noopen',
  'x-frame-options': 'DENY',
  'x-xss-protection': '1; mode=block',
  'cross-origin-opener-policy': 'same-origin'
}

async function main () {
  const json = cloneDeep(JSON_TEMPLATE)

  const exportDir = path.resolve(__dirname, '../__sapper__/export')

  for (const { pattern } of routes) {
    const route = {
      src: pattern.source,
      headers: cloneDeep(HTML_HEADERS)
    }

    // remove all the regexy stuff in the regex
    const filename = pattern.source.replace(/^\^\\\//, '').replace(/(\\\/)?\?\$$/, '').replace(/\\\//g, '/')

    // try two different possible paths
    const filePath = [
      `${filename}.html`,
      path.join(filename, 'index.html')
    ].map(_ => path.resolve(exportDir, _)).find(_ => fs.existsSync(_))

    if (!filePath) { // dynamic route, e.g. /accounts/<accountId/
      // serve calls to dynamic routes via the generic "service worker" index.html,
      // since we can't generate the dynamic content using Zeit's static server
      route.dest = 'service-worker-index.html'
    }
    json.routes.push(route)
  }

  // push a generic route to handle everything else
  json.routes.push({
    src: '^/(.*)',
    headers: cloneDeep(HTML_HEADERS)
  })

  await writeFile(path.resolve(__dirname, '../vercel.json'), JSON.stringify(json, null, '  '), 'utf8')
}

main().catch(err => {
  console.error(err)
  process.exit(1)
})