index.js

import { getAssetFromKV, mapRequestToAsset } from '@cloudflare/kv-asset-handler'

const DEBUG = false

addEventListener('fetch', event => {
  try {
    event.respondWith(handleEvent(event))
  } catch (e) {
    if (DEBUG) {
      return event.respondWith(
        new Response(e.message || e.toString(), {
          status: 500,
        }),
      )
    }
    event.respondWith(new Response('Internal Error', { status: 500 }))
  }
})

async function handleEvent(event) {
  let options = {}

  try {
    if (DEBUG) {
      // customize caching
      options.cacheControl = {
        bypassCache: true,
      }
    }
    const commitSha = await CONTROL.get('show_commit')
    options.mapRequestToAsset = handleCommitSha(commitSha)

    return await getAssetFromKV(event, options)
  } catch (e) {
    // if an error is thrown try to serve the asset at 404.html
    if (!DEBUG) {
      try {
        let notFoundResponse = await getAssetFromKV(event, {
          mapRequestToAsset: req => new Request(`${new URL(req.url).origin}/404.html`, req),
        })

        return new Response(notFoundResponse.body, { ...notFoundResponse, status: 404 })
      } catch (e) {}
    }

    return new Response(e.message || e.toString(), { status: 500 })
  }
}


function handleCommitSha(commitSha) {
  return request => {
    let defaultAssetKey = mapRequestToAsset(request)
    let url = new URL(defaultAssetKey.url)
    url.pathname = `/${commitSha}${url.pathname}`
    return new Request(url.toString(), defaultAssetKey)
  }
}