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

/**
 * The DEBUG flag will do two things that help during development:
 * 1. we will skip caching on the edge, which makes it easier to
 *    debug.
 * 2. we will return an error message on exception in your Response rather
 *    than the default 404.html page.
 */
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 = {
    cacheControl: {
      browserTTL: 3600,
    }
  }

  let headers = {
    'X-XSS-Protection': '1; mode=block',
    'X-Frame-Options': 'DENY',
    'X-Content-Type-Options': 'nosniff',
    'x-y2k-backend': 'v5',
    'x-y2k-debug': DEBUG,
  }

  try {
    if (DEBUG) options.cacheControl.bypassCache = true

    // asset was found, the good stuff goes here
    let asset = await getAssetFromKV(event, options)

    // set various security headers above
    Object.keys(headers).forEach((name) => {
      asset.headers.set(name, headers[name])
    })

    return asset
  } 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(), { headers, status: 500 })
  }
}