Cloudflare worker media proxy (for Mastodon)

cfworker.js

// DO Spaces isn't handling OPTIONS properly so I am manually setting them. It does not affect user experience, though.
// For DO Spaces, if Origin header is not set, DO won't return CORS headers at all. Must be set in the worker.
// Other references:
// https://community.cloudflare.com/t/injecting-cors-headers-in-response-larger-requests-fail/98479/7
// https://www.digitalocean.com/community/questions/setting-access-control-allow-origin-in-my-space-doesn-t-work-with

addEventListener('fetch', event => {
  event.respondWith(handleRequest(event.request))
})

async function handleRequest(request) {
  if (request.method === "OPTIONS") {
    return handleOptions(request)
  } else if (request.method === "GET" || request.method == "HEAD") {
    const parsedUrl = new URL(request.url)
    let path = parsedUrl.pathname
    const url = new URL("https://YOUR_BUCKET_NAME.YOUR_DATA_CENTER.digitaloceanspaces.com" + path)
    const newRequest = new Request(
      url.toString(),
      new Request(request),
    )
    //Origin:https://YOUR_DOMAIN
    newRequest.headers.set('Origin', 'https://YOUR_DOMAIN')
    
    try {
      return await fetch(newRequest)
    } catch (e) {
      return new Response(JSON.stringify({ error: e.message }), { status: 500 })
    }
  } else {
    return new Response(null, {
      status: 405,
      statusText: "Method Not Allowed",
    })
  }
}

const corsHeaders = {
  "Access-Control-Allow-Origin": "*",
  "Access-Control-Allow-Methods": "GET, HEAD, OPTIONS",
  "Access-Control-Allow-Headers": "Content-Type",
}

function handleOptions(request) {
  if (request.headers.get("Origin") !== null &&
    request.headers.get("Access-Control-Request-Method") !== null &&
    request.headers.get("Access-Control-Request-Headers") !== null) {
    // Handle CORS pre-flight request.
    return new Response(null, {
      headers: corsHeaders
    })
  } else {
    // Handle standard OPTIONS request.
    return new Response(null, {
      headers: {
        "Allow": "GET, HEAD, OPTIONS",
      }
    })
  }
}