R2 Storage — Zero Egress Fees

// worker.js — serve images from R2 instead of your origin
// Route: *yourdomain.com/images/*
// Your origin server: ZERO code changes required
//
// wrangler.toml bindings needed:
//   [[r2_buckets]]
//   binding  = "R2"
//   bucket_name = "your-media-bucket"

export default {
  async fetch(request, env, ctx) {
    const url = new URL(request.url)

    // Only intercept image requests — everything else passes to origin unchanged
    if (!url.pathname.startsWith('/images/')) {
      return fetch(request)
    }

    // Strip leading slash to get the R2 object key
    // e.g. "/images/products/chair.jpg" → "products/chair.jpg"
    const key = url.pathname.slice('/images/'.length)

    // 1. Check R2 first — zero egress fee, served from nearest Cloudflare PoP
    const r2Object = await env.R2.get(key)
    if (r2Object !== null) {
      const headers = new Headers()
      r2Object.writeHttpMetadata(headers)    // copies Content-Type from stored metadata
      headers.set('Cache-Control', 'public, max-age=86400')
      headers.set('X-Served-From', 'cloudflare-r2')
      headers.set('X-Egress-Cost', '$0.00')
      return new Response(r2Object.body, { headers })
    }

    // 2. Not in R2 yet — fetch from origin once, return immediately,
    //    store in R2 in the background so next request is free
    const originResponse = await fetch(request)
    if (!originResponse.ok) return originResponse

    ctx.waitUntil((async () => {
      const buffer = await originResponse.clone().arrayBuffer()
      await env.R2.put(key, buffer, {
        httpMetadata: {
          contentType:  originResponse.headers.get('content-type') ?? 'image/jpeg',
          cacheControl: 'public, max-age=86400',
        },
        customMetadata: {
          'cached-at':  new Date().toISOString(),
          'origin-url': request.url,
        },
      })
    })())

    // Return origin response to user — next request will hit R2
    const respHeaders = new Headers(originResponse.headers)
    respHeaders.set('X-Served-From', 'origin-first-load')
    return new Response(originResponse.body, {
      status:  originResponse.status,
      headers: respHeaders,
    })
  },
}