proxy-fetch.ts

import { Hono } from 'hono'
import type { Context } from 'hono'

interface ProxyFetch {
  (
    c: Context,
    input: RequestInfo | URL,
    modifyRequest: (req: Request) => void | undefined,
    modifyResponse: (res: Response) => void | undefined
  ): Promise<Response>
}

const proxyFetch: ProxyFetch = async (c, input, modifyRequest, modifyResponse) => {
  const req = new Request(input, c.req.raw)
  req.headers.delete('accept-encoding')
  const modifiedRequest = modifyRequest(req) ?? req
  const fetchResponse = (await fetch(modifiedRequest)) as unknown as Response
  const res = new Response(fetchResponse.body, fetchResponse)
  res.headers.delete('content-encoding')
  res.headers.delete('content-length')
  const modifiedResposne = modifyResponse(res) ?? res
  return modifiedResposne
}

const app = new Hono()

const origin = 'example.com'

app.get('/proxy/:path', async (c) => {
  return proxyFetch(
    c,
    `http://${origin}/${c.req.param('path')}`,
    (req) => req.headers.set('X-Forwarded-For', '127.0.0.1'),
    (res) => res.headers.delete('Cookie')
  )
})

export default app