Implementing a token refresh logic inside a middleware

[pke]

I'd like to implement an OpenID-Connect refresh logic inside a middleware that adds an Access Token to a request and reacts on 401 responses by fetching a new access token and repeating the request with the new token.

However, inside the middleware I only have access to the "next" middleware in the chain and not the "start" of the middleware chain, so middleware that would transform bodies would not work.

function middleware() {
  return function(url:string, options: RequestInit, next: FetchFunction) {
    const fetch = next
    if (accessToken) {
      options = {
        ...options,
        headers: {
          ...options.headers,
          "Authorization": "Bearer " + accessToken,
        },
      }
    }
    return next(url, options).then(response => {
      if (response.status === 401 && refreshToken) {
        return fetch(tokenURI, {
          method: "POST",
          headers: {
            "Content-Type": "application/x-www-form-urlencoded",
          },
          body: {
            grant_type: "refresh_token",
            client_id: clientId,
            client_secret: clientSecret,
            refresh_token: refreshToken,
          },
        })
      } else {
        return response
      }
    })
  }
}

I have a sendFormEncoded middleware that should take care of converting an object body to urlencoded but its not triggered in my request to fetch a new access token. Any idea how to hand in the original start of the middle ware chain into each middleware?