Adapters

import { toExpressHandler, toWinterCgHandler } from '@rasenganjs/futon';

Both adapters convert a Futon instance's fetch() into the handler shape a specific host expects. See Express Adapter, WinterCG Adapter, and Runtime Adapters for usage and deployment notes.

toExpressHandler()

function toExpressHandler(
  app: Futon,
  runtime?: RuntimeContext
): (
  req: ExpressRequest,
  res: ExpressResponse,
  next: ExpressNextFunction
) => Promise<void>;

Bridges the WinterCG pipeline to an Express (req, res, next) handler:

1. Builds a Web API Request from the Express request (headers, method, and body — including piping the raw Node stream when no body-parsing Express middleware ran first).
2. Calls app.fetch(request, runtime).
3. Writes the resulting status, headers, and body back onto the Express response, streaming the body chunk-by-chunk.

Errors thrown while building the request or running fetch() are forwarded to Express via next(error).

import express from 'express';
import { Futon, toExpressHandler } from '@rasenganjs/futon';
 
const app = new Futon();
// ...routes
 
const expressApp = express();
expressApp.use(toExpressHandler(app));
expressApp.listen(3000);

toWinterCgHandler()

function toWinterCgHandler(
  app: Futon,
  defaultRuntime?: RuntimeContext
): (
  request: Request,
  envOrCtx?: Record<string, unknown> | WinterCgFetchContext,
  platformCtx?: WinterCgFetchContext
) => Promise<Response>;

Produces a { fetch }-shaped handler compatible with every WinterCG runtime — Cloudflare Workers (request, env, ctx), Deno / Bun (request, info), and plain Service Workers (request). It normalizes whichever argument shape the platform passes, merges the platform's env into defaultRuntime.env, and forwards ctx.waitUntil when the platform provides one and the response sets an X-Rasengan-Background header.

import { Futon, toWinterCgHandler } from '@rasenganjs/futon';
 
const app = new Futon();
// ...routes
 
export default { fetch: toWinterCgHandler(app) };

FetchHandler

type FetchHandler = (request: Request, runtime?: any) => Promise<Response>;

The fundamental request-handler shape every adapter ultimately produces or consumes — Futon.fetch itself conforms to this signature. Every middleware, route handler, and error handler exists to eventually produce a Response this way; adapters exist purely to translate a platform's native handler shape into (and the resulting Response out of) this one.