handler.ts

import type { IncomingMessage, ServerResponse } from 'node:http'
import type {
  WebHandler,
  NodeHandler,
  BuildDependencies,
  RequestOptions,
} from '../types'
import { buildToFetchEvent } from '../node-to-edge/fetch-event'
import { buildToRequest } from '../node-to-edge/request'
import { mergeIntoServerResponse, toOutgoingHeaders } from './headers'
import { toToReadable } from './stream'

export function buildToNodeHandler(
  dependencies: BuildDependencies,
  options: RequestOptions,
) {
  const toRequest = buildToRequest(dependencies)
  const toFetchEvent = buildToFetchEvent(dependencies)
  return function toNodeHandler(webHandler: WebHandler): NodeHandler {
    return (
      incomingMessage: IncomingMessage,
      serverResponse: ServerResponse,
    ) => {
      const request = toRequest(incomingMessage, options)
      const maybePromise = webHandler(request, toFetchEvent(request))
      if (maybePromise instanceof Promise) {
        maybePromise.then((response) =>
          toServerResponse(response, serverResponse),
        )
      } else {
        toServerResponse(maybePromise, serverResponse)
      }
    }
  }
}

function toServerResponse(
  webResponse: Response | null | undefined,
  serverResponse: ServerResponse,
) {
  if (!webResponse) {
    serverResponse.end()
    return
  }
  mergeIntoServerResponse(
    toOutgoingHeaders(webResponse.headers),
    serverResponse,
  )

  serverResponse.statusCode = webResponse.status
  serverResponse.statusMessage = webResponse.statusText
  if (!webResponse.body) {
    serverResponse.end()
    return
  }
  toToReadable(webResponse.body).pipe(serverResponse)
}