src/controllers/chatController.js

import { Readable } from "node:stream";

async function relayError(response, res) {
  const contentType = response.headers.get("content-type") ?? "application/json";
  const rawBody = await response.text();

  res.status(response.status);
  res.setHeader("content-type", contentType);
  res.send(rawBody);
}

export function createChatController({
  openAiService,
  requestNormalizationService,
  responseNormalizationService
}) {
  return async function chatController(req, res, next) {
    try {
      const { normalizedBody, responseContext } = await requestNormalizationService.normalize(req.body);
      const upstreamResponse = await openAiService.createChatCompletion(normalizedBody);

      if (!upstreamResponse.ok) {
        await relayError(upstreamResponse, res);
        return;
      }

      if (normalizedBody.stream) {
        res.status(upstreamResponse.status);
        res.setHeader("content-type", upstreamResponse.headers.get("content-type") ?? "text/event-stream");
        Readable.fromWeb(upstreamResponse.body).pipe(res);
        return;
      }

      const responseJson = await upstreamResponse.json();
      const publicBaseUrl = `${req.protocol}://${req.get("host")}`;
      const normalizedResponse = responseNormalizationService.normalize(responseJson, {
        publicBaseUrl,
        audioFormat: responseContext.audioFormat,
        exposeMediaUrls: responseContext.exposeMediaUrls
      });

      res.status(upstreamResponse.status).json(normalizedResponse);
    } catch (error) {
      next(error);
    }
  };
}