Dirigent/services/no-reply-api/server.mjs

import http from "node:http";

const modelName = process.env.NO_REPLY_MODEL || "no-reply";
const authToken = process.env.AUTH_TOKEN || "";

function sendJson(res, status, payload) {
  res.writeHead(status, { "Content-Type": "application/json; charset=utf-8" });
  res.end(JSON.stringify(payload));
}

function isAuthorized(req) {
  if (!authToken) return true;
  const header = req.headers.authorization || "";
  return header === `Bearer ${authToken}`;
}

function noReplyChatCompletion(reqBody) {
  return {
    id: `chatcmpl_dirigent_${Date.now()}`,
    object: "chat.completion",
    created: Math.floor(Date.now() / 1000),
    model: reqBody?.model || modelName,
    choices: [
      {
        index: 0,
        message: { role: "assistant", content: "NO_REPLY" },
        finish_reason: "stop",
      },
    ],
    usage: { prompt_tokens: 0, completion_tokens: 1, total_tokens: 1 },
  };
}

function noReplyResponses(reqBody) {
  return {
    id: `resp_dirigent_${Date.now()}`,
    object: "response",
    created_at: Math.floor(Date.now() / 1000),
    model: reqBody?.model || modelName,
    output: [
      {
        type: "message",
        role: "assistant",
        content: [{ type: "output_text", text: "NO_REPLY" }],
      },
    ],
    usage: { input_tokens: 0, output_tokens: 1, total_tokens: 1 },
  };
}

function listModels() {
  return {
    object: "list",
    data: [
      {
        id: modelName,
        object: "model",
        created: Math.floor(Date.now() / 1000),
        owned_by: "dirigent",
      },
    ],
  };
}

/**
 * Returns a Node.js HTTP request handler for the no-reply API.
 * When used as a sub-service inside main.mjs, the caller strips
 * the "/no-reply" prefix from req.url before calling this handler.
 */
export function createNoReplyHandler() {
  return function noReplyHandler(req, res) {
    const url = req.url ?? "/";

    if (req.method === "GET" && url === "/health") {
      return sendJson(res, 200, {
        ok: true,
        service: "dirigent-no-reply-api",
        model: modelName,
      });
    }

    if (req.method === "GET" && url === "/v1/models") {
      if (!isAuthorized(req)) return sendJson(res, 401, { error: "unauthorized" });
      return sendJson(res, 200, listModels());
    }

    if (req.method !== "POST") {
      return sendJson(res, 404, { error: "not_found" });
    }

    if (!isAuthorized(req)) {
      return sendJson(res, 401, { error: "unauthorized" });
    }

    let body = "";
    req.on("data", (chunk) => {
      body += chunk;
      if (body.length > 1_000_000) req.destroy();
    });

    req.on("end", () => {
      let parsed = {};
      try {
        parsed = body ? JSON.parse(body) : {};
      } catch {
        return sendJson(res, 400, { error: "invalid_json" });
      }

      if (url === "/v1/chat/completions") {
        return sendJson(res, 200, noReplyChatCompletion(parsed));
      }

      if (url === "/v1/responses") {
        return sendJson(res, 200, noReplyResponses(parsed));
      }

      return sendJson(res, 404, { error: "not_found" });
    });
  };
}

// Standalone mode: run HTTP server if this file is the entry point
const isMain = process.argv[1] && process.argv[1].endsWith("server.mjs");
if (isMain) {
  const port = Number(process.env.PORT || 8787);
  const handler = createNoReplyHandler();
  const server = http.createServer(handler);
  server.listen(port, () => {
    console.log(`[dirigent-no-reply-api] listening on :${port}`);
  });
}