backend/src/index.ts

import Fastify from "fastify";
import cors from "@fastify/cors";
import { z } from "zod";
import { handleChat } from "./ai/engine.js";
import { ChatRequest } from "./types.js";

const server = Fastify({
  logger: true
});

await server.register(cors, {
  origin: true,
  credentials: true
});

server.get("/health", async () => ({ status: "ok" }));

server.post("/api/chat", async (request, reply) => {
  const body = request.body as ChatRequest;
  const schema = z.object({
    sessionId: z.string().min(1),
    message: z.string().min(1),
    mode: z.enum(["auto", "search", "no-search"]).optional()
  });
  const parsed = schema.safeParse(body);
  if (!parsed.success) {
    reply.status(400);
    return { error: parsed.error.flatten() };
  }

  const chunks: string[] = [];
  await handleChat(parsed.data, {
    onStatus: () => {},
    onToken: (token) => chunks.push(token),
    onDone: () => {},
    onError: () => {}
  });

  return { message: chunks.join("") };
});

server.get("/api/chat/stream", async (request, reply) => {
  const query = request.query as Record<string, string>;
  const schema = z.object({
    sessionId: z.string().min(1),
    message: z.string().min(1),
    mode: z.enum(["auto", "search", "no-search"]).optional()
  });
  const parsed = schema.safeParse(query);
  if (!parsed.success) {
    reply.status(400);
    return reply.send({ error: parsed.error.flatten() });
  }

  reply.raw.writeHead(200, {
    "Content-Type": "text/event-stream",
    "Cache-Control": "no-cache, no-transform",
    Connection: "keep-alive",
    "X-Accel-Buffering": "no"
  });
  reply.raw.flushHeaders?.();

  const writeEvent = (event: string, data: string) => {
    reply.raw.write(`event: ${event}\n`);
    reply.raw.write(`data: ${data}\n\n`);
  };

  const requestPayload: ChatRequest = {
    sessionId: parsed.data.sessionId,
    message: parsed.data.message,
    mode: parsed.data.mode
  };

  let closed = false;
  request.raw.on("close", () => {
    closed = true;
  });

  await handleChat(requestPayload, {
    onStatus: (message) => !closed && writeEvent("status", JSON.stringify({ message })),
    onToken: (token) => !closed && writeEvent("delta", JSON.stringify({ token })),
    onDone: () => !closed && writeEvent("done", JSON.stringify({ ok: true })),
    onError: (message) => !closed && writeEvent("error", JSON.stringify({ message }))
  });

  reply.raw.end();
});

const port = Number(process.env.PORT ?? 8080);
server.listen({ port, host: "0.0.0.0" }).catch((err) => {
  server.log.error(err);
  process.exit(1);
});