index.ts

/**
 * index.ts — Users subgraph entry point.
 *
 * Apollo Server v5 + Express 5 + Federation.
 * Query/Mutation only — no subscriptions, no Kafka.
 *
 * Also contributes the `user` field to the Notification entity via @requires,
 * allowing the Router to stitch user data onto subscription payloads from
 * the notifications subgraph.
 *
 * Port: 4002 (matches supergraph-config.yaml routing URL)
 */

import { readFileSync } from "fs";
import { fileURLToPath } from "url";
import { dirname, join } from "path";
import { ApolloServer } from "@apollo/server";
import { expressMiddleware } from "@as-integrations/express5";
import { buildSubgraphSchema } from "@apollo/subgraph";
import gql from "graphql-tag";
import express from "express";
import cors from "cors";
import { resolvers } from "./resolvers.js";

// ── Load schema from .graphql file ──
const __filename = fileURLToPath(import.meta.url);
const __dirname = dirname(__filename);
const schemaSource = readFileSync(join(__dirname, "schema.graphql"), "utf-8");
const typeDefs = (gql as unknown as typeof gql.default)(schemaSource);

// ── Build federated subgraph schema ──
const schema = buildSubgraphSchema({ typeDefs, resolvers });

// ── Create Apollo Server ──
const server = new ApolloServer({
  schema,
  introspection: true,
});

// ── Bootstrap ──
async function main() {
  const PORT = parseInt(process.env.PORT ?? "4002", 10);

  await server.start();

  const app = express();

  // Health check endpoint (for Docker/K8s probes)
  app.get("/health", (_req, res) => {
    res.json({ status: "ok" });
  });

  // Mount Apollo Server as Express middleware
  app.use(
    "/graphql",
    cors<cors.CorsRequest>(),
    express.json(),
    expressMiddleware(server)
  );

  const httpServer = app.listen(PORT, () => {
    console.log(`🚀 Users subgraph ready at http://localhost:${PORT}/graphql`);
    console.log(`💚 Health check at http://localhost:${PORT}/health`);
  });

  // ── Graceful shutdown ──
  const shutdown = async (signal: string) => {
    console.log(`\n${signal} received — shutting down gracefully...`);
    httpServer.close();
    await server.stop();
    console.log("👋 Users subgraph stopped.");
    process.exit(0);
  };

  process.on("SIGTERM", () => shutdown("SIGTERM"));
  process.on("SIGINT", () => shutdown("SIGINT"));
}

main().catch((err) => {
  console.error("❌ Failed to start users subgraph:", err);
  process.exit(1);
});