index.js

const express = require("express");
const { createFeaturevisor } = require("@featurevisor/sdk");

/**
 * Constants
 */
const PORT = 3000;

const DATAFILE_URL =
  process.env.environment === "production"
    ? "https://featurevisor-example-cloudflare.pages.dev/production/featurevisor-tag-all.json"
    : "https://featurevisor-example-cloudflare.pages.dev/staging/featurevisor-tag-all.json";

/**
 * Featurevisor instance
 */
const f = createFeaturevisor({});

/**
 * Express app with middleware
 */
const app = express();

app.use((req, res, next) => {
  req.f = f;
  next();
});

function evaluateMessage(instance = f) {
  const featureKey = "baz";
  const context = { userId: "user-123" };

  return instance.isEnabled(featureKey, context)
    ? "Hello World!"
    : "Not enabled yet!";
}

/**
 * Routes
 */
app.get("/", (req, res) => {
  res.send(evaluateMessage(req.f));
});

/**
 * Start the server
 */
async function start() {
  try {
    const response = await fetch(DATAFILE_URL);

    if (!response.ok) {
      throw new Error(`Failed to fetch datafile: HTTP ${response.status}`);
    }

    const datafile = await response.json();

    if (!f.setDatafile(datafile, true)) {
      throw new Error("Datafile was rejected");
    }

    return app.listen(PORT, () => {
      console.log(`Server running at http://localhost:${PORT}`);
    });
  } catch (error) {
    console.error("Error fetching datafile:", error);
    process.exitCode = 1;
  }
}

if (require.main === module) {
  start();
}

module.exports = { app, evaluateMessage, start };