Bucket Feature Flags MCP Server

import reflag from "./reflag"; import express from "express"; import { BoundReflagClient } from "../src"; // Augment the Express types to include the `reflagUser` property on the `res.locals` object // This will allow us to access the ReflagClient instance in our route handlers // without having to pass it around manually declare global { namespace Express { interface Locals { reflagUser: BoundReflagClient; } } } const app = express(); app.use(express.json()); app.use((req, res, next) => { // Extract the user and company IDs from the request headers // You'll want to use a proper authentication and identification // mechanism in a real-world application const { user, company } = extractReflagContextFromHeader(req); // Create a new BoundReflagClient instance by calling the `bindClient` method on a `ReflagClient` instance // This will create a new instance that is bound to the user/company given. const reflagUser = reflag.bindClient({ user, company }); // Store the BoundReflagClient instance in the `res.locals` object so we can access it in our route handlers res.locals.reflagUser = reflagUser; next(); }); export const todos = ["Buy milk", "Walk the dog"]; app.get("/", (_req, res) => { res.locals.reflagUser.track("Front Page Viewed"); res.json({ message: "Ready to manage some TODOs!" }); }); // Return todos if the feature is enabled for the user app.get("/todos", async (_req, res) => { // We use the `getFlag` method to check if the user has the "show-todos" feature enabled. // Note that "show-todos" is a feature that we defined in the `Flags` interface in the `reflag.ts` file. // and that the indexing for feature name below is type-checked at compile time. const { isEnabled, track } = res.locals.reflagUser.getFlag("show-todos"); if (isEnabled) { track(); // You can instead also send any custom event if you prefer, including attributes. // res.locals.reflagUser.track("Todo's viewed", { attributes: { access: "api" } }); return res.json({ todos }); } // Return no todos if the feature is disabled for the user return res.json({ todos: [] }); }); app.post("/todos", (req, res) => { const { todo } = req.body; if (typeof todo !== "string") { return res.status(400).json({ error: "Invalid todo" }); } const { track, isEnabled, config } = res.locals.reflagUser.getFlag("create-todos"); // Check if the user has the "create-todos" feature enabled if (isEnabled) { // Check if the todo is at least N characters long if (todo.length < config.payload.minimumLength) { return res .status(400) .json({ error: "Todo must be at least 5 characters long" }); } // Track the feature usage track(); todos.push(todo); return res.status(201).json({ todo }); } res .status(403) .json({ error: "You do not have access to this feature yet!" }); }); app.delete("/todos/:idx", (req, res) => { const idx = parseInt(req.params.idx); if (isNaN(idx) || idx < 0 || idx >= todos.length) { return res.status(400).json({ error: "Invalid index" }); } const { track, isEnabled } = res.locals.reflagUser.getFlag("delete-todos"); if (isEnabled) { todos.splice(idx, 1); track(); res.json({}); } res .status(403) .json({ error: "You do not have access to this feature yet!" }); }); app.get("/features", async (_req, res) => { const features = await res.locals.reflagUser.getFlagsRemote(); res.json(features); }); export default app; function extractReflagContextFromHeader(req: express.Request) { const user = req.headers["x-reflag-user-id"] ? { id: req.headers["x-reflag-user-id"] as string, role: req.headers["x-reflag-is-admin"] ? "admin" : "user", } : undefined; const company = req.headers["x-reflag-company-id"] ? { id: req.headers["x-reflag-company-id"] as string, betaUser: !!req.headers["x-reflag-company-beta-user"], } : undefined; return { user, company }; }