Inline middleware

For one-off hooks, register callbacks on the HTTP arc or inside a route group:

import { FlareHost, FlareResponse, flareState, Logger } from "@flare-ts/core";
import { node } from "@flare-ts/core/node";

const AuthUser = flareState<{ id: string }>("AuthUser");

const host = new FlareHost(node);

host.http.before({ provides: [AuthUser] }, (ctx) => {
  ctx.state.set(AuthUser, { id: "u1" });
});

host.http.after((_ctx, result) => {
  if (result instanceof FlareResponse) {
    result.headers["x-flare-version"] = "1.0";
  }
});

host.http.finally({ inject: { log: Logger } }, (_ctx, _result, scope) => {
  scope.log.debug("finished");
});

host.http.get("/me", { state: [AuthUser] }, (ctx) => {
  return new FlareResponse(200, ctx.state.require(AuthUser));
});

const app = host.build();
app.run();

Registration API

Method	Signature
before(handler)	(ctx, scope) => override
before(options, handler)	Same with HttpMiddlewareOptions
after(handler)	(ctx, result, scope) => override
after(options, handler)	Same with options
finally(handler)	(ctx, result, scope) => override
finally(options, handler)	Same with options

All hooks may be async. Return undefined or void to continue the pipeline.

HttpMiddlewareOptions

Option	Purpose
inject	Named map { name: Token } for scope.name
state	State tokens this hook reads via ctx.state
provides	State tokens written in a before hook
name	Display name for the synthetic middleware wrapper

A route or middleware that declares state: [Token] compiles only when an upstream before hook provides each token. Middleware that only implements after or finally does not satisfy route state, even if provides is set. Put token writes in before().

Short-circuit from before

import { FlareHost, FlareResponse } from "@flare-ts/core";
import { node } from "@flare-ts/core/node";

const host = new FlareHost(node);

host.http.before((ctx) => {
  if (ctx.req.headers.get("x-blocked") === "1") {
    return new FlareResponse(429, { error: "rate limited" });
  }
});

host.http.get("/ok", () => new FlareResponse(200, { ok: true }));

const app = host.build();
app.run();

Group-scoped hooks

Register inside host.http.group:

host.http.group("/api", (g) => {
  g.before((ctx) => { /* only /api/* routes */ });
  g.get("/status", () => new FlareResponse(200, { ok: true }));
  return g.register();
});

Related

• MiddlewareBase classes
• Middleware overview: execution order and error interaction
• Named inject map