plugin.ts

/**
 * Plugins are plain functions from app to app — guards, derives and routes
 * they add carry their types through .use().
 *
 *   bun run examples/plugin.ts
 */
import { HttpError, Ma, mc } from "@ma/core"
import type { ContextState, RouteMap } from "@ma/core"

type User = { name: string; role: "admin" | "member" }

/** Auth plugin: derives a user from the authorization header and requires it. */
function auth<TCtx extends ContextState, TRoutes extends RouteMap>(app: Ma<TCtx, TRoutes>) {
  return app
    .derive((c) => ({
      user:
        c.header("authorization") === "Bearer valid"
          ? ({ name: "Alice", role: "admin" } as User)
          : null,
    }))
    .guard<{ user: User }>((c) => {
      if (!c.get("user")) throw new HttpError(401, { message: "log in first" })
    })
}

const app = new Ma()
  .get("/public", () => "anyone can read this")
  .use(auth)
  .get("/me", (c) => ({ name: c.get("user").name })) // user is User — narrowed, no null check
  .group("/admin", (g) =>
    g
      .guard((c) => {
        if (c.get("user").role !== "admin")
          return Response.json({ message: "admins only" }, { status: 403 })
      })
      .get("/stats", () => ({ uptime: process.uptime() })),
  )

const anonymous = mc(app)
console.log("public:", (await anonymous.public.get()).data)
console.log("me (no token):", (await anonymous.me.get()).status) // 401

const authed = mc(app, { headers: { authorization: "Bearer valid" } })
console.log("me:", (await authed.me.get()).data)
console.log("admin stats:", (await authed.admin.stats.get()).data)