# @wrnexus/authz

> Composable authorization for WrNexus — role-based (RBAC), policy-based (PBAC), and attribute-based (ABAC) access control that reduces to a boolean check plus an `authorize()` guard.

Part of the **WrNexus** framework — an SSR-first, Bun-native full-stack web framework.

## Overview

`@wrnexus/authz` is a small, server-side authorization toolkit. It gives you three
interchangeable models — RBAC (roles → permissions), PBAC (policy predicates), and
ABAC (attribute matchers) — that all collapse to a `boolean | Promise<boolean>` decision.
Wrap any decision in a `Middleware` guard (`authorize`, `requireRole`, `requirePermission`)
to protect WrNexus routes. Reach for it whenever a route or action needs to be gated on who
the user is, what roles they hold, or attributes of the user and the resource. It plugs into
`@wrnexus/core` by reading `ctx.user` as the authorization subject.

## Installation

```bash
bun add @wrnexus/authz
```

> Private package — the machine must be authenticated to the `wrnexus` npm org
> (a read token in `~/.npmrc`). Requires **Bun** (Node is not supported).

## API

The package has a single entry point (`@wrnexus/authz`) exporting the following.

### Types

| Symbol                             | Description                                                                                   |
| ---------------------------------- | --------------------------------------------------------------------------------------------- |
| `Subject`                          | The authorized principal: `{ id?: string; roles?: string[]; [attribute: string]: unknown }`.  |
| `Rbac`                             | An RBAC checker: `{ can(subject, permission): boolean; permissionsFor(roles): Set<string> }`. |
| `Policy<S = Subject, R = unknown>` | A predicate `(subject: S, resource?: R) => boolean \| Promise<boolean>`.                      |

### RBAC

#### `defineRbac(roles: Record<string, string[]>): Rbac`

Builds an RBAC checker from a role → permissions map. Supported permission forms:

- `"*"` — grants every permission.
- `"ns:*"` — namespace wildcard (e.g. `"post:*"` grants `"post:write"`).
- `"role:<name>"` — inherits all permissions of another role (resolved recursively, cycle-safe).

The returned `Rbac` provides:

- `can(subject, permission)` — `true` if any of `subject.roles` grants `permission` (honouring `*` and namespace wildcards). Returns `false` when the subject has no roles.
- `permissionsFor(roles)` — the resolved `Set<string>` of all permissions granted to a set of roles.

#### `hasRole(subject: Subject | undefined, ...required: string[]): boolean`

`true` if the subject holds **all** of the given roles.

### PBAC / ABAC combinators

- `any<S, R>(...policies: Policy<S, R>[]): Policy<S, R>` — allow if **any** policy passes (OR); awaits async policies.
- `all<S, R>(...policies: Policy<S, R>[]): Policy<S, R>` — allow only if **all** policies pass (AND); awaits async policies.
- `attr<S extends Subject>(name: string, match: unknown | ((value: unknown) => boolean)): Policy<S>` — ABAC helper that allows when `subject[name]` equals `match`, or when `match` is a function, when `match(value)` is truthy.

### Guards (middleware)

Each guard returns a `@wrnexus/core` `Middleware`. A denied request short-circuits with
`Response.json({ ok: false, error: "Forbidden" }, { status: 403 })`.

- `authorize(policy: (ctx: Context) => boolean | Promise<boolean>): Middleware` — runs `policy` against the request `Context`; calls `next()` when it resolves truthy, otherwise returns 403.
- `requireRole(...roles: string[]): Middleware` — allows when `ctx.user` holds **any** of the listed roles.
- `requirePermission(rbac: Rbac, permission: string): Middleware` — allows when `rbac.can(ctx.user, permission)` is `true`.

## Usage

### RBAC

```ts
import { defineRbac, hasRole } from "@wrnexus/authz";

const rbac = defineRbac({
  admin: ["*"],
  editor: ["post:read", "post:write"],
  viewer: ["post:read"],
  // role inheritance: lead gets everything an editor has, plus post:publish
  lead: ["role:editor", "post:publish"],
});

const user = { id: "u1", roles: ["editor"] };

rbac.can(user, "post:write"); // true
rbac.can(user, "post:delete"); // false
rbac.permissionsFor(["lead"]); // Set { "post:read", "post:write", "post:publish" }
hasRole(user, "editor"); // true
```

### Guarding routes

```ts
import { authorize, requireRole, requirePermission, defineRbac } from "@wrnexus/authz";

const rbac = defineRbac({ admin: ["*"], editor: ["post:read", "post:write"] });

// Only admins or editors
app.get("/dashboard", requireRole("admin", "editor"), handler);

// Requires a specific permission
app.post("/posts", requirePermission(rbac, "post:write"), handler);

// Arbitrary policy over the request context
app.delete(
  "/posts/:id",
  authorize((ctx) => hasRole(ctx.user, "admin")),
  handler,
);
```

### PBAC / ABAC policies

```ts
import { any, all, attr, authorize, type Policy } from "@wrnexus/authz";

interface User {
  id: string;
  department?: string;
  roles?: string[];
}
interface Post {
  authorId: string;
}

// Ownership policy (subject + resource)
const ownsPost: Policy<User, Post> = (u, post) => u.id === post?.authorId;

// ABAC: attribute equality, or a predicate
const inEngineering = attr<User>("department", "engineering");
const isVerified = attr<User>("verified", (v) => v === true);

// Compose: allow if the user owns the post OR is in engineering AND verified
const canEdit = any(ownsPost, all(inEngineering, isVerified));

app.put(
  "/posts/:id",
  authorize((ctx) => canEdit(ctx.user as User, loadPost(ctx))),
  handler,
);
```

## Requirements / Notes

- **Bun-only** — like the rest of WrNexus, this package targets the Bun runtime; Node is not supported.
- Works with [`@wrnexus/core`](../core) — the guards return `Middleware` and read the subject from `ctx.user` on the request `Context`. Both types are imported from `@wrnexus/core`.
- Policy combinators (`any`, `all`) and `authorize` are async-aware, so policies may return a `Promise<boolean>` (e.g. for a database ownership check).
