@alxia/janus

Identities, sessions and permissions for alxia, on @softistx/janus: your process, your database. The user typed in the context, the session cookie kept and renewed, janus's refusals answered with their status and a safe body. No dependency.

bun add @alxia/janus @softistx/janus @alxia/core
bun add -d typescript

@softistx/janus is private, on GitHub Packages. Map its scope in your bunfig.toml and export a token that reads packages (read:packages):

[install.scopes]
"@softistx" = { url = "https://npm.pkg.github.com/", token = "$GITHUB_TOKEN" }

It mirrors @softistx/janus-hono: the same cookie, the same rules, the same bodies.

A BFF that calls a janus API, rather than running @softistx/janus itself, wants @alxia/react-router/session.

Usage

import { alxia, validate } from '@alxia/core';
import { janusErrors, session } from '@alxia/janus';
import { createMemoryStores, janus, scryptHasher } from '@softistx/janus';
import { z } from 'zod';

const accounts = janus({
    user: z.object({ email: z.email(), name: z.string() }),
    password: { login: 'email' },
    store: createMemoryStores(),       // your database's adapter in production
    hasher: scryptHasher(),
});

const SignIn = z.object({ email: z.string(), password: z.string() });

const app = alxia()
    .use(janusErrors(), session(accounts))                // errors first, then the session: anonymous may sign in
    .post('/signin', validate({ body: SignIn }), async ({ body, auth, reply }) => {
        const signedIn = await accounts.signIn(body);
        return reply.ok({ id: auth.send(signedIn).id });  // the token in the cookie
    })
    .post('/signout', async ({ auth, reply }) => reply.ok(await auth.signOut()))
    .use(session(accounts, { required: true }))           // the routes after it, and any unmatched request
    .get('/me', ({ user, reply }) => reply.ok(user));     // user typed by the schema

janusErrors() and session() are middlewares. janusErrors() answers what is thrown behind it, so give it to use before session().

session(accounts, options?)

The routes after it read user, session and auth. With required: true, an anonymous request is a 401 { error: 'unauthenticated' } and user is never null. On the app, a required session also runs on a request no route matches: an anonymous request to a missing path gets the 401, not the 404. Put it in a group to guard only some routes; without, it is null for an anonymous request. A boolean known only at run time types both: the 401, and a user that may be null. type narrows to one user type of a multi-type janus(); device names the device cookie.

The session is read from Authorization: Bearer, X-Session-Token, or the cookie. One renewed in passing is sent again as a cookie after the route — only to a request that presented it as one, and never over a session cookie the route set itself. An outage is not anonymous: a store that cannot answer is STORE_FAILED, answered 503 by janusErrors().

ctx.auth: signing in and out

Sign-in stays on your janus() instance — accounts.signIn, accounts.signUp, accounts.patient.signIn, a code, a link — and ctx.auth does the request's part, bound to it:

Put the sign-in routes behind a session(accounts) that is not required: behind required: true, an anonymous request — anyone signing in — is a 401. Outside a route (a job, a test), sendSession(ctx, accounts, signedIn), signOut(ctx, accounts) and deviceOf(ctx) are the same functions, unbound.

janusErrors(options?)

A try/catch middleware: every JanusError thrown behind it — by session(), permission() or a route — is answered with janus's status and a body holding its code and only what a client can act on — the issues, a minimum length, attempts left, seconds to wait (with Retry-After). Never a login, a reason or a cause. report(error, ctx) is called for the 5xx. Anything else goes on, thrown, to the middlewares before it. On an app with alxia({ errors: 'problem' }), it answers an RFC 9457 problem instead, the code and the rest of that body its extensions; a required session()'s 401 and permission()'s 401, 404 and 403 follow the app's format too. Declared after session(), it would not see the session's STORE_FAILED: it goes first, and after the observers (logger(), secureHeaders()), so that they see its reply. An observer settles next() without swallowing the error, so janusErrors() before one, or before createI18n(), still answers it.

permission(access, permission, type, load, options?)

A guard on @softistx/janus/permissions: the routes after it run only if the subject — the session's user, or options.subject(ctx) — holds permission on the object load finds, which they read as object. Anonymous is a 401, nothing loaded a 404, a denial a 403, each typed. Scope it with group:

import { alxia } from '@alxia/core';
import { byParam, janusErrors, permission, session } from '@alxia/janus';
import { createMemoryStores, janus, scryptHasher } from '@softistx/janus';
import { createMemoryRelations, defineModel, permissions } from '@softistx/janus/permissions';
import { z } from 'zod';

const relations = createMemoryRelations();
const accounts = janus({
    user: z.object({ email: z.email() }),
    password: { login: 'email' },
    store: createMemoryStores(),
    relations,
    hasher: scryptHasher(),
});
const access = permissions({
    model: defineModel({
        subjects: accounts.types,
        types: { record: { related: { owners: ['user'] }, permits: { view: ['owners'] } } },
    }),
    store: relations,
});

const records = new Map([['r1', { id: 'r1', title: 'Blood test' }]]);
const findRecord = (id: string) => records.get(id) ?? null;

const app = alxia()
    .use(janusErrors())
    .use(session(accounts))
    .group('/records/:id', (record) =>
        record
            .use(permission(access, 'view', 'record', byParam('id', findRecord)))
            .get('/', ({ object, reply }) => reply(200, object)), // object: what findRecord found
    );

byParam(name, find) loads by a path parameter. A permission whose condition needs a context takes ctx: (ctx, object) => …, required by the types exactly then.

Reading the app's context

Annotate load, subject or ctx's parameter to read what an earlier middleware added. The guard then requires it: an app that does not give it before the guard cannot use it.

import type { BaseContext } from '@alxia/core';

const byTenant = permission(
    access,
    'view',
    'record',
    ({ tenant, pathParams }: BaseContext & { tenant: { records: Map<string, { id: string; title: string }> } }) =>
        tenant.records.get(pathParams['id'] ?? '') ?? null,
);

alxia().plugin(tenancy).use(session(accounts)).use(byTenant); // tenancy derives tenant
alxia().use(session(accounts)).use(byTenant); // a compile error: this app gives no `tenant`

A callback annotated any would require nothing, so the guard is refused on every app: annotate what it reads, or leave it unannotated.

API

Documentation

• Guide: a page per area — sessions, signing in and out with ctx.auth and the device cookie, janus's errors and their statuses, and the permission guard, reading what an earlier middleware added included.
• Troubleshooting: an error message, or a request anonymous, refused or a 404 when it should not be, and what to do about it.
• Roadmap: what is coming, and what is not planned.
• Recipes: Authenticate requests, Answer errors consistently.