ng-eventually/packages/polyfill/README.md

# @ng-eventually/polyfill

One entry point. Most of what it publishes has the same signature as the future SDK —
`ng`, `useShape`, `watchShape`, `docs`, `inbox`, `storeRegistry`, `readUnion` (+ types) —
and is a drop-in for `@ng-org/web` / `@ng-org/orm`: as NextGraph matures it resolves to
the real SDK (build alias removed) with no code change.

**One call does not, and it is the whole of what you will delete:** `configure`. It
exists because one shared wallet hosts every user; upstream, an application imports the
SDK and each user opens their own wallet. `src/index.ts` groups it under a heading that
says so. (`ensureIdentity` is a second in substance — the shared-wallet gate — but its
call site survives: an application still awaits a session before it renders.)

*(There were two entry points until 2026-08-07, `.` and `./polyfill`, and the second one
WAS that list. One door is easier to import from and says less — hence the grouping, and
hence `docs/api-contract.md`, whose export inventory a test keeps honest.)*

Per-symbol, with the target signature and an epistemic label on every claim:
[`docs/api-contract.md`](../../docs/api-contract.md).

> **Reading is key possession, and the isolation here is still fake.** The cap surface
> has the shape of the real model — you hold a document's `ReadCap` or you do not read
> it, and there is no authorization list anywhere — but nothing is encrypted yet and
> the stand-in key is a constant. Nothing this library does may be described as
> "anonymous" or "private" until per-document encryption lands (P1b).

```ts
import {
  // SDK-shaped — the real SDK replaces these in place.
  ensureIdentity, storeRegistry, inbox, readUnion, docs,
  // Polyfill-era — one call, and it is the whole of what goes away.
  configure,
} from "@ng-eventually/polyfill";

configure({ ng: realNg, useShape: realUseShape, getSession, sharedWallet });
await ensureIdentity();              // who I am (returned), connection work awaited
const doc = await storeRegistry.createEntityDoc("protected");
await docs.sparqlUpdate(sid, `INSERT DATA { … }`, doc);
const subjects = await readUnion(await storeRegistry.listMyEntityDocs("protected"));
```

## Principle — the polyfill compensates, it never extends

**Its only reason to exist is to bridge a NextGraph implementation gap.** Every
non-SDK surface must map to something NextGraph will provide natively, and must fall
away at that point — no bespoke features, no observability, no convenience API that
isn't strictly *"NextGraph will do this later"*. The test for any proposed addition:
*does it compensate a real, exhibited gap?* If not, it belongs in the consumer
application. And a compensation whose gap is not actually exhibited on the target
broker is dead weight, not defensive code.

Both halves are binding — **the surface AND the implementation** stay as close as
possible to what NextGraph plans. The question to ask at every choice: *would this
make a caller learn something it has to UNLEARN at migration?* If yes, it is a
deviation, whatever it buys.

What the polyfill adds, each emulated now and native later:

- **Shared-wallet identity** — one wallet hosts every user, so the library fabricates
  *virtual users* and confines every access to the connected one
  (`emulated-verifier/reach.ts`). Upstream, each user opens their own wallet.
- **Capability emulation** — per-identity cap possession plus a read filter over it:
  you read the documents whose cap you hold. There is no authorization list, because
  the real model has none.
- **Inbox** — `post`, `postToDocument`, `share`, and the recipient's processing.
  The model is verified (an inbox is a keypair on one repo); no JS surface exists yet.

Generic by construction: no application domain here. See
[`examples/notebook`](../../examples/notebook) for an application written against it,
which the e2e suite drives.

## How a document is reached — the three acts, and no others

```ts
import { storeRegistry, inbox, readUnion } from "@ng-eventually/polyfill";

// 1. CREATE — you hold its cap, with nothing to declare. No identity parameter: a
//    session belongs to one user, exactly as the target's own `doc_create` assumes.
const doc = await storeRegistry.createEntityDoc("protected");

// 2. GIVE TO READ — name the document and the person. The key is looked up and
//    sealed into a deposit; the recipient applies it by connecting, with nothing
//    to call. Irreversible: there is no revoking a key already handed out.
await inbox.share(doc, "bob");

// 3. CIRCULATE THE REFERENCE — no call at all. Every reference this surface returns
//    is BARE: it names the document and grants nothing. If the document sits in a
//    PUBLIC store, the store serves its read cap to whoever asks, so the bare
//    reference is enough to read it — and if it does not, the reference still names
//    it and opens nothing.
const publicDoc = await storeRegistry.createEntityDoc("public");
// …put `publicDoc` in a QR code, a message, another document. Nothing else to do.
await readUnion([publicDoc]);   // a stranger holding only this reads it
```

**The invariant behind all three: you never derive a cap from a bare reference.** You
look it up in what you hold, you were given it, or a public store served it. A
`did:ng:o:…` without `:r:` names a document and opens nothing — which is what makes
confidentiality composable: a widely circulated document may point at a restricted
one, and following the reference gets you a name, not a key. See
[`docs/readcap-and-nuri-model.md`](../../docs/readcap-and-nuri-model.md) § 0.

## The types carry that invariant

`Nuri` and `ReadCap` are **template literal types**, not `string` aliases:

```ts
type Nuri    = `did:ng:${string}`
type ReadCap = `did:ng:${string}:r:${string}`
```

They are still strings — assignable to `string`, JSON-serializable, no wrapper — but
the distinction is checked. A `ReadCap` goes wherever a `Nuri` is expected (a cap *is*
a NURI with the key inside); the reverse does not compile.

**Permissive in, precise out.** Public entries take `NuriLike` (`Nuri | string`) and
validate at the door, so a value coming from storage, a URL or a form needs no
narrowing and no cast on your side; what they *return* is a precise `Nuri`. The
runtime checks stay regardless — a JavaScript caller never meets the compiler.

```ts
const saved = localStorage.getItem("doc");        // string | null
if (saved) await readUnion([saved]);              // ✓ validated at the door
```