# in-memory-store

## Purpose

Deterministic `Map`-backed invoice store consumed by every business
rule in `invoice-rules.ts`. The store performs zero IO and runs
identically on Node, Bun, and Javy/QuickJS — both the trusted-tier
route handlers and the wasm-tier `handleRequest` hold one of these as
their single source of truth for invoice persistence.

The store exposes the minimal vocabulary the rules need: monotonic id
allocation, create/get/list/setState/delete, plus `clear()` for
disposal and `setCounter()` for test pinning. Keeping the surface small
makes the shape-conformance test trivial — both tiers issue the same
sequence of store operations for the same input.

## Features

- Monotonic `inv-N` id allocator (`nextId()`).
- Strict create: throws when the id already exists.
- Get / list / setState / delete primitives.
- Bulk `clear()` for the wasm-tier `dispose()` hook.
- `setCounter(n)` for deterministic id pinning in tests.

## Usage: Basic

```ts
import { createInMemoryStore } from "@suaveplan/api-plugin-example/domain";

const store = createInMemoryStore();
const inv = store.create({ id: store.nextId(), status: "open", amountCents: 1500, currency: "USD" });
console.log(store.list()); // [inv]
```

## Usage: Advanced

```ts
import { createInMemoryStore } from "@suaveplan/api-plugin-example/domain";

const store = createInMemoryStore();
store.setCounter(99); // next id will be inv-100
const seeded = store.create({ id: store.nextId(), status: "open", amountCents: 1, currency: "USD" });
store.setState(seeded.id, "paid");
store.delete(seeded.id);
store.clear();
```

## API Reference

- `createInMemoryStore(): InMemoryStore` — factory.
- `nextId(): string` — `inv-1`, `inv-2`, ...
- `create(invoice): Invoice` — inserts, throws on duplicate id.
- `get(id): Invoice | undefined`.
- `list(): readonly Invoice[]` — insertion-ordered snapshot.
- `setState(id, state): Invoice` — throws when id absent.
- `delete(id): boolean` — `true` when removed.
- `clear(): void` — erases every entry and resets the counter.
- `setCounter(value): void` — pin counter; next `nextId()` returns `inv-${value+1}`.

## Implementation Notes

The store is a closure over a private `Map` and a private counter — no
prototype methods, no `this` binding, no shared global state. Tests
instantiate a fresh store per test for isolation; the wasm-tier holds
a module-singleton instance because the WASI-stdio surface has no
request-scoped context to thread one through.