# @suaveplan/i18n-backend-memory - Universal in-memory translation backend for the @suaveplan/i18n family. Backed by Map<locale, Map<namespace, TranslationRecord>> plus a modification ledger; implements the full Backend contract (read, readMulti, save, lastModified). Designed for tests, seeded defaults, and the cache layer of a ChainedBackend. Zero runtime dependencies on @suaveplan/i18n core.

## Summary

Universal in-memory translation backend for the
`@suaveplan/i18n` family. Backed by `Map<locale, Map<namespace,
TranslationRecord>>` plus a modification ledger; implements the full
`Backend` contract (`read`, `readMulti`, `save`, `lastModified`).
Designed for tests, seeded defaults, and the cache layer of a
`ChainedBackend`. Zero runtime dependencies on `@suaveplan/i18n`
core.

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## Documentation tree

- [backend](./src/backend/backend.md) — <!-- begin:auto-docs --> _(no submodules)_ <!-- end:auto-docs -->
  - [backend](./src/backend/backend.md) — <!-- begin:auto-docs --> _(no submodules)_ <!-- end:auto-docs -->
- [factory](./src/factory/factory.md) — <!-- begin:auto-docs --> _(no submodules)_ <!-- end:auto-docs -->
  - [factory](./src/factory/factory.md) — <!-- begin:auto-docs --> _(no submodules)_ <!-- end:auto-docs -->
- [observability](./src/observability/observability.md) — <!-- begin:auto-docs --> _(no submodules)_ <!-- end:auto-docs -->
  - [observability](./src/observability/observability.md) — <!-- begin:auto-docs --> _(no submodules)_ <!-- end:auto-docs -->

<!-- end:auto-docs -->  - [backend](./src/backend/backend.md) — <!-- begin:auto-docs --> _(no submodules)_- [factory](./src/factory/factory.md) — <!-- begin:auto-docs --> _(no submodules)_- [factory](./src/factory/factory.md) — <!-- begin:auto-docs --> _(no submodules)_- [observability](./src/observability/observability.md) — <!-- begin:auto-docs --> _(no submodules)_- [observability](./src/observability/observability.md) — <!-- begin:auto-docs --> _(no submodules)_- [backend](./src/backend/backend.md) — <!-- begin:auto-docs --> _(no submodules)_- [factory](./src/factory/factory.md) — <!-- begin:auto-docs --> _(no submodules)_- [factory](./src/factory/factory.md) — <!-- begin:auto-docs --> _(no submodules)_- [observability](./src/observability/observability.md) — <!-- begin:auto-docs --> _(no submodules)_- [observability](./src/observability/observability.md) — <!-- begin:auto-docs --> _(no submodules)_- [backend](./src/backend/backend.md) — <!-- begin:auto-docs --> _(no submodules)_- [factory](./src/factory/factory.md) — <!-- begin:auto-docs --> _(no submodules)_- [factory](./src/factory/factory.md) — <!-- begin:auto-docs --> _(no submodules)_- [observability](./src/observability/observability.md) — <!-- begin:auto-docs --> _(no submodules)_- [observability](./src/observability/observability.md) — <!-- begin:auto-docs --> _(no submodules)_- [backend](./src/backend/backend.md) — <!-- begin:auto-docs --> _(no submodules)_- [factory](./src/factory/factory.md) — <!-- begin:auto-docs --> _(no submodules)_  - [factory](./src/factory/factory.md) — <!-- begin:auto-docs --> _(no submodules)_- [observability](./src/observability/observability.md) — <!-- begin:auto-docs --> _(no submodules)_  - [observability](./src/observability/observability.md) — <!-- begin:auto-docs --> _(no submodules)_

## Why this exists

The Wave 5 modular split lifts each backend out of the
`@suaveplan/i18n` monolith into its own sibling so consumers can
install only the backends they need (matching the `crypto-*` /
`drive-*` / `network-plugin-*` granularity established elsewhere in
the project). The in-memory backend is the simplest and most
universal of the five — it has zero external runtime deps, runs
identically in browser and server, and is the canonical seed source
for every other backend's tests.

## Install

```bash
bun add @suaveplan/i18n-backend-memory
```

## Quick Start

```ts
import { memoryBackend } from "@suaveplan/i18n-backend-memory";

const backend = memoryBackend({
    seed: {
        en: { common: { hello: "Hello" } },
        fr: { common: { hello: "Bonjour" } },
    },
});

const enCommon = await backend.read("en", "common");
// { hello: "Hello" }

await backend.save("en", "auth", { login: { title: "Sign in" } });
const t = await backend.lastModified("en", "auth"); // number (ms)
```

## Modules

| Subpath | Description |
|---|---|
| `@suaveplan/i18n-backend-memory` | Root barrel — class + factory + types + schemas + observability |
| `@suaveplan/i18n-backend-memory/backend` | `MemoryBackend` class only |
| `@suaveplan/i18n-backend-memory/factory` | `memoryBackend` factory function only |
| `@suaveplan/i18n-backend-memory/schemas` | Zod boundary schemas |
| `@suaveplan/i18n-backend-memory/observability` | OTel instruments + in-memory state ring |

## Modules Documentation

- [backend.md](src/backend/backend.md) — `MemoryBackend` class + capability matrix
- [factory.md](src/factory/factory.md) — `memoryBackend` factory function
- [observability.md](src/observability/observability.md) — OTel instruments + metric names + cardinality

## Capabilities

| Flag | Value | Notes |
|---|---|---|
| `canRead` | `true` | always — every backend reads |
| `canReadMulti` | `true` | bulk-load O(N) over the namespace map |
| `canSave` | `true` | persists into the in-memory store |
| `canTrackModification` | `true` | injectable `now()` clock |
| `canWatch` | `false` | no reactive `loaded` events |

## Testing

The package's own tests use the shared `runBackendConformance`
harness from `@suaveplan/i18n-shared/testing` so the universal
`Backend` contract is exercised against a fresh in-memory backend
per assertion:

```ts
import { runBackendConformance } from "@suaveplan/i18n-shared/testing";
import { MemoryBackend } from "@suaveplan/i18n-backend-memory";

runBackendConformance("MemoryBackend", async () => {
    const backend = new MemoryBackend();
    return {
        backend,
        async seed(locale, namespace, record) {
            await backend.save(locale, namespace, record as never);
        },
    };
});
```

## Versioning

This package is part of the i18n modular-split rollout. Stays at
`0.1.0` until the slim core (Wave 6) cuts the family `1.0.0`
release. The metric names under `i18n.backend.memory.*` are part of
the public API contract and will not change without a major bump.

## Wave 5 Scope

This package is Wave 5a of the 14-package i18n modular split. It
ships pure additions only — `packages/i18n/i18n/src/core/backend/memory/`
retains its copy of the backend until Wave 6 deletes it. Both copies
coexist during Wave 5; downstream consumers continue to import from
the monolith and observe no behaviour change.