# @cozy-games/move-log

A **game-agnostic** container for a recorded run of move events. It wraps any game's event stream in a schema-versioned, ordered, timestamped log.

```js
import {
  createMoveLog, withReceivedTs,
  serializeMoveLog, deserializeMoveLog, isMoveLog, SCHEMA_VERSION
} from '@cozy-games/move-log'

// `T` is your game's own event vocabulary — supplied by you, unknown to us.
const log = createMoveLog([
  { seq: 1, t: 0, event: { type: 'reveal', r: 0, c: 0 } },
  { seq: 2, t: 50, event: { type: 'flag', r: 1, c: 2 } }
])
// → { schema_version: 1, events: [ { seq, t, event }, ... ] }

const json = serializeMoveLog(log)          // → JSON string
const restored = deserializeMoveLog(json)    // → validated MoveLog, or throws

// A consumer records WHEN it received events (host clock), additively:
const stamped = withReceivedTs(restored, () => hostNow())
// → each event now also carries `receivedTs`; still a valid v1 log
```

## Shape

| field            | type              | meaning                                            |
| ---------------- | ----------------- | -------------------------------------------------- |
| `schema_version` | `1`               | the move-log container version                     |
| `events`         | `MoveEvent<T>[]`  | ordered, each `{ seq, t, event, receivedTs? }`     |

`MoveEvent<T> = { seq: number, t: number, event: T, receivedTs?: number }` — the
log owns the per-event recording metadata (a strictly increasing `seq`, a
source-side timestamp `t`, and an **optional** received-side `receivedTs`), so
`T` stays a pure game payload with no required shape. `receivedTs` is
purpose-neutral: it records only *that* a consumer received the event at some
time, never why or from where.

`deserializeMoveLog` round-trips a serialized log with full fidelity (order,
timestamps, sequence numbers, and any `receivedTs`) and rejects malformed input —
bad JSON, missing or wrong-typed fields, or non-monotonic `seq` — with a clear
error, never returning a partially-parsed log.

## Versioning: `receivedTs` is additive within `schema_version: 1`

`receivedTs` was added **without** bumping `schema_version`. It is optional and
purely additive: a v1 log is valid whether every event, some events, or no
events carry a `receivedTs`, and a reader that doesn't know the field simply
ignores it. A version bump is reserved for *breaking* container changes (a
renamed/removed field or a newly required one), which would be dispatched on in
`deserializeMoveLog`. See the `SCHEMA_VERSION` doc comment for the full policy.

## Invariant: zero game-specific imports

This module **must never import a game package** (e.g. mnswpr) or any game
vocabulary. `T` is always supplied by the consumer; the log only ever sees
opaque payloads. This independence is the whole point — it lets one move-log
format serve every game.

The rule is enforced by a dependency-graph guard in `test/move-log.test.js`
(scans the package's source and manifest for game references). Keep it green.