# `Kotoba.Collab.Store`
[🔗](https://github.com/hattoriai/kotoba/blob/v0.5.0/lib/kotoba/collab/store.ex#L1)

Atomic persistence for collaboration state and its rendered content.

`save/5` must compare the stored `{epoch, revision}` with `expected`
and commit state and content together. `nil` means the document has no
collaboration state yet. A stale owner must receive `{:error, :conflict}`.
A document process acknowledges edits only after this callback succeeds.

The context is supplied by the application, for example a repository
module or an options map. The guide includes an Ecto implementation.

# `load`

```elixir
@callback load(context :: term(), document_id :: String.t()) ::
  {:ok, %{state: map() | nil, content: Kotoba.Content.t() | nil}}
  | {:error, term()}
```

# `save`

```elixir
@callback save(
  context :: term(),
  document_id :: String.t(),
  expected :: {String.t(), non_neg_integer()} | nil,
  state :: map(),
  content :: Kotoba.Content.t()
) :: :ok | {:error, term()}
```

---

*Consult [api-reference.md](api-reference.md) for complete listing*