Where documents last. Your app implements it on its database;
Issho.Store.Memory is for development and tests.
load/2 gives the document as last saved, or nil for one that has
never been saved. A store on your app's own table, which has the
content before anyone opens it together (a post's body), gives
{:initial, content}: the document starts from it, in place of the
spec's :initial, and is saved at once, with expected nil.
save/5 must compare the stored {epoch, revision} with expected
and save the document and its content together, in one atomic write,
and answer {:error, :conflict} to a stale writer. The
authority confirms an edit to its author only after save/5 answers
:ok, so answering before the write is durable breaks that promise.
The document is a map of JSON values (save it as a JSON or map column).
The content is what the engine's Issho.Engine.validate/2 gave: keep
it beside the document for your app to read and publish.
The context is your app's, given with the store: a repo, an options map.
{Issho, name: MyApp.Issho, store: {MyApp.CollabStore, MyApp.Repo}, ...}Summary
Callbacks
The document as last saved, nil, or {:initial, content} to start one from.
Saves the document and its content, if the stored version is expected.
Types
@type document() :: map()
@type expected() :: {epoch :: String.t(), revision :: non_neg_integer()} | nil
Callbacks
@callback load(context :: term(), document_id :: String.t()) :: {:ok, document() | nil | {:initial, term()}} | {:error, term()}
The document as last saved, nil, or {:initial, content} to start one from.
@callback save( context :: term(), document_id :: String.t(), expected(), document(), content :: term() ) :: :ok | {:error, :conflict} | {:error, term()}
Saves the document and its content, if the stored version is expected.