Pluggable store for Plaid transaction sync cursors.

Cursors represent the position in Plaid's transaction event log. They MUST be persisted durably — if a cursor is lost, the next sync call will restart from the beginning (full historical replay).

Production persistence note

By default, cursors are persisted via PlaidEx.Sync.CursorStore.EtsBackend, which means cursors are LOST on application restart. For production systems, implement Behaviour with a database backend (Ecto, Redix, etc.) and configure it:

config :plaid_ex,
  cursor_store: MyApp.PlaidCursorStore

Custom cursor store

defmodule MyApp.PlaidCursorStore do
  @behaviour PlaidEx.Sync.CursorStore.Behaviour

  @impl true
  def get(item_id) do
    case Repo.get_by(PlaidItem, item_id: item_id) do
      nil -> nil
      item -> item.sync_cursor
    end
  end

  @impl true
  def put(item_id, cursor) do
    Repo.update_all(
      from(i in PlaidItem, where: i.item_id == ^item_id),
      set: [sync_cursor: cursor]
    )
    :ok
  end

  @impl true
  def delete(item_id) do
    Repo.delete_all(from(i in PlaidItem, where: i.item_id == ^item_id))
    :ok
  end
end