-module(kura_backend_ets).
-moduledoc """
ETS backend aggregator. One config knob for users:

```erlang
{repos, #{
    my_repo => #{
        backend => kura_backend_ets
    }
}}.
```

The aggregator wires up:

- `pool_module` -> `kura_ets_pool`
- `driver_module` -> `kura_ets_driver`
- `dialect` -> `kura_ets_dialect`
- `capabilities` -> declared on `kura_ets_pool`

Unlike the SQL backends, this backend does not compile queries to SQL.
The dialect emits an opaque `{kura_ets, Plan}` term (the portable
`#kura_query{}` AST plus operation data) and the driver interprets it
against per-table ETS tables, in the same spirit as
[etso](https://hex.pm/packages/etso) does for Ecto.

Intended for tests, caches, and small in-memory datasets. Data lives in
ETS and is lost when the pool stops.

## Feature coverage

Supported: insert / insert_all (with `on_conflict` targeting the
primary key), get / get_by / one / all with wheres (`=`, `!=`, `<`,
`>`, `<=`, `>=`, `in`, `not_in`, `between`, `like`, `ilike`, `is_nil`,
`is_not_nil`, `and` / `or` / `not`, composite-column `in`), order_by,
limit / offset, distinct, aggregates (count / sum / avg / min / max),
update / delete by primary key, update_all / delete_all, soft delete,
and attribute-based multitenancy.

Not supported (queries return `{error, {kura_ets_unsupported, _}}`):
joins, group_by / having, CTEs, combinations (union etc.), subqueries,
fragments, full-text `matches`, row locks, prefix-based multitenancy,
raw SQL (including migrations, `many_to_many` association persistence
and optimistic locking, which build SQL strings directly).

`transaction/4` runs the fun without atomicity: there is no rollback,
so a failed multi-step operation leaves earlier writes in place.
""".

-export([
    pool_module/0,
    driver_module/0,
    dialect/0,
    capabilities/0
]).

-spec pool_module() -> module().
pool_module() -> kura_ets_pool.

-spec driver_module() -> module().
driver_module() -> kura_ets_driver.

-spec dialect() -> module().
dialect() -> kura_ets_dialect.

-doc "Forwards to `kura_ets_pool:capabilities/0` so consumers can query the backend's feature set without knowing the impl module names.".
-spec capabilities() -> kura_capabilities:capability_set().
capabilities() -> kura_ets_pool:capabilities().