-module(kura_ets_driver).
-moduledoc """
ETS driver impl. Receives the `{kura_ets, Plan}` terms emitted by
`kura_ets_dialect` in place of SQL and executes them via
`kura_ets_query`.

## Result shape

Returns `#{rows := Rows, num_rows := N, command := C}` to match
`kura_driver_pgo`'s shape. `Rows` are maps keyed by atom field names.

## Raw SQL

Anything that reaches the driver as actual SQL bytes (raw
`kura_repo_worker:query/3`, migrations, kura's built-in
`many_to_many` join-row persistence, optimistic-lock updates) is
rejected with `{error, {kura_ets, raw_sql_unsupported}}` — there is no
SQL engine here.

## Transactions

ETS has no transactions. `transaction/4` simply runs the fun: queries
inside it hit the tables directly, and there is no rollback on error.
The backend deliberately does not declare the `transactions`
capability.
""".

-behaviour(kura_driver).

-export([
    query/5,
    query_on/4,
    transaction/4,
    ensure_database/1,
    probe_pool/1
]).

%%----------------------------------------------------------------------
%% kura_driver callbacks
%%----------------------------------------------------------------------

-spec query(module(), atom(), dynamic(), [term()], map()) -> dynamic().
query(_PoolMod, Pool, Plan, _Params, _Opts) ->
    run(Pool, Plan).

-spec query_on(kura_pool:conn(), dynamic(), [term()], map()) -> dynamic().
query_on(Conn, Plan, _Params, _Opts) ->
    %% checkout/2 hands out the pool name as the conn, so the sandbox
    %% path lands here with everything needed to resolve tables.
    run(Conn, Plan).

-spec transaction(module(), atom(), fun(() -> term()), map()) -> term().
transaction(_PoolMod, _Pool, Fun, _Opts) ->
    Fun().

-spec ensure_database(map()) -> ok.
ensure_database(_Config) ->
    ok.

-spec probe_pool(kura_pool:name()) -> ok | {error, term()}.
probe_pool(Pool) ->
    case erlang:whereis(Pool) of
        undefined -> {error, no_pool};
        _Pid -> ok
    end.

%%----------------------------------------------------------------------
%% Internal
%%----------------------------------------------------------------------

-spec run(atom(), dynamic()) -> dynamic().
run(Pool, {kura_ets, Plan}) ->
    kura_ets_query:run(Pool, Plan);
run(_Pool, _SQL) ->
    {error, {kura_ets, raw_sql_unsupported}}.