smut

-module(erl_shim).
-export([get_table/0, lookup/2, insert_new/2, replace/3]).

%% The documentation for the smut module advises the user to call
%% `init()` (which ultimately calls this function) early in their
%% program and pass out the returned handle to any piece of code that
%% needs to instantiate a slot of state. This is the "proper, functional"
%% way to do things.
%%
%% However, it's actually possible to just call `init()` anywhere. This
%% function will create the global ETS table for this module if it doesn't
%% exist, and will just return a handle to it if it does.
%%
%% Shhhh. Don't tell the Gleam programmers.
get_table() ->
    case ets:whereis(?MODULE) of
        undefined ->
            ets:new(?MODULE, [named_table, public]),
            ets:insert(?MODULE, {key_counter, 0}),
            ets:whereis(?MODULE);
        Ref -> Ref
    end.

lookup(Table, Key) ->
    case ets:lookup(Table, Key) of
        [{Key, Value} | _Rest] -> {ok, Value};
        _ -> {error, nil}
    end.

insert_new(Table, Value) ->
    NewKey = ets:update_counter(Table, key_counter, 1),
    ets:insert(Table, {NewKey, Value}),
    NewKey.

replace(Table, Key, Value) ->
    ets:insert(Table, {Key, Value}),
    nil.