%% Copyright (c) Meta Platforms, Inc. and affiliates.
%%
%% This source code is licensed under both the MIT license found in the
%% LICENSE-MIT file in the root directory of this source tree and the Apache
%% License, Version 2.0 found in the LICENSE-APACHE file in the root directory
%% of this source tree.
%% @format
-module(bounded_buffer).
-compile(warn_missing_spec).
-moduledoc """
A bounded FIFO queue
""".
%% Public API
-export([new/1, put/2, get_elements/1]).
-export_type([buffer/1]).
-opaque buffer(T) :: {{queue:queue(T), integer()}, integer(), boolean()}.
-spec new(integer()) -> buffer(term()).
new(MaxElements) -> {{queue:new(), 0}, MaxElements, false}.
-spec put(buffer(T), T) -> buffer(T).
put({{Queue, LenQueue}, MaxElements, Truncated}, Chars) when LenQueue < MaxElements ->
{{queue:in(Chars, Queue), LenQueue + 1}, MaxElements, Truncated};
put({{Queue, LenQueue}, MaxElements, _Truncated} = _Buffer, Chars) when LenQueue == MaxElements ->
{_, NewQueue} = queue:out(Queue),
{{queue:in(Chars, NewQueue), LenQueue}, MaxElements, true}.
-spec get_elements(buffer(T)) -> {[T], boolean()}.
get_elements({{Queue, _LenQueue}, _MaxElements, Truncated}) ->
{queue:to_list(Queue), Truncated}.
