-module(puddle).
-compile([no_auto_import, nowarn_unused_vars]).

-export([apply/4, start/2]).
-export_type([bookkeeping_message/2, usage_message/2]).

-opaque bookkeeping_message(GVS, GVT) :: shutdown |
    {check_in, gleam@erlang@process:subject(usage_message(GVS, GVT))} |
    {check_out,
        gleam@erlang@process:subject({ok,
                gleam@erlang@process:subject(usage_message(GVS, GVT))} |
            {error, nil})}.

-opaque usage_message(GVU, GVV) :: {usage_message,
        fun((GVU) -> GVV),
        gleam@erlang@process:subject({ok, GVV} | {error, nil})}.

-spec check_out(
    gleam@erlang@process:subject(bookkeeping_message(GWS, GWT)),
    integer()
) -> {ok, gleam@erlang@process:subject(usage_message(GWS, GWT))} | {error, nil}.
check_out(Manager, Timeout) ->
    gleam@erlang@process:call(
        Manager,
        fun(Field@0) -> {check_out, Field@0} end,
        Timeout
    ).

-spec utilize(
    gleam@erlang@process:subject(usage_message(GWY, GWZ)),
    fun((GWY) -> GWZ),
    gleam@erlang@process:subject({ok, GWZ} | {error, nil})
) -> nil.
utilize(Subject, Fun, Mine) ->
    gleam@erlang@process:send(Subject, {usage_message, Fun, Mine}).

-spec check_in(
    gleam@erlang@process:subject(bookkeeping_message(GXH, GXI)),
    gleam@erlang@process:subject(usage_message(GXH, GXI))
) -> nil.
check_in(Manager, Subject) ->
    gleam@erlang@process:send(Manager, {check_in, Subject}).

-spec apply(
    gleam@erlang@process:subject(bookkeeping_message(GWL, GWM)),
    fun((GWL) -> GWM),
    integer(),
    fun(({ok, GWM} | {error, nil}) -> {ok, GZI} | {error, nil})
) -> {ok, GZI} | {error, nil}.
apply(Manager, Fun, Timeout, Rest) ->
    gleam@result:then(
        check_out(Manager, Timeout),
        fun(Subject) ->
            Mine = gleam@erlang@process:new_subject(),
            utilize(Subject, Fun, Mine),
            Selector = begin
                _pipe = gleam_erlang_ffi:new_selector(),
                gleam@erlang@process:selecting(_pipe, Mine, fun(R) -> R end)
            end,
            Result = begin
                _pipe@1 = gleam_erlang_ffi:select(Selector, Timeout),
                gleam@result:flatten(_pipe@1)
            end,
            check_in(Manager, Subject),
            Rest(Result)
        end
    ).

-spec handle_bookkeeping_message(
    bookkeeping_message(GXY, GXZ),
    list({gleam@erlang@process:pid_(),
        gleam@erlang@process:subject(usage_message(GXY, GXZ))})
) -> gleam@otp@actor:next(any(), list({gleam@erlang@process:pid_(),
    gleam@erlang@process:subject(usage_message(GXY, GXZ))})).
handle_bookkeeping_message(Msg, Puddle) ->
    case Msg of
        shutdown ->
            gleam@list:each(
                Puddle,
                fun(Item) ->
                    gleam@erlang@process:kill(erlang:element(1, Item))
                end
            ),
            {stop, normal};

        {check_in, Subject} ->
            Pid = gleam@erlang@process:subject_owner(Subject),
            gleam@otp@actor:continue(gleam@list:prepend(Puddle, {Pid, Subject}));

        {check_out, Client} ->
            case Puddle of
                [] ->
                    gleam@otp@actor:send(Client, {error, nil}),
                    gleam@otp@actor:continue(Puddle);

                [{_, Chosen} | New_puddle] ->
                    gleam@otp@actor:send(Client, {ok, Chosen}),
                    gleam@otp@actor:continue(New_puddle)
            end
    end.

-spec handle_usage_message(usage_message(GYF, any()), GYF) -> gleam@otp@actor:next(any(), GYF).
handle_usage_message(Msg, Resource) ->
    case Msg of
        {usage_message, Fun, Client} ->
            Result = Fun(Resource),
            gleam@otp@actor:send(Client, {ok, Result}),
            gleam@otp@actor:continue(Resource)
    end.

-spec new(integer(), fun(() -> {ok, GXQ} | {error, nil})) -> {ok,
        list({gleam@erlang@process:pid_(),
            gleam@erlang@process:subject(usage_message(GXQ, any()))})} |
    {error, nil}.
new(Size, New_resource) ->
    _pipe = gleam@list:repeat(<<""/utf8>>, Size),
    gleam@list:try_map(_pipe, fun(_) -> case New_resource() of
                {ok, Initial_state} ->
                    _pipe@1 = gleam@otp@actor:start(
                        Initial_state,
                        fun handle_usage_message/2
                    ),
                    _pipe@2 = gleam@result:map(
                        _pipe@1,
                        fun(Subject) ->
                            Pid = gleam@erlang@process:subject_owner(Subject),
                            {Pid, Subject}
                        end
                    ),
                    gleam@result:nil_error(_pipe@2);

                {error, nil} ->
                    {error, nil}
            end end).

-spec start(integer(), fun(() -> {ok, GWC} | {error, nil})) -> {ok,
        gleam@erlang@process:subject(bookkeeping_message(GWC, any()))} |
    {error, gleam@otp@actor:start_error()}.
start(Size, New_resource) ->
    gleam@result:then(
        begin
            _pipe = new(Size, New_resource),
            gleam@result:map_error(
                _pipe,
                fun(_) ->
                    {init_failed,
                        {abnormal, <<"Failed to create new resource"/utf8>>}}
                end
            )
        end,
        fun(Puddle) ->
            gleam@otp@actor:start(Puddle, fun handle_bookkeeping_message/2)
        end
    ).