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

-export([start_manager/2]).
-export_type([usage_message/2, bookkeeping_message/2]).

-type usage_message(GVS, GVT) :: {usage_message,
        fun((GVS) -> GVT),
        gleam@erlang@process:subject({ok, GVT} | {error, nil})}.

-type bookkeeping_message(GVU, GVV) :: shutdown |
    {put_back, gleam@erlang@process:subject(usage_message(GVU, GVV))} |
    {checkout,
        gleam@erlang@process:subject({ok,
                gleam@erlang@process:subject(usage_message(GVU, GVV))} |
            {error, nil})}.

-spec handle_bookkeeping_message(
    bookkeeping_message(GWT, GWU),
    list({gleam@erlang@process:pid_(),
        gleam@erlang@process:subject(usage_message(GWT, GWU))})
) -> gleam@otp@actor:next(any(), list({gleam@erlang@process:pid_(),
    gleam@erlang@process:subject(usage_message(GWT, GWU))})).
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};

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

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

-spec new(integer(), fun(() -> {ok, GWL} | {error, nil})) -> {ok,
        list({gleam@erlang@process:pid_(),
            gleam@erlang@process:subject(usage_message(GWL, 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_manager(integer(), fun(() -> {ok, GWC} | {error, nil})) -> {ok,
        gleam@erlang@process:subject(bookkeeping_message(GWC, any()))} |
    {error, nil}.
start_manager(Size, New_resource) ->
    gleam@result:then(
        new(Size, New_resource),
        fun(Puddle) ->
            _pipe = gleam@otp@actor:start(
                Puddle,
                fun handle_bookkeeping_message/2
            ),
            gleam@result:nil_error(_pipe)
        end
    ).