-module(process_waiter).
-compile([no_auto_import, nowarn_unused_vars, nowarn_unused_function, nowarn_nomatch]).

-export([await_forever/1]).

-spec await_forever_loop(
    gleam@dict:dict(gleam@erlang@process:pid_(), gleam@erlang@process:process_monitor()),
    gleam@erlang@process:selector(gleam@erlang@process:pid_())
) -> nil.
await_forever_loop(Pids, Selector) ->
    Pid = gleam_erlang_ffi:select(Selector),
    Pids@1 = gleam@dict:delete(Pids, Pid),
    case maps:size(Pids@1) of
        0 ->
            nil;

        _ ->
            await_forever_loop(Pids@1, Selector)
    end.

-spec selector_for_monitors(
    gleam@dict:dict(gleam@erlang@process:pid_(), gleam@erlang@process:process_monitor())
) -> gleam@erlang@process:selector(gleam@erlang@process:pid_()).
selector_for_monitors(Monitors) ->
    _pipe = gleam@dict:values(Monitors),
    gleam@list:fold(
        _pipe,
        gleam_erlang_ffi:new_selector(),
        fun(Selector, Monitor) ->
            gleam@erlang@process:selecting_process_down(
                Selector,
                Monitor,
                fun(Msg) -> erlang:element(2, Msg) end
            )
        end
    ).

-spec await_forever(list(gleam@erlang@process:pid_())) -> nil.
await_forever(Pids) ->
    Monitors = begin
        _pipe = Pids,
        _pipe@1 = gleam@list:map(
            _pipe,
            fun(Pid) -> {Pid, gleam@erlang@process:monitor_process(Pid)} end
        ),
        maps:from_list(_pipe@1)
    end,
    Selector = selector_for_monitors(Monitors),
    await_forever_loop(Monitors, Selector).