-module(birl@instant).
-compile(no_auto_import).

-export([now/0, compare/2, difference/2, add/2, subtract/2]).
-export_type([instant/0]).

-opaque instant() :: {instant, integer()}.

-spec now() -> instant().
now() ->
    _pipe = birl_ffi:monotonic_now(),
    {instant, _pipe}.

-spec compare(instant(), instant()) -> gleam@order:order().
compare(A, B) ->
    {instant, Ia} = A,
    {instant, Ib} = B,
    case Ia =:= Ib of
        true ->
            eq;

        false ->
            case Ia < Ib of
                true ->
                    lt;

                false ->
                    gt
            end
    end.

-spec difference(instant(), instant()) -> birl@duration:duration().
difference(A, B) ->
    {instant, Ia} = A,
    {instant, Ib} = B,
    {duration, Ib - Ia}.

-spec add(instant(), birl@duration:duration()) -> instant().
add(Value, Duration) ->
    {instant, Instant} = Value,
    {duration, Duration@1} = Duration,
    {instant, Instant + Duration@1}.

-spec subtract(instant(), birl@duration:duration()) -> instant().
subtract(Value, Duration) ->
    {instant, Instant} = Value,
    {duration, Duration@1} = Duration,
    {instant, Instant - Duration@1}.