-module(whisper).
-compile([no_auto_import, nowarn_unused_vars, nowarn_unused_function, nowarn_nomatch, inline]).
-define(FILEPATH, "src/whisper.gleam").
-export([on/2, subscribe/1, publish/2, close/1, new_topic/2]).
-export_type([receive_error/0, receive_result/1, subscription/1, topic_error/0, whisper/1]).

-if(?OTP_RELEASE >= 27).
-define(MODULEDOC(Str), -moduledoc(Str)).
-define(DOC(Str), -doc(Str)).
-else.
-define(MODULEDOC(Str), -compile([])).
-define(DOC(Str), -compile([])).
-endif.

-type receive_error() :: topic_is_not_registered | subscription_cancelled.

-type receive_result(DVK) :: {message, DVK} | empty | {closed, receive_error()}.

-type subscription(DVL) :: {subscription,
        fun(() -> receive_result(DVL)),
        fun(() -> nil)}.

-type topic_error() :: invalid_topic | invalid_capacity | already_registered.

-type whisper(DVM) :: {whisper, binary(), integer()} | {gleam_phantom, DVM}.

-file("src/whisper.gleam", 68).
?DOC(
    " Registers a listener function that will be called whenever a message is\n"
    " published to the topic.\n"
    "\n"
    " Returns a function that can be called to unregister the listener. Multiple\n"
    " listeners can be registered on the same topic, and each will receive all\n"
    " published messages.\n"
    "\n"
    " ## Examples\n"
    "\n"
    " ```gleam\n"
    " let close = on(whisper, fn(message) {\n"
    "   io.println(\"Received: \" <> message)\n"
    " })\n"
    " // Later, to stop listening:\n"
    " close()\n"
    " ```\n"
).
-spec on(whisper(DVV), fun((DVV) -> nil)) -> fun(() -> nil).
on(Whisper, Listener) ->
    whisper_ffi:on(erlang:element(2, Whisper), Listener).

-file("src/whisper.gleam", 96).
?DOC(
    " Creates a subscription that allows pulling messages from the topic on demand.\n"
    "\n"
    " Unlike `on`, which pushes messages to a callback, `subscribe` returns a\n"
    " `Subscription` that can be polled using its `receive` function. The subscription\n"
    " maintains its own message queue up to the topic's capacity.\n"
    "\n"
    " Call the subscription's `cancel` function to stop receiving messages.\n"
    "\n"
    " ## Examples\n"
    "\n"
    " ```gleam\n"
    " let sub = subscribe(whisper)\n"
    " case sub.receive() {\n"
    "   Message(msg) -> io.println(\"Got: \" <> msg)\n"
    "   Empty -> io.println(\"No messages\")\n"
    "   Closed(err) -> io.println(\"Subscription closed\")\n"
    " }\n"
    " // Later, to cancel:\n"
    " sub.cancel()\n"
    " ```\n"
).
-spec subscribe(whisper(DVY)) -> subscription(DVY).
subscribe(Whisper) ->
    {Receive_fn, Cancel_fn} = whisper_ffi:subscribe(erlang:element(2, Whisper)),
    {subscription, Receive_fn, Cancel_fn}.

-file("src/whisper.gleam", 116).
?DOC(
    " Publishes a message to all listeners and subscribers of the topic.\n"
    "\n"
    " The message will be queued for each subscription up to the topic's capacity.\n"
    " If a subscription's queue is full, older messages may be dropped depending on\n"
    " the platform implementation.\n"
    "\n"
    " ## Examples\n"
    "\n"
    " ```gleam\n"
    " publish(whisper, \"Hello, world!\")\n"
    " ```\n"
).
-spec publish(whisper(DWD), DWD) -> nil.
publish(Whisper, Message) ->
    whisper_ffi:publish(erlang:element(2, Whisper), Message).

-file("src/whisper.gleam", 135).
?DOC(
    " Closes the topic and notifies all active subscriptions.\n"
    "\n"
    " After closing, subscribers will receive `Closed(TopicIsNotRegistered)` when\n"
    " attempting to receive messages, and new subscriptions or listeners cannot be\n"
    " created for this topic.\n"
    "\n"
    " ## Examples\n"
    "\n"
    " ```gleam\n"
    " close(whisper)\n"
    " ```\n"
).
-spec close(whisper(any())) -> nil.
close(Whisper) ->
    whisper_ffi:close(erlang:element(2, Whisper)).

-file("src/whisper.gleam", 143).
-spec validate_topic(binary()) -> {ok, binary()} | {error, topic_error()}.
validate_topic(Topic) ->
    case Topic of
        <<""/utf8>> ->
            {error, invalid_topic};

        _ ->
            {ok, Topic}
    end.

-file("src/whisper.gleam", 150).
-spec validate_capacity(integer()) -> {ok, integer()} | {error, topic_error()}.
validate_capacity(Capacity) ->
    case Capacity of
        C when C > 0 ->
            {ok, C};

        _ ->
            {error, invalid_capacity}
    end.

-file("src/whisper.gleam", 39).
?DOC(
    " Creates a new topic with the specified capacity for message buffering.\n"
    "\n"
    " The topic name must be non-empty and the capacity must be greater than zero.\n"
    " Returns an error if the topic name is invalid, capacity is invalid, or the\n"
    " topic is already registered.\n"
    "\n"
    " ## Examples\n"
    "\n"
    " ```gleam\n"
    " let assert Ok(whisper) = new_topic(\"notifications\", capacity: 100)\n"
    " ```\n"
).
-spec new_topic(binary(), integer()) -> {ok, whisper(any())} |
    {error, topic_error()}.
new_topic(Topic, Capacity) ->
    gleam@result:'try'(
        validate_topic(Topic),
        fun(Topic@1) ->
            gleam@result:'try'(
                validate_capacity(Capacity),
                fun(Capacity@1) -> whisper_ffi:register(Topic@1, Capacity@1) end
            )
        end
    ).