-module(telega@telemetry).
-compile([no_auto_import, nowarn_unused_vars, nowarn_unused_function, nowarn_nomatch, inline]).
-define(FILEPATH, "src/telega/telemetry.gleam").
-export([execute/3, attach_many/3, detach/1, monotonic_time/0, system_time/0, native_to_millisecond/1, span/3]).
-export_type([value/0]).

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

?MODULEDOC(
    " Telemetry events for production observability.\n"
    "\n"
    " Telega emits [`telemetry`](https://hexdocs.pm/telemetry/) events at every\n"
    " key point of the update lifecycle, so standard BEAM exporters (PromEx,\n"
    " `opentelemetry_telemetry`, custom handlers) work out of the box.\n"
    " Emitting an event with no attached handlers is nearly free (a single ETS\n"
    " lookup), so instrumentation costs nothing until you attach a handler.\n"
    "\n"
    " ## Event reference\n"
    "\n"
    " | Event | Measurements | Metadata |\n"
    " |---|---|---|\n"
    " | `telega.update.start` | `system_time` | `update_type`, `chat_id`, `from_id` |\n"
    " | `telega.update.stop` | `duration` | `update_type`, `chat_id`, `from_id` |\n"
    " | `telega.update.exception` | `duration` | `error`, `update_type`, `chat_id`, `from_id` |\n"
    " | `telega.api_call.start` | `system_time` | `method` |\n"
    " | `telega.api_call.stop` | `duration` | `method`, `status` |\n"
    " | `telega.api_call.exception` | `duration` | `method`, `error` |\n"
    " | `telega.api_call.retry` | `retry_after` (ms) | `method`, `attempt` |\n"
    " | `telega.request_queue.depth` | `depth` | `rule_id`, `priority` |\n"
    " | `telega.rate_limit.hit` | `count` | `update_type`, `chat_id`, `from_id` |\n"
    " | `telega.chat_instance.spawn` | `count` | `chat_id`, `from_id` |\n"
    " | `telega.chat_instance.terminate` | `count` | `key`, `reason` |\n"
    " | `telega.flow.step` | `duration` | `flow_name`, `step` |\n"
    " | `telega.flow.timeout` | `count` | `flow_name`, `step` |\n"
    " | `telega.flow.cancel` | `count` | `flow_name`, `step` |\n"
    " | `telega.shutdown.start` | `system_time` | — |\n"
    " | `telega.shutdown.stop` | `duration`, `drained` | `timed_out` |\n"
    "\n"
    " - Update and API call events follow the **span convention**\n"
    "   (`start`/`stop`/`exception` with a monotonic `duration`), the same\n"
    "   pattern used by Phoenix and Ecto.\n"
    " - `duration` and `system_time` are in **native time units** — convert\n"
    "   with `native_to_millisecond`.\n"
    " - `telega.update.exception` fires when a handler returns `Error(...)`,\n"
    "   before your `catch_handler` runs.\n"
    " - `telega.chat_instance.terminate` fires only for abnormal stops;\n"
    "   `reason` tells you which.\n"
    " - `telega.rate_limit.hit` fires for every update rejected by\n"
    "   `router.with_rate_limit`.\n"
    " - `telega.shutdown.start`/`stop` wrap `telega.shutdown`'s graceful drain;\n"
    "   `drained` is the number of in-flight updates waited for and `timed_out`\n"
    "   is `True` if the drain timeout elapsed first.\n"
    "\n"
    " ## Attaching a handler\n"
    "\n"
    " `attach_many` subscribes one handler (identified by a unique id) to a\n"
    " list of events. The handler receives the event name, measurements, and\n"
    " metadata as lists of pairs:\n"
    "\n"
    " ```gleam\n"
    " import gleam/int\n"
    " import gleam/io\n"
    " import gleam/list\n"
    " import telega/telemetry\n"
    "\n"
    " pub fn attach_slow_update_logger() {\n"
    "   telemetry.attach_many(\n"
    "     id: \"my-bot-slow-updates\",\n"
    "     events: [[\"telega\", \"update\", \"stop\"]],\n"
    "     handler: fn(_event, measurements, metadata) {\n"
    "       let assert Ok(duration) = list.key_find(measurements, \"duration\")\n"
    "       let ms = telemetry.native_to_millisecond(duration)\n"
    "\n"
    "       case ms > 1000 {\n"
    "         True -> {\n"
    "           let update_type = case list.key_find(metadata, \"update_type\") {\n"
    "             Ok(telemetry.StringValue(t)) -> t\n"
    "             _ -> \"unknown\"\n"
    "           }\n"
    "           io.println(\n"
    "             \"slow update: \" <> update_type <> \" took \" <> int.to_string(ms) <> \"ms\",\n"
    "           )\n"
    "         }\n"
    "         False -> Nil\n"
    "       }\n"
    "     },\n"
    "   )\n"
    " }\n"
    " ```\n"
    "\n"
    " Call it once at startup, before `telega.init_for_polling()` /\n"
    " `telega.init()`. Detach with `telemetry.detach(\"my-bot-slow-updates\")`.\n"
    "\n"
    " **Handlers run synchronously in the process that emitted the event.**\n"
    " Keep them fast, never call the Telegram API from a handler, and offload\n"
    " anything heavy to another process (see below). A handler that crashes is\n"
    " automatically detached by telemetry.\n"
    "\n"
    " ## Forwarding events to a process\n"
    "\n"
    " To get events out of the hot path, forward them to a subject and consume\n"
    " them from your own process (an actor, a metrics aggregator, a test\n"
    " assertion):\n"
    "\n"
    " ```gleam\n"
    " import gleam/erlang/process\n"
    " import telega/telemetry\n"
    "\n"
    " pub type Event {\n"
    "   Event(\n"
    "     name: List(String),\n"
    "     measurements: List(#(String, Int)),\n"
    "     metadata: List(#(String, telemetry.Value)),\n"
    "   )\n"
    " }\n"
    "\n"
    " pub fn attach_forwarder(\n"
    "   id id: String,\n"
    "   events events: List(List(String)),\n"
    " ) -> process.Subject(Event) {\n"
    "   let subject = process.new_subject()\n"
    "   telemetry.attach_many(id:, events:, handler: fn(name, measurements, metadata) {\n"
    "     process.send(subject, Event(name:, measurements:, metadata:))\n"
    "   })\n"
    "   subject\n"
    " }\n"
    " ```\n"
    "\n"
    " This is also the easiest way to assert on telemetry in tests:\n"
    "\n"
    " ```gleam\n"
    " pub fn api_call_emits_stop_test() {\n"
    "   let subject =\n"
    "     attach_forwarder(id: \"test-api-call\", events: [\n"
    "       [\"telega\", \"api_call\", \"stop\"],\n"
    "     ])\n"
    "\n"
    "   // ... call the bot / client ...\n"
    "\n"
    "   let assert Ok(Event(name:, ..)) = process.receive(subject, 100)\n"
    "   assert name == [\"telega\", \"api_call\", \"stop\"]\n"
    "\n"
    "   telemetry.detach(\"test-api-call\")\n"
    " }\n"
    " ```\n"
    "\n"
    " ## Exporters\n"
    "\n"
    " Because events follow the standard telemetry span convention, any BEAM\n"
    " exporter can consume them — attach it to the event names from the table\n"
    " above:\n"
    "\n"
    " - **Prometheus**: the [`prometheus`](https://hex.pm/packages/prometheus)\n"
    "   Erlang package — register counters/histograms at startup and update\n"
    "   them from an `attach_many` handler (convert durations with\n"
    "   `native_to_millisecond`).\n"
    " - **Elixir releases**: [`telemetry_metrics`](https://hexdocs.pm/telemetry_metrics/) +\n"
    "   [`telemetry_metrics_prometheus`](https://hexdocs.pm/telemetry_metrics_prometheus/),\n"
    "   or a custom [PromEx](https://hexdocs.pm/prom_ex/) plugin — declare\n"
    "   metrics like `counter(\"telega.update.stop.duration\")`.\n"
    " - **OpenTelemetry**: [`opentelemetry_telemetry`](https://hexdocs.pm/opentelemetry_telemetry/)\n"
    "   bridges the `start`/`stop`/`exception` spans into traces.\n"
).

-type value() :: {string_value, binary()} |
    {int_value, integer()} |
    {float_value, float()} |
    {bool_value, boolean()}.

-file("src/telega/telemetry.gleam", 273).
-spec value_to_dynamic(value()) -> gleam@dynamic:dynamic_().
value_to_dynamic(Value) ->
    case Value of
        {string_value, String} ->
            gleam_stdlib:identity(String);

        {int_value, Int} ->
            gleam_stdlib:identity(Int);

        {float_value, Float} ->
            gleam_stdlib:identity(Float);

        {bool_value, Bool} ->
            gleam_stdlib:identity(Bool)
    end.

-file("src/telega/telemetry.gleam", 199).
?DOC(
    " Emit a telemetry event.\n"
    "\n"
    " ```gleam\n"
    " telemetry.execute([\"telega\", \"update\", \"start\"], [#(\"system_time\", now)], [\n"
    "   #(\"update_type\", telemetry.StringValue(\"text\")),\n"
    " ])\n"
    " ```\n"
).
-spec execute(
    list(binary()),
    list({binary(), integer()}),
    list({binary(), value()})
) -> nil.
execute(Event, Measurements, Metadata) ->
    _ = telemetry:execute(
        gleam@list:map(Event, fun erlang:binary_to_atom/1),
        begin
            _pipe = Measurements,
            _pipe@1 = gleam@list:map(
                _pipe,
                fun(Pair) ->
                    {erlang:binary_to_atom(erlang:element(1, Pair)),
                        erlang:element(2, Pair)}
                end
            ),
            maps:from_list(_pipe@1)
        end,
        begin
            _pipe@2 = Metadata,
            _pipe@3 = gleam@list:map(
                _pipe@2,
                fun(Pair@1) ->
                    {erlang:binary_to_atom(erlang:element(1, Pair@1)),
                        value_to_dynamic(erlang:element(2, Pair@1))}
                end
            ),
            maps:from_list(_pipe@3)
        end
    ),
    nil.

-file("src/telega/telemetry.gleam", 282).
-spec dynamic_to_value(gleam@dynamic:dynamic_()) -> value().
dynamic_to_value(Value) ->
    Decoder = gleam@dynamic@decode:one_of(
        gleam@dynamic@decode:map(
            {decoder, fun gleam@dynamic@decode:decode_string/1},
            fun(Field@0) -> {string_value, Field@0} end
        ),
        [gleam@dynamic@decode:map(
                {decoder, fun gleam@dynamic@decode:decode_bool/1},
                fun(Field@0) -> {bool_value, Field@0} end
            ),
            gleam@dynamic@decode:map(
                {decoder, fun gleam@dynamic@decode:decode_int/1},
                fun(Field@0) -> {int_value, Field@0} end
            ),
            gleam@dynamic@decode:map(
                {decoder, fun gleam@dynamic@decode:decode_float/1},
                fun(Field@0) -> {float_value, Field@0} end
            )]
    ),
    case gleam@dynamic@decode:run(Value, Decoder) of
        {ok, Value@1} ->
            Value@1;

        {error, _} ->
            {string_value, gleam@string:inspect(Value)}
    end.

-file("src/telega/telemetry.gleam", 224).
?DOC(
    " Attach a handler to several events. The `id` must be unique.\n"
    "\n"
    " The handler runs synchronously in the process that emitted the event —\n"
    " keep it fast and never call the Telegram API from it. A handler that\n"
    " crashes is detached by telemetry.\n"
).
-spec attach_many(
    binary(),
    list(list(binary())),
    fun((list(binary()), list({binary(), integer()}), list({binary(), value()})) -> nil)
) -> nil.
attach_many(Id, Events, Handler) ->
    _ = telemetry:attach_many(
        Id,
        gleam@list:map(
            Events,
            fun(Event) -> gleam@list:map(Event, fun erlang:binary_to_atom/1) end
        ),
        fun(Event@1, Measurements, Metadata, _) ->
            Handler(
                gleam@list:map(Event@1, fun erlang:atom_to_binary/1),
                begin
                    _pipe = Measurements,
                    _pipe@1 = maps:to_list(_pipe),
                    gleam@list:map(
                        _pipe@1,
                        fun(Pair) ->
                            {erlang:atom_to_binary(erlang:element(1, Pair)),
                                erlang:element(2, Pair)}
                        end
                    )
                end,
                begin
                    _pipe@2 = Metadata,
                    _pipe@3 = maps:to_list(_pipe@2),
                    gleam@list:map(
                        _pipe@3,
                        fun(Pair@1) ->
                            {erlang:atom_to_binary(erlang:element(1, Pair@1)),
                                dynamic_to_value(erlang:element(2, Pair@1))}
                        end
                    )
                end
            )
        end,
        nil
    ),
    nil.

-file("src/telega/telemetry.gleam", 252).
?DOC(" Detach a previously attached handler by its id.\n").
-spec detach(binary()) -> nil.
detach(Id) ->
    _ = telemetry:detach(Id),
    nil.

-file("src/telega/telemetry.gleam", 259).
?DOC(" Current monotonic time in native units. Use for measuring durations.\n").
-spec monotonic_time() -> integer().
monotonic_time() ->
    erlang:monotonic_time().

-file("src/telega/telemetry.gleam", 263).
?DOC(" Current system time in native units.\n").
-spec system_time() -> integer().
system_time() ->
    erlang:system_time().

-file("src/telega/telemetry.gleam", 269).
?DOC(" Convert a native time unit value (e.g. a `duration` measurement) to milliseconds.\n").
-spec native_to_millisecond(integer()) -> integer().
native_to_millisecond(Time) ->
    erlang:convert_time_unit(
        Time,
        erlang:binary_to_atom(<<"native"/utf8>>),
        erlang:binary_to_atom(<<"millisecond"/utf8>>)
    ).

-file("src/telega/telemetry.gleam", 301).
?DOC(
    " Wrap a `Result`-returning function in a `start`/`stop`/`exception` span,\n"
    " following the Phoenix/Ecto span convention:\n"
    "\n"
    " - `event + [start]` with `system_time` before the function runs\n"
    " - `event + [stop]` with monotonic `duration` on `Ok`\n"
    " - `event + [exception]` with `duration` and inspected `error` metadata on `Error`\n"
).
-spec span(
    list(binary()),
    list({binary(), value()}),
    fun(() -> {ok, KCL} | {error, KCM})
) -> {ok, KCL} | {error, KCM}.
span(Event, Metadata, Run) ->
    Started_at = erlang:monotonic_time(),
    execute(
        lists:append(Event, [<<"start"/utf8>>]),
        [{<<"system_time"/utf8>>, erlang:system_time()}],
        Metadata
    ),
    Result = Run(),
    Duration = erlang:monotonic_time() - Started_at,
    case Result of
        {ok, _} ->
            execute(
                lists:append(Event, [<<"stop"/utf8>>]),
                [{<<"duration"/utf8>>, Duration}],
                Metadata
            );

        {error, Error} ->
            execute(
                lists:append(Event, [<<"exception"/utf8>>]),
                [{<<"duration"/utf8>>, Duration}],
                [{<<"error"/utf8>>, {string_value, gleam@string:inspect(Error)}} |
                    Metadata]
            )
    end,
    Result.