-module(otel_propagator_instana).

-behaviour(otel_propagator_text_map).

-export([fields/1,
         inject/4,
         extract/5]).

-include_lib("opentelemetry_api/include/opentelemetry.hrl").

-define(TRACE_ID_KEY, <<"X-INSTANA-T">>).
-define(SPAN_ID_KEY, <<"X-INSTANA-S">>).
-define(TRACE_LEVEL_KEY, <<"X-INSTANA-L">>).

fields(_) ->
    [?TRACE_ID_KEY, ?SPAN_ID_KEY, ?TRACE_LEVEL_KEY].

-spec inject(Context, Carrier, CarrierSetFun, Options) -> Carrier
              when Context :: otel_ctx:t(),
                   Carrier :: otel_propagator:carrier(),
                   CarrierSetFun :: otel_propagator_text_map:carrier_set(),
                   Options :: otel_propagator_text_map:propagator_options().
inject(Ctx, Carrier, CarrierSet, _Options) ->
    case otel_tracer:current_span_ctx(Ctx) of
        #span_ctx{trace_id=TraceId,
                  span_id=SpanId,
                  trace_flags=TraceFlags} when TraceId =/= 0 andalso SpanId =/= 0 ->
            TraceIdB = integer_to_binary(TraceId, 16),
            SpanIdB = integer_to_binary(SpanId, 16),
            TraceFlagsB = integer_to_binary(TraceFlags, 16),
            Carrier1 = CarrierSet(?TRACE_ID_KEY, TraceIdB, Carrier),
            Carrier2 = CarrierSet(?SPAN_ID_KEY, SpanIdB, Carrier1),
            CarrierSet(?TRACE_LEVEL_KEY, TraceFlagsB, Carrier2);
        _ ->
            Carrier
    end.


-spec extract(Context, Carrier, CarrierKeysFun, CarrierGetFun, Options) -> Context
              when Context :: otel_ctx:t(),
                   Carrier :: otel_propagator:carrier(),
                   CarrierKeysFun :: otel_propagator_text_map:carrier_keys(),
                   CarrierGetFun :: otel_propagator_text_map:carrier_get(),
                   Options :: otel_propagator_text_map:propagator_options().
extract(Ctx, Carrier, _CarrierKeysFun, CarrierGet, _Options) ->
    try extract1(Ctx, Carrier, _CarrierKeysFun, CarrierGet, _Options) of
        {TraceId, SpanId, TraceLevel} ->
            SpanCtx = otel_tracer:from_remote_span(TraceId, SpanId, TraceLevel),
            otel_tracer:set_current_span(Ctx, SpanCtx)
    catch
        _:_ -> Ctx
    end.

extract1(_Ctx, Carrier, _CarrierKeysFun, CarrierGet, _Options) ->
    TraceId = binary_to_integer(CarrierGet(?TRACE_ID_KEY, Carrier), 16),
    SpanId = binary_to_integer(CarrierGet(?SPAN_ID_KEY, Carrier), 16),
    TraceLevel = binary_to_integer(CarrierGet(?TRACE_LEVEL_KEY, Carrier), 16),
    if
    (TraceId > 1) and (SpanId > 1) and (TraceLevel >= 0) and (TraceLevel =< 1) ->
        {TraceId, SpanId, TraceLevel};
    true ->
        exit("")
    end.