#pragma once

#include <memory>

#include "envoy/extensions/tracers/opentelemetry/samplers/v3/parent_based_sampler.pb.h"

#include "envoy/server/factory_context.h"

#include "source/common/common/logger.h"

#include "source/extensions/tracers/opentelemetry/samplers/sampler.h"

namespace Envoy {

namespace Extensions {

namespace Tracers {

namespace OpenTelemetry {

/**

 * This is a sampler decorator. If the parent context is empty or doesn't have a valid traceId,

 * the ParentBasedSampler will delegate the decision to the wrapped sampler.

 * Otherwise, it will decide based on the sampled flag of the parent context:

 * if parent_context->sampled -> return RecordAndSample

 * else -> return Decision::Drop

 * Check https://opentelemetry.io/docs/specs/otel/trace/sdk/#parentbased for the official docs and

 * https://github.com/open-telemetry/opentelemetry-cpp/blob/eb2b9753ea2df64079e07d40489388ea1b323108/sdk/src/trace/samplers/parent.cc#L30

 * for an official implementation

 */

class ParentBasedSampler : public Sampler, Logger::Loggable<Logger::Id::tracing> {

public:

  explicit ParentBasedSampler(const Protobuf::Message& /*config*/,

                              Server::Configuration::TracerFactoryContext& /*context*/,

                              SamplerSharedPtr wrapped_sampler)

  SamplingResult shouldSample(const StreamInfo::StreamInfo& stream_info,

                              const absl::optional<SpanContext> parent_context,

                              const std::string& trace_id, const std::string& name,

                              OTelSpanKind spankind,

                              OptRef<const Tracing::TraceContext> trace_context,

                              const std::vector<SpanContext>& links) override;

  std::string getDescription() const override;

private:

  SamplerSharedPtr wrapped_sampler_;

};

} // namespace OpenTelemetry

} // namespace Tracers

} // namespace Extensions

} // namespace Envoy