#pragma once

#include <memory>

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

#include "envoy/server/factory_context.h"

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

#include "source/common/config/datasource.h"

#include "source/extensions/tracers/opentelemetry/samplers/dynatrace/sampler_config_provider.h"

#include "source/extensions/tracers/opentelemetry/samplers/dynatrace/sampling_controller.h"

#include "source/extensions/tracers/opentelemetry/samplers/dynatrace/stream_summary.h"

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

#include "absl/synchronization/mutex.h"

namespace Envoy {

namespace Extensions {

namespace Tracers {

namespace OpenTelemetry {

/**

 * @brief A Dynatrace specific sampler.

 *

 * For sampling, the requests are categorized based on the http method and the http path.

 * A sampling multiplicity is calculated for every request category based on the

 * number of requests. A Dynatrace specific tag is added to the http tracestate header.

 */

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

public:

  DynatraceSampler(

      const envoy::extensions::tracers::opentelemetry::samplers::v3::DynatraceSamplerConfig& config,

      Server::Configuration::TracerFactoryContext& context,

      SamplerConfigProviderPtr sampler_config_provider);

  /** @see Sampler#shouldSample */

  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:

  std::string dt_tracestate_key_; // used as key in the http tracestate header

  Event::TimerPtr timer_;         // used to periodically calculate sampling multiplicity

  SamplingController sampling_controller_;

};

} // namespace OpenTelemetry

} // namespace Tracers

} // namespace Extensions

} // namespace Envoy