#include "source/extensions/tracers/xray/tracer.h"

#include <algorithm>

#include <chrono>

#include <string>

#include "envoy/http/header_map.h"

#include "envoy/network/listener.h"

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

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

#include "source/common/protobuf/utility.h"

#include "source/common/tracing/http_tracer_impl.h"

#include "source/extensions/tracers/xray/daemon.pb.validate.h"

namespace Envoy {

namespace Extensions {

namespace Tracers {

namespace XRay {

namespace {

constexpr absl::string_view XRaySerializationVersion = "1";

constexpr absl::string_view DirectionKey = "direction";

// X-Ray Trace ID Format

//

// A trace_id consists of three parts separated by hyphens.

// For example, 1-58406cf0-a006649127e371903a2de979.

// This includes:

//

// - The version number, that is, 1.

// - The time of the original request, in Unix epoch time, in 8 hexadecimal digits.

// - A 96-bit unique identifier in 24 hexadecimal digits.

//

// For more details see:

// https://docs.aws.amazon.com/xray/latest/devguide/xray-api-segmentdocuments.html#api-segmentdocuments-fields

std::string generateTraceId(SystemTime point_in_time, Random::RandomGenerator& random) {

  using std::chrono::seconds;

  using std::chrono::time_point_cast;

  // epoch in seconds represented as 8 hexadecimal characters

  const auto epoch = time_point_cast<seconds>(point_in_time).time_since_epoch().count();

  std::string uuid = random.uuid();

  // unique id represented as 24 hexadecimal digits and no dashes

  uuid.erase(std::remove(uuid.begin(), uuid.end(), '-'), uuid.end());

  ASSERT(uuid.length() >= 24);

  const std::string out =

      absl::StrCat(XRaySerializationVersion, "-", Hex::uint32ToHex(epoch), "-", uuid.substr(0, 24));

  return out;

}

} // namespace

void Span::finishSpan() {

  using std::chrono::time_point_cast;

  using namespace source::extensions::tracers::xray;

  // X-Ray expects timestamps to be in epoch seconds with milli/micro-second precision as a fraction

  using SecondsWithFraction = std::chrono::duration<double>;

  if (!sampled()) {

    return;

  }

  daemon::Segment s;

  s.set_name(name());

  s.set_id(id());

  s.set_trace_id(traceId());

  s.set_start_time(time_point_cast<SecondsWithFraction>(startTime()).time_since_epoch().count());

  s.set_end_time(

      time_point_cast<SecondsWithFraction>(time_source_.systemTime()).time_since_epoch().count());

  s.set_origin(origin());

  s.set_parent_id(parentId());

  s.set_error(clientError());

  s.set_fault(serverError());

  s.set_throttle(isThrottled());

  if (type() == Subsegment) {

    s.set_type(std::string(Subsegment));

  }

  auto* aws = s.mutable_aws()->mutable_fields();

  for (const auto& field : aws_metadata_) {

    aws->insert({field.first, field.second});

  }

  auto* request_fields = s.mutable_http()->mutable_request()->mutable_fields();

  for (const auto& field : http_request_annotations_) {

    request_fields->insert({field.first, field.second});

  }

  auto* response_fields = s.mutable_http()->mutable_response()->mutable_fields();

  for (const auto& field : http_response_annotations_) {

    response_fields->insert({field.first, field.second});

  }

  for (const auto& item : custom_annotations_) {

    s.mutable_annotations()->insert({item.first, item.second});

  }

  // `direction` will be either "ingress" or "egress"

  s.mutable_annotations()->insert({std::string(DirectionKey), direction()});

  const std::string json = MessageUtil::getJsonStringFromMessageOrError(

      s, false /* pretty_print  */, false /* always_print_primitive_fields */);

  broker_.send(json);

} // namespace XRay

void Span::injectContext(Tracing::TraceContext& trace_context,

                         const Upstream::HostDescriptionConstSharedPtr&) {

  const std::string xray_header_value =

      fmt::format("Root={};Parent={};Sampled={}", traceId(), id(), sampled() ? "1" : "0");

  trace_context.setByReferenceKey(XRayTraceHeader, xray_header_value);

}

Tracing::SpanPtr Span::spawnChild(const Tracing::Config& config, const std::string& operation_name,

                                  Envoy::SystemTime start_time) {

  auto child_span = std::make_unique<XRay::Span>(time_source_, random_, broker_);

  child_span->setName(operation_name);

  child_span->setOperation(operation_name);

  child_span->setDirection(Tracing::TracerUtility::toString(config.operationName()));

  child_span->setStartTime(start_time);

  child_span->setParentId(id());

  child_span->setTraceId(traceId());

  child_span->setSampled(sampled());

  child_span->setType(Subsegment);

  return child_span;

}

Tracing::SpanPtr Tracer::startSpan(const Tracing::Config& config, const std::string& operation_name,

                                   Envoy::SystemTime start_time,

                                   const absl::optional<XRayHeader>& xray_header,

                                   const absl::optional<absl::string_view> client_ip) {

  auto span_ptr = std::make_unique<XRay::Span>(time_source_, random_, *daemon_broker_);

  span_ptr->setName(segment_name_);

  span_ptr->setOperation(operation_name);

  span_ptr->setDirection(Tracing::TracerUtility::toString(config.operationName()));

  // Even though we have a TimeSource member in the tracer, we assume the start_time argument has a

  // more precise value than calling the systemTime() at this point in time.

  span_ptr->setStartTime(start_time);

  span_ptr->setOrigin(origin_);

  span_ptr->setAwsMetadata(aws_metadata_);

  if (client_ip) {

    span_ptr->addToHttpRequestAnnotations(SpanClientIp,

                                          ValueUtil::stringValue(std::string(*client_ip)));

    // The `client_ip` is the address specified in the HTTP X-Forwarded-For header.

    span_ptr->addToHttpRequestAnnotations(SpanXForwardedFor, ValueUtil::boolValue(true));

  }

  if (xray_header) {

    // There's a previous span that this span should be based-on.

    span_ptr->setParentId(xray_header->parent_id_);

    span_ptr->setTraceId(xray_header->trace_id_);

    switch (xray_header->sample_decision_) {

    case SamplingDecision::Sampled:

      span_ptr->setSampled(true);

      break;

    case SamplingDecision::NotSampled:

      // should never get here. If the header has Sampled=0 then we never call startSpan().

      IS_ENVOY_BUG("unexpected code path hit");

    default:

      break;

    }

  } else {

    span_ptr->setTraceId(generateTraceId(time_source_.systemTime(), random_));

  }

  return span_ptr;

}

XRay::SpanPtr Tracer::createNonSampledSpan(const absl::optional<XRayHeader>& xray_header) const {

  auto span_ptr = std::make_unique<XRay::Span>(time_source_, random_, *daemon_broker_);

  if (xray_header) {

    // There's a previous span that this span should be based-on.

    span_ptr->setParentId(xray_header->parent_id_);

    span_ptr->setTraceId(xray_header->trace_id_);

  } else {

    span_ptr->setTraceId(generateTraceId(time_source_.systemTime(), random_));

  }

  span_ptr->setSampled(false);

  return span_ptr;

}

void Span::setTag(absl::string_view name, absl::string_view value) {

  // For the full set of values see:

  // https://docs.aws.amazon.com/xray/latest/devguide/xray-api-segmentdocuments.html#api-segmentdocuments-http

  constexpr auto SpanContentLength = "content_length";

  constexpr auto SpanMethod = "method";

  constexpr auto SpanUrl = "url";

  if (name.empty() || value.empty()) {

    return;

  }

  if (name == Tracing::Tags::get().HttpUrl) {

    addToHttpRequestAnnotations(SpanUrl, ValueUtil::stringValue(std::string(value)));

  } else if (name == Tracing::Tags::get().HttpMethod) {

    addToHttpRequestAnnotations(SpanMethod, ValueUtil::stringValue(std::string(value)));

  } else if (name == Tracing::Tags::get().UserAgent) {

    addToHttpRequestAnnotations(Tracing::Tags::get().UserAgent,

                                ValueUtil::stringValue(std::string(value)));

  } else if (name == Tracing::Tags::get().HttpStatusCode) {

    uint64_t status_code;

    if (!absl::SimpleAtoi(value, &status_code)) {

      ENVOY_LOG(debug, "{} must be a number, given: {}", Tracing::Tags::get().HttpStatusCode,

                value);

      return;

    }

    setResponseStatusCode(status_code);

    addToHttpResponseAnnotations(Tracing::Tags::get().Status, ValueUtil::numberValue(status_code));

  } else if (name == Tracing::Tags::get().ResponseSize) {

    uint64_t response_size;

    if (!absl::SimpleAtoi(value, &response_size)) {

      ENVOY_LOG(debug, "{} must be a number, given: {}", Tracing::Tags::get().ResponseSize, value);

      return;

    }

    addToHttpResponseAnnotations(SpanContentLength, ValueUtil::numberValue(response_size));

  } else if (name == Tracing::Tags::get().PeerAddress) {

    // Use PeerAddress if client_ip is not already set from the header.

    if (!hasKeyInHttpRequestAnnotations(SpanClientIp)) {

      addToHttpRequestAnnotations(SpanClientIp, ValueUtil::stringValue(std::string(value)));

      // In this case, PeerAddress refers to the client's actual IP address, not

      // the address specified in the HTTP X-Forwarded-For header.

      addToHttpRequestAnnotations(SpanXForwardedFor, ValueUtil::boolValue(false));

    }

  } else if (name == Tracing::Tags::get().Error && value == Tracing::Tags::get().True) {

    setServerError();

  } else {

    custom_annotations_.emplace(name, value);

  }

}

} // namespace XRay

} // namespace Tracers

} // namespace Extensions

} // namespace Envoy