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#include <chrono>
#include <memory>
#include <mutex>
#include <sstream>
#include <string>
#include <thread>
#include <vector>

#include <grpc++/channel.h>
#include <grpc++/client_context.h>
#include <grpc++/server.h>
#include <grpc++/server_builder.h>
#include <grpc/grpc.h>
#include <grpc/support/alloc.h>
#include <grpc/support/host_port.h>
#include <grpc/support/log.h>
#include <grpc/support/time.h>
#include <gtest/gtest.h>

#include "src/core/lib/profiling/timers.h"
#include "src/proto/grpc/testing/services.grpc.pb.h"
#include "test/cpp/qps/client.h"
#include "test/cpp/qps/interarrival.h"
#include "test/cpp/qps/usage_timer.h"

namespace grpc {
namespace testing {

static std::unique_ptr<BenchmarkService::Stub> BenchmarkStubCreator(
    std::shared_ptr<Channel> ch) {
  return BenchmarkService::NewStub(ch);
}

class SynchronousClient
    : public ClientImpl<BenchmarkService::Stub, SimpleRequest> {
 public:
  SynchronousClient(const ClientConfig& config)
      : ClientImpl<BenchmarkService::Stub, SimpleRequest>(
            config, BenchmarkStubCreator) {
    num_threads_ =
        config.outstanding_rpcs_per_channel() * config.client_channels();
    responses_.resize(num_threads_);
    SetupLoadTest(config, num_threads_);
  }

  virtual ~SynchronousClient(){};

 protected:
  // WaitToIssue returns false if we realize that we need to break out
  bool WaitToIssue(int thread_idx) {
    if (!closed_loop_) {
      const gpr_timespec next_issue_time = NextIssueTime(thread_idx);
      // Avoid sleeping for too long continuously because we might
      // need to terminate before then. This is an issue since
      // exponential distribution can occasionally produce bad outliers
      while (true) {
        const gpr_timespec one_sec_delay =
            gpr_time_add(gpr_now(GPR_CLOCK_MONOTONIC),
                         gpr_time_from_seconds(1, GPR_TIMESPAN));
        if (gpr_time_cmp(next_issue_time, one_sec_delay) <= 0) {
          gpr_sleep_until(next_issue_time);
          return true;
        } else {
          gpr_sleep_until(one_sec_delay);
          if (gpr_atm_acq_load(&thread_pool_done_) != static_cast<gpr_atm>(0)) {
            return false;
          }
        }
      }
    }
    return true;
  }

  size_t num_threads_;
  std::vector<SimpleResponse> responses_;

 private:
  void DestroyMultithreading() override final { EndThreads(); }
};

class SynchronousUnaryClient final : public SynchronousClient {
 public:
  SynchronousUnaryClient(const ClientConfig& config)
      : SynchronousClient(config) {
    StartThreads(num_threads_);
  }
  ~SynchronousUnaryClient() {}

  bool ThreadFunc(HistogramEntry* entry, size_t thread_idx) override {
    if (!WaitToIssue(thread_idx)) {
      return true;
    }
    auto* stub = channels_[thread_idx % channels_.size()].get_stub();
    double start = UsageTimer::Now();
    GPR_TIMER_SCOPE("SynchronousUnaryClient::ThreadFunc", 0);
    grpc::ClientContext context;
    grpc::Status s =
        stub->UnaryCall(&context, request_, &responses_[thread_idx]);
    if (s.ok()) {
      entry->set_value((UsageTimer::Now() - start) * 1e9);
    }
    entry->set_status(s.error_code());
    return true;
  }
};

class SynchronousStreamingClient final : public SynchronousClient {
 public:
  SynchronousStreamingClient(const ClientConfig& config)
      : SynchronousClient(config),
        context_(num_threads_),
        stream_(num_threads_),
        messages_per_stream_(config.messages_per_stream()),
        messages_issued_(num_threads_) {
    for (size_t thread_idx = 0; thread_idx < num_threads_; thread_idx++) {
      auto* stub = channels_[thread_idx % channels_.size()].get_stub();
      stream_[thread_idx] = stub->StreamingCall(&context_[thread_idx]);
      messages_issued_[thread_idx] = 0;
    }
    StartThreads(num_threads_);
  }
  ~SynchronousStreamingClient() {
    std::vector<std::thread> cleanup_threads;
    for (size_t i = 0; i < num_threads_; i++) {
      cleanup_threads.emplace_back([this, i]() {
        auto stream = &stream_[i];
        if (*stream) {
          (*stream)->WritesDone();
          Status s = (*stream)->Finish();
          if (!s.ok()) {
            gpr_log(GPR_ERROR, "Stream %" PRIuPTR " received an error %s", i,
                    s.error_message().c_str());
          }
        }
      });
    }
    for (size_t i = 0; i < num_threads_; i++) {
      cleanup_threads[i].join();
    }
  }

  bool ThreadFunc(HistogramEntry* entry, size_t thread_idx) override {
    if (!WaitToIssue(thread_idx)) {
      return true;
    }
    GPR_TIMER_SCOPE("SynchronousStreamingClient::ThreadFunc", 0);
    double start = UsageTimer::Now();
    if (stream_[thread_idx]->Write(request_) &&
        stream_[thread_idx]->Read(&responses_[thread_idx])) {
      entry->set_value((UsageTimer::Now() - start) * 1e9);
      // don't set the status since there isn't one yet
      if ((messages_per_stream_ != 0) &&
          (++messages_issued_[thread_idx] < messages_per_stream_)) {
        return true;
      } else if (messages_per_stream_ == 0) {
        return true;
      } else {
        // Fall through to the below resetting code after finish
      }
    }
    stream_[thread_idx]->WritesDone();
    Status s = stream_[thread_idx]->Finish();
    // don't set the value since this is either a failure (shouldn't be timed)
    // or a stream-end (already has been timed)
    entry->set_status(s.error_code());
    if (!s.ok()) {
      gpr_log(GPR_ERROR, "Stream %" PRIuPTR " received an error %s", thread_idx,
              s.error_message().c_str());
    }
    auto* stub = channels_[thread_idx % channels_.size()].get_stub();
    context_[thread_idx].~ClientContext();
    new (&context_[thread_idx]) ClientContext();
    stream_[thread_idx] = stub->StreamingCall(&context_[thread_idx]);
    messages_issued_[thread_idx] = 0;
    return true;
  }

 private:
  // These are both conceptually std::vector but cannot be for old compilers
  // that expect contained classes to support copy constructors
  std::vector<grpc::ClientContext> context_;
  std::vector<
      std::unique_ptr<grpc::ClientReaderWriter<SimpleRequest, SimpleResponse>>>
      stream_;
  const int messages_per_stream_;
  std::vector<int> messages_issued_;
};

std::unique_ptr<Client> CreateSynchronousUnaryClient(
    const ClientConfig& config) {
  return std::unique_ptr<Client>(new SynchronousUnaryClient(config));
}
std::unique_ptr<Client> CreateSynchronousStreamingClient(
    const ClientConfig& config) {
  return std::unique_ptr<Client>(new SynchronousStreamingClient(config));
}

}  // namespace testing
}  // namespace grpc