nearby/cpp/platform/impl/g3/settable_future_impl.h

#ifndef PLATFORM_IMPL_G3_SETTABLE_FUTURE_IMPL_H_
#define PLATFORM_IMPL_G3_SETTABLE_FUTURE_IMPL_H_

#include <utility>

#include "platform/api/platform.h"
#include "platform/api/settable_future.h"
#include "absl/synchronization/mutex.h"
#include "absl/time/clock.h"
#include "absl/types/any.h"

namespace location {
namespace nearby {
namespace platform {

class SettableFutureImpl : public SettableFuture<absl::any> {
 public:
  explicit SettableFutureImpl() = default;
  ~SettableFutureImpl() override = default;

  bool set(absl::any value) override {
    absl::MutexLock lock(&mutex_);
    if (!done_) {
      value_ = std::move(value);
      done_ = true;
      exception_ = {Exception::kSuccess};
      completed_.SignalAll();
    }
    return true;
  }

  bool setException(Exception exception) override {
    absl::MutexLock lock(&mutex_);
    return SetExceptionLocked(exception);
  }

  void addListener(Ptr<Runnable> runnable, Executor* executor) override {}

  ExceptionOr<std::any> get() override {
    absl::MutexLock lock(&mutex_);
    while (!done_) {
      completed_.Wait(&mutex_);
    }
    return exception_.value != Exception::kSuccess
               ? ExceptionOr<std::any>{exception_.value}
               : ExceptionOr<std::any>{value_};
  }

  ExceptionOr<std::any> get(std::int64_t timeout_ms) override {
    absl::MutexLock lock(&mutex_);
    absl::Duration timeout = absl::Milliseconds(timeout_ms);
    while (!done_) {
      absl::Time start_time = absl::Now();
      if (completed_.WaitWithTimeout(&mutex_, timeout)) {
        SetExceptionLocked({Exception::kTimeout});
        break;
      }
      absl::Duration spent = absl::Now() - start_time;
      if (spent < timeout) {
        timeout -= spent;
      } else if (!done_) {
        SetExceptionLocked({Exception::kTimeout});
        break;
      }
    }
    return exception_.value != Exception::kSuccess
               ? ExceptionOr<std::any>{exception_.value}
               : ExceptionOr<std::any>{value_};
  }

 private:
  bool SetExceptionLocked(Exception exception) {
    if (!done_) {
      exception_ = exception.value != Exception::kSuccess
                       ? exception
                       : Exception{Exception::kFailed};
      done_ = true;
      completed_.SignalAll();
    }
    return true;
  }

  absl::Mutex mutex_;
  absl::CondVar completed_;
  bool done_{false};
  absl::any value_;
  Exception exception_{Exception::kFailed};
};

}  // namespace platform
}  // namespace nearby
}  // namespace location

#endif  // PLATFORM_IMPL_G3_SETTABLE_FUTURE_IMPL_H_