#define MS_CLASS "BackoffTimerHandle"
// #define MS_LOG_DEV_LEVEL 3

#include "handles/BackoffTimerHandle.hpp"
#include "Logger.hpp"
#include "MediaSoupErrors.hpp"
#include <algorithm> // std::min()

/* Instance methods. */

BackoffTimerHandle::BackoffTimerHandle(BackoffTimerHandleOptions options)
  : listener(options.listener),
    label(std::move(options.label)),
    baseTimeoutMs(options.baseTimeoutMs),
    backoffAlgorithm(options.backoffAlgorithm),
    maxBackoffTimeoutMs(options.maxBackoffTimeoutMs),
    maxRestarts(options.maxRestarts)
{
	MS_TRACE();

	if (!this->listener)
	{
		MS_THROW_TYPE_ERROR("options.listener must be given");
	}

	if (this->label.empty())
	{
		MS_THROW_TYPE_ERROR("options.label must be given");
	}

	if (this->baseTimeoutMs > BackoffTimerHandleInterface::MaxTimeoutMs)
	{
		MS_THROW_ERROR(
		  "[%s] base timeout (%" PRIu64 " ms) cannot be greater than %" PRIu64 " ms",
		  this->label.c_str(),
		  this->baseTimeoutMs,
		  BackoffTimerHandleInterface::MaxTimeoutMs);
	}

	this->timer = new TimerHandle(this);
}

BackoffTimerHandle::~BackoffTimerHandle()
{
	MS_TRACE();

	delete this->timer;
	this->timer = nullptr;
}

void BackoffTimerHandle::Start()
{
	MS_TRACE();

	this->timer->Start(this->baseTimeoutMs);

	this->running         = true;
	this->expirationCount = 0;
}

void BackoffTimerHandle::Stop()
{
	MS_TRACE();

	this->timer->Stop();

	this->running         = false;
	this->expirationCount = 0;
}

void BackoffTimerHandle::SetBaseTimeoutMs(uint64_t baseTimeoutMs)
{
	MS_TRACE();

	if (baseTimeoutMs > BackoffTimerHandleInterface::MaxTimeoutMs)
	{
		MS_THROW_ERROR(
		  "[%s] base timeout (%" PRIu64 " ms) cannot be greater than %" PRIu64 " ms",
		  this->label.c_str(),
		  baseTimeoutMs,
		  BackoffTimerHandleInterface::MaxTimeoutMs);
	}

	this->baseTimeoutMs = baseTimeoutMs;
}

uint64_t BackoffTimerHandle::ComputeNextTimeoutMs() const
{
	MS_TRACE();

	auto expirationCount = this->expirationCount;

	switch (this->backoffAlgorithm)
	{
		case BackoffAlgorithm::FIXED:
		{
			return this->baseTimeoutMs;
		}

		case BackoffAlgorithm::EXPONENTIAL:
		{
			auto timeoutMs = this->baseTimeoutMs;

			while (expirationCount > 0 && timeoutMs < BackoffTimerHandleInterface::MaxTimeoutMs)
			{
				timeoutMs *= 2;
				--expirationCount;

				if (this->maxBackoffTimeoutMs.has_value() && timeoutMs > this->maxBackoffTimeoutMs.value())
				{
					return this->maxBackoffTimeoutMs.value();
				}
			}

			return std::min<uint64_t>(timeoutMs, BackoffTimerHandleInterface::MaxTimeoutMs);
		}

			NO_DEFAULT_GCC();
	}
}

void BackoffTimerHandle::OnTimer(TimerHandleInterface* /*timer*/)
{
	MS_TRACE();

	this->expirationCount++;

	// Compute whether the BackoffTimer should still be running after this timeout
	// expiration so the parent can check IsRunning() within the `OnBackoffTimer()`
	// callback.
	this->running =
	  !this->maxRestarts.has_value() || this->expirationCount <= this->maxRestarts.value();

	uint64_t baseTimeoutMs{ this->baseTimeoutMs };
	bool stop{ false };

	// Call the listener by passing base timeout as reference so the parent has
	// a chance to change it and affect the next timeout.
	this->listener->OnBackoffTimer(this, baseTimeoutMs, stop);

	// If the parent has set `stop` to true it means that it has deleted the
	// instance, so stop here.
	if (stop)
	{
		return;
	}

	// NOTE: This may throw.
	SetBaseTimeoutMs(baseTimeoutMs);

	// The caller may have called Stop() within the callback so we must check
	// the `running` flag.
	if (this->running)
	{
		auto nextTimeoutMs = ComputeNextTimeoutMs();

		this->timer->Start(nextTimeoutMs);
	}
}