#include <config.h>
#include <iostream>
#include <chrono>
#include <algorithm>
#include <boost/asio/io_context.hpp>
#include <opts.h>
#include <componentThread.h>
#include <adapters/boostAsio/deadlineTimerAReq.h>
#include <spinscale/spinLock.h>
#include <user/stimulusProducer.h>
#include <user/stimulusBuffer.h>

namespace smo {
namespace stim_buff {

std::shared_ptr<StimulusBuffer> StimulusProducer::getAttachedStimulusBuffer(
	const std::shared_ptr<device::DeviceAttachmentSpec>& spec) const
{
	for (const auto& buffer : attachedStimulusBuffers)
	{
		if (buffer && buffer->deviceAttachmentSpec &&
			*buffer->deviceAttachmentSpec == *spec)
		{
			return buffer;
		}
	}

	return nullptr;
}

bool StimulusProducer::hasBufferWithQualeIfaceApi(
	const std::string& qualeIfaceApi) const
{
	for (const auto& buffer : attachedStimulusBuffers)
	{
		if (!buffer || !buffer->deviceAttachmentSpec)
		{
			throw std::runtime_error(
				"StimulusProducer::hasBufferWithQualeIfaceApi: encountered "
				"null buffer or null deviceAttachmentSpec in "
				"attachedStimulusBuffers (should never happen)");
		}

		if (buffer->deviceAttachmentSpec->qualeIfaceApi != qualeIfaceApi)
			{ continue; }

		return true;
	}

	return false;
}

bool StimulusProducer::addAttachedStimulusBufferIfNotExists(
	const std::shared_ptr<StimulusBuffer>& buffer)
{
	if (!buffer) { return false; }

	auto it = std::find_if(
		attachedStimulusBuffers.begin(),
		attachedStimulusBuffers.end(),
		[&](const std::shared_ptr<StimulusBuffer>& buf) {
			return buf && buffer &&
				buf->deviceAttachmentSpec && buffer->deviceAttachmentSpec &&
				*(buf->deviceAttachmentSpec) == *(buffer->deviceAttachmentSpec);
		});

	if (it != attachedStimulusBuffers.end()) {
		return false;
	}

	attachedStimulusBuffers.push_back(buffer);
	return true;
}

void StimulusProducer::destroyAttachedStimulusBuffer(
	const std::shared_ptr<StimulusBuffer>& buffer)
{
	if (!buffer) { return; }

	auto it = std::find(
		attachedStimulusBuffers.begin(),
		attachedStimulusBuffers.end(),
		buffer);

	if (it != attachedStimulusBuffers.end()) {
		attachedStimulusBuffers.erase(it);
	}
}

sscl::co::NonViralNonPostingInvoker StimulusProducer::productionCDaemon(
	std::exception_ptr &, std::function<void()>,
	sscl::SyncCancelerForAsyncWork &canceler)
{
	int nextDelayMs = CONFIG_STIMBUFF_FRAME_PERIOD_MS;

	do
	{
		bool shouldProduceFrame = false;

		if (!canceler.execUncancelableSegmentOrAbort([&]()
		{
			/**	EXPLANATION:
			 * We need to ensure that there's only ever one stimframe being
			 * produced during any CONFIG_STIMBUFF_FRAME_PERIOD_MS period. To
			 * guarantee this, we use a spinlock.
			 *
			 * When a new frame is to be produced, the async producer will
			 * first acquire the frameAssemblyLimiter spinlock. This ensures
			 * that only one stimframe is produced during any
			 * CONFIG_STIMBUFF_FRAME_PERIOD_MS interval. When the next 
			 * timeout fires, it checks if the previous stimframe has 
			 * finished production. If the previous stimframe is still 
			 * being produced, we will sleep for 
			 * CONFIG_STIMBUFF_FRAME_RETRY_DELAY_MS ms before retrying.
			 */
			if (frameAssemblyRateLimiter.tryAcquire())
			{
				nextDelayMs = CONFIG_STIMBUFF_FRAME_PERIOD_MS;

				// Check if we're ending a deferral period
				if (nDeferrals > 0)
				{
					auto deferralEndTime =
						std::chrono::high_resolution_clock::now();
					auto duration = deferralEndTime - deferralStartTime;
					auto durationMs = std::chrono::duration_cast<
						std::chrono::milliseconds>(duration);

					std::cout << "productionCDaemon: Deferral period ended. "
						<< "Total deferrals: " << nDeferrals
						<< ", Duration: " << durationMs.count()
						<< "ms" << std::endl;

					nDeferrals = 0;
				}

				shouldProduceFrame = true;
			}
			else
			{
				nextDelayMs = CONFIG_STIMBUFF_FRAME_RETRY_DELAY_MS;

				++nDeferrals;
				// If this is first deferral, capture start stamp and print message
				if (nDeferrals == 1)
				{
					deferralStartTime =
						std::chrono::high_resolution_clock::now();
					std::cerr << "productionCDaemon: Deferral period "
						"beginning. Configured deferral period: "
						<< nextDelayMs << "ms" << std::endl;
				}
			}
		}))
			{ break; }

		if (shouldProduceFrame)
		{
			/**	EXPLANATION:
			 * Call the derived class's frame production handler
			 * Note: The derived class's frame production handler (aka
			 * its implementation of stimFrameProductionTimesliceCInd()) must
			 * release the lock when frame production completes
			 */
			co_await stimFrameProductionTimesliceCInd(canceler);
		}
		else if (OptionParser::getOptions().verbose)
		{
			std::cerr << "productionCDaemon: Deferring frame by "
				<< nextDelayMs << "ms due to rate limit." << std::endl;
		}

		// Schedule the next timeout using the provided delay
		const bool expiredNormally = co_await
			adapters::boostAsio::getDeadlineTimerAReqAwaiter(
				ioContext,
				daemonTimer,
				boost::posix_time::milliseconds(nextDelayMs));

		if (!expiredNormally) {
			// Timer was cancelled, which is expected when stopping
			break;
		}

		// FIXME: We should be able to release the start/stop lock at this point.

	} while (!canceler.isCancellationRequested());

	co_return;
}

void StimulusProducer::start()
{
	std::cout << __func__ << ": Starting stimulus producer for device "
		<< deviceAttachmentSpec->deviceSelector << std::endl;

	nDeferrals = 0;
	taskNursery.openAdmission();
	taskNursery.launch(
		[this](sscl::co::NonViralTaskNursery::Slot::Lease &lease)
		{
			return productionCDaemon(
				lease.getExceptionStorage(),
				lease.getCallerLambda(),
				lease.getSyncCanceler());
		});
}

void StimulusProducer::stop()
{
	// Cancel timer immediately
	daemonTimer.cancel();
	taskNursery.requestCancelOnAll();
	taskNursery.closeAdmission();
	taskNursery.syncAwaitAllSettlements(
		sscl::ComponentThread::getSelf()->getIoContext());

	std::cout << __func__ << ": Stopped stimulus producer for device "
		<< deviceAttachmentSpec->deviceSelector << std::endl;
}

} // namespace stim_buff
} // namespace smo