#include "opencv2/opencv.hpp"
#include "opencv2/videoio.hpp"
#include "opencv2/highgui.hpp"

const int FPS = 15;
bool isDiscardData = true;
int countDiscard = 0;
const int DISCARD_DURATION = 5;
const int BUFFER_DURATION = 30        ;
const int I = 1;

bool isBufferFull = false;
int sampleIdBuffer = 0;

std::vector<double> greenFFTModule;

template <typename T>
cv::Mat plotGraph(std::vector<T>& vals, int YRange[2])
{
	auto it = minmax_element(vals.begin(), vals.end());
	float scale = 1./ceil(*it.second - *it.first);
	float bias = *it.first;
	int rows = YRange[1] - YRange[0] + 1;
	cv::Mat image = 255*cv::Mat::ones( rows, vals.size(), CV_8UC3 );
	image.setTo(255);
	for (int i = 0; i < (int)vals.size()-1; i++)
	{
		cv::line(image, cv::Point(i, rows - 1 - (vals[i] - bias)*scale*YRange[1]), cv::Point(i+1, rows - 1 - (vals[i+1] - bias)*scale*YRange[1]), cv::Scalar(255, 0, 0), 1);
	}
	return image;
}

int main() 
{ 
  cv::VideoCapture cap;
  cap.open(0);
  //If Haard Cascade not found: error
  cv::CascadeClassifier faceDetector;
	if( !faceDetector.load("./haarcascade_frontalface_alt.xml"))
	{
	std::cerr << "[ERROR] Unable to load face cascade" << std::endl;
	return -1;
	};
  cv::Rect foreheadROI;
  if (!cap.isOpened())
  {
    std::cerr << "[ERROR] Unable to open camera!" << std::endl;
    return -2;
  }
  
  while (true)
	{
		if (isDiscardData)
		{
			countDiscard++;
			if (countDiscard == DISCARD_DURATION*FPS)
				isDiscardData = false;
		}
		else
		{
			// create a matrix to store the image from the cam
			cv::Mat frame;
			// wait for a new frame from camera and store it into 'frame'
			cap.read(frame);
			// check if we succeeded
			if (frame.empty())
			{
				std::cerr << "[ERROR] blank frame grabbed" << std::endl;
				break;
			}
						
			//Draw Rectangle around the face
			std::vector<cv::Rect> faceRectangles;
			faceDetector.detectMultiScale(frame, faceRectangles, 1.1, 3, 0,cv::Size(20, 20));
			
			if (faceRectangles.size() > 0)
			{
				foreheadROI = faceRectangles[0];
				foreheadROI.height *= 0.3;
				
				cv::rectangle(frame, faceRectangles[0], cv::Scalar(0, 0, 255), 1, 1, 0);
				cv::rectangle(frame, foreheadROI, cv::Scalar(255, 0, 0), 1, 1, 0);
				
				cv::Mat frame_forehead = frame(foreheadROI);
				cv::Scalar avg_forehead = mean(frame_forehead);
				
				//
				cv::Mat greenSignal(1, FPS*BUFFER_DURATION, CV_64F);
				if (!isBufferFull)
				{
					greenSignal.at<double>(0, sampleIdBuffer) = avg_forehead[1] ;
					sampleIdBuffer++;
					if (sampleIdBuffer == FPS*BUFFER_DURATION)
					{
						isBufferFull = true;
					}
				}
				else
				{
					std::vector<double> greenSignalNormalized;
					cv::Scalar mean, stddev;
					cv::meanStdDev(greenSignal, mean, stddev);
					for (int l_sample=0; l_sample < FPS*BUFFER_DURATION; l_sample++)
					{
						greenSignalNormalized.push_back((greenSignal.at<double>(0, l_sample) - mean[0])/stddev[0]);
					}
					
					
					int range[2] = {0, (int)(FPS*BUFFER_DURATION)};
					
					cv::Mat greenFFT;
					///
					cv::dft(greenSignalNormalized,greenFFT,cv::DFT_ROWS|cv::DFT_COMPLEX_OUTPUT);
					cv::Mat planes[] = {cv::Mat::zeros(greenSignalNormalized.size(),1, CV_64F),
					cv::Mat::zeros(greenSignalNormalized.size(),1, CV_64F)};
					cv::split(greenFFT, planes); //planes[0] = Re(DFT(I),
					//planes[1] = Im(DFT(I))
					greenFFTModule.clear();
					for (int l=0; l < planes[1].cols; l++)
					{
						double moduleFFT = pow(planes[1].at<double>(0,l),2) + pow(planes[0].at<double>(0,l),2);
						greenFFTModule.push_back(sqrt(moduleFFT));
					}
					// display green FFT
					cv::imshow("FFT module green", plotGraph(greenFFTModule, range));
					
				}
				
			}
			
			cv::imshow("Your Face PLS", frame);
			if (cv::waitKey(1000.0/FPS) >= 0)
			break;
			
		}
		
	}
	return 0;
}