// fourier.cpp : Defines the entry point for the console application.
//

#include "stdafx.h"
#include <fstream>
#include <vector>
#include <iostream>
#include <math.h>

# define M_PI 3.14159265358979323846

void dump_to_file(const std::vector<double>& vec)
{
    std::ofstream file;
    file.open("output.txt");
    for (auto item : vec)
    {
        file << item << std::endl;
    }
    file.close();
}

// Pass the input vector, as well as references to target vectors
void dft(const std::vector<double>& input, std::vector<double>& real_output, std::vector<double>& imaginary_output)
{
    int N = input.size();

    // Pre-resize our vectors so we don't reallocate memory by pushing every time
    real_output.resize(N/2);
    imaginary_output.resize(N/2);

    // For output X_k from k = 0 to N/2
    for (int k = 0; k < N/2; k++)
    {
        // Fake complex numbers lul
        double real_sum = 0;
        double imaginary_sum = 0;

        // Iterate over input elements X_n from n = 0 to N/2
        for (int n = 0; n < N; n++)
        {
            double angle = 2 * M_PI * k * n / N;

            real_sum += input[n] * std::cos(angle);
            imaginary_sum += input[n] * std::sin(angle);
        }

        real_output[k] = real_sum;
        imaginary_output[k] = imaginary_sum;
    }
}

int main()
{
    std::ifstream file;
    file.open("1.txt");

    std::vector<double> input;
    int trash;
    double buffer;
    while (!file.eof())
    {
        // Discard the item number and read the signal value
        file >> trash >> buffer;
        input.push_back(buffer);
    }

    std::vector<double> real;
    std::vector<double> imaginary;

    dft(input, real, imaginary);

    // Combine into a modulus vector
    std::vector<double> output(real.size());

    for (int i = 0; i < output.size(); i++)
    {
        output[i] = sqrt(real[i] * real[i] + imaginary[i] * imaginary[i]);
    }

    // Dump to file
    dump_to_file(output);

    std::cout << real[0];

    return 0;
}