#include <iostream>
#include <string>
#include <vector>
#include <cstdlib>
#include <cmath>
#include <random>
#include <ctime>

std::random_device rd;
std::mt19937 rng(rd());

class KMeans {
private:
    std::vector< std::pair<int, int> > points;
    std::vector< std::pair<int, int> > centroids;
    std::vector<int> clusters;
    int cluster_tot; /* Total number of clusters */
    int points_tot;

    const int max_iter = 10 * 1000; /* Max number of iteration */
    const double threshold = 1e-3; /* Stopping criterion */

    double compute_score();
    void reassign();
    void recompute();

public:
    KMeans(int bound, int cluster_tot, int points_tot);
    int numPoints() { return points_tot; }
    int getCluster(int i) { return clusters[i]; }
    std::vector<int> getClusters() { return clusters; }
    std::pair<int, int> getPoint(int i) { return points[i]; }
    void run();
};

KMeans::KMeans(int bound, int cluster_tot_, int points_tot_) {
    std::uniform_int_distribution<int> uni(0, bound);

    cluster_tot = cluster_tot_;
    points_tot = points_tot_;
    points = std::vector< std::pair<int, int> >(points_tot);
    clusters = std::vector<int>(points_tot);

    centroids = std::vector< std::pair<int, int> >(cluster_tot);

    for (int i = 0; i < points_tot; i++) {
        points[i] = std::make_pair(uni(rng), uni(rng));
        clusters[i] = i % cluster_tot;
    }

    for (int k = 0; k < cluster_tot; k++) {
        centroids[k] = std::make_pair(uni(rng), uni(rng));
    }
}

double euclid(std::pair<int, int> p1, std::pair<int, int> p2) {
    return sqrt(pow(p1.first - p2.first, 2.0) + pow(p1.second - p2.second, 2.0));
}

double KMeans::compute_score() {
    double score = 0.0;

    for (int i = 0; i < points_tot; i++) {
        //std::cout << "LOL" << std::endl;
        std::pair<int, int> coord = points[i];
        //std::cout << "LOL2 " << clusters[i] <<  std::endl;

        std::pair<int, int> cent = centroids[clusters[i]];

        double d = euclid(coord, cent);
        score += d;
    }

    return score;
}

void KMeans::run() {
    double current_score = 0.0;
    int iter = 0;

    while (true) {
        //std::cout << "ITER " << iter << std::endl;
        double sc = compute_score();
        //std::cout << "New score " << sc << std::endl;

        if (std::abs(sc - current_score) < threshold || iter >= max_iter) {
            std::cout << iter << " iterations" << std::endl;
            break;
        }
        current_score = sc;

        reassign();
        recompute();
        iter++;
    }
}

/* Reassign each point to its nearest centroid */
void KMeans::reassign() {
    for (int i = 0; i < points_tot; i++) {
      double dmin = 1e25;
      int kmin = 0;

      //std::cout << "LAULE " << i << " / " << points_tot << std::endl;

      for (int k = 0; k < cluster_tot; k++) {
          double d = euclid(points[i], centroids[k]);
          if (d < dmin) {
              kmin = k;
              dmin = d;
          }
      }

      clusters[i] = kmin;
    }
}

void KMeans::recompute() {
    std::vector<int> clusters_size = std::vector<int>(cluster_tot, 0);
    std::vector<int> clusters_x = std::vector<int>(cluster_tot, 0);
    std::vector<int> clusters_y = std::vector<int>(cluster_tot, 0);

    for (int i = 0; i < points_tot; i++) {
        clusters_size[clusters[i]]++;
        clusters_x[clusters[i]] += points[i].first;
        clusters_y[clusters[i]] += points[i].second;
    }

    for (int k = 0; k < cluster_tot; k++) {
        if (!clusters_size[k]) {
            continue;
        }
        centroids[k] =
            std::make_pair(
                           (int) (clusters_x[k] / clusters_size[k]),
                           (int) (clusters_y[k] / clusters_size[k])
                           );
    }
}



int main(int argc, char **argv) {
    const int WINDOW_SIZE = 1500;

    /*if (SDL_Init(SDL_INIT_EVERYTHING) != 0) {
        std::cerr << "SDL_Init error: " << SDL_GetError() << std::endl;
        return 1;
    }

    SDL_Window *window;
    SDL_Renderer *renderer;
    SDL_Event event;

    SDL_CreateWindowAndRenderer(WINDOW_SIZE, WINDOW_SIZE, 0, &window, &renderer);


    while (false) {
        SDL_SetRenderDrawColor(renderer, 10, 10, 10, 0);
        SDL_RenderClear(renderer);

        for (int i = 0; i < kmeans.numPoints(); i++) {
            int c = kmeans.getCluster(i);
            std::pair<int, int> coord = kmeans.getPoint(i);

            SDL_SetRenderDrawColor(renderer, c, 255-c, c, 255);
            SDL_RenderDrawPoint(renderer, coord.first, coord.second);
        }

        SDL_RenderPresent(renderer);

        if (SDL_PollEvent(&event) && event.type == SDL_MOUSEBUTTONDOWN)
            break;
            }*/

    KMeans kmeans = KMeans(WINDOW_SIZE, 200, 10000);

    std::cout << "BEGIN" << std::endl;
    std::clock_t start = std::clock();
    double duration;

    kmeans.run();

    duration = ( std::clock() - start ) / (double) CLOCKS_PER_SEC;
    std::cout << " # DURATION: " << duration << "s" << std::endl;
    std::cout << "END" << std::endl;

    //SDL_DestroyRenderer(renderer);
    //SDL_DestroyWindow(window);
    // SDL_Quit();
    return 0;
}