#include <iostream>
#include <string>
#include <random>
#include <vector>
//Command-line parsing
#include "CLI11.hpp"

//Image filtering and I/O
#define STB_IMAGE_WRITE_IMPLEMENTATION
#include <stb_image_write.h>

//Global flag to silent verbose messages
bool silent;

typedef struct point {
  int x, y;
} point_t;

typedef struct triangle {
  point_t p, q, r;
} triangle_t;

void print_triangle(triangle_t t) {
  printf("(%d %d) (%d %d) (%d %d)", t.p.x, t.p.y, t.q.x, t.q.y, t.r.x, t.r.y);
}

int sig(int x) {
  return (x != 0) * (x > 0 ? 1 : -1);
}

int dist(point_t p, point_t q) {
  return sqrt((p.x-q.x)*(p.x-q.x) + (p.y-q.y)*(p.y-q.y));
}

int determinant(point_t p, point_t q, point_t r) {
  int a, b, c, d;
  a = q.x-p.x;
  b = q.y-p.y;
  c = r.x-p.x;
  d = r.y-p.y;
  return a*d - b*c;
}

unsigned char isInside(point_t a, triangle_t t) {
  /* returns : 0 is not inside, 1 if inside, 2 if on edge */
  int det_a1 = determinant(a, t.q, t.r);
  int det_a2 = determinant(a, t.p, t.q);
  int det_a3 = determinant(a, t.r, t.p);

  if ((sig(det_a1)==sig(det_a2)) && (sig(det_a1)==sig(det_a3))) {
    int dist_t1 = dist(t.q, t.r)*1.5;
    int dist_t2 = dist(t.p, t.q)*1.5;
    int dist_t3 = dist(t.r, t.p)*1.5;
    if ((dist_t1 > abs(det_a1)) || (dist_t2 > abs(det_a2)) || (dist_t3 > abs(det_a3))) return 2;
    return 1;
  };
  return 0;
}

int main(int argc, char **argv)
{
  CLI::App app{"rasterizer"};
  std::string outputImage= "output.png";
  app.add_option("-o,--output", outputImage, "Output image")->required();
  unsigned int nbTriangles = 5;
  app.add_option("-n,--ntriangles", nbTriangles, "Number of triangles (5)");

  CLI11_PARSE(app, argc, argv);
  srand(time(0));

  //Image loading
  int width=640,height=480, nbChannels=3;
  std::vector<unsigned char> output(width*height*nbChannels);

  int* colors = (int*)malloc(sizeof(int)*3*nbTriangles);
  triangle_t* t = (triangle_t*)malloc(sizeof(triangle_t)*nbTriangles);
  for (auto i=0; i < nbTriangles; i++) {
    t[i] = {rand()%width, rand()%height, rand()%width, rand()%height, rand()%width, rand()%height};
    colors[3*i] = rand()%255;
    colors[3*i+1] = rand()%255;
    colors[3*i+2] = rand()%255;
    print_triangle(t[i]);
    printf(" : (%d, %d, %d)\n", colors[3*i], colors[3*i+1], colors[3*i+2]);
  }

  for(auto i = 0 ; i < width ; ++i) {
    for(auto j = 0; j < height; ++j) {
      auto indexPixel = nbChannels*(width*j+i);
      output[indexPixel] = output[indexPixel+1] = output[indexPixel+2] = 0;

      for (auto triangle_id=0; triangle_id < nbTriangles; triangle_id++) {
        int valid = isInside({i, j}, t[triangle_id]);
        if (valid == 1) {
          output[ indexPixel ] = colors[3*triangle_id];
          output[ indexPixel + 1 ] = colors[3*triangle_id+1];
          output[ indexPixel + 2 ] = colors[3*triangle_id+2];
        } else if (valid == 2) {
          output[indexPixel] = output[indexPixel+1] = output[indexPixel+2] = 255;
        }
      }
    }
  }
  
  //Final export
  std::cout<<"Exporting.."<<std::endl;
  int errcode = stbi_write_png(outputImage.c_str(), width, height, nbChannels, output.data(), nbChannels*width);
  if (!errcode)
  {
    std::cout<<"Error while exporting the resulting image."<<std::endl;
    exit(errcode);
  }
  
  exit(0);
}