#include <SFML/Graphics.hpp>
using namespace sf;

int width = 1024;
int height = 768;
int roadW = 2000; // road width
int segL = 200; // segment length
float camD = 0.84; // base scale factor for distant objects

// a line in the 3d world w/ a 'project' method to draw it on the 2d screen
struct Line
{
  float x,y,z; // 3d center of line
  float X,Y,W; // paramterization of line on screen
  float scale;

  Line() { x=y=z=0; }

  // project the line from 3d world onto 2d screen. X=horizontal, Y=vertical, Z=depth
  void project(int camX, int camY, int camZ)
  {
    scale = camD/(z-camZ); // scale factor for the line. An object looks bigger when its closer (smaller z) and smaller when its farther (large z)
    // lines are closer to the center and smaller when they are far away.
    X = (1 + scale*(x - camX)) * width/2;
    Y = (1 - scale*(y - camY)) * height/2;
    W = scale * roadW * width/2;
  }
};

// draw a quadrilateral in w with color c, parameterized by two center points of opposing sides
// (x1, y1), (x2, y2) and 2 radiuses w1, w2.
// You may wonder why we parameterize with w1 and w2 instead of 2 more points...this paramterization
// makes the math for perspectives easier
void drawQuad(RenderWindow &w, Color c, int x1, int y1, int w1, int x2, int y2, int w2)
{
  ConvexShape shape(4);
  shape.setFillColor(c);
  shape.setPoint(0, Vector2f(x1-w1, y1));
  shape.setPoint(1, Vector2f(x2-w2, y2));
  shape.setPoint(2, Vector2f(x2+w2, y2));
  shape.setPoint(3, Vector2f(x1+w1, y1));
  w.draw(shape);
}

int main()
{
  RenderWindow app(VideoMode(width, height), "Outrun Racing!");
  app.setFramerateLimit(60);

  // data for 1600 segments (side of the road)
  std::vector<Line> lines;
  for (int i = 0; i < 1600; i++)
  {
    Line line;
    line.z = i * segL;

    lines.push_back(line);
  }

  int N = lines.size();
  int pos = 0;


  while (app.isOpen())
  {
    Event e;
    while (app.pollEvent(e))
    {
      if (e.type == Event::Closed)
        app.close();
    }

    // move the racer
    if (Keyboard::isKeyPressed(Keyboard::Up)) pos += 200;
    if (Keyboard::isKeyPressed(Keyboard::Down)) pos -= 200;

    app.clear();
    int startPos = pos/segL;

    // draw road
    for (int n = startPos; n < startPos + 300; n++)
    {
      Line &l = lines[n%N]; // select line to render
      l.project(0, 1500, pos);

      // alternate grass/rumble/road color every 6 lines
      Color grass = (n/3)%2 ? Color(16,200,16) : Color(0,154,0);
      Color rumble = (n/3)%2 ? Color(255,255,255) : Color(0,0,0);
      Color road = (n/3)%2 ? Color(107,107,107) : Color(105,105,105);

      Line p = lines[(n-1)%N]; // previous line

      drawQuad(app, grass, 0, p.Y, width, 0, l.Y, width); // draw grass across the whole screen
      drawQuad(app, rumble, p.X, p.Y, p.W*1.2, l.X, l.Y, l.W*1.2); // draw rumble across the middle of the screen
      drawQuad(app, road, p.X, p.Y, p.W, l.X, l.Y, l.W); // draw road in center of screen
    }

    app.display();
  }

  return 0;
}