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

int width = 1024;
int height = 768;
int roadW = 2000;
int segL = 200; // segment length
float camD = 0.84; // camera depth

struct Line
{
  float x,y,z; // center of line in the 3d world
  float X,Y,W; // parameterization of the line on the screen
  float scale, curve;

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

  // project onto the given camera position
  void project(int camX, int camY, int camZ)
  {
    scale = camD/(z-camZ);
    X = (1 + scale*(x - camX)) * width/2;
    Y = (1 - scale*(y - camY)) * height/2;
    W = scale * roadW * width/2;
  }
};

// draw a quadtrilateral parameterized by two midpoints (x1,y1), (x2,y2) and 2 widths w1, w2.
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);

  Texture bg;
  bg.loadFromFile("/Users/alleyuan/code-snippets/16_games/08 Outrun/images/bg.png");
  bg.setRepeated(true);
  Sprite sBackground(bg);
  sBackground.setTextureRect(IntRect(0,0,5000,411));
  sBackground.setPosition(-2000,0);

  std::vector<Line> lines;

  for (int i = 0; i < 1600; i++)
  {
    Line line;
    line.z = i * segL;

    if (i > 300 && i < 700) line.curve = 0.5;

    if (i > 750) line.y = sin(i/30.0) * 1500; // add wavy terrain to the end of the track

    lines.push_back(line);
  }

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

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

    if (Keyboard::isKeyPressed(Keyboard::Right)) playerX += 200;
    if (Keyboard::isKeyPressed(Keyboard::Left)) playerX -= 200;
    if (Keyboard::isKeyPressed(Keyboard::Up)) pos += 200;
    if (Keyboard::isKeyPressed(Keyboard::Down)) pos -= 200;

    // loop the track
    while (pos >= N*segL) pos -= N*segL;
    while (pos < 0) pos += N*segL;

    app.clear(Color(105,205,4));
    app.draw(sBackground);
    int startPos = pos/segL;
    int camH = 1500 + lines[startPos].y;
    float x = 0, dx = 0; // curvature offset, dx = rate of change of the curvature
    int maxy = height;

    for (int n = startPos; n < startPos+300; n++)
    {
      Line &l = lines[n%N];
      l.project(playerX - x, camH, pos - (n>=N?N*segL:0));
      x += dx;
      dx += l.curve;

      if (l.Y >= maxy) continue;
      maxy = l.Y;

      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]; // prev line

      drawQuad(app, grass, 0, p.Y, width, 0, l.Y, width);
      drawQuad(app, rumble, p.X, p.Y, p.W*1.2, l.X, l.Y, l.W*1.2);
      drawQuad(app, road, p.X, p.Y, p.W, l.X, l.Y, l.W);
    }

    app.display();
  }

  return 0;
}