#include <stdio.h>
#include <chipmunk.h>

int main(void){
  // cpVect is a 2D vector and cpv() is a shortcut for initializing them.
  cpVect gravity = cpv(0, -100);
  
  // Create an empty space.
  cpSpace *space = cpSpaceNew();
  cpSpaceSetGravity(space, gravity);
  
  // Add a static line segment shape for the ground.
  // We'll make it slightly tilted so the ball will roll off.
  // We attach it to a static body to tell Chipmunk it shouldn't be movable.
  cpShape *ground = cpSegmentShapeNew(cpSpaceGetStaticBody(space), cpv(-20, 5), cpv(20, -5), 0);
  cpShapeSetFriction(ground, 1);
  cpSpaceAddShape(space, ground);
  
  // Now let's make a ball that falls onto the line and rolls off.
  // First we need to make a cpBody to hold the physical properties of the object.
  // These include the mass, position, velocity, angle, etc. of the object.
  // Then we attach collision shapes to the cpBody to give it a size and shape.
  
  cpFloat radius = 5;
  cpFloat mass = 1;
  
  // The moment of inertia is like mass for rotation
  // Use the cpMomentFor*() functions to help you approximate it.
  cpFloat moment = cpMomentForCircle(mass, 0, radius, cpvzero);
  
  // The cpSpaceAdd*() functions return the thing that you are adding.
  // It's convenient to create and add an object in one line.
  cpBody *ballBody = cpSpaceAddBody(space, cpBodyNew(mass, moment));
  cpBodySetPosition(ballBody, cpv(0, 15));
  
  // Now we create the collision shape for the ball.
  // You can create multiple collision shapes that point to the same body.
  // They will all be attached to the body and move around to follow it.
  cpShape *ballShape = cpSpaceAddShape(space, cpCircleShapeNew(ballBody, radius, cpvzero));
  cpShapeSetFriction(ballShape, 0.7);
  
  // Now that it's all set up, we simulate all the objects in the space by
  // stepping forward through time in small increments called steps.
  // It is *highly* recommended to use a fixed size time step.
  cpFloat timeStep = 1.0/60.0;
  for(cpFloat time = 0; time < 2; time += timeStep){
    cpVect pos = cpBodyGetPosition(ballBody);
    cpVect vel = cpBodyGetVelocity(ballBody);
    printf(
      "Time is %5.2f. ballBody is at (%5.2f, %5.2f). It's velocity is (%5.2f, %5.2f)\n",
      time, pos.x, pos.y, vel.x, vel.y
    );
    
    cpSpaceStep(space, timeStep);
  }
  
  // Clean up our objects and exit!
  cpShapeFree(ballShape);
  cpBodyFree(ballBody);
  cpShapeFree(ground);
  cpSpaceFree(space);
  
  return 0;
}