/*
 * This file is part of MXE.
 * See index.html for further information.
 */

#include <stdio.h>
#include <chipmunk/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 space->staticBody to tell Chipmunk it shouldn't be movable.
    cpShape *ground = cpSegmentShapeNew(space->staticBody, 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));
    cpBodySetPos(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 = cpBodyGetPos(ballBody);
        cpVect vel = cpBodyGetVel(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;
}