#include <stdlib.h>
#include "cog.h"

struct cog
{
    float radius;
    float circumference;
    int numteeth;
};

static int isvalidcog(cog_t *);

/*
 * In the ctor (constructor) you can do ALL KINDS OF THINGS to "mark" your
 * cogs so that when someone passes a pointer into an interface function you
 * can perform thorough validation of that cog pointer and what it points to.
 * This keeps bad things from happening if people accidentally pass bogus cog
 * pointers in across your interface.  We don't do any of that in this example.
 */
extern
cog_t *
cog_ctor(void)
{
    cog_t * rslt;

    rslt = calloc(1, sizeof(struct cog));

    return rslt;
}

/*
 * For the dtor (destructor) we require the user to pass a pointer to a pointer
 * to a cog... this requires that the user be able to take the address of the
 * cog ptr that is passed in to the dtor, which decreases the likelihood that
 * someone will pass in a wild pointer, but it can still happen.  This also
 * allows us to set the original pointer to NULL after the memory is released
 * so that if the user checks he can tell that the cog is no longer valid.
 */
extern
void
cog_dtor(cog_t ** p)
{

    if (p == NULL || *p == NULL)
        /*
         * User made a mistake...
         */
        return;

    free(*p);
    *p = NULL;
}

extern
float
cog_radius(cog_t * cog)
{
    if (!isvalidcog(cog))
        return Cog_InvalidRadius;
    else
        return (*cog).radius;
}

extern
int
cog_radius_set(cog_t * cog, float radius)
{
    if (!isvalidcog(cog))
        return 0;

    cog->radius = radius;
    return 1;
}

static
int
isvalidcog(cog_t * cog)
{
    if (cog == NULL)
        return 0;

    return 1;
}