#include <stdio.h>
#include <stdlib.h>
/* Using a struct so that we never dereference a NULL pointer if someone passes in too short of an int * */
typedef struct myTime
{
    int *arr; // must have three integers only
} myTime;
myTime *timeConstruct(void); // returns an initialized myTime structure pointer
void timeSet(myTime *time,int h,int m,int s); // sets the structure to a valid time
int secConvert(myTime *time); // convert hour:min:sec to seconds
int *timeConvert(int seconds); // convert seconds into a three position int *
void timePrint(myTime *time); // print time in hr:min:sec format
void timePrintSecs(myTime *time); // print time in seconds
myTime *timeAdd(myTime *t1,myTime *t2);
int main(void)
{
    myTime *t1=timeConstruct();
    myTime *t2=timeConstruct();
    timeSet(t1,1,2,3);
    timeSet(t2,4,5,6);
    timePrint(t1);
    timePrintSecs(t1);
    timePrint(t2);
    timePrintSecs(t2);
    myTime *t3=timeAdd(t1,t2);
    timePrint(t3);
    timePrintSecs(t3);
    return 0;
}
myTime *timeAdd(myTime *t1,myTime *t2)
{
    if(t1==NULL)
    {
        fprintf(stderr,"Error: t1 points to NULL in timeAdd.\n");
        exit(EXIT_FAILURE);
    }
    if(t2==NULL)
    {
        fprintf(stderr,"Error: t2 points to NULL in timeAdd.\n");
        exit(EXIT_FAILURE);
    }
    int seconds=0;
    seconds+=secConvert(t1);
    seconds+=secConvert(t2);
    myTime *ret=timeConstruct();
    free(ret->arr); // no memory leaks!
    ret->arr=timeConvert(seconds);
    return ret;
}
void timePrintSecs(myTime *time)
{
    if(time==NULL)
    {
        fprintf(stderr,"Error: time points to NULL in timePrintSecs.\n");
        exit(EXIT_FAILURE);
    }
    printf("%d seconds\n",secConvert(time));
}
void timePrint(myTime *time)
{
    if(time==NULL)
    {
        fprintf(stderr,"Error: time points to NULL in timePrint.\n");
        exit(EXIT_FAILURE);
    }
    printf("%d:%d:%d\n",time->arr[0],time->arr[1],time->arr[2]);
}
void timeSet(myTime *time,int h,int m,int s)
{
    if(time==NULL)
    {
        fprintf(stderr,"Error: time points to NULL in timeSet.\n");
        exit(EXIT_FAILURE);
    }
    if(m>60)
    {
        fprintf(stderr,"Error: m>60 in timeSet.\n");
        exit(EXIT_FAILURE);
    }
    if(s>60)
    {
        fprintf(stderr,"Error: s>60 in timeSet.\n");
        exit(EXIT_FAILURE);
    }
    time->arr[0]=h;
    time->arr[1]=m;
    time->arr[2]=s;
}
myTime *timeConstruct(void)
{
    myTime *ret=malloc(sizeof(myTime));
    if(ret==NULL)
    {
        fprintf(stderr,"Error: malloc returns NULL for ret in timeConstruct.\n");
        exit(EXIT_FAILURE);
    }
    int *arr=calloc(3,sizeof(int));
    if(arr==NULL)
    {
        fprintf(stderr,"Error: calloc returns NULL for arr in timeConstruct.\n");
        exit(EXIT_FAILURE);
    }
    ret->arr=arr;
    return ret;
}
int secConvert(myTime *time)
{
    if(time==NULL)
    {
        fprintf(stderr,"Error: time points to NULL in secConvert.\n");
        exit(EXIT_FAILURE);
    }
    int ret=0;
    ret+=3600*(time->arr[0]);
    ret+=60*(time->arr[1]);
    ret+=(time->arr[2]);
    return ret;
}
int *timeConvert(int seconds)
{
    int *ret=calloc(3,sizeof(int));
    if(ret==NULL)
    {
        fprintf(stderr,"Error: calloc returns NULL for ret in timeConvert.\n");
        exit(EXIT_FAILURE);
    }
    ret[0]=seconds/3600;
    ret[1]=(seconds%3600)/60;
    ret[2]=seconds%60;
    return ret;
}