/*
 * This procedure adds a contact into a contacts list
 * @ls:     The contacts list
 * @name:   Name of the contact
 * @num:    Phone number of the contact
 */
void
add_to_list(struct node **ls, char *name, char *num)
{
    struct node *p      = NULL;
    struct node *crt    = NULL;
    struct node *prev   = NULL;
    int comp        = 0;

    p = malloc(sizeof(struct node));

    if (p == NULL){
        perror("Error allocating memory ");
        exit(-1);
    }

    p->firstname = name;
    p->telnum = num;
    p->next = NULL;

    /* We put a capital as first letter of the firstname */
    p->firstname[0] = toupper(p->firstname[0]);

    /* We check if the list contains no contact */
    if (*ls == NULL){
        *ls = p;
    } else{
        crt = *ls;
        prev    = *ls;

        while (crt != NULL){
            comp = strcmp(p->firstname,crt->firstname);
            if (comp < 0){
                /*
                 * We check if the new element is before
                 * the head of the list
                 */
                if (crt == *ls){
                    *ls = p;
                    (*ls)->next = prev;
                } else{
                    prev->next = p;
                    p->next = crt;
                }

                break;
            } else if (comp == 0){
                /* If contact already exists */
                (void)printf("\nContact already exists!\n");
                break;
            }

            /* We check if we are at the tail of the list */
            if (crt->next == NULL){
                crt->next = p;
                break;
            }

            prev = crt;
            crt = crt->next;
        }
    }
}