#include <stdio.h>
#include <stdlib.h>
#include <string.h>

struct Person
{
    char firstname[64];
    char lastname[64];
    int age;
};

int Person_cmp_firstname(const void* x, const void* y) {

    struct Person *p1 = (struct Person*)x;
    struct Person *p2 = (struct Person*)y;
    return strcmp(p1->firstname, p2->firstname);

}


int Person_cmp_lastname(const void* x, const void* y ) {

    struct Person *p1 = (struct Person*)x;
    struct Person *p2 = (struct Person*)y;

    return strcmp(p1->lastname, p2->lastname);

}

int Person_cmp_age(const void* x, const void* y) {

    int p1 = ((struct Person*)x)->age;
    int p2 = ((struct Person*)y)->age;

    if (p1 < p2)
        return -1;
    else if (p1 > p2)
        return 1;
    else
        return 0;
}

struct Person createP(){
    struct Person *p;
    p = (struct Person *)malloc(sizeof(struct Person));
    printf("Enter the Firstname:");
    scanf("%s", p->firstname);
    printf("Enter the Lastname:");
    scanf("%s", p->lastname);
    printf("Enter the Age:");
    scanf("%d", &p->age);

    return *p;
}

int main(void)
{

    char answer = 0;
    struct Person* arr[3];
    arr[0]=createP();
    arr[1]=createP();
    arr[2]=createP();

    printf("Sort by [F]irstname, [L]astname or [A]ge:");
    scanf(" %c", &answer);
    switch(answer){
        case 'f': case 'F':
            qsort(arr, 3, sizeof(struct Person), Person_cmp_firstname);
            printf("1.Person Firstname: %s, Lastname: %s, Age: %d\n",arr[0].firstname, arr[0].lastname, arr[0].age);
            printf("2.Person Firstname: %s, Lastname: %s, Age: %d\n",arr[1].firstname, arr[1].lastname, arr[1].age);
            printf("3.Person Firstname: %s, Lastname: %s, Age: %d\n",arr[2].firstname, arr[2].lastname, arr[2].age);
            break;
        case 'l': case 'L':
            qsort(arr, 3, sizeof(struct Person), Person_cmp_lastname);
            printf("1.Person Firstname: %s, Lastname: %s, Age: %d\n",arr[0].firstname, arr[0].lastname, arr[0].age);
            printf("2.Person Firstname: %s, Lastname: %s, Age: %d\n",arr[1].firstname, arr[1].lastname, arr[1].age);
            printf("3.Person Firstname: %s, Lastname: %s, Age: %d\n",arr[2].firstname, arr[2].lastname, arr[2].age);
            break;
        case 'a': case 'A':
            qsort(arr, 3, sizeof(struct Person), Person_cmp_age);
            printf("1.Person Firstname: %s, Lastname: %s, Age: %d\n",arr[0].firstname, arr[0].lastname, arr[0].age);
            printf("2.Person Firstname: %s, Lastname: %s, Age: %d\n",arr[1].firstname, arr[1].lastname, arr[1].age);
            printf("3.Person Firstname: %s, Lastname: %s, Age: %d\n",arr[2].firstname, arr[2].lastname, arr[2].age);
            break;
        default:
            printf("Only F, L or A are accepted commands\n");
            break;
    }
    free(&arr[0]);
    free(&arr[1]);
    free(&arr[2]);
    free(arr);

    return EXIT_SUCCESS;
}