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

#define MAX_SIZE 5   // static array size

typedef struct {
    void *data[MAX_SIZE];   //Level 2
    int top;
} PtrStack;


// Initialize stack
void initStack(PtrStack *s) {   s->top = -1;}

// Check if stack is empty
int isEmpty(PtrStack *s) {   return s->top == -1;}

// Check if stack is full
int isFull(PtrStack *s) {   return s->top == MAX_SIZE - 1;}

// Push pointer onto stack
int push(PtrStack *s, void *ptr) {
    if (isFull(s)) {
        printf("Stack overflow! Cannot push.\n");
        return 0;
    }
    s->data[++s->top] = ptr;
    return 1;
}

// Pop pointer from stack
void *pop(PtrStack *s) {
    if (isEmpty(s)) {
        printf("Stack underflow! Cannot pop.\n");
        return NULL;
    }
    return s->data[s->top--];
}

// Get top element without removing it
void *top(PtrStack *s) {
    if (isEmpty(s)) {
        printf("Stack is empty.\n");
        return NULL;
    }
    return s->data[s->top];
}

// Get current stack size
int size(PtrStack *s) {   return s->top + 1;}

// Example object
typedef struct {
    int id;
    Zchar name[32];
} Person;

Person *newPerson(int id, const char *name) {
    Person *p = malloc(sizeof(Person));  //Level 3
    p->id = id;
    snprintf(p->name, sizeof(p->name), "%s", name);
    return p;
}

// Example usage
int main() {
    PtrStack stack;    //Level 1
    initStack(&stack);

    Person *p1 = newPerson(1, "Alice");
    Person *p2 = newPerson(2, "Bob");
    Person *p3 = newPerson(3, "Charlie");

    push(&stack, p1);
    push(&stack, p2);
    push(&stack, p3);

    printf("Stack size: %d\n", size(&stack));

    Person *t = (Person *)top(&stack);
    printf("Top element: id=%d name=%s\n", t->id, t->name);

    while (!isEmpty(&stack)) {
        Person *p = (Person *)pop(&stack);
        printf("Popped: id=%d name=%s\n", p->id, p->name);
        free(p);  //Free p L3
    }

    printf("Stack empty? %s\n", isEmpty(&stack) ? "Yes" : "No");
    //Stack and Stack Array get free after the scope L1 (stack) and L2 (array of Ptr)
    return 0;
}