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

typedef struct {
	int* st;
	int cnt;
	int size;
} STACK;

STACK* init_stack(int size) {
	if (size <= 0) {
		return NULL;
	}
	STACK *buf;
	buf = malloc(sizeof(STACK));
	if (buf == NULL) {
		fprintf(stderr, "Error allocating structure\n");
		return NULL;
	}
	buf -> st = malloc(sizeof(int)*size);
	if (buf -> st == NULL) {
		fprintf(stderr, "Error allocating array\n");
		free(buf);
		return NULL;
	}
	buf -> cnt = 0;
	buf -> size = size;
	return buf;
}

void destroy_stack(STACK* s) {
	free(s -> st);
	free(s); 
}

void push(STACK* st, int val) {
	if ((st -> cnt) < (st -> size)) {
		st -> st[st -> cnt] = val;
		(st -> cnt)++;
	} else {
		fprintf(stderr, "Stack is full! Stack size is %d, value to add is %d\n", st -> size, val);
	}
}

int pop(STACK* st) {
	if ((st -> cnt) > 0) {
		(st -> cnt)--;
		return st -> st[st -> cnt];

	} else {
		fprintf(stderr, "Attempted to pop an empty stack\n");
		return NULL;
	}
}

int main() {
	printf("What's the meaning of my life?\n");
	STACK* huh = init_stack(5);
	push(huh, 3);
	push(huh, 2);
	push(huh, 4);
	printf("%d", pop(huh));
	printf("%d\n", pop(huh));
	printf("Nice. Let's try to overflow this stack now,\n");
	push(huh, 3);
	push(huh, 3);
	push(huh, 3);
	push(huh, 3);
	push(huh, 3);
	printf("thx bye\n");
	return 0;
}