#include <stdio.h>
#include <stdlib.h>
#include <assert.h>
#include "stack.h"

// Helper: create int on heap
static int *make_int(int value) {
    int *p = malloc(sizeof(int));
    if (!p) {
        fprintf(stderr, "Memory allocation failed\n");
        exit(1);
    }
    *p = value;
    return p;
}

int main(void) {

    printf("Running stack unit tests...\n");

    StackNode *stack = NULL;

    // --- Test 1: push() on empty stack ---
    int *a = make_int(10);
    stack = push(stack, a);
    assert(stack != NULL);
    assert(top(stack) == a);
    assert(*(int*)top(stack) == 10);

    // --- Test 2: push() on non-empty stack ---
    int *b = make_int(20);
    stack = push(stack, b);
    assert(top(stack) == b);
    assert(*(int*)top(stack) == 20);

    // --- Test 3: pop() returns previous element ---
    stack = pop(stack);  // removes 20
    assert(top(stack) == a);
    assert(*(int*)top(stack) == 10);

    // --- Test 4: pop() on single element returns NULL ---
    stack = pop(stack);  // removes 10
    assert(stack == NULL);

    // --- Test 5: pop() on empty stack returns NULL ---
    stack = pop(stack);
    assert(stack == NULL);

    // --- Test 6: clearStack() empties a multi-element stack ---
    int *c = make_int(1);
    int *d = make_int(2);
    int *e = make_int(3);
    stack = push(stack, c);
    stack = push(stack, d);
    stack = push(stack, e);

    clearStack(stack);
    // stack pointer still points to old top; we must reset manually
    stack = NULL;

    // no crash = success

    // free remaining data
    free(a);
    free(b);
    free(c);
    free(d);
    free(e);

    printf("All tests passed successfully.\n");

    return 0;
}