#include "stack.h"
#include "unity.h"
#include "unity_internals.h"

void setUp(void) { }
void tearDown(void) { }

void test_push_should_add_new_node_at_top(void)
{
    StackNode *stack = NULL;

    int value = 42;
    stack = push(stack, &value);

    TEST_ASSERT_NOT_NULL(stack);
    TEST_ASSERT_EQUAL_PTR(&value, stack->data);
    TEST_ASSERT_NULL(stack->next);

    clearStack(stack);
}

void test_push_multiple_should_chain_nodes_correctly(void)
{
    int a = 1, b = 2;
    
    StackNode *first = push(NULL, &a);
    
    StackNode *second = push(first, &b);

    TEST_ASSERT_EQUAL_PTR(&b, second->data);
    TEST_ASSERT_EQUAL_PTR(first, second->next);
    TEST_ASSERT_EQUAL_PTR(&a, first->data);

    clearStack(second);
}

void test_top_should_return_null_on_empty_stack(void)
{
    StackNode *stack = NULL;
    TEST_ASSERT_NULL(top(stack));
}

void test_top_should_return_data_of_existing_node(void)
{
    StackNode node;
    int x = 99;

    node.data = &x;
    node.next = NULL;

    TEST_ASSERT_EQUAL_PTR(&x, top(&node));
}

void test_pop_should_return_null_when_stack_empty(void)
{
    StackNode *stack = NULL;
    TEST_ASSERT_NULL(pop(stack));
}

void test_pop_should_remove_single_element(void)
{
    StackNode *stack = malloc(sizeof(StackNode));
    int x = 7;

    stack->data = &x;
    stack->next = NULL;

    StackNode *result = pop(stack);

    TEST_ASSERT_NULL(result); // Kein Element mehr übrig
}

void test_pop_should_remove_top_node_only(void)
{
    // Manuell verkettete Liste aufbauen
    StackNode *n1 = malloc(sizeof(StackNode));
    StackNode *n2 = malloc(sizeof(StackNode));
    int a = 1, b = 2;

    n1->data = &a;
    n1->next = NULL;

    n2->data = &b;
    n2->next = n1;

    StackNode *result = pop(n2);

    TEST_ASSERT_EQUAL_PTR(n1, result);

    clearStack(result);
}

int main()
{
    UNITY_BEGIN();

    RUN_TEST(test_push_should_add_new_node_at_top);
    RUN_TEST(test_push_multiple_should_chain_nodes_correctly);
    RUN_TEST(test_top_should_return_null_on_empty_stack);
    RUN_TEST(test_top_should_return_data_of_existing_node);
    RUN_TEST(test_pop_should_return_null_when_stack_empty);
    RUN_TEST(test_pop_should_remove_single_element);
    RUN_TEST(test_pop_should_remove_top_node_only);

    return UNITY_END();
}