pub module function_test;

void greet()
{
    let mut x = 1;
    x++;
}

pub void test_basic_function()
{
    greet();
}

i32 add(i32 a, i32 b)
{
    a + b
}

pub void test_fn_params()
{
    assert_eq!(add(2, 3), 5);
}

pub i32 test_fn_return()
{
    42
}

pub i32 test_fn_early_return()
{
    return 100;
    0
}

pub i32 test_fn_mut_param(i32 mut x)
{
    x = x + 10;
    x
}

pub void test_method_call()
{
    let s = "hello";
    assert_eq!(s.len(), 5);
    assert_eq!(s.to_uppercase(), "HELLO");
}

i32 triple(i32 x)
{
    add(x, add(x, x))
}

pub void test_nested_fn_calls()
{
    assert_eq!(triple(5), 15);
}

i32 factorial(i32 n)
{
    if n <= 1 {
        1
    } else {
        n * factorial(n - 1)
    }
}

pub void test_recursive_fn()
{
    assert_eq!(factorial(5), 120);
}

T identity<T>(T x)
{
    x
}

pub void test_fn_generic()
{
    assert_eq!(identity(42), 42);
    assert_eq!(identity("hello"), "hello");
}

pub void run_tests()
{
    test_basic_function();
    test_fn_params();
    assert_eq!(test_fn_return(), 42);
    assert_eq!(test_fn_early_return(), 100);
    assert_eq!(test_fn_mut_param(5), 15);
    test_method_call();
    test_nested_fn_calls();
    test_recursive_fn();
    test_fn_generic();
}