import pytest
from fifth import FifthStack


# Test the functions
def test_push_and_pop():
    stack = FifthStack()
    stack.push(10)
    stack.push(20)
    assert stack.stack == [10, 20]
    stack.pop()
    assert stack.stack == [10]
    stack.pop()
    assert stack.stack == []


def test_push_invalid_value(capsys):
    stack = FifthStack()
    stack.push("abc")
    captured = capsys.readouterr()
    assert "ERROR: integer required" in captured.out
    assert stack.stack == []


def test_pop_empty_stack(capsys):
    stack = FifthStack()
    stack.pop()
    captured = capsys.readouterr()
    assert "ERROR: stack empty" in captured.out


def test_swap():
    stack = FifthStack()
    stack.push(1)
    stack.push(2)
    stack.swap()
    assert stack.stack == [2, 1]


def test_swap_insufficient_elements(capsys):
    stack = FifthStack()
    stack.push(1)
    stack.swap()
    captured = capsys.readouterr()
    assert "ERROR: two numbers required" in captured.out
    assert stack.stack == [1]


def test_dup():
    stack = FifthStack()
    stack.push(5)
    stack.dup()
    assert stack.stack == [5, 5]


def test_dup_empty_stack(capsys):
    stack = FifthStack()
    stack.dup()
    captured = capsys.readouterr()
    assert "ERROR: stack empty" in captured.out


def test_addition():
    stack = FifthStack()
    stack.push(2)
    stack.push(3)
    stack.execute("+")
    assert stack.stack == [5]


def test_subtraction():
    stack = FifthStack()
    stack.push(5)
    stack.push(2)
    stack.execute("-")
    assert stack.stack == [3]


def test_multiplication():
    stack = FifthStack()
    stack.push(4)
    stack.push(3)
    stack.execute("*")
    assert stack.stack == [12]


def test_division():
    stack = FifthStack()
    stack.push(8)
    stack.push(2)
    stack.execute("/")
    assert stack.stack == [4]


def test_division_by_zero(capsys):
    stack = FifthStack()
    stack.push(8)
    stack.push(0)
    stack.execute("/")
    captured = capsys.readouterr()
    assert "ERROR: division by zero" in captured.out
    assert stack.stack == [8, 0]


def test_binary_op_insufficient_elements(capsys):
    stack = FifthStack()
    stack.push(1)
    stack.execute("+")
    captured = capsys.readouterr()
    assert "ERROR: two numbers required" in captured.out
    assert stack.stack == [1]


# Test executions
def test_execute_unknown_command(capsys):
    stack = FifthStack()
    stack.execute("foobar")
    captured = capsys.readouterr()
    assert "ERROR: unknown command" in captured.out


def test_execute_push_command():
    stack = FifthStack()
    stack.execute("push 42")
    assert stack.stack == [42]


def test_execute_pop_command():
    stack = FifthStack()
    stack.push(99)
    stack.execute("pop")
    assert stack.stack == []


def test_execute_swap_command():
    stack = FifthStack()
    stack.push(1)
    stack.push(2)
    stack.execute("swap")
    assert stack.stack == [2, 1]


def test_execute_dup_command():
    stack = FifthStack()
    stack.push(7)
    stack.execute("dup")
    assert stack.stack == [7, 7]


# Help and edge cases
def test_help(capsys):
    stack = FifthStack()
    stack.help()
    captured = capsys.readouterr()
    assert "Available commands:" in captured.out
    assert "Available operations:" in captured.out

def test_execute_empty_command():
    stack = FifthStack()
    stack.execute("")  # Should do nothing
    assert stack.stack == []


def test_execute_whitespace_command():
    stack = FifthStack()
    stack.execute("   ")  # Should do nothing
    assert stack.stack == []


def test_case_insensitivity():
    stack = FifthStack()
    stack.execute("PUSH 42")
    assert stack.stack == [42]