import pytest

from src.matrixmania.compute import transpose


def test_square_matrix():
    """Tests a standard 2x2 square matrix."""
    matrix = [[1, 2], [3, 4]]
    expected = [[1, 3], [2, 4]]
    assert transpose(matrix) == expected


def test_rectangular_matrix_wide():
    """Tests a 2x3 rectangular matrix (more columns than rows)."""
    matrix = [[1, 2, 3], [4, 5, 6]]
    expected = [[1, 4], [2, 5], [3, 6]]
    assert transpose(matrix) == expected


def test_rectangular_matrix_tall():
    """Tests a 3x2 rectangular matrix (more rows than columns)."""
    matrix = [[1, 2], [3, 4], [5, 6]]
    expected = [[1, 3, 5], [2, 4, 6]]
    assert transpose(matrix) == expected


def test_row_vector():
    """Tests a single row matrix (1x4)."""
    matrix = [[10, 20, 30, 40]]
    expected = [[10], [20], [30], [40]]
    assert transpose(matrix) == expected


def test_column_vector():
    """Tests a single column matrix (4x1)."""
    matrix = [[10], [20], [30], [40]]
    expected = [[10, 20, 30, 40]]
    assert transpose(matrix) == expected


def test_single_element_matrix():
    """Tests a 1x1 matrix."""
    matrix = [[-5]]
    expected = [[-5]]
    assert transpose(matrix) == expected


def test_identity_matrix():
    """Tests an identity matrix, which is its own transpose."""
    matrix = [[1, 0, 0], [0, 1, 0], [0, 0, 1]]
    expected = [[1, 0, 0], [0, 1, 0], [0, 0, 1]]
    assert transpose(matrix) == expected


# --- Error Handling Tests (Invalid Inputs) ---

def test_raises_error_if_not_list():
    """Tests that a ValueError is raised if the input is not a list (e.g., None)."""
    with pytest.raises(ValueError, match="Argument needs to be a nested list of integers"):
        transpose(None)


def test_raises_error_if_not_nested_list():
    """Tests that a ValueError is raised if the input is a flat list (not nested)."""
    with pytest.raises(ValueError, match="Argument needs to be a nested list of integers"):
        transpose([1, 2, 3])


def test_raises_error_if_not_list_of_int():
    """
    Tests that a ValueError is raised if the matrix contains non-integers.
    Note: The function's current check only validates the very first element (matrix[0][0]).
    """
    with pytest.raises(ValueError, match="Argument needs to be a nested list of integers"):
        transpose([[1.0, 2.0], [3.0, 4.0]])


def test_raises_error_on_empty_list_inner():
    """
    Tests how the function handles a list with an empty inner list.
    The check 'isinstance(matrix[0][0], int)' will fail with an IndexError.
    The function *should* raise a ValueError, but it raises an IndexError due to brittle validation.
    We test for the 'ValueError' that the *validation line itself* is supposed to catch.

    Update: If the input is [[]], matrix[0] is [], and matrix[0][0] causes an IndexError.
    This IndexError happens *before* the ValueError can be raised by the 'if' condition.
    Therefore, we must test for the actual error that occurs.
    """
    with pytest.raises(IndexError):
        transpose([[]])


def test_raises_error_on_empty_list_outer():
    """
    Tests how the function handles a completely empty list.
    The check 'isinstance(matrix[0], list)' will fail with an IndexError.
    """
    with pytest.raises(IndexError):
        transpose([])