use lb::mat;
use lb::mat::Matrix;
use lb::mat::MatrixMut;

#[test]
fn matrix_vec_new() {
    let vec = vec![0, 1, 2, 3];
    let mat = mat::MatrixVec::new(vec.clone(), (2, 2).into()).unwrap();

    assert_eq!(mat.as_slice(), [0, 1, 2, 3]);
    assert_eq!(mat.size(), (2, 2).into());

    let err = mat::MatrixVec::<i32>::new(vec.clone(), (99, 99).into());

    assert_eq!(err, Err(mat::Error::InvalidSize));
}

#[test]
fn matrix_ref_new() {
    let values = [
        0, 1, 2, //
        3, 4, 5, //
    ];

    let mat = mat::MatrixRef::new(&values, (3, 2).into()).unwrap();

    assert_eq!(mat.as_slice(), [0, 1, 2, 3, 4, 5]);
    assert_eq!(mat.size(), (3, 2).into());

    let err = mat::MatrixRef::new(&values[1..], (3, 2).into());

    assert_eq!(err, Err(mat::Error::InvalidSize));
}

#[test]
fn matrix_mut_new() {
    let mut values = [
        0, 1, 2, //
        3, 4, 5, //
    ];

    let mat = mat::MatrixRefMut::new(&mut values, (3, 2).into()).unwrap();

    assert_eq!(mat.as_slice(), [0, 1, 2, 3, 4, 5]);
    assert_eq!(mat.size(), (3, 2).into());

    let err = mat::MatrixRefMut::new(&mut values[1..], (3, 2).into());

    assert_eq!(err, Err(mat::Error::InvalidSize));
}

#[test]
fn matrix_to_owned() {
    let mat = lb::MatrixRef::from(&[
        [00, 01, 02, 03], //
        [04, 05, 06, 07], //
        [08, 09, 10, 11], //
    ]);

    let own0 = mat.to_owned();

    assert_eq!(
        own0,
        lb::MatrixVec::from([
            [00, 01, 02, 03], //
            [04, 05, 06, 07], //
            [08, 09, 10, 11], //
        ])
    );

    let window = mat.window((1, 0), (2, 2).into()).unwrap();

    let own1 = window.to_owned();

    assert_eq!(
        own1,
        lb::MatrixVec::from([
            [01, 02], //
            [05, 06], //
        ])
    );
}

#[test]
fn matrix_vec_with_default() {
    let mat = mat::MatrixVec::<i32>::with_default((3, 2).into());

    assert_eq!(mat.as_slice(), [0i32; 6]);
    assert_eq!(mat.size(), (3, 2).into());
}

#[test]
fn matrix_vec_with() {
    let mat = mat::MatrixVec::with(42, (2, 2).into());

    assert_eq!(mat.as_slice(), [42, 42, 42, 42]);
    assert_eq!(mat.size(), (2, 2).into());
}

#[test]
fn matrix_index() {
    let values = [
        0, 1, 2, //
        3, 4, 5, //
    ];

    let mat = mat::MatrixRef::new(&values, (3, 2).into()).unwrap();

    assert_eq!(mat[(2, 1)], 5);
}

#[test]
fn matrix_index_mut() {
    let mut values = [
        0, 1, //
        2, 3, //
        4, 5, //
    ];

    let mut mat = mat::MatrixRefMut::new(&mut values, (2, 3).into()).unwrap();

    mat[(0, 2)] = 42;

    assert_eq!(values, [0, 1, 2, 3, 42, 5]);
}

#[test]
fn matrix_get_pair_mut() {
    let mut values = [
        0, 1, //
        2, 3, //
        4, 5, //
    ];

    let mut mat = mat::MatrixRefMut::new(&mut values, (2, 3).into()).unwrap();

    let pair = mat.get_pair_mut((1, 2), (1, 0));
    assert_eq!(pair, Some((&mut 5, &mut 1)));

    let pair = mat.get_pair_mut((1, 3), (1, 0));
    assert_eq!(pair, None);

    let pair = mat.get_pair_mut((0, 0), (0, 0));
    assert_eq!(pair, None);
}

#[test]
fn matrix_vec_from() {
    let mat = lb::MatrixVec::from([
        [00, 01, 02], //
        [03, 04, 05], //
        [06, 07, 08], //
        [09, 10, 11], //
    ]);

    assert_eq!(mat.as_slice(), [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11]);
    assert_eq!(mat.size(), (3, 4).into());
    assert_eq!(mat.stride(), 3);

    let mat = lb::MatrixVec::<i32>::from([[]]);

    assert_eq!(mat.as_slice(), []);
    assert_eq!(mat.size(), (0, 1).into());
    assert_eq!(mat.stride(), 0);
}

#[test]
fn matrix_ref_from() {
    let mat = lb::MatrixRef::from(&[
        [00, 01, 02], //
        [03, 04, 05], //
        [06, 07, 08], //
        [09, 10, 11], //
    ]);

    assert_eq!(mat.as_slice(), [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11]);
    assert_eq!(mat.size(), (3, 4).into());
    assert_eq!(mat.stride(), 3);

    let mat = lb::MatrixRef::<i32>::from(&[[]]);

    assert_eq!(mat.as_slice(), []);
    assert_eq!(mat.size(), (0, 1).into());
    assert_eq!(mat.stride(), 0);
}

#[test]
fn matrix_ref_mut_from() {
    let mut arr = [
        [00, 01, 02], //
        [03, 04, 05], //
        [06, 07, 08], //
        [09, 10, 11], //
    ];
    let mat = lb::MatrixRefMut::from(&mut arr);

    assert_eq!(mat.as_slice(), [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11]);
    assert_eq!(mat.size(), (3, 4).into());
    assert_eq!(mat.stride(), 3);

    let mut arr = [[]];
    let mat = lb::MatrixRefMut::<i32>::from(&mut arr);

    assert_eq!(mat.as_slice(), []);
    assert_eq!(mat.size(), (0, 1).into());
    assert_eq!(mat.stride(), 0);
}

#[test]
fn window() {
    let mat = lb::MatrixRef::from(&[
        [00, 01, 02, 03, 04, 05, 06], //
        [07, 08, 09, 10, 11, 12, 13], //
        [14, 15, 16, 17, 18, 19, 20], //
        [21, 22, 23, 24, 25, 26, 27], //
    ]);

    assert_eq!(mat.window((0, 0), (7, 4).into()), Ok(mat.as_ref()));

    assert_eq!(
        mat.window((1, 2), (3, 2).into()),
        Ok(lb::MatrixRef::from(&[
            [15, 16, 17], //
            [22, 23, 24], //
        ]))
    );

    assert_eq!(
        mat.window((0, 0), (1, 1).into()),
        Ok(lb::MatrixRef::from(&[[00]]))
    );

    assert_eq!(
        mat.window((6, 3), (1, 1).into()),
        Ok(lb::MatrixRef::from(&[[27]]))
    );

    use lb::mat::Error::OutOfBounds;
    assert_eq!(mat.window((7, 0), (1, 1).into()), Err(OutOfBounds));
    assert_eq!(mat.window((0, 4), (1, 1).into()), Err(OutOfBounds));

    use lb::mat::Error::InvalidSize;
    assert_eq!(mat.window((0, 0), (8, 4).into()), Err(InvalidSize));
    assert_eq!(mat.window((0, 0), (7, 5).into()), Err(InvalidSize));

    assert_eq!(
        mat.window((0, 0), (0, 0).into()),
        lb::MatrixRef::<i32>::new(&[], (0, 0).into())
    );
    assert_eq!(
        mat.window((0, 1), (0, 0).into()),
        lb::MatrixRef::<i32>::new(&[], (0, 0).into())
    );
    assert_eq!(
        mat.window((1, 0), (0, 0).into()),
        lb::MatrixRef::<i32>::new(&[], (0, 0).into())
    );
    assert_eq!(
        mat.window((0, 0), (0, 1).into()),
        lb::MatrixRef::<i32>::new(&[], (0, 1).into())
    );
    assert_eq!(
        mat.window((0, 0), (1, 0).into()),
        lb::MatrixRef::<i32>::new(&[], (1, 0).into())
    );
}

#[test]
fn window_mut() {
    let mut mat = lb::MatrixVec::from([
        [00, 01, 02, 03, 04, 05, 06], //
        [07, 08, 09, 10, 11, 12, 13], //
        [14, 15, 16, 17, 18, 19, 20], //
        [21, 22, 23, 24, 25, 26, 27], //
    ]);

    assert_eq!(
        mat.window_mut((0, 0), (7, 4).into()),
        Ok(lb::MatrixRefMut::from(&mut [
            [00, 01, 02, 03, 04, 05, 06], //
            [07, 08, 09, 10, 11, 12, 13], //
            [14, 15, 16, 17, 18, 19, 20], //
            [21, 22, 23, 24, 25, 26, 27], //
        ]))
    );

    assert_eq!(
        mat.window_mut((1, 2), (3, 2).into()),
        Ok(lb::MatrixRefMut::from(&mut [
            [15, 16, 17], //
            [22, 23, 24], //
        ]))
    );

    assert_eq!(
        mat.window_mut((0, 0), (1, 1).into()),
        Ok(lb::MatrixRefMut::from(&mut [[00]]))
    );

    assert_eq!(
        mat.window_mut((6, 3), (1, 1).into()),
        Ok(lb::MatrixRefMut::from(&mut [[27]]))
    );

    use lb::mat::Error::OutOfBounds;
    assert_eq!(mat.window_mut((7, 0), (1, 1).into()), Err(OutOfBounds));
    assert_eq!(mat.window_mut((0, 4), (1, 1).into()), Err(OutOfBounds));

    use lb::mat::Error::InvalidSize;
    assert_eq!(mat.window_mut((0, 0), (8, 4).into()), Err(InvalidSize));
    assert_eq!(mat.window_mut((0, 0), (7, 5).into()), Err(InvalidSize));

    assert_eq!(
        mat.window_mut((0, 0), (0, 0).into()),
        lb::MatrixRefMut::<i32>::new(&mut [], (0, 0).into())
    );
    assert_eq!(
        mat.window_mut((0, 1), (0, 0).into()),
        lb::MatrixRefMut::<i32>::new(&mut [], (0, 0).into())
    );
    assert_eq!(
        mat.window_mut((1, 0), (0, 0).into()),
        lb::MatrixRefMut::<i32>::new(&mut [], (0, 0).into())
    );
    assert_eq!(
        mat.window_mut((0, 0), (0, 1).into()),
        lb::MatrixRefMut::<i32>::new(&mut [], (0, 1).into())
    );
    assert_eq!(
        mat.window_mut((0, 0), (1, 0).into()),
        lb::MatrixRefMut::<i32>::new(&mut [], (1, 0).into())
    );
}

#[test]
fn rows_size_hint() {
    let mat = mat::MatrixVec::<i32>::from([[]]);
    assert_eq!(mat.rows().size_hint(), (0, Some(0)));

    let mat = mat::MatrixVec::from([
        [00, 01, 02], //
        [03, 04, 05], //
        [06, 07, 08], //
        [09, 10, 11], //
    ]);
    assert_eq!(mat.rows().size_hint(), (4, Some(4)));

    let win = mat.window((1, 1), (2, 3).into()).unwrap();
    assert_eq!(win.rows().size_hint(), (3, Some(3)));
}

#[test]
fn matrix_ref_rows() {
    let mat = mat::MatrixVec::<i32>::from([[]]);
    let mut rows = mat.rows();
    assert_eq!(rows.next(), None);

    let values = [
        0, 1, 2, //
        3, 4, 5, //
        6, 7, 8, //
    ];

    let mat = mat::MatrixRef::new(&values, (3, 3).into()).unwrap();
    let mut rows = mat.rows();

    assert_eq!(rows.next().unwrap(), [0, 1, 2]);
    assert_eq!(rows.next().unwrap(), [3, 4, 5]);
    assert_eq!(rows.next().unwrap(), [6, 7, 8]);
    assert_eq!(rows.next(), None);

    let mut rows = mat.rows();
    assert_eq!(rows.next_back().unwrap(), [6, 7, 8]);
    assert_eq!(rows.next_back().unwrap(), [3, 4, 5]);
    assert_eq!(rows.next_back().unwrap(), [0, 1, 2]);
    assert_eq!(rows.next_back(), None);

    {
        let win = mat.window((1, 1), (2, 2).into()).unwrap();

        let mut rows = win.rows();
        assert_eq!(rows.next().unwrap(), [4, 5]);
        assert_eq!(rows.next().unwrap(), [7, 8]);
        assert_eq!(rows.next(), None);
    }
}

#[test]
fn rows_mut_size_hint() {
    let mut mat = mat::MatrixVec::<i32>::from([[]]);
    assert_eq!(mat.rows_mut().size_hint(), (0, Some(0)));

    let mut mat = mat::MatrixVec::from([
        [00, 01, 02], //
        [03, 04, 05], //
        [06, 07, 08], //
        [09, 10, 11], //
    ]);
    assert_eq!(mat.rows_mut().size_hint(), (4, Some(4)));

    let mut win = mat.window_mut((1, 1), (2, 3).into()).unwrap();
    assert_eq!(win.rows_mut().size_hint(), (3, Some(3)));
}

#[test]
fn matrix_mut_rows_mut() {
    let mut mat = mat::MatrixVec::<i32>::from([[]]);
    let mut rows = mat.rows_mut();
    assert_eq!(rows.next(), None);

    let mut values = [0, 1, 2, 3, 4, 5, 6, 7, 8];
    let mut mat = mat::MatrixRefMut::new(&mut values, (3, 3).into()).unwrap();

    {
        let mut rows = mat.rows_mut();
        assert_eq!(rows.next_back().unwrap(), [6, 7, 8]);
        assert_eq!(rows.next_back().unwrap(), [3, 4, 5]);
        assert_eq!(rows.next_back().unwrap(), [0, 1, 2]);
        assert_eq!(rows.next_back(), None);
    }

    {
        let win = mat.window_mut((1, 1), (2, 2).into()).unwrap();
        let mut rows = win.rows();

        assert_eq!(rows.next().unwrap(), [4, 5]);
        assert_eq!(rows.next().unwrap(), [7, 8]);
        assert_eq!(rows.next(), None);
    }

    let mut rows = mat.rows_mut();

    assert_eq!(rows.next().unwrap(), [0, 1, 2]);

    let middle = rows.next().unwrap();
    assert_eq!(middle, [3, 4, 5]);
    middle[1] = 42;

    assert_eq!(rows.next().unwrap(), [6, 7, 8]);
    assert_eq!(rows.next(), None);

    assert_eq!(values, [0, 1, 2, 3, 42, 5, 6, 7, 8]);
}

#[test]
fn splits_size_hint() {
    let mat = mat::MatrixVec::from([
        [00, 01, 02], //
        [03, 04, 05], //
        [06, 07, 08], //
        [09, 10, 11], //
    ]);

    assert_eq!(mat.splits(1).size_hint(), (4, Some(4)));
    assert_eq!(mat.splits(2).size_hint(), (2, Some(2)));
    assert_eq!(mat.splits(3).size_hint(), (2, Some(2)));
    assert_eq!(mat.splits(4).size_hint(), (1, Some(1)));
    assert_eq!(mat.splits(5).size_hint(), (1, Some(1)));

    let win = mat.window((1, 1), (2, 3).into()).unwrap();

    assert_eq!(win.splits(1).size_hint(), (3, Some(3)));
    assert_eq!(win.splits(2).size_hint(), (2, Some(2)));
    assert_eq!(win.splits(3).size_hint(), (1, Some(1)));
    assert_eq!(win.splits(4).size_hint(), (1, Some(1)));
}

#[test]
fn splits_next() {
    let mat = mat::MatrixVec::from([
        [00, 01, 02, 03],
        [04, 05, 06, 07],
        [08, 09, 10, 11],
        [12, 13, 14, 15],
        [16, 17, 18, 19],
        [20, 21, 22, 23],
    ]);

    {
        let win = mat.window((1, 1), (2, 5).into()).unwrap();
        let mut splits = win.splits(2);

        assert_eq!(
            splits.next(),
            Some(lb::MatrixRef::from(&[
                [05, 06], //
                [09, 10], //
            ]))
        );

        assert_eq!(
            splits.next(),
            Some(lb::MatrixRef::from(&[
                [13, 14], //
                [17, 18], //
            ]))
        );

        assert_eq!(splits.next(), Some(lb::MatrixRef::from(&[[21, 22]])));

        assert_eq!(splits.next(), None);
    }

    {
        let mut splits = mat.splits(2);

        assert_eq!(
            splits.next(),
            Some(lb::MatrixRef::from(&[
                [00, 01, 02, 03], //
                [04, 05, 06, 07], //
            ]))
        );

        assert_eq!(
            splits.next(),
            Some(lb::MatrixRef::from(&[
                [08, 09, 10, 11], //
                [12, 13, 14, 15], //
            ]))
        );

        assert_eq!(
            splits.next(),
            Some(lb::MatrixRef::from(&[
                [16, 17, 18, 19], //
                [20, 21, 22, 23], //
            ]))
        );

        assert_eq!(splits.next(), None);
    }

    {
        let mut splits = mat.splits(4);

        assert_eq!(
            splits.next(),
            Some(lb::MatrixRef::from(&[
                [00, 01, 02, 03], //
                [04, 05, 06, 07], //
                [08, 09, 10, 11], //
                [12, 13, 14, 15], //
            ]))
        );

        assert_eq!(
            splits.next(),
            Some(lb::MatrixRef::from(&[
                [16, 17, 18, 19], //
                [20, 21, 22, 23], //
            ]))
        );

        assert_eq!(splits.next(), None);
    }

    // If number of `rows` exceeds the height of the matrix, `Splits` will consist of only a single
    // which is identical to the original matrix.
    let mut splits = mat.splits(7);
    assert_eq!(splits.next(), Some(mat.as_ref()));
    assert_eq!(splits.next(), None);

    let mat = mat::MatrixVec::from([[0]]);
    let mut splits = mat.splits(0);
    assert_eq!(splits.next(), None);

    let mat = mat::MatrixVec::<i32>::from([[]]);
    let mut splits = mat.splits(1);
    assert_eq!(splits.next(), None);
}

#[test]
fn splits_mut_size_hint() {
    let mut mat = mat::MatrixVec::from([
        [00, 01, 02], //
        [03, 04, 05], //
        [06, 07, 08], //
        [09, 10, 11], //
    ]);

    assert_eq!(mat.splits_mut(1).size_hint(), (4, Some(4)));
    assert_eq!(mat.splits_mut(2).size_hint(), (2, Some(2)));
    assert_eq!(mat.splits_mut(3).size_hint(), (2, Some(2)));
    assert_eq!(mat.splits_mut(4).size_hint(), (1, Some(1)));
    assert_eq!(mat.splits_mut(5).size_hint(), (1, Some(1)));

    let mut win = mat.window_mut((1, 1), (2, 3).into()).unwrap();

    assert_eq!(win.splits_mut(1).size_hint(), (3, Some(3)));
    assert_eq!(win.splits_mut(2).size_hint(), (2, Some(2)));
    assert_eq!(win.splits_mut(3).size_hint(), (1, Some(1)));
    assert_eq!(win.splits_mut(4).size_hint(), (1, Some(1)));
}

#[test]
fn splits_mut_next() {
    let mut mat = mat::MatrixVec::from([
        [00, 01, 02, 03],
        [04, 05, 06, 07],
        [08, 09, 10, 11],
        [12, 13, 14, 15],
        [16, 17, 18, 19],
        [20, 21, 22, 23],
    ]);

    {
        let mut win = mat.window_mut((1, 1), (2, 5).into()).unwrap();
        let mut splits = win.splits_mut(2);

        assert_eq!(
            splits.next(),
            Some(lb::MatrixRefMut::from(&mut [
                [05, 06], //
                [09, 10], //
            ]))
        );

        assert_eq!(
            splits.next(),
            Some(lb::MatrixRefMut::from(&mut [
                [13, 14], //
                [17, 18], //
            ]))
        );

        assert_eq!(splits.next(), Some(lb::MatrixRefMut::from(&mut [[21, 22]])));

        assert_eq!(splits.next(), None);
    }

    {
        let mut splits = mat.splits_mut(2);

        assert_eq!(
            splits.next(),
            Some(lb::MatrixRefMut::from(&mut [
                [00, 01, 02, 03], //
                [04, 05, 06, 07], //
            ]))
        );

        assert_eq!(
            splits.next(),
            Some(lb::MatrixRefMut::from(&mut [
                [08, 09, 10, 11], //
                [12, 13, 14, 15], //
            ]))
        );

        assert_eq!(
            splits.next(),
            Some(lb::MatrixRefMut::from(&mut [
                [16, 17, 18, 19], //
                [20, 21, 22, 23], //
            ]))
        );

        assert_eq!(splits.next(), None);
    }

    {
        let mut splits = mat.splits_mut(4);

        assert_eq!(
            splits.next(),
            Some(lb::MatrixRefMut::from(&mut [
                [00, 01, 02, 03], //
                [04, 05, 06, 07], //
                [08, 09, 10, 11], //
                [12, 13, 14, 15], //
            ]))
        );

        assert_eq!(
            splits.next(),
            Some(lb::MatrixRefMut::from(&mut [
                [16, 17, 18, 19], //
                [20, 21, 22, 23], //
            ]))
        );

        assert_eq!(splits.next(), None);
    }

    // If number of `rows` exceeds the height of the matrix, `SplitsMut` will consist of only a
    // single item which is identical to the original matrix.
    let mut expected = mat.to_owned();
    let mut splits = mat.splits_mut(7);
    assert_eq!(splits.next(), Some(expected.as_mut()));
    assert_eq!(splits.next(), None);

    let mut mat = mat::MatrixVec::from([[0]]);
    let mut splits = mat.splits_mut(0);
    assert_eq!(splits.next(), None);

    let mut mat = mat::MatrixVec::<i32>::from([[]]);
    let mut splits = mat.splits_mut(1);
    assert_eq!(splits.next(), None);
}

#[test]
fn windows_size_hint() {
    let mat = lb::MatrixRef::from(&[
        [00, 01, 02, 03, 04, 05], //
        [06, 07, 08, 09, 10, 11], //
        [12, 13, 14, 15, 16, 17], //
        [18, 19, 20, 21, 22, 23], //
    ]);

    assert_eq!(mat.windows((0, 0).into()).size_hint(), (0, Some(0)));
    assert_eq!(mat.windows((0, 1).into()).size_hint(), (0, Some(0)));
    assert_eq!(mat.windows((1, 0).into()).size_hint(), (0, Some(0)));
    assert_eq!(mat.windows((6, 4).into()).size_hint(), (1, Some(1)));
    assert_eq!(mat.windows((5, 4).into()).size_hint(), (2, Some(2)));
    assert_eq!(mat.windows((6, 3).into()).size_hint(), (2, Some(2)));
    assert_eq!(mat.windows((2, 3).into()).size_hint(), (10, Some(10)));

    let win = mat.window((1, 1), (4, 2).into()).unwrap();

    let mut windows = win.windows((2, 2).into());

    assert_eq!(windows.size_hint(), (3, Some(3)));
    _ = windows.next();
    assert_eq!(windows.size_hint(), (2, Some(2)));
    _ = windows.next();
    assert_eq!(windows.size_hint(), (1, Some(1)));
    _ = windows.next();
    assert_eq!(windows.size_hint(), (0, Some(0)));
    _ = windows.next();
    assert_eq!(windows.size_hint(), (0, Some(0)));
    assert_eq!(windows.count(), 0);
}

#[test]
fn windows_next() {
    let mat = lb::MatrixRef::from(&[
        [00, 01, 02], //
        [04, 05, 06], //
        [08, 09, 10], //
    ]);

    {
        let mut windows = mat.windows((3, 3).into());

        assert_eq!(
            windows.next(),
            Some(lb::MatrixRef::from(&[
                [00, 01, 02], //
                [04, 05, 06], //
                [08, 09, 10], //
            ]))
        );

        assert_eq!(windows.next(), None);
    }

    {
        assert_eq!(mat.windows((0, 0).into()).next(), None);
        assert_eq!(mat.windows((0, 1).into()).next(), None);
        assert_eq!(mat.windows((1, 0).into()).next(), None);
    }

    {
        let mut windows = mat.windows((2, 2).into());

        assert_eq!(
            windows.next(),
            Some(lb::MatrixRef::from(&[
                [00, 01], //
                [04, 05], //
            ]))
        );

        assert_eq!(
            windows.next(),
            Some(lb::MatrixRef::from(&[
                [01, 02], //
                [05, 06], //
            ]))
        );

        assert_eq!(
            windows.next(),
            Some(lb::MatrixRef::from(&[
                [04, 05], //
                [08, 09], //
            ]))
        );

        assert_eq!(
            windows.next(),
            Some(lb::MatrixRef::from(&[
                [05, 06], //
                [09, 10], //
            ]))
        );

        assert_eq!(windows.next(), None);
    }

    {
        let arr: [[i32; 0]; 0] = [];
        let mat = lb::MatrixRef::<i32>::from(&arr);

        assert_eq!(mat.windows((0, 0).into()).next(), None);
        assert_eq!(mat.windows((0, 1).into()).next(), None);
        assert_eq!(mat.windows((1, 0).into()).next(), None);
    }

    {
        let mat = lb::MatrixRef::<i32>::from(&[[]]);

        assert_eq!(mat.windows((0, 0).into()).next(), None);
        assert_eq!(mat.windows((0, 1).into()).next(), None);
        assert_eq!(mat.windows((1, 0).into()).next(), None);
    }

    {
        let mat = lb::MatrixRef::from(&[
            [00, 00, 00, 00],
            [00, 00, 01, 02],
            [00, 03, 04, 05],
            [00, 06, 07, 08],
            [00, 09, 10, 11],
            [00, 00, 00, 00],
        ]);

        let win = mat.window((1, 1), (3, 4).into()).unwrap();
        let mut windows = win.windows((2, 3).into());

        assert_eq!(
            windows.next(),
            Some(lb::MatrixRef::from(&[
                [00, 01], //
                [03, 04], //
                [06, 07], //
            ]))
        );

        assert_eq!(
            windows.next(),
            Some(lb::MatrixRef::from(&[
                [01, 02], //
                [04, 05], //
                [07, 08], //
            ]))
        );

        assert_eq!(
            windows.next(),
            Some(lb::MatrixRef::from(&[
                [03, 04], //
                [06, 07], //
                [09, 10], //
            ]))
        );

        assert_eq!(
            windows.next(),
            Some(lb::MatrixRef::from(&[
                [04, 05], //
                [07, 08], //
                [10, 11], //
            ]))
        );

        assert_eq!(windows.next(), None);
    }
}