"""CIFAR10 small images classification dataset."""

import os

import numpy as np

from keras.src import backend
from keras.src.api_export import keras_export
from keras.src.datasets.cifar import load_batch
from keras.src.utils.file_utils import get_file


@keras_export("keras.datasets.cifar10.load_data")
def load_data():
    """Loads the CIFAR10 dataset.

    This is a dataset of 50,000 32x32 color training images and 10,000 test
    images, labeled over 10 categories. See more info at the
    [CIFAR homepage](https://www.cs.toronto.edu/~kriz/cifar.html).

    The classes are:

    | Label | Description |
    |:-----:|-------------|
    |   0   | airplane    |
    |   1   | automobile  |
    |   2   | bird        |
    |   3   | cat         |
    |   4   | deer        |
    |   5   | dog         |
    |   6   | frog        |
    |   7   | horse       |
    |   8   | ship        |
    |   9   | truck       |

    Returns:
        Tuple of NumPy arrays: `(x_train, y_train), (x_test, y_test)`.

    **`x_train`**: `uint8` NumPy array of grayscale image data with shapes
      `(50000, 32, 32, 3)`, containing the training data. Pixel values range
      from 0 to 255.

    **`y_train`**: `uint8` NumPy array of labels (integers in range 0-9)
      with shape `(50000, 1)` for the training data.

    **`x_test`**: `uint8` NumPy array of grayscale image data with shapes
      `(10000, 32, 32, 3)`, containing the test data. Pixel values range
      from 0 to 255.

    **`y_test`**: `uint8` NumPy array of labels (integers in range 0-9)
      with shape `(10000, 1)` for the test data.

    Example:

    ```python
    (x_train, y_train), (x_test, y_test) = keras.datasets.cifar10.load_data()
    assert x_train.shape == (50000, 32, 32, 3)
    assert x_test.shape == (10000, 32, 32, 3)
    assert y_train.shape == (50000, 1)
    assert y_test.shape == (10000, 1)
    ```
    """
    dirname = "cifar-10-batches-py-target"
    origin = "https://www.cs.toronto.edu/~kriz/cifar-10-python.tar.gz"
    path = get_file(
        fname=dirname,
        origin=origin,
        extract=True,
        file_hash=(  # noqa: E501
            "6d958be074577803d12ecdefd02955f39262c83c16fe9348329d7fe0b5c001ce"
        ),
    )

    num_train_samples = 50000

    x_train = np.empty((num_train_samples, 3, 32, 32), dtype="uint8")
    y_train = np.empty((num_train_samples,), dtype="uint8")

    # batches are within an inner folder
    path = os.path.join(path, "cifar-10-batches-py")
    for i in range(1, 6):
        fpath = os.path.join(path, "data_batch_" + str(i))
        (
            x_train[(i - 1) * 10000 : i * 10000, :, :, :],
            y_train[(i - 1) * 10000 : i * 10000],
        ) = load_batch(fpath)

    fpath = os.path.join(path, "test_batch")
    x_test, y_test = load_batch(fpath)

    y_train = np.reshape(y_train, (len(y_train), 1))
    y_test = np.reshape(y_test, (len(y_test), 1))

    if backend.image_data_format() == "channels_last":
        x_train = x_train.transpose(0, 2, 3, 1)
        x_test = x_test.transpose(0, 2, 3, 1)

    x_test = x_test.astype(x_train.dtype)
    y_test = y_test.astype(y_train.dtype)

    return (x_train, y_train), (x_test, y_test)