# Copyright 2017 The TensorFlow Authors. All Rights Reserved.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
# ==============================================================================
"""CIFAR-10 data set.

See http://www.cs.toronto.edu/~kriz/cifar.html.
"""
import os

import tensorflow as tf

HEIGHT = 32
WIDTH = 32
DEPTH = 3


class Cifar10DataSet(object):
    """Cifar10 data set.

    Described by http://www.cs.toronto.edu/~kriz/cifar.html.
    """

    def __init__(self, data_dir, subset="train", use_distortion=True):
        self.data_dir = data_dir
        self.subset = subset
        self.use_distortion = use_distortion

    def get_filenames(self):
        if self.subset in ["train", "validation", "eval"]:
            return [os.path.join(self.data_dir, self.subset + ".tfrecords")]
        else:
            raise ValueError('Invalid data subset "%s"' % self.subset)

    def parser(self, serialized_example):
        """Parses a single tf.Example into image and label tensors."""
        # Dimensions of the images in the CIFAR-10 dataset.
        # See http://www.cs.toronto.edu/~kriz/cifar.html for a description of the
        # input format.
        features = tf.parse_single_example(
            serialized_example,
            features={
                "image": tf.FixedLenFeature([], tf.string),
                "label": tf.FixedLenFeature([], tf.int64),
            },
        )
        image = tf.decode_raw(features["image"], tf.uint8)
        image.set_shape([DEPTH * HEIGHT * WIDTH])

        # Reshape from [depth * height * width] to [depth, height, width].
        image = tf.cast(tf.transpose(tf.reshape(image, [DEPTH, HEIGHT, WIDTH]), [1, 2, 0]), tf.float32)
        label = tf.cast(features["label"], tf.int32)

        # Custom preprocessing.
        image = self.preprocess(image)

        return image, label

    def make_batch(self, batch_size):
        """Read the images and labels from 'filenames'."""
        filenames = self.get_filenames()
        # Repeat infinitely.
        dataset = tf.data.TFRecordDataset(filenames).repeat()

        # Parse records.
        dataset = dataset.map(self.parser, num_parallel_calls=batch_size)

        # Potentially shuffle records.
        if self.subset == "train":
            min_queue_examples = int(Cifar10DataSet.num_examples_per_epoch(self.subset) * 0.4)
            # Ensure that the capacity is sufficiently large to provide good random
            # shuffling.
            dataset = dataset.shuffle(buffer_size=min_queue_examples + 3 * batch_size)

        # Batch it up.
        dataset = dataset.batch(batch_size)
        iterator = dataset.make_one_shot_iterator()
        image_batch, label_batch = iterator.get_next()

        return image_batch, label_batch

    def preprocess(self, image):
        """Preprocess a single image in [height, width, depth] layout."""
        if self.subset == "train" and self.use_distortion:
            # Pad 4 pixels on each dimension of feature map, done in mini-batch
            image = tf.image.resize_image_with_crop_or_pad(image, 40, 40)
            image = tf.random_crop(image, [HEIGHT, WIDTH, DEPTH])
            image = tf.image.random_flip_left_right(image)
        return image

    @staticmethod
    def num_examples_per_epoch(subset="train"):
        if subset == "train":
            return 45000
        elif subset == "validation":
            return 5000
        elif subset == "eval":
            return 10000
        else:
            raise ValueError('Invalid data subset "%s"' % subset)
