"""Converts MNIST data to TFRecords file format with Example protos."""
import os
import tensorflow as tf


def _int64_feature(value):
    return tf.train.Feature(int64_list=tf.train.Int64List(value=[value]))


def _bytes_feature(value):
    return tf.train.Feature(bytes_list=tf.train.BytesList(value=[value]))


def convert_to(data_set, name, directory):
    """Converts a dataset to tfrecords."""
    images = data_set.images
    labels = data_set.labels
    num_examples = data_set.num_examples

    if images.shape[0] != num_examples:
        raise ValueError('Images size %d does not match label size %d.' %
                         (images.shape[0], num_examples))
    rows = images.shape[1]
    cols = images.shape[2]
    depth = images.shape[3]

    filename = os.path.join(directory, name + '.tfrecords')
    print('Writing', filename)
    writer = tf.python_io.TFRecordWriter(filename)
    for index in range(num_examples):
        image_raw = images[index].tostring()
        example = tf.train.Example(features=tf.train.Features(feature={
            'height': _int64_feature(rows),
            'width': _int64_feature(cols),
            'depth': _int64_feature(depth),
            'label': _int64_feature(int(labels[index])),
            'image_raw': _bytes_feature(image_raw)}))
        writer.write(example.SerializeToString())
    writer.close()