# Copyright 2022 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.

"""Data parser and processing for Panoptic Deeplab."""

from typing import List, Optional

import numpy as np
import tensorflow as tf

from official.vision.configs import common
from official.vision.dataloaders import parser
from official.vision.dataloaders import tf_example_decoder
from official.vision.ops import preprocess_ops
from official.vision.ops import augment


def _compute_gaussian_from_std(sigma):
  """Computes the Gaussian and its size from a given standard deviation."""
  size = int(6 * sigma + 3)
  x = np.arange(size, dtype=np.float)
  y = x[:, np.newaxis]
  x0, y0 = 3 * sigma + 1, 3 * sigma + 1
  gaussian = tf.constant(
      np.exp(-((x - x0)**2 + (y - y0)**2) / (2 * sigma**2)),
      dtype=tf.float32)
  return gaussian, size


class TfExampleDecoder(tf_example_decoder.TfExampleDecoder):
  """Tensorflow Example proto decoder."""

  def __init__(self, regenerate_source_id):
    super(TfExampleDecoder,
          self).__init__(
              include_mask=True,
              regenerate_source_id=regenerate_source_id)

    self._panoptic_keys_to_features = {
        'image/panoptic/category_mask':
            tf.io.FixedLenFeature((), tf.string, default_value=''),
        'image/panoptic/instance_mask':
            tf.io.FixedLenFeature((), tf.string, default_value='')
    }

  def decode(self, serialized_example):
    decoded_tensors = super(TfExampleDecoder,
                            self).decode(serialized_example)
    parsed_tensors = tf.io.parse_single_example(
        serialized_example, self._panoptic_keys_to_features)

    category_mask = tf.io.decode_image(
        parsed_tensors['image/panoptic/category_mask'], channels=1)
    instance_mask = tf.io.decode_image(
        parsed_tensors['image/panoptic/instance_mask'], channels=1)
    category_mask.set_shape([None, None, 1])
    instance_mask.set_shape([None, None, 1])

    decoded_tensors.update({
        'groundtruth_panoptic_category_mask': category_mask,
        'groundtruth_panoptic_instance_mask': instance_mask
    })
    return decoded_tensors


class Parser(parser.Parser):
  """Parser to parse an image and its annotations into a dictionary of tensors."""

  def __init__(
      self,
      output_size: List[int],
      resize_eval_groundtruth: bool = True,
      groundtruth_padded_size: Optional[List[int]] = None,
      ignore_label: int = 0,
      aug_rand_hflip: bool = False,
      aug_scale_min: float = 1.0,
      aug_scale_max: float = 1.0,
      aug_type: Optional[common.Augmentation] = None,
      sigma: float = 8.0,
      small_instance_area_threshold: int = 4096,
      small_instance_weight: float = 3.0,
      dtype: str = 'float32'):
    """Initializes parameters for parsing annotations in the dataset.

    Args:
      output_size: `Tensor` or `list` for [height, width] of output image. The
        output_size should be divided by the largest feature stride 2^max_level.
      resize_eval_groundtruth: `bool`, if True, eval groundtruth masks are
        resized to output_size.
      groundtruth_padded_size: `Tensor` or `list` for [height, width]. When
        resize_eval_groundtruth is set to False, the groundtruth masks are
        padded to this size.
      ignore_label: `int` the pixel with ignore label will not used for training
        and evaluation.
      aug_rand_hflip: `bool`, if True, augment training with random
        horizontal flip.
      aug_scale_min: `float`, the minimum scale applied to `output_size` for
        data augmentation during training.
      aug_scale_max: `float`, the maximum scale applied to `output_size` for
        data augmentation during training.
      aug_type: An optional Augmentation object with params for AutoAugment.
      sigma: `float`, standard deviation for generating 2D Gaussian to encode
        centers.
      small_instance_area_threshold: `int`, 
      small_instance_weight: `float`, 
      dtype: `str`, data type. One of {`bfloat16`, `float32`, `float16`}.
    """
    self._output_size = output_size
    self._resize_eval_groundtruth = resize_eval_groundtruth
    if (not resize_eval_groundtruth) and (groundtruth_padded_size is None):
      raise ValueError(
          'groundtruth_padded_size ([height, width]) needs to be'
          'specified when resize_eval_groundtruth is False.')
    self._groundtruth_padded_size = groundtruth_padded_size
    self._ignore_label = ignore_label

    # Data augmentation.
    self._aug_rand_hflip = aug_rand_hflip
    self._aug_scale_min = aug_scale_min
    self._aug_scale_max = aug_scale_max

    if aug_type:
      if aug_type.type == 'autoaug':
        self._augmenter = augment.AutoAugment(
            augmentation_name=aug_type.autoaug.augmentation_name,
            cutout_const=aug_type.autoaug.cutout_const,
            translate_const=aug_type.autoaug.translate_const)
      else:
        raise ValueError('Augmentation policy {} not supported.'.format(
            aug_type.type))
    else:
      self._augmenter = None

    # dtype.
    self._dtype = dtype

    self._sigma = sigma
    self._gaussian, self._gaussian_size = _compute_gaussian_from_std(
        self._sigma)
    self._gaussian = tf.reshape(self._gaussian, shape=[-1])
    self._small_instance_area_threshold = small_instance_area_threshold
    self._small_instance_weight = small_instance_weight

  def _resize_and_crop_mask(self, mask, image_info, is_training):
    """Resizes and crops mask using `image_info` dict"""
    height = image_info[0][0]
    width = image_info[0][1]
    mask = tf.reshape(mask, shape=[1, height, width, 1])
    mask += 1

    if is_training or self._resize_eval_groundtruth:
      image_scale = image_info[2, :]
      offset = image_info[3, :]
      mask = preprocess_ops.resize_and_crop_masks(
          mask,
          image_scale,
          self._output_size,
          offset)
    else:
      mask = tf.image.pad_to_bounding_box(
          mask, 0, 0,
          self._groundtruth_padded_size[0],
          self._groundtruth_padded_size[1])
    mask -= 1

    # Assign ignore label to the padded region.
    mask = tf.where(
        tf.equal(mask, -1),
        self._ignore_label * tf.ones_like(mask),
        mask)
    mask = tf.squeeze(mask, axis=0)
    return mask

  def _parse_data(self, data, is_training):
    image = data['image']

    if self._augmenter is not None and is_training:
      image = self._augmenter.distort(image)

    image = preprocess_ops.normalize_image(image)

    category_mask = tf.cast(
        data['groundtruth_panoptic_category_mask'][:, :, 0],
        dtype=tf.float32)
    instance_mask = tf.cast(
        data['groundtruth_panoptic_instance_mask'][:, :, 0],
        dtype=tf.float32)

    # Flips image randomly during training.
    if self._aug_rand_hflip and is_training:
      masks = tf.stack([category_mask, instance_mask], axis=0)
      image, _, masks = preprocess_ops.random_horizontal_flip(
          image=image, masks=masks)
      category_mask = masks[0]
      instance_mask = masks[1]

    # Resizes and crops image.
    image, image_info = preprocess_ops.resize_and_crop_image(
        image,
        self._output_size,
        self._output_size,
        aug_scale_min=self._aug_scale_min if is_training else 1.0,
        aug_scale_max=self._aug_scale_max if is_training else 1.0)

    category_mask = self._resize_and_crop_mask(
        category_mask,
        image_info,
        is_training=is_training)
    instance_mask = self._resize_and_crop_mask(
        instance_mask,
        image_info,
        is_training=is_training)

    (instance_centers_heatmap,
     instance_centers_offset,
     semantic_weights) = self._encode_centers_and_offets(
         instance_mask=instance_mask[:, :, 0])

    # Cast image and labels as self._dtype
    image = tf.cast(image, dtype=self._dtype)
    category_mask = tf.cast(category_mask, dtype=self._dtype)
    instance_mask = tf.cast(instance_mask, dtype=self._dtype)
    instance_centers_heatmap = tf.cast(
        instance_centers_heatmap, dtype=self._dtype)
    instance_centers_offset = tf.cast(
        instance_centers_offset, dtype=self._dtype)

    valid_mask = tf.not_equal(
        category_mask, self._ignore_label)
    things_mask = tf.not_equal(
        instance_mask, self._ignore_label)

    labels = {
        'category_mask': category_mask,
        'instance_mask': instance_mask,
        'instance_centers_heatmap': instance_centers_heatmap,
        'instance_centers_offset': instance_centers_offset,
        'semantic_weights': semantic_weights,
        'valid_mask': valid_mask,
        'things_mask': things_mask,
        'image_info': image_info
    }
    return image, labels

  def _parse_train_data(self, data):
    """Parses data for training."""
    return self._parse_data(data=data, is_training=True)

  def _parse_eval_data(self, data):
    """Parses data for evaluation."""
    return self._parse_data(data=data, is_training=False)

  def _encode_centers_and_offets(self, instance_mask):
    """Generates center heatmaps and offets from instance id mask

    Args:
      instance_mask: `tf.Tensor` of shape [height, width] representing
        groundtruth instance id mask.
    Returns:
      instance_centers_heatmap: `tf.Tensor` of shape [height, width, 1]
      instance_centers_offset: `tf.Tensor` of shape [height, width, 2]
    """
    shape = tf.shape(instance_mask)
    height, width = shape[0], shape[1]

    padding_start = int(3 * self._sigma + 1)
    padding_end = int(3 * self._sigma + 2)

    # padding should be equal to self._gaussian_size which is calculated
    # as size = int(6 * sigma + 3)
    padding = padding_start + padding_end

    instance_centers_heatmap = tf.zeros(
        shape=[height + padding, width + padding],
        dtype=tf.float32)
    centers_offset_y = tf.zeros(
        shape=[height, width],
        dtype=tf.float32)
    centers_offset_x = tf.zeros(
        shape=[height, width],
        dtype=tf.float32)
    semantic_weights = tf.ones(
        shape=[height, width],
        dtype=tf.float32)

    unique_instance_ids, _ = tf.unique(tf.reshape(instance_mask, [-1]))

    # The following method for encoding center heatmaps and offets is inspired
    # by the reference implementation available at
    # https://github.com/google-research/deeplab2/blob/main/data/sample_generator.py  # pylint: disable=line-too-long
    for instance_id in unique_instance_ids:
      if instance_id == self._ignore_label:
        continue

      mask = tf.equal(instance_mask, instance_id)
      mask_area = tf.reduce_sum(tf.cast(mask, dtype=tf.float32))
      mask_indices = tf.cast(tf.where(mask), dtype=tf.float32)
      mask_center = tf.reduce_mean(mask_indices, axis=0)
      mask_center_y = tf.cast(tf.round(mask_center[0]), dtype=tf.int32)
      mask_center_x = tf.cast(tf.round(mask_center[1]), dtype=tf.int32)

      if mask_area < self._small_instance_area_threshold:
        semantic_weights = tf.where(
            mask,
            self._small_instance_weight,
            semantic_weights)

      gaussian_size = self._gaussian_size
      indices_y = tf.range(mask_center_y, mask_center_y + gaussian_size)
      indices_x = tf.range(mask_center_x, mask_center_x + gaussian_size)

      indices = tf.stack(tf.meshgrid(indices_y, indices_x))
      indices = tf.reshape(
          indices, shape=[2, gaussian_size * gaussian_size])
      indices = tf.transpose(indices)

      instance_centers_heatmap = tf.tensor_scatter_nd_max(
          tensor=instance_centers_heatmap,
          indices=indices,
          updates=self._gaussian)

      centers_offset_y = tf.tensor_scatter_nd_update(
          tensor=centers_offset_y,
          indices=tf.cast(mask_indices, dtype=tf.int32),
          updates=tf.cast(mask_center_y, dtype=tf.float32) - mask_indices[:, 0])

      centers_offset_x = tf.tensor_scatter_nd_update(
          tensor=centers_offset_x,
          indices=tf.cast(mask_indices, dtype=tf.int32),
          updates=tf.cast(mask_center_x, dtype=tf.float32) - mask_indices[:, 1])

    instance_centers_heatmap = instance_centers_heatmap[
        padding_start:padding_start + height,
        padding_start:padding_start + width]
    instance_centers_heatmap = tf.expand_dims(instance_centers_heatmap, axis=-1)
    
    instance_centers_offset = tf.stack(
        [centers_offset_y, centers_offset_x], 
        axis=-1)

    return (instance_centers_heatmap,
            instance_centers_offset,
            semantic_weights)
