# coding=utf-8
# Copyright 2021 The HuggingFace Inc. team.
#
# 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.

import os
from typing import List, Union

import numpy as np
import PIL.Image
import PIL.ImageOps

import requests

from .utils import is_torch_available
from .utils.constants import (  # noqa: F401
    IMAGENET_DEFAULT_MEAN,
    IMAGENET_DEFAULT_STD,
    IMAGENET_STANDARD_MEAN,
    IMAGENET_STANDARD_STD,
)
from .utils.generic import _is_torch


ImageInput = Union[
    PIL.Image.Image, np.ndarray, "torch.Tensor", List[PIL.Image.Image], List[np.ndarray], List["torch.Tensor"]  # noqa
]


def is_torch_tensor(obj):
    return _is_torch(obj) if is_torch_available() else False


def load_image(image: Union[str, "PIL.Image.Image"]) -> "PIL.Image.Image":
    """
    Loads `image` to a PIL Image.

    Args:
        image (`str` or `PIL.Image.Image`):
            The image to convert to the PIL Image format.

    Returns:
        `PIL.Image.Image`: A PIL Image.
    """
    if isinstance(image, str):
        if image.startswith("http://") or image.startswith("https://"):
            # We need to actually check for a real protocol, otherwise it's impossible to use a local file
            # like http_huggingface_co.png
            image = PIL.Image.open(requests.get(image, stream=True).raw)
        elif os.path.isfile(image):
            image = PIL.Image.open(image)
        else:
            raise ValueError(
                f"Incorrect path or url, URLs must start with `http://` or `https://`, and {image} is not a valid path"
            )
    elif isinstance(image, PIL.Image.Image):
        image = image
    else:
        raise ValueError(
            "Incorrect format used for image. Should be an url linking to an image, a local path, or a PIL image."
        )
    image = PIL.ImageOps.exif_transpose(image)
    image = image.convert("RGB")
    return image


# In the future we can add a TF implementation here when we have TF models.
class ImageFeatureExtractionMixin:
    """
    Mixin that contain utilities for preparing image features.
    """

    def _ensure_format_supported(self, image):
        if not isinstance(image, (PIL.Image.Image, np.ndarray)) and not is_torch_tensor(image):
            raise ValueError(
                f"Got type {type(image)} which is not supported, only `PIL.Image.Image`, `np.array` and "
                "`torch.Tensor` are."
            )

    def to_pil_image(self, image, rescale=None):
        """
        Converts `image` to a PIL Image. Optionally rescales it and puts the channel dimension back as the last axis if
        needed.

        Args:
            image (`PIL.Image.Image` or `numpy.ndarray` or `torch.Tensor`):
                The image to convert to the PIL Image format.
            rescale (`bool`, *optional*):
                Whether or not to apply the scaling factor (to make pixel values integers between 0 and 255). Will
                default to `True` if the image type is a floating type, `False` otherwise.
        """
        self._ensure_format_supported(image)

        if is_torch_tensor(image):
            image = image.numpy()

        if isinstance(image, np.ndarray):
            if rescale is None:
                # rescale default to the array being of floating type.
                rescale = isinstance(image.flat[0], np.floating)
            # If the channel as been moved to first dim, we put it back at the end.
            if image.ndim == 3 and image.shape[0] in [1, 3]:
                image = image.transpose(1, 2, 0)
            if rescale:
                image = image * 255
            image = image.astype(np.uint8)
            return PIL.Image.fromarray(image)
        return image

    def convert_rgb(self, image):
        """
        Converts `PIL.Image.Image` to RGB format.

        Args:
            image (`PIL.Image.Image`):
                The image to convert.
        """
        self._ensure_format_supported(image)
        if not isinstance(image, PIL.Image.Image):
            return image

        return image.convert("RGB")

    def to_numpy_array(self, image, rescale=None, channel_first=True):
        """
        Converts `image` to a numpy array. Optionally rescales it and puts the channel dimension as the first
        dimension.

        Args:
            image (`PIL.Image.Image` or `np.ndarray` or `torch.Tensor`):
                The image to convert to a NumPy array.
            rescale (`bool`, *optional*):
                Whether or not to apply the scaling factor (to make pixel values floats between 0. and 1.). Will
                default to `True` if the image is a PIL Image or an array/tensor of integers, `False` otherwise.
            channel_first (`bool`, *optional*, defaults to `True`):
                Whether or not to permute the dimensions of the image to put the channel dimension first.
        """
        self._ensure_format_supported(image)

        if isinstance(image, PIL.Image.Image):
            image = np.array(image)

        if is_torch_tensor(image):
            image = image.numpy()

        if rescale is None:
            rescale = isinstance(image.flat[0], np.integer)

        if rescale:
            image = image.astype(np.float32) / 255.0

        if channel_first and image.ndim == 3:
            image = image.transpose(2, 0, 1)

        return image

    def expand_dims(self, image):
        """
        Expands 2-dimensional `image` to 3 dimensions.

        Args:
            image (`PIL.Image.Image` or `np.ndarray` or `torch.Tensor`):
                The image to expand.
        """
        self._ensure_format_supported(image)

        # Do nothing if PIL image
        if isinstance(image, PIL.Image.Image):
            return image

        if is_torch_tensor(image):
            image = image.unsqueeze(0)
        else:
            image = np.expand_dims(image, axis=0)
        return image

    def normalize(self, image, mean, std):
        """
        Normalizes `image` with `mean` and `std`. Note that this will trigger a conversion of `image` to a NumPy array
        if it's a PIL Image.

        Args:
            image (`PIL.Image.Image` or `np.ndarray` or `torch.Tensor`):
                The image to normalize.
            mean (`List[float]` or `np.ndarray` or `torch.Tensor`):
                The mean (per channel) to use for normalization.
            std (`List[float]` or `np.ndarray` or `torch.Tensor`):
                The standard deviation (per channel) to use for normalization.
        """
        self._ensure_format_supported(image)

        if isinstance(image, PIL.Image.Image):
            image = self.to_numpy_array(image)

        if isinstance(image, np.ndarray):
            if not isinstance(mean, np.ndarray):
                mean = np.array(mean).astype(image.dtype)
            if not isinstance(std, np.ndarray):
                std = np.array(std).astype(image.dtype)
        elif is_torch_tensor(image):
            import torch

            if not isinstance(mean, torch.Tensor):
                mean = torch.tensor(mean)
            if not isinstance(std, torch.Tensor):
                std = torch.tensor(std)

        if image.ndim == 3 and image.shape[0] in [1, 3]:
            return (image - mean[:, None, None]) / std[:, None, None]
        else:
            return (image - mean) / std

    def resize(self, image, size, resample=PIL.Image.BILINEAR, default_to_square=True, max_size=None):
        """
        Resizes `image`. Enforces conversion of input to PIL.Image.

        Args:
            image (`PIL.Image.Image` or `np.ndarray` or `torch.Tensor`):
                The image to resize.
            size (`int` or `Tuple[int, int]`):
                The size to use for resizing the image. If `size` is a sequence like (h, w), output size will be
                matched to this.

                If `size` is an int and `default_to_square` is `True`, then image will be resized to (size, size). If
                `size` is an int and `default_to_square` is `False`, then smaller edge of the image will be matched to
                this number. i.e, if height > width, then image will be rescaled to (size * height / width, size).
            resample (`int`, *optional*, defaults to `PIL.Image.BILINEAR`):
                The filter to user for resampling.
            default_to_square (`bool`, *optional*, defaults to `True`):
                How to convert `size` when it is a single int. If set to `True`, the `size` will be converted to a
                square (`size`,`size`). If set to `False`, will replicate
                [`torchvision.transforms.Resize`](https://pytorch.org/vision/stable/transforms.html#torchvision.transforms.Resize)
                with support for resizing only the smallest edge and providing an optional `max_size`.
            max_size (`int`, *optional*, defaults to `None`):
                The maximum allowed for the longer edge of the resized image: if the longer edge of the image is
                greater than `max_size` after being resized according to `size`, then the image is resized again so
                that the longer edge is equal to `max_size`. As a result, `size` might be overruled, i.e the smaller
                edge may be shorter than `size`. Only used if `default_to_square` is `False`.

        Returns:
            image: A resized `PIL.Image.Image`.
        """
        self._ensure_format_supported(image)

        if not isinstance(image, PIL.Image.Image):
            image = self.to_pil_image(image)

        if isinstance(size, list):
            size = tuple(size)

        if isinstance(size, int) or len(size) == 1:
            if default_to_square:
                size = (size, size) if isinstance(size, int) else (size[0], size[0])
            else:
                width, height = image.size
                # specified size only for the smallest edge
                short, long = (width, height) if width <= height else (height, width)
                requested_new_short = size if isinstance(size, int) else size[0]

                if short == requested_new_short:
                    return image

                new_short, new_long = requested_new_short, int(requested_new_short * long / short)

                if max_size is not None:
                    if max_size <= requested_new_short:
                        raise ValueError(
                            f"max_size = {max_size} must be strictly greater than the requested "
                            f"size for the smaller edge size = {size}"
                        )
                    if new_long > max_size:
                        new_short, new_long = int(max_size * new_short / new_long), max_size

                size = (new_short, new_long) if width <= height else (new_long, new_short)

        return image.resize(size, resample=resample)

    def center_crop(self, image, size):
        """
        Crops `image` to the given size using a center crop. Note that if the image is too small to be cropped to the
        size given, it will be padded (so the returned result has the size asked).

        Args:
            image (`PIL.Image.Image` or `np.ndarray` or `torch.Tensor` of shape (n_channels, height, width) or (height, width, n_channels)):
                The image to resize.
            size (`int` or `Tuple[int, int]`):
                The size to which crop the image.

        Returns:
            new_image: A center cropped `PIL.Image.Image` or `np.ndarray` or `torch.Tensor` of shape: (n_channels,
            height, width).
        """
        self._ensure_format_supported(image)

        if not isinstance(size, tuple):
            size = (size, size)

        # PIL Image.size is (width, height) but NumPy array and torch Tensors have (height, width)
        if is_torch_tensor(image) or isinstance(image, np.ndarray):
            if image.ndim == 2:
                image = self.expand_dims(image)
            image_shape = image.shape[1:] if image.shape[0] in [1, 3] else image.shape[:2]
        else:
            image_shape = (image.size[1], image.size[0])

        top = (image_shape[0] - size[0]) // 2
        bottom = top + size[0]  # In case size is odd, (image_shape[0] + size[0]) // 2 won't give the proper result.
        left = (image_shape[1] - size[1]) // 2
        right = left + size[1]  # In case size is odd, (image_shape[1] + size[1]) // 2 won't give the proper result.

        # For PIL Images we have a method to crop directly.
        if isinstance(image, PIL.Image.Image):
            return image.crop((left, top, right, bottom))

        # Check if image is in (n_channels, height, width) or (height, width, n_channels) format
        channel_first = True if image.shape[0] in [1, 3] else False

        # Transpose (height, width, n_channels) format images
        if not channel_first:
            if isinstance(image, np.ndarray):
                image = image.transpose(2, 0, 1)
            if is_torch_tensor(image):
                image = image.permute(2, 0, 1)

        # Check if cropped area is within image boundaries
        if top >= 0 and bottom <= image_shape[0] and left >= 0 and right <= image_shape[1]:
            return image[..., top:bottom, left:right]

        # Otherwise, we may need to pad if the image is too small. Oh joy...
        new_shape = image.shape[:-2] + (max(size[0], image_shape[0]), max(size[1], image_shape[1]))
        if isinstance(image, np.ndarray):
            new_image = np.zeros_like(image, shape=new_shape)
        elif is_torch_tensor(image):
            new_image = image.new_zeros(new_shape)

        top_pad = (new_shape[-2] - image_shape[0]) // 2
        bottom_pad = top_pad + image_shape[0]
        left_pad = (new_shape[-1] - image_shape[1]) // 2
        right_pad = left_pad + image_shape[1]
        new_image[..., top_pad:bottom_pad, left_pad:right_pad] = image

        top += top_pad
        bottom += top_pad
        left += left_pad
        right += left_pad

        new_image = new_image[
            ..., max(0, top) : min(new_image.shape[-2], bottom), max(0, left) : min(new_image.shape[-1], right)
        ]

        return new_image

    def flip_channel_order(self, image):
        """
        Flips the channel order of `image` from RGB to BGR, or vice versa. Note that this will trigger a conversion of
        `image` to a NumPy array if it's a PIL Image.

        Args:
            image (`PIL.Image.Image` or `np.ndarray` or `torch.Tensor`):
                The image whose color channels to flip. If `np.ndarray` or `torch.Tensor`, the channel dimension should
                be first.
        """
        self._ensure_format_supported(image)

        if isinstance(image, PIL.Image.Image):
            image = self.to_numpy_array(image)

        return image[::-1, :, :]
