import numpy as np
import torch
from PIL import Image


def convert_img(img):
    """Converts (H, W, C) numpy.ndarray to (C, W, H) format"""
    if len(img.shape) == 3:
        img = img.transpose(2, 0, 1)
    if len(img.shape) == 2:
        img = np.expand_dims(img, 0)
    return img


class ClipToTensor(object):
    """Convert a list of m (H x W x C) numpy.ndarrays in the range [0, 255]
    to a torch.FloatTensor of shape (C x m x H x W) in the range [0, 1.0]
    """

    def __init__(self, channel_nb=3, div_255=True, numpy=False):
        self.channel_nb = channel_nb
        self.div_255 = div_255
        self.numpy = numpy

    def __call__(self, clip):
        """
        Args: clip (list of numpy.ndarray): clip (list of images)
        to be converted to tensor.
        """
        # Retrieve shape
        if isinstance(clip[0], np.ndarray):
            h, w, ch = clip[0].shape
            assert ch == self.channel_nb, "Got {0} instead of 3 channels".format(ch)
        elif isinstance(clip[0], Image.Image):
            w, h = clip[0].size
        elif isinstance(clip[0], torch.Tensor):
            tensor_clip = torch.stack(clip)
            # Converting (T, C, H, W) -> (C, T, H, W) to match what `convert_img` followed by
            # `np_clip[:, img_idx, :, :] = img` does for other data types.
            tensor_clip = tensor_clip.permute(1, 0, 2, 3)
            if not isinstance(tensor_clip, torch.FloatTensor):
                tensor_clip = tensor_clip.float()
            if self.div_255:
                tensor_clip = torch.div(tensor_clip, 255)
            return tensor_clip
        else:
            raise TypeError(
                "Expected numpy.ndarray or PIL.Image or torch.Tensor\
            but got list of {0}".format(
                    type(clip[0])
                )
            )

        np_clip = np.zeros([self.channel_nb, len(clip), int(h), int(w)])

        # Convert
        for img_idx, img in enumerate(clip):
            if isinstance(img, np.ndarray):
                pass
            elif isinstance(img, Image.Image):
                img = np.array(img, copy=False)
            else:
                raise TypeError(
                    "Expected numpy.ndarray or PIL.Image\
                but got list of {0}".format(
                        type(clip[0])
                    )
                )
            img = convert_img(img)
            np_clip[:, img_idx, :, :] = img

        if self.numpy:
            if self.div_255:
                np_clip = np_clip / 255.0
            return np_clip

        else:
            tensor_clip = torch.from_numpy(np_clip)

            if not isinstance(tensor_clip, torch.FloatTensor):
                tensor_clip = tensor_clip.float()
            if self.div_255:
                tensor_clip = torch.div(tensor_clip, 255)
            return tensor_clip


# Note this norms data to -1/1
class ClipToTensor_K(object):
    """Convert a list of m (H x W x C) numpy.ndarrays in the range [0, 255]
    to a torch.FloatTensor of shape (C x m x H x W) in the range [0, 1.0]
    """

    def __init__(self, channel_nb=3, div_255=True, numpy=False):
        self.channel_nb = channel_nb
        self.div_255 = div_255
        self.numpy = numpy

    def __call__(self, clip):
        """
        Args: clip (list of numpy.ndarray): clip (list of images)
        to be converted to tensor.
        """
        # Retrieve shape
        if isinstance(clip[0], np.ndarray):
            h, w, ch = clip[0].shape
            assert ch == self.channel_nb, "Got {0} instead of 3 channels".format(ch)
        elif isinstance(clip[0], Image.Image):
            w, h = clip[0].size
        else:
            raise TypeError(
                "Expected numpy.ndarray or PIL.Image\
            but got list of {0}".format(
                    type(clip[0])
                )
            )

        np_clip = np.zeros([self.channel_nb, len(clip), int(h), int(w)])

        # Convert
        for img_idx, img in enumerate(clip):
            if isinstance(img, np.ndarray):
                pass
            elif isinstance(img, Image.Image):
                img = np.array(img, copy=False)
            else:
                raise TypeError(
                    "Expected numpy.ndarray or PIL.Image\
                but got list of {0}".format(
                        type(clip[0])
                    )
                )
            img = convert_img(img)
            np_clip[:, img_idx, :, :] = img
        if self.numpy:
            if self.div_255:
                np_clip = (np_clip - 127.5) / 127.5
            return np_clip

        else:
            tensor_clip = torch.from_numpy(np_clip)

            if not isinstance(tensor_clip, torch.FloatTensor):
                tensor_clip = tensor_clip.float()
            if self.div_255:
                tensor_clip = torch.div(torch.sub(tensor_clip, 127.5), 127.5)
            return tensor_clip


class ToTensor(object):
    """Converts numpy array to tensor"""

    def __call__(self, array):
        tensor = torch.from_numpy(array)
        return tensor
