"""
This file is part of the private API. Please do not use directly these classes as they will be modified on
future versions without warning. The classes should be accessed only via the transforms argument of Weights.
"""
from typing import Optional, Tuple

import torch
from torch import Tensor, nn

from . import functional as F, InterpolationMode


__all__ = [
    "ObjectDetection",
    "ImageClassification",
    "VideoClassification",
    "SemanticSegmentation",
    "OpticalFlow",
]


class ObjectDetection(nn.Module):
    def forward(self, img: Tensor) -> Tensor:
        if not isinstance(img, Tensor):
            img = F.pil_to_tensor(img)
        return F.convert_image_dtype(img, torch.float)


class ImageClassification(nn.Module):
    def __init__(
        self,
        *,
        crop_size: int,
        resize_size: int = 256,
        mean: Tuple[float, ...] = (0.485, 0.456, 0.406),
        std: Tuple[float, ...] = (0.229, 0.224, 0.225),
        interpolation: InterpolationMode = InterpolationMode.BILINEAR,
    ) -> None:
        super().__init__()
        self._crop_size = [crop_size]
        self._size = [resize_size]
        self._mean = list(mean)
        self._std = list(std)
        self._interpolation = interpolation

    def forward(self, img: Tensor) -> Tensor:
        img = F.resize(img, self._size, interpolation=self._interpolation)
        img = F.center_crop(img, self._crop_size)
        if not isinstance(img, Tensor):
            img = F.pil_to_tensor(img)
        img = F.convert_image_dtype(img, torch.float)
        img = F.normalize(img, mean=self._mean, std=self._std)
        return img


class VideoClassification(nn.Module):
    def __init__(
        self,
        *,
        crop_size: Tuple[int, int],
        resize_size: Tuple[int, int],
        mean: Tuple[float, ...] = (0.43216, 0.394666, 0.37645),
        std: Tuple[float, ...] = (0.22803, 0.22145, 0.216989),
        interpolation: InterpolationMode = InterpolationMode.BILINEAR,
    ) -> None:
        super().__init__()
        self._crop_size = list(crop_size)
        self._size = list(resize_size)
        self._mean = list(mean)
        self._std = list(std)
        self._interpolation = interpolation

    def forward(self, vid: Tensor) -> Tensor:
        need_squeeze = False
        if vid.ndim < 5:
            vid = vid.unsqueeze(dim=0)
            need_squeeze = True

        vid = vid.permute(0, 1, 4, 2, 3)  # (N, T, H, W, C) => (N, T, C, H, W)
        N, T, C, H, W = vid.shape
        vid = vid.view(-1, C, H, W)
        vid = F.resize(vid, self._size, interpolation=self._interpolation)
        vid = F.center_crop(vid, self._crop_size)
        vid = F.convert_image_dtype(vid, torch.float)
        vid = F.normalize(vid, mean=self._mean, std=self._std)
        H, W = self._crop_size
        vid = vid.view(N, T, C, H, W)
        vid = vid.permute(0, 2, 1, 3, 4)  # (N, T, C, H, W) => (N, C, T, H, W)

        if need_squeeze:
            vid = vid.squeeze(dim=0)
        return vid


class SemanticSegmentation(nn.Module):
    def __init__(
        self,
        *,
        resize_size: Optional[int],
        mean: Tuple[float, ...] = (0.485, 0.456, 0.406),
        std: Tuple[float, ...] = (0.229, 0.224, 0.225),
        interpolation: InterpolationMode = InterpolationMode.BILINEAR,
    ) -> None:
        super().__init__()
        self._size = [resize_size] if resize_size is not None else None
        self._mean = list(mean)
        self._std = list(std)
        self._interpolation = interpolation

    def forward(self, img: Tensor) -> Tensor:
        if isinstance(self._size, list):
            img = F.resize(img, self._size, interpolation=self._interpolation)
        if not isinstance(img, Tensor):
            img = F.pil_to_tensor(img)
        img = F.convert_image_dtype(img, torch.float)
        img = F.normalize(img, mean=self._mean, std=self._std)
        return img


class OpticalFlow(nn.Module):
    def forward(self, img1: Tensor, img2: Tensor) -> Tuple[Tensor, Tensor]:
        if not isinstance(img1, Tensor):
            img1 = F.pil_to_tensor(img1)
        if not isinstance(img2, Tensor):
            img2 = F.pil_to_tensor(img2)

        img1 = F.convert_image_dtype(img1, torch.float)
        img2 = F.convert_image_dtype(img2, torch.float)

        # map [0, 1] into [-1, 1]
        img1 = F.normalize(img1, mean=[0.5, 0.5, 0.5], std=[0.5, 0.5, 0.5])
        img2 = F.normalize(img2, mean=[0.5, 0.5, 0.5], std=[0.5, 0.5, 0.5])

        img1 = img1.contiguous()
        img2 = img2.contiguous()

        return img1, img2
